Co-reporter:Virginia Gomez, Shirin Alexander, Andrew R. Barron
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 513() pp:297-305
Publication Date(Web):5 January 2017
DOI:10.1016/j.colsurfa.2016.10.058
•MWCNTs facilitate the aggregation of coated proppants through localized microwave heating.•Covalently functionalized proppants are used as linkage points for polymer coatings.•MWCNTs result in melting of the coating under microwave irradiation joining the particles.The application of multi-walled carbon nanotubes (MWCNTs) to facilitate the aggregation of ceramic particles (proppants) by embedding in the coating through localized microwave heating is reported. Thermogravimetric analysis (TGA), scanning electron microscopy (SEM) along with energy dispersive X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize a series of covalently functionalized proppants with carboxylic acids (lysine and fumaric acid). The bi-functional acids allow for a controlled reaction with a coating (resin and polymer). The addition of carbon nanotubes results in the melting of the coating under exposure to microwave irradiation (20 s @ 100 W) joining the particles. The significant reduction in reaction time (compared to the thermal treatments of 2–24 h) is due to the presence of the MWCNTs. The microwave heating of the MWCNTs can thus be used to create interaction and adhesion between functionalized particles subject to a specific stimulus.
Co-reporter:Brittany L. Oliva-Chatelain, Thomas M. Ticich and Andrew R. Barron
Nanoscale 2016 vol. 8(Issue 4) pp:1733-1745
Publication Date(Web):22 Dec 2015
DOI:10.1039/C5NR04978D
The ability to incorporate a dopant element into silicon nanocrystals (NC) and quantum dots (QD) is one of the key technical challenges for the use of these materials in a number of optoelectronic applications. Unlike doping of traditional bulk semiconductor materials, the location of the doping element can be either within the crystal lattice (c-doping), on the surface (s-doping) or within the surrounding matrix (m-doping). A review of the various synthetic strategies for doping silicon NCs and QDs is presented, concentrating on the efficacy of the synthetic routes, both in situ and post synthesis, with regard to the structural location of the dopant and the doping level. Methods that have been applied to the characterization of doped NCs and QDs are summarized with regard to the information that is obtained, in particular to provide researchers with a guide to the suitable techniques for determining dopant concentration and location, as well as electronic and photonic effectiveness of the dopant.
Co-reporter:Shirin Alexander, Charles W. Dunnill, Andrew R. Barron
Journal of Colloid and Interface Science 2016 Volume 466() pp:275-283
Publication Date(Web):15 March 2016
DOI:10.1016/j.jcis.2015.12.038
•Hierarchical structures demonstrating two new immobile proppant concepts.•Bi-functionalized molecular anchors for resin attachment to the proppant surface.•The resin-coated proppants cures to create porous hierarchical structures.•A pH-responsive reversible bridging layer between the proppant particles.HypothesisThe assembly of temperature/pH sensitive complex microparticle structures through chemisorption and physisorption provides a responsive system that offers application as routes to immobilization of proppants in-situ.ExperimentsThermogravimetric analysis (TGA) and scanning electron microscopy (SEM) along with energy dispersive X-ray analysis (EDX) have been used to characterize a series of bi-functionalized monolayers and/or multilayers grown on alumina microparticles and investigate the reactive nature of both temperature sensitive cross-linker (epoxy resin) with the layers and pH-responsive bridging layer (polyetheramine).FindingsThe bifunctional acids, behaving as molecular anchors, allow for a controlled reaction with a cross-linker (resin or polymer) with the formation of networks, which is either irreversible or reversible based on the nature of the cross-linker. The networks results in formation of porous hierarchical particles that offer a potential route to the creation of immobile proppant pack.
Co-reporter:Virginia Gomez, Silvia Irusta, Olawale B. Lawal, Wade Adams, Robert H. Hauge, Charles W. Dunnill and Andrew R. Barron
RSC Advances 2016 vol. 6(Issue 14) pp:11895-11902
Publication Date(Web):22 Jan 2016
DOI:10.1039/C5RA24854J
A new two-step purification method of carbon nanotubes (CNTs) involving a microwave treatment followed by a gas-phase chlorination process is reported. The significant advantage of this method over conventional cleaning carbon nanotubes procedures is that under microwave treatment in air, the carbon shells that encase the residual metal catalyst particles are removed and the metallic iron is exposed and subsequently oxidized making it accessible for chemical removal. The products from microwave and chlorine treatment have been characterized by TG/DTA, SEM, TEM, EDX, XPS, and Raman spectroscopy. The oxidation state of the iron residue is observed to change from Fe(0) to Fe(II)/Fe(III) after microwave treatment and atmospheric exposure. The effects of the duration and number of microwave exposures has been investigated. This rapid and effective microwave step favours the subsequent chlorination treatment enabling a more effective cleaning procedure to take place, yielding higher purity single- and multi-walled CNTs.
Co-reporter:Andrew R. Barron
Materials Today 2015 Volume 18(Issue 1) pp:2-3
Publication Date(Web):January–February 2015
DOI:10.1016/j.mattod.2014.10.022
Co-reporter:Shirin Alexander, Lauren Morrow, Alex M. Lord, Charles W. Dunnill and Andrew R. Barron
Journal of Materials Chemistry A 2015 vol. 3(Issue 18) pp:10052-10059
Publication Date(Web):07 Apr 2015
DOI:10.1039/C5TA01294E
The formation of a pH-sensitive coupling layer, through both physisorption and chemisorption, provides a responsive surface that can be assembled and disassembled in relation to external stimuli. Contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Fourier transform IR-attenuated reflectance spectroscopy (FTIR-ATR) have been used to characterize a series of bi-functionalized self-assembled monolayers (SAMs) grown on aluminium oxide wafers/nanoparticles and investigate the reaction nature of pH-responsive coupling layer (octylamine) with the SAMs. Contact angle, XPS, and AFM analyses indicate that the surface of native aluminium oxide was covered considerably as the contact angle of the surfaces decreased, carbon atomic % and roughness of the surfaces increased.
Co-reporter:Enrico Andreoli and Andrew R. Barron
Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:4323-4329
Publication Date(Web):14 Jan 2015
DOI:10.1039/C4TA06936F
The high CO2 capacity of PEI-C60 conjugates is impeded by a slow rate of absorption. A limiting factor to this rate is proposed to be the surface area available for the rapid contact between amine functional groups of PEI and CO2. Increasing the surface area by spray-drying a solution of reagents is proposed as a route to larger surface area products. In this work we investigate process changes to control absorption chemistry. Reagent solutions were spray-dried in different experimental conditions of concentration, drying temperature, and feed pressure. The results indicate that the rate of CO2 absorption at room temperature can be improved by a factor of 2.5 times by spray drying the product when compared to the product obtained using sonication. Given the rubbery nature of PEI-C60 the surface area, and hence CO2 capacity, could be increased using cryogenic grinding in liquid nitrogen; however, the results show that this has limited effect on the surface area of the absorbent prepared using sonication. Only compared to the hard chunks obtained via stir bar synthesis was the surface area doubled, in contrast to the rubbery product obtained using ultrasonication the area did not change significantly. Interestingly, doubling the surface area, the rate of absorption of wet CO2 at high temperature did not change, while that at low temperature doubled in rate, consistent with the presence of diffusion limitations manly at low temperature.
Co-reporter:Yen-Tien Lu and Andrew R. Barron
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 22) pp:11802
Publication Date(Web):May 13, 2015
DOI:10.1021/acsami.5b01008
Silicon solar cells with nanopore-type black silicon (b-Si) antireflection (AR) layers and self-aligned selective emitter (SE) are reported in which the b-Si structure is prepared without the traditional addition of a nanoparticle (NP) catalyst. The contact-assisted chemical etching (CACE) method is reported here for the first time, in which the metal top contacts on silicon solar cell surfaces function as the catalysts for b-Si fabrication and the whole etching process can be done in minutes at room temperature. The CACE method is based on the metal-assisted chemical etching (MACE) solution but without or metal precursor in the Si etchant (HF:H2O2:H2O), and the Au top contacts, or catalysts, are not removed from the solar cell surface after the etching. The effects of etching time, HF and H2O2 concentration, and the HF:H2O2 ratio on the b-Si morphology, surface reflectivity, and solar cell efficiency have been investigated. Higher [HF] and [H2O2] with longer etching time cause collapse of the b-Si nanoporous structure and penetration of the p–n junctions, which are detrimental to the solar cell efficiency. The b-Si solar cell fabricated with the HF:H2O2:H2O volume ratio of 3:3:20 and a 3 min etch time shows the highest efficiency 8.99% along with a decrease of reflectivity from 36.1% to 12.6% compared to that of the nonetched Si solar cell.Keywords: antireflection; black silicon; contact; porous; selective emitter; solar cell;
Co-reporter:Jessica Heimann, Lauren Morrow, Robin E. Anderson and Andrew R. Barron
Dalton Transactions 2015 vol. 44(Issue 9) pp:4380-4388
Publication Date(Web):26 Jan 2015
DOI:10.1039/C4DT03376K
Metal contamination of water is a serious challenge faced by environmental chemists, but there is also economic value in the removal of metals for recycling or extraction. Our prior observation that hydroxyfullerenes [C60Ox(OH)y]n− act as chelate agents to Fe3+ suggests that these material, or derivatives, may be used for co-precipitation. We report the removal of main group (Al3+, Ag+, Ca2+, and Zn2+) as well transition metal (Fe3+, Co2+, Cu2+, Mn2+, and Ni2+) and lanthanide (La3+ and Nd3+) ions from solution. The resulting complexes have been characterized by XPS, SEM, TEM, and DLS. The competitive binding with Fe3+ shows that the binding affinity with hydroxyfullerenes follows the order: Zn2+ > Co2+ > Mn2+ > Ni2+ > La3+ > Nd3+ > Cd2+ > Cu2+ > Ag+ > Ca2+ > Fe3+ > Al3+. The relative binding ability is dependent on ionic radius; however, divergent trends are observed for M2+ and M3+, i.e., for divalent ions the binding is stronger for smaller ions, while the opposite trend is observed for trivalent ions. Previously the coordination of hydroxyfullerene to metals was assumed to be analogous to a 1,2-diol or catechol. However, while ab initio calculations using [M(catecholate)n]n− (n = 2, 3) provide an explanation of the observed trend for M2+, the use of cis–cis-1,3,5-cyclohexanetriol and cis-1,3-cyclohexanediol as model ligands provides insight into the relative binding efficiency for M3+.
Co-reporter:Enrico Andreoli, Laurie Cullum, and Andrew R. Barron
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 3) pp:878-889
Publication Date(Web):December 26, 2014
DOI:10.1021/ie504277s
The kinetics of absorption of dry and wet CO2 of polyethylenimine-functionalized single walled carbon nanotube (PEI-SWNT), graphite oxide (PEI-GO), and fullerene C60 (PEI-C60) were analyzed in detail using six different kinetic models: Elovich, pseudo-1st-order, pseudo-2nd-order, pseudo-nth-order, modified Avrami, and extended model. It is found that PEI-SWNT follows a pseudo-2nd-order kinetics both in dry and wet CO2, whereas PEI-GO follows a modified Avrami kinetics with values of the parameter m close to 1, being this a simple correction to a pure pseudo-1st-order kinetics. The kinetics of PEI-C60 appears to be more complex and slower due to gas diffusion limitations. A comparison of the kinetics of PEI-GO and PEI-SWNT supports the hypothesis that carbon scaffolds of higher curvature can activate and enhance the CO2 absorption capability of PEI.
Co-reporter:Alvin W. Orbaek; Mary M. McHale
Journal of Chemical Education 2015 Volume 92(Issue 2) pp:339-344
Publication Date(Web):October 6, 2014
DOI:10.1021/ed500036b
The aim of this simple, quick, and safe laboratory exercise is to provide undergraduate students an introduction to nanotechnology using nanoparticle (NP) synthesis. Students are provided two procedures that allow for the synthesis of different yet controlled sizes of silver NPs. After preparing the NPs, the students perform UV–visible spectroscopy and full-width-half-maximum (fwhm) analysis to determine the size of the NPs they have synthesized. In doing so, the students made nanoparticles of size ranges from 10–100 nm, thus spanning the range of nanotechnology. The experiments are designed to be accomplished in a single 90 min session and have been successfully conducted with over 1000 first-year-level students over a three-year period.
Co-reporter:Enrico Andreoli, Rei Suzuki, Alvin W. Orbaek, Manoop S. Bhutani, Robert H. Hauge, Wade Adams, Jason B. Fleming and Andrew R. Barron
Journal of Materials Chemistry A 2014 vol. 2(Issue 29) pp:4740-4747
Publication Date(Web):21 May 2014
DOI:10.1039/C4TB00778F
High quality single-walled carbon nanotubes (SWNTs) were obtained following a new purification procedure, based on using Cl2 gas at high temperature. Cl2-treated SWNTs were fluorinated and modified with branched polyethyleneimine (PEI) to afford covalently functionalised PEI–SWNTs, which were then tested for cytotoxicity both in vitro (HPNE and BxPC3 pancreatic cell lines) and in vivo (BxPC3 xenografts from nude mice) to establish that functionalization with lower molecular weight PEI (600 and 1800 Da) achieved higher cell viability in MTT assay. A shortened version of the nanotubes, PEI(1800)-cut-SWNT (1800 Da branched PEI), was also prepared and tested for cellular internalization in the BxPC3 adenocarcinoma cell line. Laser confocal imaging of the cells after incubation in the presence of RhoB-PEI(1800)-cut-SWNT (covalently labelled with rhodamine B) indicates that the PEI(1800)-cut-SWNTs can reach both the cytoplasm and nucleus of pancreatic cancer cells.
Co-reporter:Yen-Tien Lu and Andrew R. Barron
Journal of Materials Chemistry A 2014 vol. 2(Issue 30) pp:12043-12052
Publication Date(Web):04 Jun 2014
DOI:10.1039/C4TA02006E
A new one-step copper-assisted chemical etching technique is reported to more economically prepare nanopore-type anti-reflective layers, which can effectively suppress reflection of Si wafer surfaces for solar cell applications. In contrast to the Au and Ag processes, phosphorous acid (rather than hydrogen peroxide) is utilized as a reducing agent to reduce Cu2+ to Cu0 nanoparticles. The Cu nanoparticles catalyse the oxidization of Si in the vicinity of the nanoparticles to SiO2, which is then etched by HF to form nanopores. The effects of the HF and H3PO3 concentrations, the HF:H2O volume ratio, and the etching time on the black silicon morphology with the corresponding Si surface reflectivity have been systematically investigated. The size and shape of the pores are controlled by [Cu2+] and the subsequent size of the NPs as controlled by [H3PO3], while the depth of the pores are limited by [HF] and the etch time. With [Cu2+] = 500 μM and [H3PO3] = 10 mM, the fabricated black silicon possesses the lowest relative effective reflectivity, 0.96%, and the shortest nanopore length (590 nm).
Co-reporter:Hannah Rutledge, Brittany L. Oliva-Chatelain, Samuel J. Maguire-Boyle, Dennis L. Flood, Andrew R. Barron
Materials Science in Semiconductor Processing 2014 Volume 17() pp:7-12
Publication Date(Web):January 2014
DOI:10.1016/j.mssp.2013.08.005
Monodispersed silica nanoparticles 20 nm in diameter were synthesized with germanium quantum dots (QDs) as seeds using a modified Stöber process. The resulting structures comprise of germanium QD core within a silica sphere (Ge@SiO2). Films of the Ge@SiO2 Stöber particles result in an average QD…QD distance of 9.6 nm, which is less than the maximum distance required for good electron transfer (10 nm). Thus, this method represents an efficient alternative to the previously reported liquid phase deposition (LPD) of silica on Ge QDs where many silica particles contained more than one QD, resulting in a wide range of QD…QD distances.
Co-reporter:Samuel J. Maguire-Boyle, David J. Garner, Jessica E. Heimann, Lucy Gao, Alvin W. Orbaek and Andrew R. Barron
Environmental Science: Nano 2014 vol. 16(Issue 2) pp:220-231
Publication Date(Web):07 Jan 2014
DOI:10.1039/C3EM00718A
Quantifying nanoparticle (NP) transport within porous geological media is imperative in the design of tracers and sensors to monitor the environmental impact of hydraulic fracturing that has seen increasing concern over recent years, in particular the potential pollution and contamination of aquifers. The surface chemistry of a NP defining many of its solubility and transport properties means that there is a wide range of functionality that it is desirable to screen for optimum transport. Most prior transport methods are limited in determining if significant adsorption occurs of a NP over a limited column distance, however, translating this to effects over large distances is difficult. Herein we report an automated method that allows for the simulation of adsorption effects of a dilute nanoparticle solution over large distances under a range of solution parameters. Using plasmonic silver NPs and UV-visible spectroscopic detection allows for low concentrations to be used while offering greater consistency in peak absorbance leading to a higher degree of data reliability and statistics. As an example, breakthrough curves were determined for mercaptosuccinic acid (MSA) and cysteamine (CYS) functionalized Ag NPs passing through Ottawa sand (typical proppant material) immobile phase (C) or bypassing the immobile phase (C0). Automation allows for multiple sequences such that the absorption plateau after each breakthrough and the rate of breakthrough can be compared for multiple runs to provide statistical analysis. The mobility of the NPs as a function of pH is readily determined. The stickiness (α) of the NP to the immobile phase calculated from the C/C0 ratio shows that MSA-Ag NPs show good mobility, with a slight decrease around neutral pH, while CYS-Ag NPs shows an almost sinusoidal variation. The automated process described herein allows for rapid screening of NP functionality, as a function of immobile phase (proppant versus reservoir material), hydraulic fracturing fluid additives (guar, surfactant) and conditions (pH, temperature).
Co-reporter:Samuel J. Maguire-Boyle and Andrew R. Barron
Environmental Science: Nano 2014 vol. 16(Issue 10) pp:2237-2248
Publication Date(Web):13 Aug 2014
DOI:10.1039/C4EM00376D
A detailed analysis is reported of the organic composition of produced water samples from typical shale gas wells in the Marcellus (PA), Eagle Ford (TX), and Barnett (NM) formations. The quality of shale gas produced (and frac flowback) waters is a current environmental concern and disposal problem for producers. Re-use of produced water for hydraulic fracturing is being encouraged; however, knowledge of the organic impurities is important in determining the method of treatment. The metal content was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Mineral elements are expected depending on the reservoir geology and salts used in hydraulic fracturing; however, significant levels of other transition metals and heavier main group elements are observed. The presence of scaling elements (Ca and Ba) is related to the pH of the water rather than total dissolved solids (TDS). Using gas chromatography mass spectrometry (GC/MS) analysis of the chloroform extracts of the produced water samples, a plethora of organic compounds were identified. In each water sample, the majority of organics are saturated (aliphatic), and only a small fraction comes under aromatic, resin, and asphaltene categories. Unlike coalbed methane produced water it appears that shale oil/gas produced water does not contain significant quantities of polyaromatic hydrocarbons reducing the potential health hazard. Marcellus and Barnett produced waters contain predominantly C6–C16 hydrocarbons, while the Eagle Ford produced water shows the highest concentration in the C17–C30 range. The structures of the saturated hydrocarbons identified generally follows the trend of linear > branched > cyclic. Heterocyclic compounds are identified with the largest fraction being fatty alcohols, esters, and ethers. However, the presence of various fatty acid phthalate esters in the Barnett and Marcellus produced waters can be related to their use in drilling fluids and breaker additives rather than their presence in connate fluids. Halogen containing compounds are found in each of the water samples, and although the fluorocarbon compounds identified are used as tracers, the presence of chlorocarbons and organobromides formed as a consequence of using chlorine containing oxidants (to remove bacteria from source water), suggests that industry should concentrate on non-chemical treatments of frac and produced waters.
Co-reporter:Alvin W. Orbaek, Neerja Aggarwal and Andrew R. Barron
Journal of Materials Chemistry A 2013 vol. 1(Issue 45) pp:14122-14132
Publication Date(Web):07 Oct 2013
DOI:10.1039/C3TA13543H
Ferrocene was used as a catalyst in a hydrocarbon solution to carry out injection chemical vapour deposition (CVD) growth of carbon nanomaterials in a horizontal tube furnace. The presence and quality of various carbon materials was determined using Raman spectroscopy, thermogravimetric analysis, and electron microscopy. Products ranged from amorphous carbon (a-C), multi walled carbon nanotubes (MWNTs) and vapour grown fibers (VGFs). Catalyst concentration, growth temperature, injection rate, carrier gas flow rate, and the choice of hydrocarbon were found to influence the product outcome. Slower injection rates gave higher isolated yield. High catalyst concentrations were found to produce less pure carbon materials with iron oxides impurities. Higher temperatures were favourable to nanotube formation. The use of benzene was found to increase yield compared with the other hydrocarbons. In this work we developed a process map to chart the various carbon nanomaterial allotropes that were created according to reaction parameters.
Co-reporter:Alvin W. Orbaek, Andrew C. Owens, Christopher C. Crouse, Cary L. Pint, Robert H. Hauge and Andrew R. Barron
Nanoscale 2013 vol. 5(Issue 20) pp:9848-9859
Publication Date(Web):14 Aug 2013
DOI:10.1039/C3NR03142J
Vertical arrays of single walled carbon nanotubes (VA-SWNTs) were grown using bi-metallic nanoparticle pro-catalysts. Iron oxide particles were doped with varying quantities of first row transition metals (Mn, Co, Ni, and Cu) for a comparative study of the growth of nanotubes. VA-CNT samples were verified using scanning electron microscopy, and characterized using resonance Raman spectroscopy. The length of the VA-CNTs is used as a measure of catalyst activity: the presence of dopants results in a change in the CNT length and length distribution. Cross correlation of the Raman spectra reveal variations in the distribution of radial breathing mode peaks according to the pro-catalyst composition. The formation of various chirality nanotubes is constant between repetitive runs with a particular catalyst, but may be controlled by the identity and concentration of the metal dopants within the iron catalyst. These results demonstrate that the composition of the catalyst is a major driving force toward type selective growth of nanotubes.
Co-reporter:Alvin W. Orbaek and Andrew R. Barron
Nanoscale 2013 vol. 5(Issue 7) pp:2790-2797
Publication Date(Web):14 Feb 2013
DOI:10.1039/C3NR00142C
Comparison of AFM and SEM images of single walled carbon nanotubes (SWNTs) grown within a dielectric matrix reveal subterranean nanotubes that are present within the matrix, and as such can be charge screened by the dielectric. Under adequate imaging conditions for the SWNT/silica sample the intensity of isolated nanotubes is found to be inversely proportional to the instrument dwell time (i.e., shorter dwell times were found to make SWNT intensities brighter). The threshold dwell time required to enable isolated tubes to be visible was found to be 10 μs; moreover, the degree change in intensity was found to be nanotube specific, i.e., different SWNTs respond in a different manner at different dwell times. The results indicate that care should be taken when attempting to quantify number density and length distributions of SWNTs on or within a dielectric matrix.
Co-reporter:Eoghan Dillon, Manoop S. Bhutani and Andrew R. Barron
Journal of Materials Chemistry A 2013 vol. 1(Issue 10) pp:1461-1465
Publication Date(Web):21 Jan 2013
DOI:10.1039/C3TB00456B
Water soluble polyethyleneimine functionalized single wall carbon nanotubes (PEI–SWNTs) can be loaded with the therapeutic agents acetic acid and the gemcitabine analogue, deoxycytidine (dC). The amount of loading is based on initial sonication time and the solubility of the agent. The use of an endoscopic ultrasound (EUS) results in the controlled release of the agents from the PEI–SWNT conjugate. The release of acetic acid occurs by first-order kinetics, however, the release of the majority of the dC occurs by the more desired zero-order release.
Co-reporter:Michael V. Liga, Samuel J. Maguire-Boyle, Huma R. Jafry, Andrew R. Barron, and Qilin Li
Environmental Science & Technology 2013 Volume 47(Issue 12) pp:6463-6470
Publication Date(Web):May 24, 2013
DOI:10.1021/es400196p
A new method of modifying TiO2 photocatalysts with SiO2 is developed in which SiO2 nanoparticles are simply mixed with TiO2 in water under ambient conditions. This method does not require the use of toxic solvents or significant energy input. Although the SiO2 modification slightly reduces hydroxyl free radical production, the composite SiO2–TiO2 nanomaterials have markedly higher photocatalytic inactivation rates for a common surrogate virus, bacteriophage MS2 (up to 270% compared to the unmodified TiO2), due to the greatly improved adsorptive density and dark inactivation of MS2. The Langmuir isotherm describes the adsorption data well and shows that the TiO2 modified with 5% SiO2 has a maximum adsorption density qmax 37 times that of the unmodified TiO2. The Langmuir–Hinshelwood model fits the photocatalytic inactivation kinetic data well. The SiO2–TiO2 material produces a greater maximum initial inactivation rate yet a lower intrinsic surface reaction rate constant, consistent with the reduced hydroxyl radical production and enhanced adsorption. These results suggest that modifying photocatalyst surface to increase contaminant adsorption is an important strategy to improve photocatalytic reaction efficiency. Simple and cheap synthesis methods such as that used in this study bring photocatalysis closer to being a viable water treatment option.
Co-reporter:Yen-Tien Lu and Andrew R. Barron
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 24) pp:9862-9870
Publication Date(Web):08 May 2013
DOI:10.1039/C3CP51835C
An effective and economical fabrication process for the synthesis of nanopore-type “black silicon”, that significantly decreases reflectivity of silicon wafer surfaces, is reported using a room temperature one-step Ag-assisted chemical etching method. The effects on the surface morphology and the corresponding surface reflectivity of the concentration of the silver catalyst (500, 50, and 5 μM), the HF and H2O2 concentration in the silicon etchant, the HF:H2O2 ratio, and etching time have been investigated. Lower reflectivity is a balance between sufficient silver catalyst to create large numbers of nanopores on a silicon surface and excessive silver that brings deeply etched channels that would potentially short-circuit a solar cell junction. The lowest relative effective reflectivity (0.17% over a range of 300–1000 nm) occurs with a silver ion concentration of 50 μM, however, with the silver ion concentration decreases to 5 μM surfaces with a low relative effective reflectivity (2.60%) and a short nanopore length (<250 nm) can be obtained with 10 minute etching time, indicating that this method can be used as a simple (one-pot), low cost (low silver concentration), energy efficient (room temperature), method for the synthesis of anti-reflection layers for silicon-based solar cell applications.
Co-reporter:Robin E. Anderson and Andrew R. Barron
Dalton Transactions 2013 vol. 42(Issue 6) pp:2186-2191
Publication Date(Web):15 Nov 2012
DOI:10.1039/C2DT32523C
Highly oxygenated fullerenes, C60On with 1 ≤ n ≤ 13, have been prepared by the Mo(O)2(acac)2 catalysed oxidation of C60 with tBuOOH. Increasing the catalyst:C60 ratio or increasing the reaction temperature increases the yield as well shifting the product distribution to higher oxygenated products, in contrast, increasing the tBuOOH concentration shifts the product distribution in the opposite manner. The MALDI mass spectra of reactions containing the highest oxygenated products (n > 5) show additional peaks (not observed for C60 under the same MS conditions) due to the cage-opened products Cx (x = 54, 56, 58) along with their oxygenated derivatives, CxOn (x = 54, 56, 58; n = 1–3).
Co-reporter:Christopher E. Hamilton, Dennis J. Flood and Andrew R. Barron
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 11) pp:3930-3938
Publication Date(Web):01 Feb 2013
DOI:10.1039/C3CP50435B
Liquid phase deposition (LPD), using CdSO4 and N,N-dimethyl selenourea, has been used to grow CdSe absorber layer onto single walled carbon nanotube (SWNT) derived back contact substrates. The nanotubes are imbedded in, and penetrate into, the CdSe absorber layer for the goal of enhancing excition dissociation and carrier transport. The Cd:Se film stoichiometry varied between 1:1.7 to 1:1.3 depending on the deposition conditions. The CdSe/SWNT layers show appropriate photoresponse. LPD was also used to grow a CuSe window layer onto which silver contacts were deposited. The resulting PV device shows a characteristic IV curve. Despite both the open circuit voltage (VOC = 1.28 mV) and short circuit current (ISC = 4.85 μA) being low, the resulting device is suggestive of the possibility of fabricating a flexible thin film (inorganic) solar cell by solution processes.
Co-reporter:Samuel J. Maguire-Boyle, Michael V. Liga, Qilin Li and Andrew R. Barron
Nanoscale 2012 vol. 4(Issue 18) pp:5627-5632
Publication Date(Web):10 Jul 2012
DOI:10.1039/C2NR31117H
A bi-functional nano-composite coating has been created on a porous Nomex® fabric support as a trap for aspirated virus contaminated water. Nomex® fabric was successively dip-coated in solutions containing cysteic acid functionalized alumina (alumoxane) nanoparticles and cysteic acid functionalized iron oxide (ferroxane) nanoparticles to form a nanoparticle coated Nomex® (NPN) fabric. From SEM and EDX the nanoparticle coating of the Nomex® fibers is uniform, continuous, and conformal. The NPN was used as a filter for aspirated bacteriophage MS2 viruses using end-on filtration. All measurements were repeated to give statistical reliability. The NPN fabrics show a large decrease as compared to Nomex® alone or alumoxane coated Nomex®. An increase in the ferroxane content results in an equivalent increase in virus retention. This suggests that it is the ferroxane that has an active role in deactivating and/or binding the virus. Heating the NPN to 160 °C results in the loss of cysteic acid functional groups (without loss of the iron nanoparticle's core structure) and the resulting fabric behaves similar to that of untreated Nomex®, showing that the surface functionalization of the nanoparticles is vital for the surface collapse of aspirated water droplets and the absorption and immobilization of the MS2 viruses. Thus, for virus immobilization, it is not sufficient to have iron oxide nanoparticles per se, but the surface functionality of a nanoparticle is vitally important in ensuring efficacy.
Co-reporter:Brittany L. Oliva, Andrew R. Barron
Materials Science in Semiconductor Processing 2012 Volume 15(Issue 6) pp:713-721
Publication Date(Web):December 2012
DOI:10.1016/j.mssp.2012.03.018
Hydrophilic silicon (0.9 nm) and germanium (2.7 nm) quantum dots (QDs), synthesized utilizing micelles to control particle size, were coated with silica using liquid phase deposition. The use of dodecyltrimethylammonium bromide as a surfactant yielded uniform spheres (Si@SiO2=57 nm; Ge@SiO2=32 nm), which could then be arrayed in three dimensions using a vertical deposition method on quartz plates. The silica coated QDs were characterized by UV–visible spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy. The thin films were characterized by UV–visible spectroscopy, scanning electron microscopy, and the measurement of a photocurrent.
Co-reporter:Alvin W. Orbaek, Andrew C. Owens, and Andrew R. Barron
Nano Letters 2011 Volume 11(Issue 7) pp:2871-2874
Publication Date(Web):June 22, 2011
DOI:10.1021/nl201315j
Single walled carbon nanotubes (SWNTs) seeds are grown using Fe–Co nanoparticles on spin-on-glass. The relative efficiency of nucleation and amplification (versus etching) was investigated as a function of the CH4/H2 feedstock ratio and growth temperature. At 900 °C, maximum amplification is obtained with CH4/H2 ratio of 80:20 but 60:40 for nucleation. Amplification is further enhanced at 800 °C, compared with etching dominating at 1000 °C. Amplification of SWNTs is in equilibrium with etching; higher carbon feedstock pressure and decreased temperature increase the rate of amplification; the converse increases etching.
Co-reporter:Huma R. Jafry, Michael V. Liga, Qilin Li, and Andrew R. Barron
Environmental Science & Technology 2011 Volume 45(Issue 4) pp:1563-1568
Publication Date(Web):December 31, 2010
DOI:10.1021/es102749e
Silica doped TiO2(P25) nanoparticles are tested for its photocatalytic activity in the degradation of bacteriophage MS2. During our studies it was found that treatment of TiO2(P25) in the glass flasks sealed with silicone grease resulted in a significant improvement in the catalytic activity of the titania. Further improvement can be made by the purposeful reaction of TiO2(P25) with 2.5 wt % silica. This non in situ method of incorporating silica to TiO2(P25) nanoparticles is tested for their role in killing of viruses, and it is found that the rate constant is three times higher to kill viruses with the addition of silica. BET measurements show no significant change/increase in the surface area of silica doped TiO2(P25)-SiO2, compared to the undoped TiO2(P25). Further studies show that the addition of silica increases the adsorption of viruses onto the catalyst. There is a significant difference in the activity of the TiO2(P25)-SiO2 samples in the presence of methanol, supporting the notion that hydroxide radical (HO·) is responsible for the antiviral action. The TiO2(P25)-SiO2 either produces more HO· than non silica-doped material, or the enhanced adsorption of MS2 to the catalyst results in greater exposure to the HO·, or both mechanisms may work in concert. XPS studies suggest the formation of silica species on the surface of the TiO2(P25), while UV−visible spectroscopy suggests that the presence of the silica results in a small increase in the measured band gap. We suggest that the enhanced catalytic activity is a result of increased adsorption and/or band bending which can occur at the interface within TiO2(P25)-SiO2. One result of this would be a reduction of the electron−hole recombination, the formation of a greater concentration of OH·, and hence an improved catalytic performance.
Co-reporter:John J. Allen and Andrew R. Barron
Dalton Transactions 2011 vol. 40(Issue 5) pp:1189-1194
Publication Date(Web):20 Dec 2010
DOI:10.1039/C0DT01301C
Complexes of the type [Cu(R-dpa)(η2-olefin)]BF4 (R = Mes and 2-iPrC6H4) for cis- and trans- isomers of 3-octene, as well as those for cis- and trans-4-octene (R = 2-iPrC6H4) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structure of [Cu(Mes-dpa)(η2-trans-3-octene)]BF4 (2) has been determined via X-ray crystallography. The asymmetric unit in the crystal lattice of 2 contains two unique conformations of the complex cation related by a pseudo center of symmetry, which differ primarily in the orientation of the olefin with respect to the rest of the molecule. The 1H and 13C NMR spectra of [Cu(Ar-dpa)(η2-olefin)]BF4 exhibit olefin resonances shifted upfield with respect to free olefin. The difference in Δδ(13C) relative magnitudes between cis- and trans- complexes, i.e., the binding, correlates with the degree of substitution at the amine nitrogen. The identity of the remote ligand substituent (Ar) controls the differentiation of binding between cis and trans isomers as a consequence of increased folding of the Ar-dpa ligand along the Cu⋯N axis.
Co-reporter:Nadjmeh Doostdar;Carissa J. Manrique;M. Bowes Hamill
Journal of Biomedical Materials Research Part A 2011 Volume 99A( Issue 2) pp:173-183
Publication Date(Web):
DOI:10.1002/jbm.a.33172
Abstract
Calcific band keratopathy (CBK) is a degenerative condition resulting in the deposition of calcium salts in the superficial layers of the cornea and causing significant visual disturbance and pain of the affected eye. Unfortunately, the amount of CBK precipitates recovered from the affected eye is very small therefore; it would be beneficial to prepare a synthetic material mimicking CBK material to further the development of therapeutics. Analyses of biological samples recovered from patients show the presence of silicon in addition to calcium, as well as a distinctive fused spherical morphology. This prompted us to study the reaction of various sources of silicon (fumed silica, silicic acid, and silicone oil) with CaCO3 under a range of reaction conditions to gain an understanding of the formation of CBK. A silicon source alone was not found to be responsible for the fused spherical morphology, and a third component, a polar surfactant-like molecule such as sodium dodecyl sulfate or tetradecylphosphonic acid, was also required. The effects of silicon:calcium ratio and reaction time have been studied. The reaction of fumed silica with CaCO3 in presence of sodium dodecyl sulfate results in the formation of spherical shapes resembling the structures and chemical composition observed in the eye samples, while no such structures were observed in the absence of silicon. Samples closely resembling human samples were also formed from the reaction of silicone oil with CaCO3 in the presence of tetradecylphosphonic acid. Samples were characterized by SEM, XRD, and XPS and Raman spectroscopy. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2011.
Co-reporter:Huma R. Jafry, Michael V. Liga, Qilin Li and Andrew R. Barron
New Journal of Chemistry 2011 vol. 35(Issue 2) pp:400-406
Publication Date(Web):05 Nov 2010
DOI:10.1039/C0NJ00604A
Single walled carbon nanotubes (SWNTs) are used as scaffolds to grow titania (TiO2) under a range of different growth conditions. It is found that the titania growth occurring on SWNTs is significantly different in the presence of silica; this is contrary to prior reports, the important controlling factor for obtaining good coverage is not “nanoscopic HF bubbles”. The silica is either sourced from the reaction vessel if made from glass or may be added in the form of fumed silica: the greater the silicon content the greater the coverage of the SWNT. The adsorption and photocatalysis of organic Congo red dye on these hybrid titania covered SWNT materials are studied; while the adsorption of the dye onto the catalyst may be high, it is only in certain cases wherein it results in superior catalytic performance. The synergy between TiO2 and SWNTs with regard to photocatalysis is not always positive. The addition of silica promotes the complete coating of SWNT with TiO2, the resulting materials show very high absorption of Congo red but essentially no catalytic activity. In order to promote catalytic activity, it is necessary to have less full coverage of the SWNTs and the smallest average particle size of the grown titania. Intimate contact between the SWNT and the TiO2 is needed (rather than a physical mixture) for any catalysis, and the electronic properties of the SWNTs are clearly important since multiwalled carbon nanotubes appear to have little effect on altering the photocatalytic activity.
Co-reporter:Huma R. Jafry, Matteo Pasquali, and Andrew R. Barron
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 6) pp:3259-3264
Publication Date(Web):February 10, 2011
DOI:10.1021/ie101836z
This study provides an insight into the effect of incorporating nanoparticles on the rheology of fracturing fluids. Vapor grown carbon fibers (VGCFs) are first coated with silica and subsequently functionalized with octadecyltrichlorosilane groups. These coated and functionalized fibers are then added to a fracturing fluid gel. XPS and rheological measurements are performed to understand the interactions and effects of VGCFs coated with silica and functionalized with silane group on the viscosity and storage modulus of the fracturing gels at three different pHs: 8.6, 9.3, and 10.3. The addition of the ODS−SiO2−VGCF to the guar gels exhibits an interaction with the gels only at a lower pH than typically used for fracturing fluids. While the presence of ODS−SiO2−VGCF minimally increases the storage modulus of the guar gels, under shear-induced conditions, gels which contain ODS−SiO2−VGCF behave similarly to the plain guar gels, displaying no permanent damage to the gels under the applied shear. The presence of ODS−SiO2−VGCF does not appear to alter the structure and the cross-links of the guar gel.
Co-reporter:Samuel J. Maguire-Boyle, Andrew R. Barron
Journal of Membrane Science 2011 382(1–2) pp: 107-115
Publication Date(Web):
DOI:10.1016/j.memsci.2011.07.046
Co-reporter:John J. Allen
Journal of Chemical Crystallography 2011 Volume 41( Issue 5) pp:654-663
Publication Date(Web):2011 May
DOI:10.1007/s10870-010-9947-8
The aryl functionalized diquinolyl amine MesN(quin)2 (1) and the pyridyl-quinolyl amine (2,6-iPr2C6H3)N(py)quin (2) have been prepared via palladium catalyzed cross-coupling of substituted anilines with 2-chloroquinoline. The HBF4 acid salts of (2,6-iPr2C6H3)N(quin)2 (3) and MesN(py)quin (4), as well as the copper complex [Cu{PhN(py)quin}Cl2] (5) have been prepared in order to probe the effect that ligand coordination has on its geometry. The molecular structures of each have been determined by X-ray crystallography. The free ligands 1 and 2 crystallize in three-bladed propellar conformations, having smaller degrees of “pitch” between the two heterocycles than either has with the aryl “blade”, allowing for greater heterocycle π-system overlap with the amine lone pair. Acid confinement of similar ligands in 3 and 4 results in forced coplanarity of the two heterocycles, which coordinate the HBF4 proton in an asymmetric fashion. The copper complex 5 crystallizes with both monomeric and dimeric forms present in the asymmetric unit. Crystal data: (1) Space group P21/c, a = 14.058(3), b = 12.202(2), c = 12.831(3) Å, β = 104.61(3)°, V = 2129.8(8) Å3, Z = 4, R = 0.0596, wR2 = 0.1453. (2) Space group P21/c, a = 22.250(4), b = 8.628(2), c = 23.031(5) Å, β = 92.88(3)°, V = 4370(2) Å3, Z = 8, R = 0.0514, wR2 = 0.1323. (3) Space group Pbca, a = 13.886(3), b = 18.016(4), c = 21.347(4) Å, V = 5340(2) Å3, Z = 8, R = 0.0722, wR2 = 0.1635. (4) Space group P21/c, a = 10.629(2), b = 18.489(4), c = 10.907(2) Å, β = 92.88(3), V = 2140.6(7) Å3, Z = 4, R = 0.0551, wR2 = 0.1531. (5) Space group \({\text P}\bar{1}\), a = 9.706(2), b = 11.325(2), c = 17.322(4) Å, α = 98.28(3), β = 94.85(3), γ = 91.83(3)°, V = 1875.6(7) Å3, Z = 1, R = 0.0481, wR2 = 0.0946.
Co-reporter:Noe T. Alvarez, Christopher E. Hamilton, Cary L. Pint, Alvin Orbaek, Jun Yao, Aldo L. Frosinini, Andrew R. Barron, James M. Tour and Robert H. Hauge
ACS Applied Materials & Interfaces 2010 Volume 2(Issue 7) pp:1851
Publication Date(Web):June 11, 2010
DOI:10.1021/am100128m
A procedure for vertically aligned carbon nanotube (VA-CNT) production has been developed through liquid-phase deposition of alumoxanes (aluminum oxide hydroxides, boehmite) as a catalyst support. Through a simple spin-coating of alumoxane nanoparticles, uniform centimer-square thin film surfaces were coated and used as supports for subsequent deposition of metal catalyst. Uniform VA-CNTs are observed to grow from this film following deposition of both conventional evaporated Fe catalyst, as well as premade Fe nanoparticles drop-dried from the liquid phase. The quality and uniformity of the VA-CNTs are comparable to growth from conventional evaporated layers of Al2O3. The combined use of alumoxane and Fe nanoparticles to coat surfaces represents an inexpensive and scalable approach to large-scale VA-CNT production that makes chemical vapor deposition significantly more competitive when compared to other CNT production techniques.Keywords: alumoxane; catalyst support; chemical vapor deposition; vertically aligned carbon nanotubes
Co-reporter:T. Amanda Strom and Andrew R. Barron
Chemical Communications 2010 vol. 46(Issue 26) pp:4764-4766
Publication Date(Web):02 Jun 2010
DOI:10.1039/C003019H
Two new fullerene amino acids have been prepared by dipolar addition to C60 of either the Boc- or Fmoc-Nα-protected azido amino acids derived from phenylalanine and lysine. UV-visible and CV studies indicate the as prepared amino acids are a mixture of 5,6-open (major product) and 6,6-closed (minor product) derivatives that may be readily separated.
Co-reporter:T. Amanda Strom, Eoghan P. Dillon, Christopher E. Hamilton and Andrew R. Barron
Chemical Communications 2010 vol. 46(Issue 23) pp:4097-4099
Publication Date(Web):10 May 2010
DOI:10.1039/C001488E
We demonstrate a high yield method of functionalizing graphene nanosheets through nitrene addition of azido-phenylalanine [Phe(N3)] to exfoliated micro-crystalline graphite (μG). This method provides a direct route to highly functionalized graphene sheets. TEM analysis of the product shows few layer (n < 5) graphene sheets. The product was determined to have 1 phenylalanine substituent per 13 carbons.
Co-reporter:Valerie C. Moore, Laura A. McJilton, Sean T. Pheasant, Carter Kittrell, Robin E. Anderson, Doug Ogrin, Feng Liang, Robert H. Hauge, Howard K. Schmidt, James M. Tour, W. Edward Billups, Andrew R. Barron, Richard E. Smalley
Carbon 2010 Volume 48(Issue 2) pp:561-565
Publication Date(Web):February 2010
DOI:10.1016/j.carbon.2009.09.070
The present study demonstrates the viability of the reductive attachment step of the single walled carbon nanotube (SWCNT) lengthening process in which long SWCNTs are grown from short nanotube seeds. Aryl sulfonate sidewall-functionalized, carboxylate end-functionalized SWCNTs are attached to an inorganic cluster pro-catalyst (FeMoC) via ligand exchange. The SWCNT–FeMoC complex was electrodeposited onto highly ordered pyrolytic graphite (HOPG), heated and exposed to etching conditions. Pre- and post-treatment AFM imaging shows that controlled reductive etching of the SWCNTs is attainable at a variety of pressures and temperatures in hot surface/cold gas and hot surface/hot gas systems.
Co-reporter:John J. Allen, Christopher E. Hamilton and Andrew R. Barron
Dalton Transactions 2010 vol. 39(Issue 47) pp:11451-11468
Publication Date(Web):28 Oct 2010
DOI:10.1039/C0DT00608D
The aryl-functionalized pyridylamine 2-iPrC6H4N(H)py (1) and bis(2-pyridyl)amines of the type ArN(py)2 for Ar = Mes (2), 2,6-Et2C6H3 (3), 2-iPrC6H4 (4), 2,6-iPr2C6H3 (5), and 1-naph (6), have been prepared by the palladium-catalyzed cross-coupling of substituted anilines with 2-bromopyridine, and have been characterized by 1H and 13C NMR NMR, FTIR, MS, and TGA. Complexes of these new N-aryl bis(2-pyridyl)amines have been prepared for the acid salts [H{ArN(py)2}]BF4 where Ar = Mes (7) and 2-iPrC6H4 (8), and the dimeric bridged complexes [Cu{ArN(py)2}(μ-X)(Y)]2 where X/Y = Cl− and Ar = Ph (9), 2-iPrC6H4 (10), and 1-naph (11), in addition to X = OH−, Y = H2O and Ar = Mes (12). The olefin complexes [Cu(Ar-dpa)(styrene)]BF4 for Ar = Ph (13), Mes (14), 2-iPrC6H4 (15), and 1-naph (16), in addition to the norborylene complexes of Ar = Mes (17) and 2-iPrC6H4 (18) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structures have been determined for compounds 1–17. Secondary amine 1 crystallizes in hydrogen-bonded head-to-tail dimers, while the N-aryl bis(2-pyridyl)amines 2–6 crystallize in a three-bladed propellar conformation, having nearly planar geometries about the amine nitrogen. The geometry about copper centers in the dimeric complexes 9–12 is distorted trigonal bypyramidal, with the axial positions occupied by one of the two pyridyl nitrogens and one of the bridging ligands (i.e., Cl or OH). The copper atoms in each of the olefin complexes 13–17 are coordinated to the two pyridine nitrogen atoms and the appropriate olefin; consistent with a pseudo three-coordinate Cu(I) cation. Distortion of pyridyl ring geometries about the copper centers, and concomitant bending of the aryl groups away from the Cu⋯N(amine) vectors were found to correlate with the steric bulk of the aryl group present in both dimeric and olefin complexes. Such distortion is also observed to a lesser extent in the acid salts as well. The 1H and 13C NMR spectra of [Cu(Ar-dpa)(olefin)]BF4 exhibit an upfield shift in the olefin signal as compared to free olefin. A good correlation exists between the 1H and 13C NMR Δδ values and olefin dissociation temperatures, confirming that the shift of the olefin NMR resonances upon coordination is associated with the binding strength of the complex.
Co-reporter:John J. Allen;Christopher E. Hamilton
Journal of Chemical Crystallography 2010 Volume 40( Issue 2) pp:137-144
Publication Date(Web):2010 February
DOI:10.1007/s10870-009-9616-y
The molecular structure of RN(py)quin, with R=H (1), Ph (2), and Mes (3) and the protonated complex [PhN(py)(H-quin)]BF4 (4) have been determined. Compounds 2 and 3 both crystallize in a three bladed propeller conformation. Any π–π stacking observed is dominated by quinolyl···quinolyl stacks. In contrast to analogous derivatives the acidic proton in compound 4 is chelated by the pyridyl and quinolyl heterocycles in an asymmetric fashion. Crystal data: 1 group P21/c, a = 11.571(2), b = 6.116(1), c = 15.585(3) Å, β = 90.00(3)°, V = 1103.0(4) Å3, Z = 4, R = 0.0440, wR2 = 0.1064. 2 group P21/n, a = 8.081(1), b = 13.920(3), c = 27.697(6) Å, β = 96.50(3)°, V = 3095(1) Å3, Z = 8, R = 0.0495, wR2 = 0.1174. 3 group P21/c, a = 12.359(3), b = 12.585(3), c = 12.457(3) Å, β = 104.09(3)°, V = 1879.4(7) Å3, Z = 4, R = 0.0709, wR2 = 0.1692. 4 group P21/c, a = 15.308(3), b = 7.585(1), c = 17.227(3) Å, β = 113.43(3)°, V = 1835.5(7) Å3, Z = 4, R = 0.0536, wR2 = 0.1341.The molecular structure of RN(py)quin, with R=H, Ph, and Mes, and the protonated complex [PhN(py)(H-quin)]BF4 have been determined. The presence of π–π stacking observed is dominated by quinolyl···quinolyl rather than pyridyl···quinolyl or pyridyl···pyridyl interactions.
Co-reporter:John J. Allen;Christopher E. Hamilton
Journal of Chemical Crystallography 2010 Volume 40( Issue 2) pp:130-136
Publication Date(Web):2010 February
DOI:10.1007/s10870-009-9615-z
The molecular structure of (2,6-iPr2C6H3)N(quin)2 (1) and both the methanol and toluene solvates of its copper complex [Cu{(2,6-iPr2C6H3)N(quin)2}2]BF4, 2·MeOH and 2.2(C6H5Me), respectively, have been determined. The quinolyl rings in 1 adopt anti-syn (CAr–N–C–Nquin) conformation as a result of π–π stacking. The cation in 2·MeOH crystallizes on a C2 axis, while the cation in 2·2(C6H5Me) is crystallographically independent. As a result of intramolecular π–π stacking there are significant changes within the coordination geometry about the copper centers between the two solvates, suggesting that the coordination around copper is supple. Crystal data: 1 group P21/c, a = 8.614(1), b = 16.137(3), c = 17.601(4) Å, β = 93.32(3)°, V = 2,442.5(9) Å3, Z = 4, R = 0.0544, wR2 = 0.1340. 2·MeOH group P3221, a = 13.254(1), b = 13.254(1), c = 27.214(5) Å, V = 4,140(1) Å3, Z = 3, R = 0.0392, wR2 = 0.0917. 2.2(C6H5Me) group P1, a = 11.677(2), b = 16.261(3), c = 17.077(3) Å, α = 93.63(3), β = 97.30(3), γ = 96.26(3)°, V = 3,187(1) Å3, Z = 4, R = 0.0526, wR2 = 0.1221.The molecular structure of (2,6-iPr2C6H3)N(quin)2 and both the methanol and toluene solvates of its copper complex [Cu{(2,6-iPr2C6H3)N(quin)2}2]BF4 have been determined. The presence of inter- and intra-molecular π–π interactions dominates the conformations of the quinolyl substituents.
Co-reporter:Christopher E. Hamilton;Jay R. Lomeda;Zhengzong Sun;James M. Tour
Nano Research 2010 Volume 3( Issue 2) pp:138-145
Publication Date(Web):2010 February
DOI:10.1007/s12274-010-1007-3
A simple one-pot reaction that serves to functionalize graphite nanosheets (graphene) and single-walled carbon nanotubes (SWNTs) with perfluorinated alkyl groups is reported. Free radical addition of 1-iodo-1H,1H,2H, 2H-perfluorododecane to ortho-dichlorobenzene suspensions of the carbon nanomaterial is initiated by thermal decomposition of benzoyl peroxide. Similarly, UV photolysis of 1-iodo-perfluorodecane serves to functionalize the carbon materials. Perfluorododecyl-SWNTs, perfluorododecyl-graphene, and perfluorodecyl-graphene are characterized by infrared (IR) and Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and atomic force microscopy (AFM). The products show enhanced dispersability in CHCl3 as compared to unfunctionalized starting materials. The advantage of this one-pot functionalization procedure lies in the use of pristine graphite as starting material thereby avoiding the use of harsh oxidizing conditions.
Co-reporter:Christopher E. Hamilton, Jay R. Lomeda, Zhengzong Sun, James M. Tour and Andrew R. Barron
Nano Letters 2009 Volume 9(Issue 10) pp:3460-3462
Publication Date(Web):July 31, 2009
DOI:10.1021/nl9016623
We report a simple, high-yield, method of producing homogeneous dispersions of unfunctionalized and nonoxidized graphene nanosheets in ortho-dichlorobenzene (ODCB). Sonication/centrifugation of various graphite materials results in stable homogeneous dispersions. ODCB dispersions of graphene avert the need for harsh oxidation chemistry and allow for chemical functionalization of graphene materials by a range of methods. Additionally, films produced from ODCB-graphene have high conductivity.
Co-reporter:Jonathan J. Brege, Christopher E. Hamilton, Christopher A. Crouse and Andrew R. Barron
Nano Letters 2009 Volume 9(Issue 6) pp:2239-2242
Publication Date(Web):May 11, 2009
DOI:10.1021/nl900080f
Ultrasmall copper nanoparticles are produced by N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPDA) reduction of aqueous Cu2+ on a hydrophobically immobilized sodium dodecylbenzenesulfonate (SDBS) surfactant template in the presence of sodium citrate at room temperature. Single-walled carbon nanotubes (SWNTs) act as a scaffold controlling the size of the SDBS micelle, which in turn confines a limited number of copper ions near the nanotube surface. TMPDA reduction forms copper nanoparticles as confirmed by X-ray photoelectron spectroscopy and electron diffraction, whose size was determined by atomic force microscopy and transmission electron microscopy to be approximately 2 nm. Particles formed in the absence of the SWNT immobilizer range from 2 to 150 nm.
Co-reporter:Laura McJilton, Charles Horton, Carter Kittrell, Doug Ogrin, Haiqing Peng, Feng Liang, W. Edward Billups, Howard K. Schmidt, Robert H. Hauge, Richard E. Smalley, Andrew R. Barron
Carbon 2009 Volume 47(Issue 10) pp:2528-2530
Publication Date(Web):August 2009
DOI:10.1016/j.carbon.2009.04.033
An ultrafine aerosol consisting of airborne single-walled carbon nanotubes (SWCNTs) was produced by nebulizing functionalized SWCNTs in methanol. Prior to atomization, purified SWCNTs were functionalized with aryl sulfonate groups via a Birch reaction. The functionalized SWCNTs were then dispersed in methanol and nebulized using a TSI-3076 constant output atomizer. Atomic force microscopy of a mica plate placed in the flow revealed both individual and bundled SWCNTs. We anticipate that this method for producing ultrafine mists of SWCNTs will enable respiratory toxicity studies of inhaled ultrafine SWCNT particulate.
Co-reporter:John J. Allen and Andrew R. Barron
Dalton Transactions 2009 (Issue 5) pp:878-890
Publication Date(Web):03 Dec 2008
DOI:10.1039/B814829E
Complexes of the type [Cu(H-dpa)(olefin)]BF4 for ethylene (1), propylene (2), 1-butene (3), 1-hexene (4), 1-octene (5), cis-2-octene (6), trans-2-octene (7), cis-3-octene (8), trans-3-octene (9), 2-norbornylene (10), 1,5-cyclooctadiene (11), styrene (12), cis-stilbene (13), trans-stilbene (14), and Ph2CCH2 (15) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structures have been determined for compounds 5, 6, 8, and 10–13. With the exception of compound 11, copper atoms in each complex are coordinated to the two pyridine nitrogen atoms and the appropriate olefin; consistent with a pseudo three-coordinate Cu(I) cation. Compound 11 has a second weaker π-interaction resulting in a distorted tetrahedral geometry. Steric hindrance between the olefin and H-dpa manifests as both a twisting of the olefin out of the plane of the H-dpa ligand and a concomitant folding of the H-dpa ligand. The shifts in the νN-H IR spectral band for H-dpa ligand are consistent with the formation of N–H⋯F hydrogen bonded interactions observed in the crystal structures. The 1H and 13C NMR spectra of [Cu(H-dpa)(olefin)]BF4 exhibit an upfield shift in the olefin signal as compared to free olefin. A comparison of the Δδ values for terminal olefins shows that the similarity of binding for H2CCHR (R = CnH2n+1, n = 1–6) mitigates any preferential complexation of various terminal olefins using the H-dpa ligand. For octenes there is a significant difference in binding between a terminal and internal olefin, but there is little preference between binding for different internal olefins and only a modest difference between the cis and trans isomers of the same olefin. A good correlation exists between the 1H NMR Δδ values and the TGA data, confirming that the shift of the olefin NMR resonances upon coordination is associated with the binding strength of the complex. Ab initio calculations using four different method/basis set combinations on the structure of [Cu(H-dpa)(1-octene)]+ were compared with the crystal structure.
Co-reporter:Jonathan J. Brege, Clayton Gallaway and Andrew R. Barron
The Journal of Physical Chemistry C 2009 Volume 113(Issue 11) pp:4270-4276
Publication Date(Web):2017-2-22
DOI:10.1021/jp808667b
The ability of cobalt, copper, and nickel salts to quench SDBS surfacted single-walled carbon nanotubes (SWNTs) with a concentration between 0.5 and 5 mM per 15 mg·L−1 of SWNT has been investigated. The following metal salts show a decrease in fluorescence of the SWNTs: CuSO4, Cu(OAc)2, CuCl2, CoSO4, Co(OAc)2, CoCl2, NiSO4, Ni(OAc)2, and NiCl2. The Stern−Volmer quenching constants are found to depend on the identity of the metal ion and the anion but not on the chirality (similar to other ions of the same size) of the SWNT. As with Group 2 and 12 metal ions, the SWNT exciton formed from light absorption is sensitive to its local environment, and the field around the metal ions has a significant effect on the exciton facilitating nonradiative decay paths. Increased quenching is observed with transition-metal ions as compared to their Group 2 and 12 analogs, and this differs from the established charge versus ionic-volume trend observed with the latter. Some of this apparent increase is due to absorption by aggregates formed between the metal ions and the surfactant; however, these effects can be mitigated by centrifugation. Despite the removal of any aggregates, the transition metals still show greater quenching efficiency than their main group homologues. This observed effect is proposed to be due to a strong M2+···SDBS attractive interaction causing a large concentration of ions near the nanotube surface compared to those of their Group 2 and 12 counterparts. With regard to the counterion, the quenching efficiency follows the trend of Cl− ≈ SO42− > OAc−. The nondissociating transition-metal acetate complexes are less efficient in an environment where charge interactions dominate over the ionic volume-based quenching found in Group 2 and 12 salts.
Co-reporter:John J. Allen;Christopher E. Hamilton
Journal of Chemical Crystallography 2009 Volume 39( Issue 8) pp:573-580
Publication Date(Web):2009 August
DOI:10.1007/s10870-009-9519-y
The molecular structures of RN(H)Py [R = 2,4,6-Me3C6H2 (1), 2,6-Et2C6H3 (2), -CPh3 (3)] have been determined along with the copper(I) complex [Cu{(2,4,6-Me3C6H2)N(H)Py}2]BF4 (4). Each of the amines exists as a hydrogen-bonded head-to-tail dimer. Compound 3 has four independent molecules in the asymmetric unit as a consequence of changes in the relative orientation of the pyridyl and phenyl rings. The copper in 4 is two-coordinate with the conformation of the aryl rings being dominated by inter-cation packing. Crystal data: 1 space group P21/c, a = 14.047(3), b = 7.154(1), c = 13.890(3) Å, β = 116.45(3)°; V = 1,249.7(4) Å3, Z = 4, R = 0.0547, wR2 = 0.1397; 2 space group P21/n, a = 13.035(3), b = 8.120(1), c = 13.562(3) Å, β = 111.87(3)°; V = 1,345.2(5) Å3, Z = 4, R = 0.0669, wR2 = 0.1512; 3 space group P21/c, a = 26.729(5), b = 17.008(3), c = 18.903(4) Å, β = 92.42(3)°; V = 8,586(3) Å3, Z = 8, R = 0.0911, wR2 = 0.163; 4 space group P21/c, a = 9.149(1), b = 15.901(3), c = 19.703(4) Å, β = 102.89(3)°; V = 2,794(1) Å3, Z = 4, R = 0.0504, wR2 = 0.1291.
Co-reporter:John J. Allen
Journal of Chemical Crystallography 2009 Volume 39( Issue 12) pp:
Publication Date(Web):2009 December
DOI:10.1007/s10870-009-9620-2
The molecular structure of the complex bis-(2-pyridyl)amine(η2-styrene)silver(I) tetrafluoroborate has been determined. The geometry about the Ag+ ion is pseudo-trigonal planar, with coordination sites occupied by the two pyridyl nitrogen atoms and the midpoint of the alkene double bond. Crystal packing of the molecule is influenced by hydrogen bonding of the amine with the tetrafluoroborate anion, in addition to intermolecular Ag+···aromatic contacts. 1H NMR confirms crystallographic data that suggest weak metal to olefin π-backbonding. Crystal data: space group P21/n, a = 12.764(3), b = 10.590(2), c = 13.624(3) Å, β = 91.17(3)°, V = 1841.3(7) Å3, Z = 4, R = 0.0453, wR2 = 0.1098.The geometry about the Ag+ ion in [Ag(H-dpa)(η2-styrene)]BF4 is pseudo-trigonal planar, with coordination sites occupied by the two pyridyl nitrogen atoms and the midpoint of the alkene double bond. Crystal packing of the molecule is influenced by hydrogen bonding of the amine with the tetrafluoroborate anion, in addition to intermolecular Ag+···aromatic contacts.
Co-reporter:Douglas Ogrin
Journal of Chemical Crystallography 2009 Volume 39( Issue 1) pp:68-72
Publication Date(Web):2009 January
DOI:10.1007/s10870-008-9485-9
The structure of [Fe3O(O2CCH2OMe)6(H2O)3][FeCl4] · 2.5H2O has been determined. The three iron atoms and the μ3-oxo are coplanar. Each carboxylic ligand is bidentate and links two iron atoms in the cluster. The clusters are linked by intra-trimer hydrogen bonding to form a zigzag motif that forms sheets via hydrogen bonding involving disordered waters of hydration. The [FeCl4]− anion is intercalated between the hydrogen-bonded sheets. Crystal data: space group P21/n, a = 10.276(2), b = 22.793(5), c = 17.091(3) Å, β = 96.66(3)°, V = 3976(1) Å3, Z = 4, R = 0.0837, wR2 = 0.1836.
Co-reporter:Christopher A. Crouse and Andrew R. Barron
Journal of Materials Chemistry A 2008 vol. 18(Issue 35) pp:4146-4153
Publication Date(Web):29 Jul 2008
DOI:10.1039/B806686H
Cobalt–iron–oxide (Co–Fe–O) nanoparticles have been prepared by the thermal decomposition in benzyl ether of Fe(acac)3 and Co(acac)2 in the presence of a mixture of oleic acid and oleylamine templating (surface capping) ligands, and 1,2-hexadecanediol (HDD) as an accelerating agent. The Co percentage may be tuned by adjusting the amount of Co(acac)2 precursor without influencing the average particle size or particle size distribution. Counter to prior reports the presence of the HDD accelerating agent results in broader nanoparticle diameter distribution; however, for the smallest average sizes a small amount of HDD appears to be beneficial. The effects of changes in the templating ligand concentration and the relative amounts of oleic acidversusoleylamine have been investigated to optimize particle size distribution. Dilution of all the reagents is detrimental to particle size control. Our method for producing 5 nm Co–Fe–O nanoparticles with narrow distributions has reduced the amount of HDD while simultaneously reducing the reaction time.
Co-reporter:Ramon Colorado, Jr., Sarah Y. Zeigler and Andrew R. Barron
Journal of Materials Chemistry A 2008 vol. 18(Issue 16) pp:1911-1918
Publication Date(Web):10 Mar 2008
DOI:10.1039/B800716K
Silica-ammonium chloride nanotubes, generated by the condensation of sodium silicate onto ammonium cation-modified anionic sodium dodecyl sulfate (SDS) micellular templates, readily create hierarchical structures through the self-assembly into thicker nanotubes, belts, and ultimately into centimetre long macrofibers. The resulting fibers possess a remarkable range of tubular dimensions (i.e., nanometre to micrometre diameters, and micrometre to centimetre lengths) within a single assembly. The silica-ammonium chloride nanotubes have a high organic content as a result of the surfactant template. The nanotubes lose structural integrity in aqueous solution, but demonstrate retention of structure in organic solvents or when dried. The dependence on each of the component reagents for the generation of these nanotube structures has been investigated. The silica-ammonium chloride nanotubes have been characterized by SEM, TEM, XRD, XPS, and TGA. The creation of three-dimensional mineral structures using anionic surfactants more closely mimics biomineralization processes than prior approaches with cationic or non-ionic organic templates.
Co-reporter:Andrea Keys, Paul T. Brain, Carole A. Morrison, Rhonda L. Callender, Bruce A. Smart, Derek A. Wann, Heather E. Robertson, David W. H. Rankin and Andrew R. Barron
Dalton Transactions 2008 (Issue 3) pp:404-410
Publication Date(Web):12 Dec 2007
DOI:10.1039/B714168H
The gas-phase structures of Al(But)3 and Ga(But)3 have been investigated by electron diffraction and are shown to consist of monomeric units with very slightly pyramidal geometries. Salient structural parameters (rh1) include rAl–C = 2.008(2) Å and rGa–C = 2.032(2) Å. For both compounds the ligand orientations and geometries are controlled by interligand interactions. The structures of M(But)3 (M = Al, Ga, In) have been calculated ab initio and those for the aluminium and gallium derivatives are in good agreement with the electron-diffraction structures. Comparison of the ab initio calculated structure of In(But)3 with those of Al(But)3 and Ga(But)3 suggests that the significantly different photochemistry exhibited by the former does not result from structural factors. In fact the compounds undergo a charge-transfer process in the UV region, with the wavelength required calculated to be slightly longer for the indium compound than for the other two.
Co-reporter:Christopher E. Hamilton, Douglas Ogrin, Laura McJilton, Valerie C. Moore, Robin Anderson, Richard E. Smalley and Andrew R. Barron
Dalton Transactions 2008 (Issue 22) pp:2937-2944
Publication Date(Web):27 Mar 2008
DOI:10.1039/B801166D
The carboxylate residues of the open ends of aryl-tert-butyl and arylsulfonic acid side-walled functionalized single walled carbon nanotubes (SWNTs) have been investigated for the complexation conditions of the iron–molybdenum cluster [HxPMo12O40CH4Mo72Fe30(O2CMe)15O254(H2O)98] (“FeMoC”). A range of alternative donor groups for the attachment of FeMoC have been investigated for piranha etched SWNTs, dodecyl side-walled functionalized SWNTs (DD-SWNTs) and ultra-short SWNTs (US-SWNTs), including include pyridines, thiols and phosphines, using coupling reactions to either the carboxylate or hydroxide residues of the SWNTs' open ends. The functionalized SWNTs have been characterized by XPS, uptake of Fe3+ and, where appropriate, MAS 31P NMR. The efficacy of binding is dependent on the presence and identity of the ligand moiety. TEM and AFM of the SWNT–FeMoC conjugates show the presence of a 2–3 nm spherical feature on the tip of individual SWNTs.
Co-reporter:Christopher L. Edwards, Rickey Morgan, Lewis Norman, Gary P. Funkhouser and Andrew R. Barron
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 15) pp:5456-5463
Publication Date(Web):June 24, 2008
DOI:10.1021/ie8000925
The physicochemical and engineering performance properties of several API class G and H ordinary Portland cements (OPCs) from various foreign and domestic sources have been investigated in comparison with the tricalcium silicate/dicalcium silicate ratio (C3S/C2S) as determined by magic angle spinning (MAS) 29Si nuclear magnetic resonance (NMR) experiments. XRF-derived oxide analysis appears to provide a lower C3S/C2S ratio than determined by NMR analysis. Furthermore, oxide analysis suggests that all the cements have a C3S/C2S ratio of 2−5, while our NMR method suggests the actual range is significantly broader. Determination of C3S/C2S ratios by NMR provides an effective method of analysis for cements, owing to NMR’s direct measurement of the minerals in question. NMR C3S/C2S ratios demonstrate predictive ability for the determination of engineering performance properties. This is especially the case for prediction of strength development; in keeping with generally accepted understanding of cement hydration behavior, the strength development correlates with increasing C3S/C2S ratio, i.e., C3S content. The observed correlation between NMR-derived silicate ratio and strength development holds for cements in the presence of either a retarder (lignosulfonate) or a fluid loss additive (N,N-dimethylformamide/2-acrylamido-2-methylpropanesulfonic acid copolymer). No significant correlation is observed between C3S/C2S ratio and the 72 h crush strength. The lack of dependency of either thickening time or Young’s modulus to the C3S/C2S ratio as determined by MAS 29Si NMR measurements suggests that these physical properties are independent of the relative silicate composition. No correlations are observed between any physical property and the silicate ratio derived from XRF data.
Co-reporter:Ramon Colorado Jr., Christopher A. Crouse, Christopher N. Zeigler and Andrew R. Barron
Langmuir 2008 Volume 24(Issue 16) pp:8912-8917
Publication Date(Web):July 1, 2008
DOI:10.1021/la800392a
Films of the molybdenum−iron nanocluster [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)68] (FeMoC) were generated on gold via the self-assembly technique using two divergent routes. The first route entails the self-assembly of unfunctionalized FeMoC onto a preprepared carboxyl-terminated SAM on gold. The second route involves the preparation of thiol-terminated functionalized FeMoC clusters, which are then allowed to self-assemble onto bare gold surfaces. Monolayer films of FeMoC clusters are attained via both routes, with the second route requiring shorter immersion times (2 days) than the first route (6 days). Multilayer films of FeMoC are formed via the second route for immersion times longer than 2 days. Characterization of these films using optical ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy confirm the self-assembly of the clusters on the surfaces.
Co-reporter:John J. Allen
Journal of Chemical Crystallography 2008 Volume 38( Issue 11) pp:879-882
Publication Date(Web):2008 November
DOI:10.1007/s10870-008-9456-1
The molecular structure of [Cu2(MeCN)2(μ-tpy)2][BPh4]2 has been determined. The two terpyridine ligands coordinate to the same Cu(I) center in a bidentate configuration, in which the copper adopted a distorted tetrahedral geometry with the four nitrogen donors. The third ring of each terpyridine ligand forms a bridge with a second Cu(I) center, whose tetrahedral coordination sphere is completed by two acetonitrile ligands. The resulting structure represents a section of a double helix. Crystal data: space group C2/c, a = 27.202(5), b = 12.995(3), c = 23.409(5) Å, β = 123.13(3)°; V = 6930(2) Å3, Z = 4, R = 0.0613, wR2 = 0.0946.
Co-reporter:John J. Allen;Christopher E. Hamilton
Journal of Chemical Crystallography 2008 Volume 38( Issue 11) pp:873-877
Publication Date(Web):2008 November
DOI:10.1007/s10870-008-9455-2
The molecular structure of quinolin-1-(2-quinolyl)-2-one mesitylimine has been determined. The Buchwald-Hartwig amination of mesitylaniline with two equivalents of 2-chloroquinoline results in dearomatization of one quinoline heterocycle, forming an imine with the mesitylaniline nitrogen and aminating the second 2-chloroquinoline via the cyclic nitrogen. The mesityl and quinoline moieties are nearly perpendicular to the plane of the central quinolyl structure. Rationalization of the imine formation is found by a consideration of the relative stability of the syn and anti conformations of the reaction intermediate. Crystal data: space group P21/c, a = 12.609(3), b = 15.010(3), c = 12.456(3) Å, β = 112.68(3)°; V = 2,175.3(8) Å3, Z = 4, R = 0.0649, wR2 = 0.1498.
Co-reporter:Liling Zeng;Lawrence B. Alemany;Christopher L. Edwards
Nano Research 2008 Volume 1( Issue 1) pp:72-88
Publication Date(Web):2008 July
DOI:10.1007/s12274-008-8004-9
Carboxylic acid-functionalized single walled carbon nanotubes (SWNTs) prepared via the reaction of an amino acid, NH2(CH2)nCO2H where n = 1 (glycine, GLY), 5 (6-aminohexanoic acid, AHA), 10 (11-aminoundecanoic acid, AUDA), with fluorinated single walled carbon nanotubes (F-SWNTs) have been characterized by MAS 13C NMR spectroscopy. The ease of observing the aliphatic CH2 groups and the resolution of the signal are dependent on the length of the amino acid’s aliphatic chain. We have proposed that where substituent chains are short (making NMR data collection difficult) chemical modification to extend the chain length should alleviate analysis problems. In this regard, we have investigated the esterification of the carboxylic acid termini. The amino acid-functionalized SWNTs were esterified with an appropriate alcohol to ensure parity of the overall substituent length, i.e., GLY-SWNT (C1) + 1-dodecanol (C12) = DOD-GLY-SWNT (1), AHA-SWNT (C5) + 1-octanol (C8) = OCT-AHA-SWNT (2), and AUDA-SWNT (C10) + 1-propanol (C3) = PRO-AUDA-SWNT (3). The 13C NMR shift for the sp3 nitrogen-substituted carbon atoms of the SWNT sidewall is observed at δ ≈ 75 ppm. Increasing the length of SWNT sidewall functional groups enhances the ability to observe the sidewall sp3 carbon. The methylene carbon signal intensity is less attenuated in the dipolar dephasing spectrum of the ester-functionalized SWNTs than their associated amino acid derivatives, suggesting more motional freedom of the side chain in the solid state. The confirmation of the dipolar dephasing spectral effects was assisted by the characterization of the ester of AUDA-SWNT with 1,3-propanediol: PPD-AUDA-SWNT (4).
Co-reporter:Douglas Ogrin;Simon G. Bott
Journal of Chemical Crystallography 2008 Volume 38( Issue 5) pp:397-401
Publication Date(Web):2008 May
DOI:10.1007/s10870-008-9329-7
The molecular structure of [Me2Al(μ-OPh)]2 has been determined. The phenoxide ring is parallel to the Al2O2 ring rather than the energetically favored perpendicular configuration determined by ab initio calculations. Ab initio calculations successfully predict the structures of sterically demanding analogs. The adoption of the parallel configuration allows for an estimation of the magnitude of crystal packing forces. A discussion of the parameters controlling the structures of dialkylaluminum phenoxides is presented. Crystal data: group Pbca, a = 12.127(2), b = 8.491(2), c = 17.299(4) Å, V = 1781.3(6) Å3, Z = 4, R = 0.0695, wR2 = 0.1390.
Co-reporter:Eoghan P. Dillon, Christopher A. Crouse and Andrew R. Barron
ACS Nano 2008 Volume 2(Issue 1) pp:156
Publication Date(Web):January 4, 2008
DOI:10.1021/nn7002713
The reaction between fluorinated single-wall carbon nanotubes (F-SWNTs) and branched (Mw = 600, 1800, 10000, and 25000 Da) or linear (Mw = 25000 Da) polyethyleneimine (PEI) yields the covalent attachment of the polymer to the sidewalls of the nanotubes. The resulting PEI-functionalized SWNTs (PEI-SWNTs) were characterized by solid-state 13C NMR, Raman spectroscopy, X-ray photoelectron spectroscopy, UV–vis spectroscopy, atomic force microscopy, transmission electron microscopy, and thermal gravimetric analysis studies. As expected, the number of polymer molecules per SWNT is larger for low molecular weight PEI than for high molecular weight PEI. However, above 1800 Da, the number of polymer molecules per SWNT does not vary as much. This is supported by Raman spectral data that shows the D:G ratio is relatively insensitive of the molecular weight for Mw > 1800 Da. The PEI-SWNTs are shown to have solubility in aqueous media of up to 0.4 mg·mL−1. Solid-state 13C NMR shows the presence of carboxylate substituents that have been attributed to carbamate formation as a consequence of the reversable CO2 absorption to the primary amine substituents of the PEI. Desorption of CO2 is accomplished by heating under argon at 75 °C, while the dependence of the quantity of CO2 absorbed on temperature and the molecular weight of the PEI is reported. Under the conditions investigated the maximum absorption of 9.2% w/w is observed for PEI(25000)-SWNT at 27 °C. The possible CO2 absorption applications of the PEI-SWNTs is discussed.Keywords: absorption; carbon dioxide; functionalization; polyethylenimine (PEI); polymer; single-wall carbon nanotubes (SWNT)
Co-reporter:Jianzhong Yang, Kuan Wang, Jonathan Driver, Jianhua Yang and Andrew R. Barron
Organic & Biomolecular Chemistry 2007 vol. 5(Issue 2) pp:260-266
Publication Date(Web):17 Nov 2006
DOI:10.1039/B614298B
We report the formation of a fullerene-peptide conjugate via the incorporation of a fullerene substituted phenylalanine derivative, “Bucky amino acid” (Baa), to a cationic peptide, which acts as a passport for intracellular delivery, enabling transport of a range of sequences into HEK-293, HepG2, and neuroblastoma cells where the peptides in the absence of the fullerene amino acid cannot enter the cell. Delivery of the fullerene species to either the cytoplasm or nucleus of the cell is demonstrated. Fullerene peptides based on the nuclear localization sequence (NLS), H-Baa-Lys(FITC)-Lys-Lys-Arg-Lys-Val-OH, can actively cross over the cell membrane and accumulate significantly around the nucleus of HEK-293 and neuroblastoma cells, while H-Baa-Lys(FITC)-Lys8-OH accumulates in the cytoplasm. Cellular studies show that the uptake for the anionic peptide Baa-Lys(FITC)Glu4Gly3Ser-OH is greatly reduced in comparison with the cationic fullerene peptides of the same concentration. The hydrophobic nature of the fullerene assisting peptide transport is suggested by the effect of γ-cyclodextrin (CD) in lowering the efficacy of transport. These data suggest that the incorporation of a fullerene-based amino acid provides a route for the intracellular delivery of peptides and as a consequence the creation of a new class of cell penetrating peptides.
Co-reporter:Christopher D. Jones, Andrew R. Barron
Materials Chemistry and Physics 2007 Volume 104(2–3) pp:460-471
Publication Date(Web):15 August 2007
DOI:10.1016/j.matchemphys.2007.04.011
Carboxylate-alumoxanes are a simple to prepare class of chemically functionalized alumina nanoparticles. The identity of the carboxylate group has a direct effect on the microstructure and temperature of phase conversion for their pyrolysis to alumina bodies. A series of carboxylate-alumoxanes with varying chain length of the organic substituent (organic content) have been investigated: acetic acid alumoxane (A-A), methoxyacetic acid alumoxane (MEA-A), methoxy(ethoxy)acetic acid alumoxane (MEA-A) and methoxy(ethoxyethoxy)acetic acid alumoxane (MEEA-A). The changes in porosity, surface area, pore volume, and pore size distributions, crystal phase and morphology of the alumina formed from each alumoxane have been studied between 600 and 1100 °C by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer, Emmett and Teller (BET). Alumina derived from A- and MEA-alumoxanes have a particulate morphology, while alumina derived from MA- and MEEA-alumoxane are composed of aggregates of smaller particles. The properties of the alumina at higher temperatures are dependent on the identity of the carboxylate periphery and hence the morphology of the alumina at the lower temperatures.
Co-reporter:Jianzhong Yang;Lawrence B. Alemany Dr.;Jonathan Driver;Jeffrey D. Hartgerink ;Andrew R. Barron
Chemistry - A European Journal 2007 Volume 13(Issue 9) pp:
Publication Date(Web):19 JAN 2007
DOI:10.1002/chem.200601186
A series of [60]fullerene-substituted phenylalanine (Baa) and lysine derivatives have been prepared by the condensation of 1,2-(4′-oxocyclohexano)fullerene with the appropriately protected (4-amino)phenylalanine and lysine, respectively. Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. The reduction of the imine is not accompanied by hydroboration of the fullerene cage. The [70]fullerene phenylalanine derivative has also been prepared as have the di-amino acid derivatives. The compounds were characterized by MALDI-TOF mass spectrometry, UV/Vis spectroscopy, and cyclic voltammetry. 1H and 13C NMR spectroscopy allowed the observation of diastereomers. Fullerene-substituted peptides may be synthesized on relatively large scale by solid-phase peptide synthesis. The presence of the C60-substituted amino acid in a peptide has a significant effect on the secondary structures and self-assembly properties of peptides as compared to the native peptide. The antioxidant assay of Baa and a Baa-derived anionic peptide was determined to be significantly more potent than Trolox.
Co-reporter:Douglas Ogrin
Journal of Cluster Science 2007 Volume 18( Issue 1) pp:113-120
Publication Date(Web):2007 March
DOI:10.1007/s10876-006-0088-3
The ligand exchange chemistry for the iron-molybdenum nanocluster [H2PMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98-x(EtOH)x], {Mo72Fe30(Mo12P)}-EtOH, with 3,5-lutidene, 3-butylpyridine, octanol, octanoic acid, 1-hexadecanethiol, tetraethylene glycol, and dodecylbenzenesulfonic acid is reported. The structure of {Mo72Fe30(Mo12P)} is preserved throughout the reaction and TGA analysis indicates between 5 and 15 ligands could be attached per {Mo72Fe30(Mo12P)}. AFM height measurements increase with increased ligand length; however, the apparent particle diameter appears to be smaller than expected as the ligands increase in size consistent with the adopting a non-extended conformation in a similar manner to that observed for self-assembled monolayers.
Co-reporter:Robin E. Anderson, Ramon Colorado, Jr., Christopher Crouse, Douglas Ogrin, Benji Maruyama, Mark J. Pender, Christopher L. Edwards, Elizabeth Whitsitt, Valerie C. Moore, Dorothy Koveal, Corina Lupu, Michael P. Stewart, Richard E. Smalley, James M. Tour and Andrew R. Barron
Dalton Transactions 2006 (Issue 25) pp:3097-3107
Publication Date(Web):20 Apr 2006
DOI:10.1039/B518395B
The synthetic conditions for the isolation of the iron–molybdenum nanocluster FeMoC [HxPMo12O40⊂H4Mo72Fe30(O2CMe)15O254(H2O)98], along with its application as a catalyst precursor for VLS growth of SWNTs have been studied. As-prepared FeMoC is contaminated with the Keplerate cage [H4Mo72Fe30(O2CMe)15O254(H2O)98] without the Keggin [HxPMo12O40]n− template, however, isolation of pure FeMoC may be accomplished by Soxhlet extraction with EtOH. The resulting EtOH solvate is consistent with the replacement of the water ligands coordinated to Fe being substituted by EtOH. FeMoC-EtOH has been characterized by IR, UV-vis spectroscopy, MS, XPS and 31P NMR. The solid-state 31P NMR spectrum for FeMoC-EtOH (δ
−5.3 ppm) suggests little effect of the paramagnetic Fe3+ centers in the Keplerate cage on the Keggin ion's phosphorous. The high chemical shift anisotropy, and calculated T1 (35 ms) and T2 (8 ms) values are consistent with a weak magnetic interaction between the Keggin ion's phosphorus symmetrically located within the Keplerate cage. Increasing the FeCl2 concentration and decreasing the pH of the reaction mixture optimizes the yield of FeMoC. The solubility and stability of FeMoC in H2O and MeOH–H2O is investigated. The TGA of FeMoC-EtOH under air, Ar and H2 (in combination with XPS) shows that upon thermolysis the resulting Fe : Mo ratio is highly dependent on the reaction atmosphere: thermolysis in air results in significant loss of volatile molybdenum components. Pure FeMoC-EtOH is found to be essentially inactive as a pre-catalyst for the VLS growth of single-walled carbon nanotubes (SWNTs) irrespective of the substrate or reaction conditions. However, reaction of FeMoC with pyrazine (pyz) results in the formation of aggregates that are found to be active catalysts for the growth of SWNTs. Activation of FeMoC may also be accomplished by the addition of excess iron. The observation of prior work's reported growth of SWNTs from FeMoC is discussed with respect to these results.
Co-reporter:Douglas Ogrin, Ramon Colorado, Jr., Benji Maruyama, Mark J. Pender, Richard E. Smalley and Andrew R. Barron
Dalton Transactions 2006 (Issue 1) pp:229-236
Publication Date(Web):09 Nov 2005
DOI:10.1039/B512885D
We present herein the VLS growth of SWNTs from oxo-hexacarboxylate–triron precursors, [Fe3O(O2CCH3)6(EtOH)3] (1) and [Fe3O(O2CCH2OMe)6(H2O)3][FeCl4] (2), on spin-on-glass surfaces, using C2H4/H2 (750 °C) and CH4/H2 (800 and 900 °C) growth conditions. The SWNTs have been characterized by AFM, SEM and Raman spectroscopy. The characteristics of the SWNTs are found to be independent of the identity of the precursor complex or the solvent from which it is spin-coated. The as grown SWNTs show a low level of side-wall defects and have an average diameter of 1.2–1.4 nm with a narrow distribution of diameters. At 750 and 800 °C the SWNTs are grown with a range of lengths (300 nm–9 µm), but at 900 °C only the longer SWNTs are observed (6–8 µm). The yield of SWNTs per unit area of catalyst nanoparticle decreases with the growth temperature. We have demonstrated that spin coating of molecular precursors allows for the formation of catalyst nanoparticles suitable for growth of SWNTs with a high degree of uniformity in the diameter, without the formation of preformed clusters of a set diameter.
Co-reporter:C. Lupu;K. L. Jackson;S. Bard;I. Rusakova;A. R. Barron
Advanced Engineering Materials 2006 Volume 8(Issue 6) pp:
Publication Date(Web):28 JUN 2006
DOI:10.1002/adem.200500280
Co-reporter:R. Colorado Jr.;M. E. Diosomito;A. R. Barron
Advanced Materials 2005 Volume 17(Issue 13) pp:
Publication Date(Web):4 MAY 2005
DOI:10.1002/adma.200400836
Freestanding “hex nuts” composed of a single-walled carbon nanotube (SWNT)–silicate composite (see Figure) have been fabricated from mats of silica-coated SWNTs using a novel dissolution/regrowth process. This approach simultaneously generates large numbers of composites with well-defined shapes and uniform dimensions. Discrete steps of this fabrication process are discussed.
Co-reporter:Elizabeth A. Whitsitt, Valerie C. Moore, Richard E. Smalley and Andrew R. Barron
Journal of Materials Chemistry A 2005 vol. 15(Issue 44) pp:4678-4687
Publication Date(Web):29 Sep 2005
DOI:10.1039/B509869F
Single walled carbon nanotubes (SWNTs) have been coated with fluorine-doped silica by liquid phase deposition (LPD) using a silica–H2SiF6 solution and a surfactant stabilized solution of SWNTs. The coating of individual SWNTs versus small ropes is controlled by the choice of surfactant. Since the LPD reaction is performed close to the isoelectric point of the silica, some of the SiO2–SWNTs are fused together but the SWNTs remain individual in these composite structures. The SiO2–SWNTs have been characterized by SEM, TEM, Raman and IR spectroscopy, and XPS. Raman fluoresence is maintained even with coatings >50 nm. Using the relative intensity of the Raman G peak and the 8,3 SWNT fluorescence as a convenient measure of bundling, it may be shown that any decrease of fluoresence during growth is not due to changes in ionic strength or pH, as a consequence of addition of the LPD solution or the presence of HF as a side product in the deposition. The Raman D and G modes show no change in intensity, while the Fano line increases, both suggesting that no sidewall functionalization or proton adsorption of the SWNTs occurs during coating. The UV-visible-near infrared spectra shows a red shift in the first Van Hove transitions of the coated SWNTs inferring that the SWNTs in SiO2–SWNTs are in a more polarizable and inhomogeneous environment than that of surfactant solutions. Mats of SiO2–SWNT may be deposited onto silicon and gold substrates and through lithography may be patterned by etching off selected areas of the silica coating.
Co-reporter:Ryan Loscutova and Andrew R. Barron
Journal of Materials Chemistry A 2005 vol. 15(Issue 40) pp:4346-4353
Publication Date(Web):23 Aug 2005
DOI:10.1039/B510255C
Non-covalently functionalized single walled carbon nanotubes (SWNTs) have been coated with CdE (E = S, Se) by liquid phase deposition (LPD) from aqueous and hydrocarbon solution. The coating of individual SWNTs versus small ropes or composite structures is controlled by the use of SDS surfactant SWNTs and the relative concentration of the SWNTs and the cadmium source. Coating reactions in non-aqueous systems result in either composite formation or incomplete coatings. The CdE-SWNTs have been characterized by SEM, TEM, EDX, and Raman spectroscopy. The Raman fluoresence of the SWNTs is maintained at 90% with coatings of CdS > 5 nm.
Co-reporter:Lei Zhang, Jianzhong Yang, Christopher L. Edwards, Lawrence B. Alemany, Valery N. Khabashesku and Andrew R. Barron
Chemical Communications 2005 (Issue 26) pp:3265-3267
Publication Date(Web):10 Jun 2005
DOI:10.1039/B500125K
Fluorinated single walled carbon nanotubes (SWNTs) undergo a facile Diels–Alder [4 + 2] cycloaddition with a range of dienes resulting in a C ∶ substituent ratio between 20 ∶ 1 to 32 ∶ 1; IR, Raman, AFM and 13C NMR characterization are consistent with sidewall functionalization.
Co-reporter:Corina Lupu, Rolf S. Arvidson, Andreas Lüttge and Andrew R. Barron
Chemical Communications 2005 (Issue 18) pp:2354-2356
Publication Date(Web):16 Mar 2005
DOI:10.1039/B500192G
Vertical scanning interferometry and XPS show the reaction of CaCO3 with the hydration retarder nitrilo-tris-(methylene)phosphonic acid follows a pathway of dissolution of the calcium followed by precipitation of a calcium phosphonate; subsequent surface reorganization/restructuring of the calcium phosphonate exposes the underlying CaCO3 for further hydration.
Co-reporter:Lei Zhang, Jun Zhang, Nicolaus Schmandt, Justin Cratty, Valery N. Khabashesku, Kevin F. Kelly and Andrew R. Barron
Chemical Communications 2005 (Issue 43) pp:5429-5431
Publication Date(Web):04 Oct 2005
DOI:10.1039/B509257D
Thiol- and thiophene-functionalized SWNTs prepared via the reaction of a substituted amine with fluoronanotubes show similar levels of sidewall functionalization, however, the use of Au nanoparticles as chemical markers for AFM gives misleading results for substituent distribution since STM shows the thiol substituents grouped in bands while the thiophene substituents uniformly distributed along the SWNTs.
Co-reporter:Naureen Shahid, Richard G. Villate, Andrew R. Barron
Composites Science and Technology 2005 Volume 65(Issue 14) pp:2250-2258
Publication Date(Web):November 2005
DOI:10.1016/j.compscitech.2005.04.001
The effect of chemically functionalized alumina nanoparticles (carboxylate-alumoxanes) on the performance of carbon fiber reinforced plastic (FRP) composite materials has been investigated. Lysine-alumoxane (L-alumoxane) and para-hydroxybenzoate-alumoxane (p-HB-alumoxane), formed from the reaction of boehmite with the appropriate carboxylic acid, can potentially react with epoxy resins to provide covalent bonding of the nanoparticles to the polymer lattice. Composite samples were prepared each using five layers of carbon fabric were prepared with alumoxane nanoparticle loadings from 5% to 16%, and characterized by SEM, EDS, and ultrasonic C-scan imaging. Tensile and flexural strength measurements were performed as per ASTM standards. Based upon these results it is clear that the miscibility of the alumoxane nanoparticle in the resin is of prime importance with regard performance. Furthermore, loadings of <5% must be used in order to provide enhanced performance. Despite issues with obtaining uniform compositions, we have shown that highly uniform density composites may be prepared with high aluminum content.
Co-reporter:Doug Ogrin, Laura H. van Poppel and Andrew R. Barron
Dalton Transactions 2005 (Issue 9) pp:1722-1726
Publication Date(Web):08 Apr 2005
DOI:10.1039/B501044F
The temperature dependence of the solution equilibrium constants for [(tBu)2Al(OPh)]2(μ-4,4′-bipy)
(1a), [(tBu)2Al(OPh)]2(μ-bipetha)
(2a, bipetha = 1,2-bis(4-pyridyl)ethane), and [(tBu)2Al(OPh)]2(μ-bipethe)
(3a, bipethe =
trans-1,2-bis(4-pyridyl)ethylene) in C6D6 and CDCl3 allow for the determination of ΔH and ΔS for the dissociation of one Al(tBu)2OPh moiety from the bridging ligand, i.e., . For compounds 2a and 3a the ΔH values in C6D6
[99(2) kJ mol−1
(2a) and 109(5) kJ mol−1
(3a)] and CDCl3
[115(5) kJ mol−1
(2a) and 139(7) kJ mol−1
(3a)] were found to be inversely proportional with the dielectric constant of the solvent. In contrast, the ΔH value for 1a in CDCl3 is surprisingly small [14.9(7) kJ mol−1] and does not fit with the trends adopted by the bipetha and bipethe derivatives or the value obtained in C6D6
[110(2) kJ mol−1]. Unlike the other compounds and the C6D6 solutions, the CDCl3 solution of 1a allows for the observation of a second equilibrium , for which the ΔH has been determined [4.5(3) kJ mol−1]. This result suggests that in CDCl3 bonding of the second Al(tBu)2OPh moiety to Al(OPh)(tBu)2(4,4′-bipy)
(1b) is stabilized by the presence of the first aluminium, which is counter to ab initio calculations that predicts the aluminium in Al(OPh)(tBu)2(L) should destabilize the Al–N interaction with a second Al(tBu)2OPh group. The BDE for dissociation of both Al(tBu)2OPh moieties from 1a–3a, and the energy of formation of hydrogen bond interactions with CHCl3, has been calculated by ab initio methods, and no unusual effects are inherent in 1a.
Co-reporter:Naureen Shahid and Andrew R. Barron
Journal of Materials Chemistry A 2004 vol. 14(Issue 8) pp:1235-1237
Publication Date(Web):18 Mar 2004
DOI:10.1039/B401363H
Carboxylate-substituted alumina nanoparticles are produced solvent free using a Rheomixer. The general nature of this method has been demonstrated for L-lysine-, stearate-, and p-hydroxybenzoate-derived materials. The reaction rate and particle size are controlled by a combination of temperature and shear rate. The nanoparticles are spectroscopically equivalent to those reported from aqueous syntheses, however, the average particle size can be decreased and the particle size distribution narrowed depending on the reaction conditions.
Co-reporter:Jianzhong Yang and Andrew R. Barron
Chemical Communications 2004 (Issue 24) pp:2884-2885
Publication Date(Web):25 Oct 2004
DOI:10.1039/B411118D
A series of fullerene substituted phenylalanine derivatives have been prepared by the condensation of 1,2-(4′-oxocyclohexano)fullerene with ester or Boc protected (4-amino)phenylalanine, H2NC6H4CH2CH(COR1)(NHCOR2)
(where R1
= OMe, R2
= Me; R1
= OH, R2
= Me, OtBu). Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. Reaction of the N-Ac amino ester with BBr3 led to the formation of the parent amino acid, while the Boc-protected derivative readily undergoes coupling with NH2–Gly–OEt. The reduction of the imine is not accompanied by hydroboration of the fullerene cage.
Co-reporter:Doug Ogrin, Laura H. van Poppel, Simon G. Bott and Andrew R. Barron
Dalton Transactions 2004 (Issue 21) pp:3689-3694
Publication Date(Web):07 Oct 2004
DOI:10.1039/B410662H
The reaction of AlMe3 and [(tBu)2Al(μ-OPh)]2 with pyrazine (pyz), 4,4′-bipyridine (4-4′-bipy), 1,2-bis(4-pyridyl)ethane (bpetha) and 1,2-bis(4-pyridyl)ethylene (bpethe) yields (Me3Al)2(μ-pyz)
(1), (Me3Al)2(μ-4,4′-bipy)
(2), (Me3Al)2(μ-bpetha)
(3), (Me3Al)2(μ-bipethe)
(4), Al(tBu)2(OPh)(pyz)
(5), [(tBu)2Al(OPh)]2(μ-4,4-bipy)
(6a), [(tBu)2Al(OPh)]2(μ-bpetha)
(7a), [(tBu)2Al(OPh)]2(μ-bipethe)
(8a). Compounds 1–4, 6a and 7a have been confirmed by X-ray crystallography. In solution compounds 1–4 undergo a rapid ligand-dissociation equilibrium resulting in a time-average spectrum in the 1H NMR. In contrast, the solution equilibria for compounds 5–8a are sufficiently slow such that the mono-aluminium compounds may be observed by 1H NMR spectroscopy: Al(tBu)2(OPh)(4,4-bipy)
(6b), Al(tBu)2(OPh)(bpetha)
(7b) and Al(tBu)2(OPh)(bpethe)
(8b). The inability to isolate [(tBu)2Al(OPh)]2(μ-pyz) and the relative stability of each complex is discussed with respect to the steric interactions across the bridging ligand (L) and the electronic effect on one Lewis acid–base interaction by the second Lewis acid–base interaction on the same ligand.
Co-reporter:Maximilienne Bishop, Naureen Shahid, Jianzhong Yang and Andrew R. Barron
Dalton Transactions 2004 (Issue 17) pp:2621-2634
Publication Date(Web):28 Jul 2004
DOI:10.1039/B406952H
The reaction product of boric acid and the polysaccharide guaran (the major component of guar gum) has been investigated by 11B NMR spectroscopy. By comparison with the 11B NMR of boric acid and phenylboronic acid complexes of 1,2-diols (HOCMe2CMe2OH, cis-C6H10(OH)2, trans-C6H10(OH)2, o-C6H4(OH)2), 1,3-diols (neol-H2), monosaccharides (L-fucose, mannose and galactose) and disaccharides (celloboise and sucrose) it is found that the guaran polymer is cross-linked via a borate complex of two 1,2-diols both forming chelate 5-membered ring cycles ([B52]), this contrasts with previous proposals. Based upon steric constraints we propose that preferential cross-linking the guaran polymer occurs via the 3,4-diols of the galactose side chain. The ΔH and ΔS for complexation of boric acid to cis- and trans-1,2-cyclohexanediol have been determined, from the temperature dependence of the appropriate equilibrium constants, and used in conjunction with ab initio calculations on model compounds, to understand prior conflicting proposals for guaran–boric acid interactions. 11B NMR derived pH dependent equilibrium constants and ab initio calculations have been used to understand the reasons for the inefficiency of boric acid to cross-link guaran (almost 2 borate ions per 3 monosaccharide repeat units are required for a viscous gel suitable as a fracturing fluid): the most reactive sites on the component saccharides (mannose and galactose) are precluded from reaction by the nature of the guar structure; the comparable acidity (pKa) of the remaining guaran alcohol substituents and the water solvent, results in a competition between cross-linking and borate formation; a significant fraction of the boric acid is ineffective in cross-linking guar due to the modest equilibrium (Keq). In contrast to prior work, we present evidence for the reaction of alcohols with boric acid, rather than the borate anion. Based upon the results obtained for phenylboronic acid, alternative cross-linking agents are proposed.
Co-reporter:Cullen T. Vogelson, Andrea Keys, Christopher L. Edwards and Andrew R. Barron
Journal of Materials Chemistry A 2003 vol. 13(Issue 2) pp:291-296
Publication Date(Web):02 Jan 2003
DOI:10.1039/B205834K
In order to produce molecular coupling layers, epoxy resins cross-linked with self-assembled monolayers (SAMs) grown on the native oxide of aluminium have been investigated. Initially, SAMs were formed by the attachment of carboxylic acids, RCO2H [R = C17H35, CH3, C6H4-3-Br, C6H4-4-OH, and C(NH2)(CH2)4NH2], to the native oxides of aluminium thin films on silicon substrates. In order to investigate the cross-linking reaction between carboxylate monolayers and an epoxide, grown monolayers of p-hydroxybenzoic acid and lysine were reacted with a mono-epoxy resin, 1,2-epoxy-3-phenoxypropane. The SAM systems have been characterized by X-ray photoelectron spectroscopy, electron dispersive X-ray analysis, and contact angle measurements. In addition to these surface materials, aluminium oxide surfaces supporting either lysine or p-hydroxybenzoic acid monolayers were reacted in pairs with a di-epoxide (the diglycidyl ether of bisphenol-A) to form an adhesive layer between the two surfaces. Finally, this epoxide–SAM interaction is shown to form a “molecular glue”-type interface, which has been characterized by scanning electron microscopy.
Co-reporter:Elizabeth A. Whitsitt and Andrew R. Barron
Chemical Communications 2003 (Issue 9) pp:1042-1043
Publication Date(Web):04 Apr 2003
DOI:10.1039/B212808J
Liquid phase deposition of silica in the presence of fullerenol, C60(OH)n, results in the formation of uniform silica spheres, whereas the use of C60 gives large non-uniform agglomerates as a result of homogeneous nucleation. Raman and UV spectroscopy indicate the C60 is retained as the core of the silica spheres.
Co-reporter:Kimberly A. DeFriend, Mark R. Wiesner, Andrew R. Barron
Journal of Membrane Science 2003 Volume 224(1–2) pp:11-28
Publication Date(Web):15 October 2003
DOI:10.1016/S0376-7388(03)00344-2
The fabrication of alumina ultrafiltration membranes using acetic acid surface stabilized alumina nanoparticles (A-alumoxanes) has been investigated. The pore size, pore size distribution, and molecular weight cut-off (MWCO) parameters of the resulting membranes are highly dependant on the uniformity of the nanoparticle precursor, which is a function of the reaction time and reaction pH during their synthesis. By the control over the alumina nanoparticles, a significant improvement of the membrane performance is observed over our prior results. The new alumoxane-derived membranes have a molecular weight cut-off in the range of <1000 g mol−1, and show good selectivity to a range of synthetic dyes. Further control over selectivity and flux of these ceramic membranes may be obtained by the use of doped alumina nanoparticles (Fe, Mn, and La) that result in the formation of the appropriate aluminate membranes. Of these, LaAlO3 shows the most promising results, with an increase in selectivity and increased flux as compared to the alumina analogue. Retention coefficients and flux values may also be altered by the chemical functionalization of the interior surface of the membranes by reacting the alumina surface with carboxylic acids.
Co-reporter:Kimberly A DeFriend, Andrew R Barron
Journal of Membrane Science 2003 Volume 212(1–2) pp:29-38
Publication Date(Web):15 February 2003
DOI:10.1016/S0376-7388(02)00450-7
Asymmetric alumina ultrafiltration membranes with a hierarchical structure have been fabricated using carboxylic acid surface stabilized alumina nanoparticles (alumoxanes). Pre-formed hollow α-alumina spheres (3 μm nominal diameter) were prepared, using 2, 5, or 8 wt.% alumoxane solutions, and suspended in an aqueous solution of acetic-alumoxane (A-alumoxane) nanoparticles. This suspension was contacted with an α-alumina support. Firing to 600 °C gave a defect-free alumina hierarchical membrane with a total thickness of ca. 2 μm. The flux and permeability for the membrane containing alumina spheres derived from 2 wt.% solution of A-alumoxane is comparable to the porous support, while those derived from 5 and 8 wt.% solution of alumoxane are similar to a “flat” alumoxane-derived membrane. An alternative route to increasing the flux and permeability of the asymmetric membranes was developed whereby colloidal polystyrene beads of either 0.75, 3, or 15 μm diameter, were suspended in an aqueous solution of either A-alumoxane (1 wt.%) or methoxy(ethoxyethoxy)acetic acid alumoxane (MEEA-alumoxane, 10 wt.%). The surface of an α-alumina support was dip coated in the polystyrene/alumoxane colloidal solution, dried then fired to 600 °C, resulting in an asymmetric alumina membrane with a hierarchical tertiary structure. As the polystyrene out-gasses during pyrolysis the top of the coated spheres burst, resulting in a macroporous membrane in which the ceramic walls have a pore size and hence MWCO defined by the alumina formed from the alumoxane nanoparticles (A-alumoxane versus MEEA-alumoxane) rather than the macroporous structure of the membrane itself. The permeabilities of these membranes are equivalent or better than the support.
Co-reporter:Laura H. van Poppel, Simon G. Bott and Andrew R. Barron
Dalton Transactions 2002 (Issue 17) pp:3327-3332
Publication Date(Web):06 Aug 2002
DOI:10.1039/B204281A
The aluminium aryloxide polymer, [{(tBu)2Al}2(μ-OC6H4O)]n (1) is synthesized by the addition of Al(tBu)3 to hydroquinone in a non-coordinating solvent, and reacts with Lewis bases, via both a solution and a solid/vapor reaction, to yield [(tBu)2Al(L)]2(μ-OC6H4O) [L = py (2), 3,5-Me2py (3) and THF (4)] via cleavage of the Al2O2 dimeric core. Thermolysis of 2–4 results in decomposition without clean formation of compound 1. However, if compound 2
is formed by the exposure of 1 to pyridine vapors, subsequent thermolysis allows for the clean solid state interconversion of compounds 1 and 2. The room temperature solid state reaction of [{(tBu)2Al}2(μ-OC6H4O)]n (1) with pyrazine (pz), 4,4′-bipyridine (4,4′-bipy) or 1,4-benzoquinone (1,4-bz) results in a rapid color change and the formation of [{(tBu)2Al}2(μ-OC6H4O)(μ-L)]n, where L = pz (5), 4,4′-bipy (6) and 1,4-bz (7).
Co-reporter:Cullen T. Vogelson, Simon G. Bott and Andrew R. Barron
Journal of Materials Chemistry A 2001 vol. 11(Issue 2) pp:284-288
Publication Date(Web):12 Dec 2000
DOI:10.1039/B005223J
For the purposes of characterizing a novel class of inorganic–organic hybrid epoxy resin materials, a series of amines were reacted with a monoepoxide (1,2-epoxy-3-phenoxypropane) under base catalyzed conditions to produce racemic mixtures of compounds with the general formula PhOCH2CH(OH)CH2N(H)R, where R = nPr (1), iPr (2), or tBu (3). The crystal structures of these compounds were determined by X-ray crystallography. Compound 1 forms infinite sheets of centrosymmetric dimers. In contrast, as a result of intermolecular hydrogen-bonding, compounds 2 and 3 arrange as tetrameric units in non-centrosymmetric space groups. Through a review of crystal structures found in the Cambridge Crystallographic Database, compounds of the general type X–CH(OH)CH2N(H)R were investigated and a rationalization for the packing of racemic mixtures in non-centrosymmetric space groups is discussed.
Co-reporter:Christopher D. Jones, Maria Fidalgo, Mark R. Wiesner, Andrew R. Barron
Journal of Membrane Science 2001 Volume 193(Issue 2) pp:175-184
Publication Date(Web):15 November 2001
DOI:10.1016/S0376-7388(01)00490-2
The fabrication of asymmetric alumina ultrafiltration membranes using acetic acid surface stabilized alumina nanoparticles (A-alumoxanes) has been investigated. Contacting α-alumina supports with an aqueous solution of A-alumoxane (after firing to 1000°C) yields a defect free alumina membrane with a thickness of ca. 2 μm. The alumoxane-derived membranes have a molecular weight cut-off in the range of 35,000–44,000 g mol−1, high porosity, and a permeability that is comparable to or greater than that of commercially available alumina membranes. SEM and AFM show that the surface of the alumoxane-derived membranes is quite smooth and contact angles show that the membrane is hydrophillic. A comparison with commercial alumina and polymer membranes, as well as those derived from sol–gel methods is presented.
Co-reporter:Simon G. Bott, Bradley D. Fahlman, Milton L. Pierson and Andrew R. Barron
Dalton Transactions 2001 (Issue 14) pp:2148-2147
Publication Date(Web):22 Jun 2001
DOI:10.1039/B104057J
A series of solid solutions have been prepared by co-crystallization of Al(acac)3 and Cr(acac)3 and studied by X-ray diffraction. The end members and seven isotopic members of the series Al1 − xCrx(acac)3, with x varying from 0.02 to 0.91, crystallize in the monoclinic space group P21/c with Z = 4. The unit cell parameters vary slightly with composition, and fall into the following ranges: a, 13.987–14.009; b, 7.534–7.553; c, 16.308–16.348 Å; β, 98.78–98.99°. The cell axes do not vary in a linear manner with the mole% Cr. The Al ∶ Cr molar ratio in each crystal studied by X-ray diffraction was determined by wavelength dispersive spectroscopy (WDS) and compared with the refinement of the Al ∶ Cr site occupancy, which was attempted by the following methods: (1) refinement based upon bulk sample analysis, (2) refinement of occupancy with common displacement parameters, (3) refinement of occupancy and displacement parameters, and (4) construction of a mixed atom type based on the results of all three methods. Results from methods 2 and 3 were found to agree with WDS data within experimental error for all crystals studied. Method 1 was the least successful, the refinement often being significantly problematic. A discussion of suitable methods for refinement of partial site occupancy in solid solutions for isomorphous structures is presented. The variance of crystal lattice parameters and the M–O and O–M–O structural parameters with Al ∶ Cr ratio is investigated.
Co-reporter:Stephen J. Obrey and Andrew R. Barron
Dalton Transactions 2001 (Issue 17) pp:2456-2458
Publication Date(Web):10 Aug 2001
DOI:10.1039/B104578B
Reaction of AlMe3 with [(tBu)2Ga(μ-OH)]3 or Ph3EOH (E = Sn, Pb) yields catalytically active MAO, [MeAlO]n, along with (tBu)2GaMe and Ph3EMe, respectively, in contrast, the reaction with Ph3EOH (E = C, Si, Ge) yields [Me2Al(μ-OEPh3)]2; the formation of MAO is proposed to occur via hydroxide exchange and the formation of unstable [Me2Al(μ-OH)]n; the propensity towards alkane elimination versus hydroxide exchange is controlled by the relative Brønsted acidity of the main group hydroxide.
Co-reporter:Bradley D. Fahlman, Andrew Daniels, Gustavo E. Scusceria and Andrew R. Barron
Dalton Transactions 2001 (Issue 22) pp:3239-3241
Publication Date(Web):19 Oct 2001
DOI:10.1039/B106998P
Reaction of [RGa(μ3-Te)]4 (R =
tBu, CMeEt2) and O2, SO2 or SeO2 yields, in addition to tellurium metal, [RGa(μ3-O)]n (R =
tBu, n
= 9; R = CMeEt2, n
= 6) and the mixed cubanes [R4Ga4(μ3-O)x(μ3-Te)4 −
x] (x
= 1, 2); neither [R4Ga4(μ3-O)3(μ3-Te)] or [RGa(μ3-O)]4 are observed; DFT calculations show no global minimum for [Me4Ga4(μ3-Te)2(μ3-O)2] or [Me4Ga4(μ3-Te)2(μ3-O)2], suggesting that these structures would rearrange to more favored structures on the pathway
to a final geometry lower in energy.
Co-reporter:Catherine S. Branch, Janusz Lewinski, Iwona Justyniak, Simon G. Bott, Janusz Lipkowski and Andrew R. Barron
Dalton Transactions 2001 (Issue 8) pp:1253-1258
Publication Date(Web):30 Mar 2001
DOI:10.1039/B008858G
Reaction of M(tBu)3 with anthranilic, salicylic and ortho-toluic acids yields [(tBu)2M(μ-O2CC6H4-2-NH2)]2, M = Al (1), Ga (2), [(tBu)2Ga(μ-O2CC6H4-2-OH)]2 (3), and [(tBu)2Ga(μ-O2CC6H4-2-Me)]2 (4), respectively. Reaction of anthranilic acid with two equivalents of Al(tBu)3 allows for the isolation of (tBu)2Al(μ-O2CC6H4-2-NH2)Al(tBu)3 (5). Compounds 1–5 have been characterized by NMR and IR spectroscopy, mass spectrometry, and X-ray crystallography. The presence of intra-molecular hydrogen bonding, in compounds 1–3, is probed by the orientation of the aromatic rings. Compound 5 is proposed to be a Lewis acid stabilized complex of the intermediate in the synthesis of compound 1.
Co-reporter:Bradley D. Fahlman
Advanced Functional Materials 2000 Volume 10(Issue 3‐5) pp:
Publication Date(Web):23 FEB 2001
DOI:10.1002/1099-0712(200005/10)10:3/5<135::AID-AMO400>3.0.CO;2-M
Deposition of highly conformal alumina thin films has been carried out by hydrolysis of the liquid alane precursor, AlH3(NMe2Et). Depositions onto Si wafers, quartz and carbon fibres were all carried out utilizing a hot-wall atmospheric pressure chemical vapour deposition (APCVD) system. Optimum growth conditions were found to be at 165°C and with an AlH3(NMe2Et):H2O ratio of less than 1:25. Films were characterized by SEM, microprobe and electrical conductivity measurements. Growth rates were of the order of 40–80 Å min−1 at 165°C. The conformality of the films was illustrated using silicon wafers that were etched prior to deposition. Deposition onto ZnS EL-phosphor particles was accomplished in a simple fluidized-bed APCVD reactor. The deposited films were conformal and continuous. No significant reduction in the initial brightness or change in the colour balance of the phosphor was observed from the coating process. Copyright © 2000 John Wiley & Sons, Ltd.
Co-reporter:Bradley D Fahlman;Andrew R Barron
Advanced Functional Materials 2000 Volume 10(Issue 3‐5) pp:
Publication Date(Web):23 FEB 2001
DOI:10.1002/1099-0712(200005/10)10:3/5<223::AID-AMO411>3.0.CO;2-M
Volatile trends are established for a series of MU(β-diketonate)n complexes, where MU = Cu (n = 2); Al, Sc, Cr, Fe, Co, Ga (n = 3); Zr (n = 4) and β-diketonate = acetylacetonate (acac), trifluoroacetylacetonate (tfac), hexafluoroacetylacetonate (hfac) and 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd). Sublimation enthalpies (ΔHsub) were calculated from thermogravimetric analysis (TGA) data, which show that the dependence of ΔHsub on the number and type of intermolecular interactions appears to be more substantial than molecular mass effects. Irrespective of the metal, the ΔHsub values for the MU(tmhd)3 derivative have a ΔHsub value of between 93 and 99% of that of the MU(acac)3 derivative. In contrast, the MU(tfac)3 and MU(hfac)3 derivatives have ΔHsub values of ca. 82% and 54% of the values for the corresponding MU(acac)3. Similar trends are observed for MU(β-diketonate)2 and MU(β-diketonate)4 derivatives. The relationship between the ΔHsub and (Tsub) of the substituted β-diketonate derivatives as compared with the values for parent MU(acac)n may be used to predict either quantity for a range of MU(β-diketonate)n complexes where the values for MU(acac)n are known. Using the TGA sublimation data, vapour pressures have been calculated for each of the MU(β-diketonate)n complexes. Copyright © 2000 John Wiley & Sons, Ltd.
Co-reporter:Maximilienne Bishop, Simon G. Bott and Andrew R. Barron
Dalton Transactions 2000 (Issue 18) pp:3100-3105
Publication Date(Web):30 Aug 2000
DOI:10.1039/B003375H
The borate ester derivatives of phenol, trans-cyclohexane-1,2-diol and mandelic acid have been prepared from NaBH4 and structurally characterized by X-ray crystallography. The product from the reaction with phenol appears as a crystallographic disorder of [(THF)2Na{B(OPh)3H}]2 (1) and [(THF)2Na{B(OPh)(OH2)H}]2 (2). Both compounds are dimeric with bridging borate groups linking the Na cations. The reaction with trans-cyclohexane-1,2-diol in DMSO yields the infinite polymer, [(DMSO)Na{B(O2C6H10)2}]∞ (3), in which the Na cations link [B(O2C6H10)2]− anions. The unusual 5-coordinate geometry of the sodium is completed by the coordination of a disordered DMSO molecule. In a similar manner, mandelic acid reacts to form an infinite lattice [Na(py)2][B{O2CC(O)Ph}2] (4), in which each sodium is coordinated to three [B{O2CC(O)Ph}2]− anions, one through two interactions involving the alkoxide and carboxylate groups of a chelate mandelic acid, and two interactions involving the carboxylate groups of adjacent anions. The role of the Group 1 cation in supporting the structural framework of the borate anions is discussed.
Co-reporter:C. Niamh McMahon, Stephen J. Obrey, Andrea Keys, Simon G. Bott and Andrew R. Barron
Dalton Transactions 2000 (Issue 13) pp:2151-2161
Publication Date(Web):08 Jun 2000
DOI:10.1039/B000332H
Reaction of M(tBu)3 (M = Al, Ga) with neol-H2 (2,2-dimethylpropane-1,3-diol) yields [M2(tBu)4(neol-H)2], M = Al (1) and Ga (2), respectively. Use of an equimolar mixture of Al(tBu)3 and Ga(tBu)3 allows for the formation of [AlGa(tBu)4(neol-H)2] (3). Compounds 1 and 2 may be considered as bifunctional (two OH groups), tetradentate (4O) ligands as highlighted by their reactivity with Group 13 hydrides and alkyls. Reaction of compound 1 with AlH3(NMe3), AlH2Cl(NMe3) and AlMe3 yields the tri-aluminium compounds, [Al3(tBu)4(X)(neol)2] with X = H (4), X = Cl (5), Me (6), respectively. Similarly, compound 2 reacts with Ga(tBu)3 to yield the tri-gallium compound, [Ga3(tBu)5(neol)2] (7). The mixed metal complexes, [Ga2Al(tBu)4(X)(neol)2], where X = H (8), Me (9) and tBu (10), are formed by the reaction of compound 2 with AlH3(NMe3), AlMe3, and Al(tBu)3, respectively. The solid state conformation of the neol backbone and the 1H NMR chemical shift of the neol's CH2 protons, in compounds 4–10, are both dependent on the steric bulk of the substituent of the central metal. Thermolysis of compound 2 in toluene results in the formation of [Ga3(tBu)4(CH2Ph)(neol)2] (11), while the reaction of 2 with LiOH in Et2O and hexane yields [Ga3Li4(tBu)6(neol)3(OH)(THF)] (12) and [Ga2Li(tBu)4(OH)2(neol-H)] (13), respectively. The molecular structures of compounds 1, 2, 4–13 and [Ga3Cl5(OSiMe2OSiMe2O)2] (14) have been determined by X-ray crystallography.
Co-reporter:Alexer S. Borovik;Simon G. Bott ;Andrew R. Barron
Angewandte Chemie 2000 Volume 112(Issue 22) pp:
Publication Date(Web):14 NOV 2000
DOI:10.1002/1521-3757(20001117)112:22<4283::AID-ANGE4283>3.0.CO;2-P
Co-reporter:Jessica Heimann, Lauren Morrow, Robin E. Anderson and Andrew R. Barron
Dalton Transactions 2015 - vol. 44(Issue 9) pp:NaN4388-4388
Publication Date(Web):2015/01/26
DOI:10.1039/C4DT03376K
Metal contamination of water is a serious challenge faced by environmental chemists, but there is also economic value in the removal of metals for recycling or extraction. Our prior observation that hydroxyfullerenes [C60Ox(OH)y]n− act as chelate agents to Fe3+ suggests that these material, or derivatives, may be used for co-precipitation. We report the removal of main group (Al3+, Ag+, Ca2+, and Zn2+) as well transition metal (Fe3+, Co2+, Cu2+, Mn2+, and Ni2+) and lanthanide (La3+ and Nd3+) ions from solution. The resulting complexes have been characterized by XPS, SEM, TEM, and DLS. The competitive binding with Fe3+ shows that the binding affinity with hydroxyfullerenes follows the order: Zn2+ > Co2+ > Mn2+ > Ni2+ > La3+ > Nd3+ > Cd2+ > Cu2+ > Ag+ > Ca2+ > Fe3+ > Al3+. The relative binding ability is dependent on ionic radius; however, divergent trends are observed for M2+ and M3+, i.e., for divalent ions the binding is stronger for smaller ions, while the opposite trend is observed for trivalent ions. Previously the coordination of hydroxyfullerene to metals was assumed to be analogous to a 1,2-diol or catechol. However, while ab initio calculations using [M(catecholate)n]n− (n = 2, 3) provide an explanation of the observed trend for M2+, the use of cis–cis-1,3,5-cyclohexanetriol and cis-1,3-cyclohexanediol as model ligands provides insight into the relative binding efficiency for M3+.
Co-reporter:John J. Allen, Christopher E. Hamilton and Andrew R. Barron
Dalton Transactions 2010 - vol. 39(Issue 47) pp:NaN11468-11468
Publication Date(Web):2010/10/28
DOI:10.1039/C0DT00608D
The aryl-functionalized pyridylamine 2-iPrC6H4N(H)py (1) and bis(2-pyridyl)amines of the type ArN(py)2 for Ar = Mes (2), 2,6-Et2C6H3 (3), 2-iPrC6H4 (4), 2,6-iPr2C6H3 (5), and 1-naph (6), have been prepared by the palladium-catalyzed cross-coupling of substituted anilines with 2-bromopyridine, and have been characterized by 1H and 13C NMR NMR, FTIR, MS, and TGA. Complexes of these new N-aryl bis(2-pyridyl)amines have been prepared for the acid salts [H{ArN(py)2}]BF4 where Ar = Mes (7) and 2-iPrC6H4 (8), and the dimeric bridged complexes [Cu{ArN(py)2}(μ-X)(Y)]2 where X/Y = Cl− and Ar = Ph (9), 2-iPrC6H4 (10), and 1-naph (11), in addition to X = OH−, Y = H2O and Ar = Mes (12). The olefin complexes [Cu(Ar-dpa)(styrene)]BF4 for Ar = Ph (13), Mes (14), 2-iPrC6H4 (15), and 1-naph (16), in addition to the norborylene complexes of Ar = Mes (17) and 2-iPrC6H4 (18) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structures have been determined for compounds 1–17. Secondary amine 1 crystallizes in hydrogen-bonded head-to-tail dimers, while the N-aryl bis(2-pyridyl)amines 2–6 crystallize in a three-bladed propellar conformation, having nearly planar geometries about the amine nitrogen. The geometry about copper centers in the dimeric complexes 9–12 is distorted trigonal bypyramidal, with the axial positions occupied by one of the two pyridyl nitrogens and one of the bridging ligands (i.e., Cl or OH). The copper atoms in each of the olefin complexes 13–17 are coordinated to the two pyridine nitrogen atoms and the appropriate olefin; consistent with a pseudo three-coordinate Cu(I) cation. Distortion of pyridyl ring geometries about the copper centers, and concomitant bending of the aryl groups away from the Cu⋯N(amine) vectors were found to correlate with the steric bulk of the aryl group present in both dimeric and olefin complexes. Such distortion is also observed to a lesser extent in the acid salts as well. The 1H and 13C NMR spectra of [Cu(Ar-dpa)(olefin)]BF4 exhibit an upfield shift in the olefin signal as compared to free olefin. A good correlation exists between the 1H and 13C NMR Δδ values and olefin dissociation temperatures, confirming that the shift of the olefin NMR resonances upon coordination is associated with the binding strength of the complex.
Co-reporter:Christopher E. Hamilton, Douglas Ogrin, Laura McJilton, Valerie C. Moore, Robin Anderson, Richard E. Smalley and Andrew R. Barron
Dalton Transactions 2008(Issue 22) pp:NaN2944-2944
Publication Date(Web):2008/03/27
DOI:10.1039/B801166D
The carboxylate residues of the open ends of aryl-tert-butyl and arylsulfonic acid side-walled functionalized single walled carbon nanotubes (SWNTs) have been investigated for the complexation conditions of the iron–molybdenum cluster [HxPMo12O40CH4Mo72Fe30(O2CMe)15O254(H2O)98] (“FeMoC”). A range of alternative donor groups for the attachment of FeMoC have been investigated for piranha etched SWNTs, dodecyl side-walled functionalized SWNTs (DD-SWNTs) and ultra-short SWNTs (US-SWNTs), including include pyridines, thiols and phosphines, using coupling reactions to either the carboxylate or hydroxide residues of the SWNTs' open ends. The functionalized SWNTs have been characterized by XPS, uptake of Fe3+ and, where appropriate, MAS 31P NMR. The efficacy of binding is dependent on the presence and identity of the ligand moiety. TEM and AFM of the SWNT–FeMoC conjugates show the presence of a 2–3 nm spherical feature on the tip of individual SWNTs.
Co-reporter:Enrico Andreoli, Rei Suzuki, Alvin W. Orbaek, Manoop S. Bhutani, Robert H. Hauge, Wade Adams, Jason B. Fleming and Andrew R. Barron
Journal of Materials Chemistry A 2014 - vol. 2(Issue 29) pp:NaN4747-4747
Publication Date(Web):2014/05/21
DOI:10.1039/C4TB00778F
High quality single-walled carbon nanotubes (SWNTs) were obtained following a new purification procedure, based on using Cl2 gas at high temperature. Cl2-treated SWNTs were fluorinated and modified with branched polyethyleneimine (PEI) to afford covalently functionalised PEI–SWNTs, which were then tested for cytotoxicity both in vitro (HPNE and BxPC3 pancreatic cell lines) and in vivo (BxPC3 xenografts from nude mice) to establish that functionalization with lower molecular weight PEI (600 and 1800 Da) achieved higher cell viability in MTT assay. A shortened version of the nanotubes, PEI(1800)-cut-SWNT (1800 Da branched PEI), was also prepared and tested for cellular internalization in the BxPC3 adenocarcinoma cell line. Laser confocal imaging of the cells after incubation in the presence of RhoB-PEI(1800)-cut-SWNT (covalently labelled with rhodamine B) indicates that the PEI(1800)-cut-SWNTs can reach both the cytoplasm and nucleus of pancreatic cancer cells.
Co-reporter:Ramon Colorado, Jr., Sarah Y. Zeigler and Andrew R. Barron
Journal of Materials Chemistry A 2008 - vol. 18(Issue 16) pp:NaN1918-1918
Publication Date(Web):2008/03/10
DOI:10.1039/B800716K
Silica-ammonium chloride nanotubes, generated by the condensation of sodium silicate onto ammonium cation-modified anionic sodium dodecyl sulfate (SDS) micellular templates, readily create hierarchical structures through the self-assembly into thicker nanotubes, belts, and ultimately into centimetre long macrofibers. The resulting fibers possess a remarkable range of tubular dimensions (i.e., nanometre to micrometre diameters, and micrometre to centimetre lengths) within a single assembly. The silica-ammonium chloride nanotubes have a high organic content as a result of the surfactant template. The nanotubes lose structural integrity in aqueous solution, but demonstrate retention of structure in organic solvents or when dried. The dependence on each of the component reagents for the generation of these nanotube structures has been investigated. The silica-ammonium chloride nanotubes have been characterized by SEM, TEM, XRD, XPS, and TGA. The creation of three-dimensional mineral structures using anionic surfactants more closely mimics biomineralization processes than prior approaches with cationic or non-ionic organic templates.
Co-reporter:Christopher E. Hamilton, Dennis J. Flood and Andrew R. Barron
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 11) pp:NaN3938-3938
Publication Date(Web):2013/02/01
DOI:10.1039/C3CP50435B
Liquid phase deposition (LPD), using CdSO4 and N,N-dimethyl selenourea, has been used to grow CdSe absorber layer onto single walled carbon nanotube (SWNT) derived back contact substrates. The nanotubes are imbedded in, and penetrate into, the CdSe absorber layer for the goal of enhancing excition dissociation and carrier transport. The Cd:Se film stoichiometry varied between 1:1.7 to 1:1.3 depending on the deposition conditions. The CdSe/SWNT layers show appropriate photoresponse. LPD was also used to grow a CuSe window layer onto which silver contacts were deposited. The resulting PV device shows a characteristic IV curve. Despite both the open circuit voltage (VOC = 1.28 mV) and short circuit current (ISC = 4.85 μA) being low, the resulting device is suggestive of the possibility of fabricating a flexible thin film (inorganic) solar cell by solution processes.
Co-reporter:Jianzhong Yang, Kuan Wang, Jonathan Driver, Jianhua Yang and Andrew R. Barron
Organic & Biomolecular Chemistry 2007 - vol. 5(Issue 2) pp:NaN266-266
Publication Date(Web):2006/11/17
DOI:10.1039/B614298B
We report the formation of a fullerene-peptide conjugate via the incorporation of a fullerene substituted phenylalanine derivative, “Bucky amino acid” (Baa), to a cationic peptide, which acts as a passport for intracellular delivery, enabling transport of a range of sequences into HEK-293, HepG2, and neuroblastoma cells where the peptides in the absence of the fullerene amino acid cannot enter the cell. Delivery of the fullerene species to either the cytoplasm or nucleus of the cell is demonstrated. Fullerene peptides based on the nuclear localization sequence (NLS), H-Baa-Lys(FITC)-Lys-Lys-Arg-Lys-Val-OH, can actively cross over the cell membrane and accumulate significantly around the nucleus of HEK-293 and neuroblastoma cells, while H-Baa-Lys(FITC)-Lys8-OH accumulates in the cytoplasm. Cellular studies show that the uptake for the anionic peptide Baa-Lys(FITC)Glu4Gly3Ser-OH is greatly reduced in comparison with the cationic fullerene peptides of the same concentration. The hydrophobic nature of the fullerene assisting peptide transport is suggested by the effect of γ-cyclodextrin (CD) in lowering the efficacy of transport. These data suggest that the incorporation of a fullerene-based amino acid provides a route for the intracellular delivery of peptides and as a consequence the creation of a new class of cell penetrating peptides.
Co-reporter:Yen-Tien Lu and Andrew R. Barron
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 24) pp:NaN9870-9870
Publication Date(Web):2013/05/08
DOI:10.1039/C3CP51835C
An effective and economical fabrication process for the synthesis of nanopore-type “black silicon”, that significantly decreases reflectivity of silicon wafer surfaces, is reported using a room temperature one-step Ag-assisted chemical etching method. The effects on the surface morphology and the corresponding surface reflectivity of the concentration of the silver catalyst (500, 50, and 5 μM), the HF and H2O2 concentration in the silicon etchant, the HF:H2O2 ratio, and etching time have been investigated. Lower reflectivity is a balance between sufficient silver catalyst to create large numbers of nanopores on a silicon surface and excessive silver that brings deeply etched channels that would potentially short-circuit a solar cell junction. The lowest relative effective reflectivity (0.17% over a range of 300–1000 nm) occurs with a silver ion concentration of 50 μM, however, with the silver ion concentration decreases to 5 μM surfaces with a low relative effective reflectivity (2.60%) and a short nanopore length (<250 nm) can be obtained with 10 minute etching time, indicating that this method can be used as a simple (one-pot), low cost (low silver concentration), energy efficient (room temperature), method for the synthesis of anti-reflection layers for silicon-based solar cell applications.
Co-reporter:Christopher A. Crouse and Andrew R. Barron
Journal of Materials Chemistry A 2008 - vol. 18(Issue 35) pp:NaN4153-4153
Publication Date(Web):2008/07/29
DOI:10.1039/B806686H
Cobalt–iron–oxide (Co–Fe–O) nanoparticles have been prepared by the thermal decomposition in benzyl ether of Fe(acac)3 and Co(acac)2 in the presence of a mixture of oleic acid and oleylamine templating (surface capping) ligands, and 1,2-hexadecanediol (HDD) as an accelerating agent. The Co percentage may be tuned by adjusting the amount of Co(acac)2 precursor without influencing the average particle size or particle size distribution. Counter to prior reports the presence of the HDD accelerating agent results in broader nanoparticle diameter distribution; however, for the smallest average sizes a small amount of HDD appears to be beneficial. The effects of changes in the templating ligand concentration and the relative amounts of oleic acidversusoleylamine have been investigated to optimize particle size distribution. Dilution of all the reagents is detrimental to particle size control. Our method for producing 5 nm Co–Fe–O nanoparticles with narrow distributions has reduced the amount of HDD while simultaneously reducing the reaction time.
Co-reporter:Eoghan Dillon, Manoop S. Bhutani and Andrew R. Barron
Journal of Materials Chemistry A 2013 - vol. 1(Issue 10) pp:NaN1465-1465
Publication Date(Web):2013/01/21
DOI:10.1039/C3TB00456B
Water soluble polyethyleneimine functionalized single wall carbon nanotubes (PEI–SWNTs) can be loaded with the therapeutic agents acetic acid and the gemcitabine analogue, deoxycytidine (dC). The amount of loading is based on initial sonication time and the solubility of the agent. The use of an endoscopic ultrasound (EUS) results in the controlled release of the agents from the PEI–SWNT conjugate. The release of acetic acid occurs by first-order kinetics, however, the release of the majority of the dC occurs by the more desired zero-order release.
Co-reporter:Alvin W. Orbaek, Neerja Aggarwal and Andrew R. Barron
Journal of Materials Chemistry A 2013 - vol. 1(Issue 45) pp:NaN14132-14132
Publication Date(Web):2013/10/07
DOI:10.1039/C3TA13543H
Ferrocene was used as a catalyst in a hydrocarbon solution to carry out injection chemical vapour deposition (CVD) growth of carbon nanomaterials in a horizontal tube furnace. The presence and quality of various carbon materials was determined using Raman spectroscopy, thermogravimetric analysis, and electron microscopy. Products ranged from amorphous carbon (a-C), multi walled carbon nanotubes (MWNTs) and vapour grown fibers (VGFs). Catalyst concentration, growth temperature, injection rate, carrier gas flow rate, and the choice of hydrocarbon were found to influence the product outcome. Slower injection rates gave higher isolated yield. High catalyst concentrations were found to produce less pure carbon materials with iron oxides impurities. Higher temperatures were favourable to nanotube formation. The use of benzene was found to increase yield compared with the other hydrocarbons. In this work we developed a process map to chart the various carbon nanomaterial allotropes that were created according to reaction parameters.
Co-reporter:Yen-Tien Lu and Andrew R. Barron
Journal of Materials Chemistry A 2014 - vol. 2(Issue 30) pp:NaN12052-12052
Publication Date(Web):2014/06/04
DOI:10.1039/C4TA02006E
A new one-step copper-assisted chemical etching technique is reported to more economically prepare nanopore-type anti-reflective layers, which can effectively suppress reflection of Si wafer surfaces for solar cell applications. In contrast to the Au and Ag processes, phosphorous acid (rather than hydrogen peroxide) is utilized as a reducing agent to reduce Cu2+ to Cu0 nanoparticles. The Cu nanoparticles catalyse the oxidization of Si in the vicinity of the nanoparticles to SiO2, which is then etched by HF to form nanopores. The effects of the HF and H3PO3 concentrations, the HF:H2O volume ratio, and the etching time on the black silicon morphology with the corresponding Si surface reflectivity have been systematically investigated. The size and shape of the pores are controlled by [Cu2+] and the subsequent size of the NPs as controlled by [H3PO3], while the depth of the pores are limited by [HF] and the etch time. With [Cu2+] = 500 μM and [H3PO3] = 10 mM, the fabricated black silicon possesses the lowest relative effective reflectivity, 0.96%, and the shortest nanopore length (590 nm).
Co-reporter:Shirin Alexander, Lauren Morrow, Alex M. Lord, Charles W. Dunnill and Andrew R. Barron
Journal of Materials Chemistry A 2015 - vol. 3(Issue 18) pp:NaN10059-10059
Publication Date(Web):2015/04/07
DOI:10.1039/C5TA01294E
The formation of a pH-sensitive coupling layer, through both physisorption and chemisorption, provides a responsive surface that can be assembled and disassembled in relation to external stimuli. Contact angle measurements, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and Fourier transform IR-attenuated reflectance spectroscopy (FTIR-ATR) have been used to characterize a series of bi-functionalized self-assembled monolayers (SAMs) grown on aluminium oxide wafers/nanoparticles and investigate the reaction nature of pH-responsive coupling layer (octylamine) with the SAMs. Contact angle, XPS, and AFM analyses indicate that the surface of native aluminium oxide was covered considerably as the contact angle of the surfaces decreased, carbon atomic % and roughness of the surfaces increased.
Co-reporter:Enrico Andreoli and Andrew R. Barron
Journal of Materials Chemistry A 2015 - vol. 3(Issue 8) pp:NaN4329-4329
Publication Date(Web):2015/01/14
DOI:10.1039/C4TA06936F
The high CO2 capacity of PEI-C60 conjugates is impeded by a slow rate of absorption. A limiting factor to this rate is proposed to be the surface area available for the rapid contact between amine functional groups of PEI and CO2. Increasing the surface area by spray-drying a solution of reagents is proposed as a route to larger surface area products. In this work we investigate process changes to control absorption chemistry. Reagent solutions were spray-dried in different experimental conditions of concentration, drying temperature, and feed pressure. The results indicate that the rate of CO2 absorption at room temperature can be improved by a factor of 2.5 times by spray drying the product when compared to the product obtained using sonication. Given the rubbery nature of PEI-C60 the surface area, and hence CO2 capacity, could be increased using cryogenic grinding in liquid nitrogen; however, the results show that this has limited effect on the surface area of the absorbent prepared using sonication. Only compared to the hard chunks obtained via stir bar synthesis was the surface area doubled, in contrast to the rubbery product obtained using ultrasonication the area did not change significantly. Interestingly, doubling the surface area, the rate of absorption of wet CO2 at high temperature did not change, while that at low temperature doubled in rate, consistent with the presence of diffusion limitations manly at low temperature.
Co-reporter:Samuel J. Maguire-Boyle and Andrew R. Barron
Environmental Science: Nano 2014 - vol. 16(Issue 10) pp:NaN2248-2248
Publication Date(Web):2014/08/13
DOI:10.1039/C4EM00376D
A detailed analysis is reported of the organic composition of produced water samples from typical shale gas wells in the Marcellus (PA), Eagle Ford (TX), and Barnett (NM) formations. The quality of shale gas produced (and frac flowback) waters is a current environmental concern and disposal problem for producers. Re-use of produced water for hydraulic fracturing is being encouraged; however, knowledge of the organic impurities is important in determining the method of treatment. The metal content was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Mineral elements are expected depending on the reservoir geology and salts used in hydraulic fracturing; however, significant levels of other transition metals and heavier main group elements are observed. The presence of scaling elements (Ca and Ba) is related to the pH of the water rather than total dissolved solids (TDS). Using gas chromatography mass spectrometry (GC/MS) analysis of the chloroform extracts of the produced water samples, a plethora of organic compounds were identified. In each water sample, the majority of organics are saturated (aliphatic), and only a small fraction comes under aromatic, resin, and asphaltene categories. Unlike coalbed methane produced water it appears that shale oil/gas produced water does not contain significant quantities of polyaromatic hydrocarbons reducing the potential health hazard. Marcellus and Barnett produced waters contain predominantly C6–C16 hydrocarbons, while the Eagle Ford produced water shows the highest concentration in the C17–C30 range. The structures of the saturated hydrocarbons identified generally follows the trend of linear > branched > cyclic. Heterocyclic compounds are identified with the largest fraction being fatty alcohols, esters, and ethers. However, the presence of various fatty acid phthalate esters in the Barnett and Marcellus produced waters can be related to their use in drilling fluids and breaker additives rather than their presence in connate fluids. Halogen containing compounds are found in each of the water samples, and although the fluorocarbon compounds identified are used as tracers, the presence of chlorocarbons and organobromides formed as a consequence of using chlorine containing oxidants (to remove bacteria from source water), suggests that industry should concentrate on non-chemical treatments of frac and produced waters.
Co-reporter:Samuel J. Maguire-Boyle, David J. Garner, Jessica E. Heimann, Lucy Gao, Alvin W. Orbaek and Andrew R. Barron
Environmental Science: Nano 2014 - vol. 16(Issue 2) pp:NaN231-231
Publication Date(Web):2014/01/07
DOI:10.1039/C3EM00718A
Quantifying nanoparticle (NP) transport within porous geological media is imperative in the design of tracers and sensors to monitor the environmental impact of hydraulic fracturing that has seen increasing concern over recent years, in particular the potential pollution and contamination of aquifers. The surface chemistry of a NP defining many of its solubility and transport properties means that there is a wide range of functionality that it is desirable to screen for optimum transport. Most prior transport methods are limited in determining if significant adsorption occurs of a NP over a limited column distance, however, translating this to effects over large distances is difficult. Herein we report an automated method that allows for the simulation of adsorption effects of a dilute nanoparticle solution over large distances under a range of solution parameters. Using plasmonic silver NPs and UV-visible spectroscopic detection allows for low concentrations to be used while offering greater consistency in peak absorbance leading to a higher degree of data reliability and statistics. As an example, breakthrough curves were determined for mercaptosuccinic acid (MSA) and cysteamine (CYS) functionalized Ag NPs passing through Ottawa sand (typical proppant material) immobile phase (C) or bypassing the immobile phase (C0). Automation allows for multiple sequences such that the absorption plateau after each breakthrough and the rate of breakthrough can be compared for multiple runs to provide statistical analysis. The mobility of the NPs as a function of pH is readily determined. The stickiness (α) of the NP to the immobile phase calculated from the C/C0 ratio shows that MSA-Ag NPs show good mobility, with a slight decrease around neutral pH, while CYS-Ag NPs shows an almost sinusoidal variation. The automated process described herein allows for rapid screening of NP functionality, as a function of immobile phase (proppant versus reservoir material), hydraulic fracturing fluid additives (guar, surfactant) and conditions (pH, temperature).
Co-reporter:Andrea Keys, Paul T. Brain, Carole A. Morrison, Rhonda L. Callender, Bruce A. Smart, Derek A. Wann, Heather E. Robertson, David W. H. Rankin and Andrew R. Barron
Dalton Transactions 2008(Issue 3) pp:NaN410-410
Publication Date(Web):2007/12/12
DOI:10.1039/B714168H
The gas-phase structures of Al(But)3 and Ga(But)3 have been investigated by electron diffraction and are shown to consist of monomeric units with very slightly pyramidal geometries. Salient structural parameters (rh1) include rAl–C = 2.008(2) Å and rGa–C = 2.032(2) Å. For both compounds the ligand orientations and geometries are controlled by interligand interactions. The structures of M(But)3 (M = Al, Ga, In) have been calculated ab initio and those for the aluminium and gallium derivatives are in good agreement with the electron-diffraction structures. Comparison of the ab initio calculated structure of In(But)3 with those of Al(But)3 and Ga(But)3 suggests that the significantly different photochemistry exhibited by the former does not result from structural factors. In fact the compounds undergo a charge-transfer process in the UV region, with the wavelength required calculated to be slightly longer for the indium compound than for the other two.
Co-reporter:John J. Allen and Andrew R. Barron
Dalton Transactions 2009(Issue 5) pp:NaN890-890
Publication Date(Web):2008/12/03
DOI:10.1039/B814829E
Complexes of the type [Cu(H-dpa)(olefin)]BF4 for ethylene (1), propylene (2), 1-butene (3), 1-hexene (4), 1-octene (5), cis-2-octene (6), trans-2-octene (7), cis-3-octene (8), trans-3-octene (9), 2-norbornylene (10), 1,5-cyclooctadiene (11), styrene (12), cis-stilbene (13), trans-stilbene (14), and Ph2CCH2 (15) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structures have been determined for compounds 5, 6, 8, and 10–13. With the exception of compound 11, copper atoms in each complex are coordinated to the two pyridine nitrogen atoms and the appropriate olefin; consistent with a pseudo three-coordinate Cu(I) cation. Compound 11 has a second weaker π-interaction resulting in a distorted tetrahedral geometry. Steric hindrance between the olefin and H-dpa manifests as both a twisting of the olefin out of the plane of the H-dpa ligand and a concomitant folding of the H-dpa ligand. The shifts in the νN-H IR spectral band for H-dpa ligand are consistent with the formation of N–H⋯F hydrogen bonded interactions observed in the crystal structures. The 1H and 13C NMR spectra of [Cu(H-dpa)(olefin)]BF4 exhibit an upfield shift in the olefin signal as compared to free olefin. A comparison of the Δδ values for terminal olefins shows that the similarity of binding for H2CCHR (R = CnH2n+1, n = 1–6) mitigates any preferential complexation of various terminal olefins using the H-dpa ligand. For octenes there is a significant difference in binding between a terminal and internal olefin, but there is little preference between binding for different internal olefins and only a modest difference between the cis and trans isomers of the same olefin. A good correlation exists between the 1H NMR Δδ values and the TGA data, confirming that the shift of the olefin NMR resonances upon coordination is associated with the binding strength of the complex. Ab initio calculations using four different method/basis set combinations on the structure of [Cu(H-dpa)(1-octene)]+ were compared with the crystal structure.
Co-reporter:John J. Allen and Andrew R. Barron
Dalton Transactions 2011 - vol. 40(Issue 5) pp:NaN1194-1194
Publication Date(Web):2010/12/20
DOI:10.1039/C0DT01301C
Complexes of the type [Cu(R-dpa)(η2-olefin)]BF4 (R = Mes and 2-iPrC6H4) for cis- and trans- isomers of 3-octene, as well as those for cis- and trans-4-octene (R = 2-iPrC6H4) have been prepared and characterized by 1H and 13C NMR, FTIR, and TGA. The crystal structure of [Cu(Mes-dpa)(η2-trans-3-octene)]BF4 (2) has been determined via X-ray crystallography. The asymmetric unit in the crystal lattice of 2 contains two unique conformations of the complex cation related by a pseudo center of symmetry, which differ primarily in the orientation of the olefin with respect to the rest of the molecule. The 1H and 13C NMR spectra of [Cu(Ar-dpa)(η2-olefin)]BF4 exhibit olefin resonances shifted upfield with respect to free olefin. The difference in Δδ(13C) relative magnitudes between cis- and trans- complexes, i.e., the binding, correlates with the degree of substitution at the amine nitrogen. The identity of the remote ligand substituent (Ar) controls the differentiation of binding between cis and trans isomers as a consequence of increased folding of the Ar-dpa ligand along the Cu⋯N axis.
Co-reporter:Robin E. Anderson and Andrew R. Barron
Dalton Transactions 2013 - vol. 42(Issue 6) pp:NaN2191-2191
Publication Date(Web):2012/11/15
DOI:10.1039/C2DT32523C
Highly oxygenated fullerenes, C60On with 1 ≤ n ≤ 13, have been prepared by the Mo(O)2(acac)2 catalysed oxidation of C60 with tBuOOH. Increasing the catalyst:C60 ratio or increasing the reaction temperature increases the yield as well shifting the product distribution to higher oxygenated products, in contrast, increasing the tBuOOH concentration shifts the product distribution in the opposite manner. The MALDI mass spectra of reactions containing the highest oxygenated products (n > 5) show additional peaks (not observed for C60 under the same MS conditions) due to the cage-opened products Cx (x = 54, 56, 58) along with their oxygenated derivatives, CxOn (x = 54, 56, 58; n = 1–3).
Co-reporter:T. Amanda Strom and Andrew R. Barron
Chemical Communications 2010 - vol. 46(Issue 26) pp:NaN4766-4766
Publication Date(Web):2010/06/02
DOI:10.1039/C003019H
Two new fullerene amino acids have been prepared by dipolar addition to C60 of either the Boc- or Fmoc-Nα-protected azido amino acids derived from phenylalanine and lysine. UV-visible and CV studies indicate the as prepared amino acids are a mixture of 5,6-open (major product) and 6,6-closed (minor product) derivatives that may be readily separated.
Co-reporter:T. Amanda Strom, Eoghan P. Dillon, Christopher E. Hamilton and Andrew R. Barron
Chemical Communications 2010 - vol. 46(Issue 23) pp:NaN4099-4099
Publication Date(Web):2010/05/10
DOI:10.1039/C001488E
We demonstrate a high yield method of functionalizing graphene nanosheets through nitrene addition of azido-phenylalanine [Phe(N3)] to exfoliated micro-crystalline graphite (μG). This method provides a direct route to highly functionalized graphene sheets. TEM analysis of the product shows few layer (n < 5) graphene sheets. The product was determined to have 1 phenylalanine substituent per 13 carbons.
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![(2s)-6-azido-2-[(2-methylpropan-2-yl)oxycarbonylamino]hexanoic Acid](http://img.cochemist.com/ccimg/846600/846549-33-5.png)
![(2s)-6-azido-2-[(2-methylpropan-2-yl)oxycarbonylamino]hexanoic Acid](http://img.cochemist.com/ccimg/846600/846549-33-5_b.png)
![L-Phenylalanine, 4-azido-N-[(9H-fluoren-9-ylmethoxy)carbonyl]-](/data/chemimg/1013900/163217-43-4.png)
![L-Phenylalanine, 4-azido-N-[(9H-fluoren-9-ylmethoxy)carbonyl]-](/data/chemimg/1013900/163217-43-4_b.png)
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![L-PHENYLALANINE, 4-AZIDO-N-[(1,1-DIMETHYLETHOXY)CARBONYL]-, METHYL ESTER](http://img.cochemist.com/ccimg/65700/65615-91-0_b.png)
![L-Phenylalanine, 4-azido-N-[(1,1-dimethylethoxy)carbonyl]-](/data/chemimg/538900/33173-55-6.png)
![L-Phenylalanine, 4-azido-N-[(1,1-dimethylethoxy)carbonyl]-](/data/chemimg/538900/33173-55-6_b.png)