Co-reporter:Lawrence A. Renna;Julia D. Lenef;Monojit Bag;D. Venkataraman
Advanced Materials Interfaces 2017 Volume 4(Issue 20) pp:
Publication Date(Web):2017/10/01
DOI:10.1002/admi.201700397
AbstractPolymer-based mixed ionic–electronic conductors (MIECs) are desired for both bulk and interfacial materials in next-generation energy storage and electronic devices. Polymer-based MIECs contain two principal components, one for electronic conduction and the other for ionic conduction. The central problem is the lack of a general approach to control the molecular packing and morphology of the constituent components that will afford the ability to easily tune transport properties. This study demonstrates the efficacy of a modular method based on polymer nanoparticle self-assembly to achieve MIECs with tunable conductivity. This work uses poly(3-hexylthiophene) nanoparticles as the electronic conductor and lithium ion-doped poly(vinylpyridine) nanoparticles as the ionic conductors. AC impedance spectroscopic studies show that nanoparticle–nanoparticle interfaces in unary assemblies do not impede ion transport in the solid state. AC impedance spectroscopy and DC steady-state conductivity measurements show that binary nanoparticle assemblies exhibit concurrent ionic and electronic conduction. The power-law scaling percolation of both the ionic and electronic transport displays nonuniversal values of transport critical exponent, revealing different transport mechanisms. The simplicity of fabrication combined with the versatility in obtainable transport properties illustrates the power of using nanoparticle assemblies as a means to realize MIEC polymer mesoscale morphologies.
Co-reporter:Yao Liu;Lawrence A. Renna;Hilary B. Thompson;Zachariah A. Page;Todd Emrick;Michael D. Barnes;Monojit Bag;D. Venkataraman;Thomas P. Russell
Advanced Energy Materials 2017 Volume 7(Issue 21) pp:
Publication Date(Web):2017/11/01
DOI:10.1002/aenm.201701235
AbstractHybrid organic/inorganic perovskite solar cells are invigorating the photovoltaic community due to their remarkable properties and efficiency. However, many perovskite solar cells show an undesirable current–voltage (I–V) hysteresis in their forward and reverse voltage scans, working to the detriment of device characterization and performance. This hysteresis likely arises from slow ion migration in the bulk perovskite active layer to interfaces which may induce charge trapping. It is shown that interfacial chemistry between the perovskite and charge transport layer plays a critical role in ion transport and I–V hysteresis in perovskite-based devices. Specifically, phenylene vinylene polymers containing cationic, zwitterionic, or anionic pendent groups are utilized to fabricate charge transport layers with specific interfacial ionic functionalities. The interfacial-adsorbing boundary induced by the zwitterionic polymer in contact with the perovskite increases the local ion concentration, which is responsible for the observed I–V hysteresis. Moreover, the ion adsorbing properties of this interface are exploited for perovskite-based memristors. This fundamental study of I–V hysteresis in perovskite-based devices introduces a new mechanism for inducing memristor behavior by interfacial ion adsorption.
Co-reporter:Yao Liu;Monojit Bag;Lawrence A. Renna;Zachariah A. Page;Paul Kim;Todd Emrick;D. Venkataraman;Thomas P. Russell
Advanced Energy Materials 2016 Volume 6( Issue 2) pp:
Publication Date(Web):
DOI:10.1002/aenm.201501606
Interface engineering is critical for achieving efficient solar cells, yet a comprehensive understanding of the interface between a metal electrode and electron transport layer (ETL) is lacking. Here, a significant power conversion efficiency (PCE) improvement of fullerene/perovskite planar heterojunction solar cells from 7.5% to 15.5% is shown by inserting a fulleropyrrolidine interlayer between the silver electrode and ETL. The interface between the metal electrode and ETL is carefully examined using a variety of electrical and surface potential techniques. Electrochemical impedance spectroscopy (EIS) measurements demonstrate that the interlayer enhances recombination resistance, increases electron extraction rate, and prolongs free carrier lifetime. Kelvin probe force microscopy (KPFM) is used to map the surface potential of the metal electrode and it indicates a uniform and continuous work function decrease in the presence of the fulleropyrrolidine interlayer. Additionally, the planar heterojunction fullerene/perovskite solar cells are shown to have good stability under ambient conditions.
Co-reporter:Yao Liu, Lawrence A. Renna, Monojit Bag, Zachariah A. Page, Paul Kim, Jaewon Choi, Todd Emrick, D. Venkataraman, and Thomas P. Russell
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 11) pp:7070
Publication Date(Web):February 26, 2016
DOI:10.1021/acsami.5b12740
Perovskite-containing tandem solar cells are attracting attention for their potential to achieve high efficiencies. We demonstrate a series connection of a ∼90 nm thick perovskite front subcell and a ∼100 nm thick polymer:fullerene blend back subcell that benefits from an efficient graded recombination layer containing a zwitterionic fullerene, silver (Ag), and molybdenum trioxide (MoO3). This methodology eliminates the adverse effects of thermal annealing or chemical treatment that occurs during perovskite fabrication on polymer-based front subcells. The record tandem perovskite/polymer solar cell efficiency of 16.0%, with low hysteresis, is 75% greater than that of the corresponding ∼90 nm thick perovskite single-junction device and 65% greater than that of the polymer single-junction device. The high efficiency of this hybrid tandem device, achieved using only a ∼90 nm thick perovskite layer, provides an opportunity to substantially reduce the lead content in the device, while maintaining the high performance derived from perovskites.Keywords: fullerene interlayers; high efficiency; high open-circuit voltage; interface engineering; inverted structure; perovskite solar cells; polymer solar cells; tandem solar cells
Co-reporter:Monojit Bag, Sanjib Banerjee, Rudolf Faust, Dhandapani Venkataraman
Solar Energy Materials and Solar Cells 2016 Volume 145(Part 3) pp:418-422
Publication Date(Web):February 2016
DOI:10.1016/j.solmat.2015.11.004
•Polyisobutylene (PIB)-based sealant for organic photovoltaic devices.•Sealants compatible with flexible substrates and roll-to-roll processing.•Sealants show enhanced device stability, increasing T80 from few hours to 20 days.Herein we demonstrate the utility of polyisobutylene (PIB) as a fully printable self-healing sealant for protecting organic photovoltaic devices from degradation under ambient conditions. These sealants can be applied on flexible substrates using drop casting, spin coating or blade coating. PIB-based crosslinked sealants show excellent device stability, especially the low molecular weight PIB.PIB-based polymer sealant materials have been successfully coated on polymer photovoltaic devices to improve the environmental stability. Low molecular weight polymer shows higher percentage of crosslinking and hence better stability.
Co-reporter:Seung Pyo Jeong, Connor J. Boyle and D. Venkataraman
RSC Advances 2016 vol. 6(Issue 8) pp:6107-6110
Publication Date(Web):08 Jan 2016
DOI:10.1039/C5RA19883F
We demonstrate that MWCNTs can be dispersed in common organic solvents as single tubes using a single hexabenzocoronene (HBC) unit at the end of a poly(methyl methacrylate) (PMMA) chain. The concentration of the HBC-based additive needed to disperse MWCNTs is substantially lower than the concentration needed for existing additives.
Co-reporter:Monojit Bag, Lawrence A. Renna, Seung Pyo Jeong, Xu Han, Christie L. Cutting, Dimitrios Maroudas, D. Venkataraman
Chemical Physics Letters 2016 Volume 662() pp:35-41
Publication Date(Web):1 October 2016
DOI:10.1016/j.cplett.2016.09.004
•Efficient MWCNT/perovskite devices were fabricated with MWCNTs in the active layer.•Impedance spectroscopy shows reduced recombination loss with MWCNT incorporation.•Drift-diffusion reaction model confirms conclusions from impedance spectroscopy.Using impedance spectroscopy and computation, we show that incorporation of multi-walled carbon nanotubes (MWCNTs) in the bulk of the active layer of perovskite-based solar cells reduces charge recombination and increases the open circuit voltage. An ∼87% reduction in recombination was achieved when MWCNTs were introduced in the planar-heterostructure perovskite solar cell containing mixed counterions. The open circuit voltage (Voc) of perovskite/MWCNTs devices was increased by 70 mV, while the short circuit current density (Jsc) and fill factor (FF) remained unchanged.
Co-reporter:Lawrence A. Renna, Monojit Bag, Timothy S. Gehan, Xu Han, Paul M. Lahti, Dimitrios Maroudas, and D. Venkataraman
The Journal of Physical Chemistry B 2016 Volume 120(Issue 9) pp:2544-2556
Publication Date(Web):February 8, 2016
DOI:10.1021/acs.jpcb.5b11716
Binary polymer nanoparticle glasses provide opportunities to realize the facile assembly of disparate components, with control over nanoscale and mesoscale domains, for the development of functional materials. This work demonstrates that tunable electrical percolation can be achieved through semiconducting/insulating polymer nanoparticle glasses by varying the relative percentages of equal-sized nanoparticle constituents of the binary assembly. Using time-of-flight charge carrier mobility measurements and conducting atomic force microscopy, we show that these systems exhibit power law scaling percolation behavior with percolation thresholds of ∼24–30%. We develop a simple resistor network model, which can reproduce the experimental data, and can be used to predict percolation trends in binary polymer nanoparticle glasses. Finally, we analyze the cluster statistics of simulated binary nanoparticle glasses, and characterize them according to their predominant local motifs as (pi, p1-i)-connected networks that can be used as a supramolecular toolbox for rational material design based on polymer nanoparticles.
Co-reporter:Timothy S. Gehan, Monojit Bag, Lawrence A. Renna, Xiaobo Shen, Dana D. Algaier, Paul M. Lahti, Thomas P. Russell, and Dhandapani Venkataraman
Nano Letters 2014 Volume 14(Issue 9) pp:5238-5243
Publication Date(Web):August 7, 2014
DOI:10.1021/nl502209s
We address here the need for a general strategy to control molecular assembly over multiple length scales. Efficient organic photovoltaics require an active layer comprised of a mesoscale interconnected networks of nanoscale aggregates of semiconductors. We demonstrate a method, using principles of molecular self-assembly and geometric packing, for controlled assembly of semiconductors at the nanoscale and mesoscale. Nanoparticles of poly(3-hexylthiophene) (P3HT) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with targeted sizes. Nanoparticles containing a blend of both P3HT and PCBM were also fabricated. The active layer morphology was tuned by the changing particle composition, particle radii, and the ratios of P3HT:PCBM particles. Photovoltaic devices were fabricated from these aqueous nanoparticle dispersions with comparable device performance to typical bulk-heterojunction devices. Our strategy opens a revolutionary pathway to study and tune the active layer morphology systematically while exercising control of the component assembly at multiple length scales.
Co-reporter:Monojit Bag, Timothy S. Gehan, Lawrence A. Renna, Dana D. Algaier, Paul M. Lahti and D. Venkataraman
RSC Advances 2014 vol. 4(Issue 85) pp:45325-45331
Publication Date(Web):05 Sep 2014
DOI:10.1039/C4RA07463G
For environmentally friendly and cost-effective manufacturing of organic photovoltaic (OPV) cells, it is highly desirable to replace haloarenes with water as the active layer fabrication solvent. Replacing an organic solvent with water requires retooling the device fabrication steps. The optimization studies were conducted using poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as active layer materials. These materials were dispersed in water as blend and separate nanoparticles using the miniemulsion method. Topologies of the active layers were investigated using atomic force microscopy and electron microscopy techniques. We have identified two essential steps to fabricate efficient OPVs from aqueous dispersions: (1) treatment of the hole-transport layer with UV-O3 to make the surface hydrophilic and (2) the use of an electron-transporting buffer layer for efficient charge extraction. We have also identified relative humidity and substrate temperature as key fabrication parameters for obtaining uniform active layer films. The OPV devices were fabricated using PEDOT:PSS as the hole-transport layer and PCBM as electron-transport layer with Ca/Al as the counter electrode. Efficiencies of 2.15% with a fill factor over 66% were obtained; the efficiency and the fill-factor is the highest among all aqueous processing of P3HT–PCBM nanoparticle solar cells.
Co-reporter:Monojit Bag;Timothy S. Gehan;Dana D. Algaier;Feng Liu;Gavvalapalli Nagarjuna;Paul M. Lahti;Thomas P. Russell;Dhapani Venkataraman
Advanced Materials 2013 Volume 25( Issue 44) pp:6411-6415
Publication Date(Web):
DOI:10.1002/adma.201301302
Co-reporter:Sravan K. Surampudi, Harik R. Patel, G. Nagarjuna and D. Venkataraman
Chemical Communications 2013 vol. 49(Issue 68) pp:7519-7521
Publication Date(Web):26 Jun 2013
DOI:10.1039/C3CC43797C
We show that ultrasound-induced mechanical force isomerizes an azobenzene centered within a poly(methyl acrylate) polymer from cis to trans configuration without cleaving the azo bond. The isomerization rate was not altered by the polarity of the solvent indicating that the isomerization occurs through a non-polar, inversion transition state.
Co-reporter:Dipankar Basak, Craig Versek, Jacob A. Harvey, Scott Christensen, Jibben Hillen, Scott M. Auerbach, Mark T. Tuominen and D. Venkataraman
Journal of Materials Chemistry A 2012 vol. 22(Issue 38) pp:20410-20417
Publication Date(Web):13 Aug 2012
DOI:10.1039/C2JM32835F
What is the impact of mixing two proton-conducting heterocycles on proton conductivity? Herein we answer this question through our investigations on two linear rod-like compounds 2-(4-(dodecyloxy)phenyl)-1H-imidazole (4) and 5-(4-(dodecyloxy)phenyl)-1H-1,2,3-triazole (10). We have found that mixtures of molecules 4 and 10 at certain compositions show enhanced proton conductivity compared to their pure components. We attribute the increased conductivity in these materials to the increased charge density due to facile co-ionization and increased mobility due to the incorporation of long alkyl chains, which prevent crystallization of protogenic groups while maintaining the required hydrogen bonded network. Our results suggest a new strategy for enhancing intrinsic proton conductivity in heterocyclic systems.
Co-reporter:G. Nagarjuna, Akshay Kokil, Jayant Kumar and D. Venkataraman
Journal of Materials Chemistry A 2012 vol. 22(Issue 31) pp:16091-16094
Publication Date(Web):21 Jun 2012
DOI:10.1039/C2JM32217J
We report a straightforward synthetic method to generate solution processable electron transporting polymers with low band gap and wide absorption range from readily available acceptor monomers. We show the efficacy of this approach using widely used electron acceptor 2,1,3-benzothiadiazole. The polymers have absorption up to 750 nm with electron mobility comparable to PCBM.
Co-reporter:Dipankar Basak, Craig Versek, Daniel T. Toscano, Scott Christensen, Mark T. Tuominen and D. Venkataraman
Chemical Communications 2012 vol. 48(Issue 47) pp:5922-5924
Publication Date(Web):18 Apr 2012
DOI:10.1039/C2CC31283B
In this communication, we introduce squaric acid derivatives as anhydrous proton conductors. We report the synthesis, characterization and proton conductivities of four squaric acid derivatives. The anhydrous proton conductivity of one of the derivatives was 2.3 × 10−3 S cm−1 at 110 °C, comparable to the conductivity of molten 1H-1,2,3-triazole or 1H-imidazole.
Co-reporter:Xi Yu, Serkan Eymur, Vijay Singh, Boqian Yang, Murat Tonga, Amarnath Bheemaraju, Graeme Cooke, Chandramouleeswaran Subramani, Dhandapani Venkataraman, Robert J. Stanley and Vincent M. Rotello
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 19) pp:6749-6754
Publication Date(Web):20 Mar 2012
DOI:10.1039/C2CP40073A
A donor–acceptor dyad model system using a flavin moiety as a photo-active acceptor has been synthesized for an energy and photo-induced electron transfer study. The photophysical investigations of the dyad revealed a multi-path energy and electron transfer process with a very high transfer efficiency. The photo-activity of flavin was believed to play an important role in the process, implying the potential application of flavin as a novel acceptor molecule for photovoltaics.
Co-reporter:Sravan K. Surampudi, G. Nagarjuna, Daiki Okamoto, Piyali D. Chaudhuri, and D. Venkataraman
The Journal of Organic Chemistry 2012 Volume 77(Issue 4) pp:2074-2079
Publication Date(Web):January 19, 2012
DOI:10.1021/jo202623u
We describe a synthetic protocol to selectively functionalize chiral bridged triarylamines at the apical position using regioselective copper-catalyzed amination reaction. This protocol allows the coupling of diphenylamines with a sterically hindered but electronically activated aryl–Br bond in the presence of a sterically unhindered but electronically unactivated aryl–Br bond. The unactivated aryl–Br bond was utilized further to synthesize a chiral heterohelicene homodimer using Stille coupling.
Co-reporter:Gavvalapalli Nagarjuna ;Dhapani Venkataraman
Journal of Polymer Science Part B: Polymer Physics 2012 Volume 50( Issue 15) pp:1045-1056
Publication Date(Web):
DOI:10.1002/polb.23073
Abstract
This review focuses on the recent developments in our understanding of active layer morphologies for organic photovoltaic cells and approaches to obtain active layer morphologies for high power conversion efficiencies. The evolution of active layer morphologies, as studied by high resolution electron microscopy, X-ray and neutron scattering, and dynamic secondary ion mass spectrometry, is covered, along with strategies including the use of small molecule additives, polymer nanowires and polymer nanoparticles to realize active layer morphologies. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Co-reporter:Gavvalapalli Nagarjuna, Mina Baghgar, Joelle A. Labastide, Dana D. Algaier, Michael D. Barnes, and Dhandapani Venkataraman
ACS Nano 2012 Volume 6(Issue 12) pp:10750
Publication Date(Web):November 25, 2012
DOI:10.1021/nn305207b
Nanoparticles derived from π-conjugated polymers have gained widespread attention as active layer materials in various organic electronics applications. The optoelectronic, charge transfer, and charge transport properties of π-conjugated polymers are intimately connected to the polymer aggregate structure. Herein we show that the internal aggregate structure of regioregular poly(3-hexylthiophene) (P3HT) within polymer nanoparticles can be tuned by solvent composition during nanoparticle fabrication through the miniemulsion process. Using absorption spectra and single-NP photoluminescence decay properties, we show that a solvent mixture consisting of a low boiling good solvent and a high boiling marginal solvent results in polymer aggregate structure with a higher degree of uniformity and structural order. We find that the impact of solvent on the nature of P3HT aggregation within nanoparticles is different from what has been reported in thin films.Keywords: aggregates; and miniemulsion; internal structure; nanoparticles; photophysics; poly(3-hexylthiophene)
Co-reporter:Burcin Erenturk, Serkan Gurbuz, Rachel E. Corbett, Sarah-Ann M. Claiborne, Jason Krizan, Dhandapani Venkataraman, and Kenneth R. Carter
Chemistry of Materials 2011 Volume 23(Issue 14) pp:3371-3376
Publication Date(Web):June 22, 2011
DOI:10.1021/cm201384p
Highly crystalline, continuous parallel arrays of CdSe nanowires have been generated through electrodeposition using photoresist templates. Easy soft imprint nanolithography (ESINL) was used to pattern a commercially available photoresist, Norland Optical Adhesive 60 (NOA 60), deposited onto the ITO substrates, prior to electrodeposition. Using the exposed ITO layer as an electrode, a thin film of CdSe was electrodeposited from an electrolyte containing CdCl2, SeO2, and HCl on the substrate, and the resist was subsequently removed in an alkaline developer solution. The resulting CdSe nanowires were 100 nm in thickness, 300–500 nm in width, and several centimeters in length. Imprinted templates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDX). The SEM analysis confirmed the formation of parallel arrays of nanowires unaffected by the resist lift-off, and the XRD results showed that the CdSe nanowires had a hexagonal structure and that the crystalline structure was unaffected by the photoresist removal.
Co-reporter:G. Nagarjuna, Abhishek Kumar, Akshay Kokil, Kedar G. Jadhav, Serkan Yurt, Jayant Kumar and D. Venkataraman
Journal of Materials Chemistry A 2011 vol. 21(Issue 41) pp:16597-16602
Publication Date(Web):20 Sep 2011
DOI:10.1039/C1JM12949J
Optical sensing, via fluorescence quenching, of nitroaromatic vapours using polythiophenes has received limited attention due to their rather low sensory response. We hypothesized that a dipolar 1,2,3-triazole moiety can enhance the interaction of DNT and TNT with the polymer in thin films and bulky side chains can decrease the chain packing in thin films resulting in enhanced analyte diffusion. Herein we show that thin films of thiophene-based polymers containing 1,2,3-triazole with appropriate alkyl side chains show enhanced fluorescence quenching in the presence of nitroaromatic vapours.
Co-reporter:Dipankar Basak, Scott Christensen, Sravan K. Surampudi, Craig Versek, Daniel T. Toscano, Mark T. Tuominen, Ryan C. Hayward and D. Venkataraman
Chemical Communications 2011 vol. 47(Issue 19) pp:5566-5568
Publication Date(Web):11 Apr 2011
DOI:10.1039/C1CC10509D
In this communication, we show that liquid crystalline phases lower the activation energy barrier for proton transport. The liquid crystalline phases were obtained using a triphenylene core with alkyl chains bearing a triazole moiety at their termini.
Co-reporter:Joelle A. Labastide, Mina Baghgar, Irene Dujovne, Yipeng Yang, Anthony D. Dinsmore, Bobby G. Sumpter, Dhandapani Venkataraman, and Michael D. Barnes
The Journal of Physical Chemistry Letters 2011 Volume 2(Issue 24) pp:3085-3091
Publication Date(Web):November 16, 2011
DOI:10.1021/jz2012275
In this Perspective, we discuss the possibility of constructing binary nanoparticle superlattices for organic photovoltaic applications and some of the interesting new photophysics emerging from preliminary studies. We summarize recent advances in nanoparticle preparation and photophysical characterization and some of the very interesting observed departures from thin-film photoluminescence dynamics. We conclude by discussing some of the challenges ahead and the possibility of new emergent physics in the assembly of polymer nanoparticles into functional devices.
Co-reporter:Joelle A. Labastide, Mina Baghgar, Irene Dujovne, B. Harihara Venkatraman, David C. Ramsdell, Dhandapani Venkataraman, and Michael D. Barnes
The Journal of Physical Chemistry Letters 2011 Volume 2(Issue 17) pp:2089-2093
Publication Date(Web):August 1, 2011
DOI:10.1021/jz200958x
We report on a remarkable size and internal structure dependence on time- and polarization-resolved photoluminescence (PL) from individual regioregular rrP3HT (poly-3-(hexylthiophine)) nanoparticles. For the smallest particles (∼34 nm) with relatively low crystallinity (40%), the time evolution of polarization contrast is nearly stationary; for intermediate-sized particles (∼ 65 nm), depolarization occurs on a 1–2 ns time scale. The largest and most crystalline particles studied (118 nm, 70%) show a PL depolarization on a time scale of <50 ps. In every time regime, we observe P3HT nanoparticle PL dynamics that are qualitatively different from those of extended films and single-polymer chains, highlighted by intriguing differences in power law dynamics in the PL intensity at long times. This work may support the hypothesis that hierarchical assemblies of conducting polymer nanoparticles could offer a route to higher efficiency in organic photovoltaic systems.Keywords: luminescence; nanoparticles; P3HT; polarization;
Co-reporter:D. Venkataraman, Serkan Yurt, B. Harihara Venkatraman and Nagarjuna Gavvalapalli
The Journal of Physical Chemistry Letters 2010 Volume 1(Issue 6) pp:947-958
Publication Date(Web):February 25, 2010
DOI:10.1021/jz1000819
What are the stumbling blocks for achieving high-efficiency organic photovoltaic devices? This question is examined from a molecular architecture and molecular packing perspective. The intermolecular interaction between the electron donor and electron acceptor influences the charge separation. The packing of electron donors and acceptors influences the charge transport. Therefore, there is a need to strike a balance between the charge-transfer interactions and packing interactions and obtain nanoscale segregated morphologies for efficient charge separation and charge transport. Molecular architecture is key toward striking this balance and, therefore, its impact on charge-transfer interactions and packing interactions; thus, the active-layer morphology and photovoltaic metrics are examined. A variety of molecular architectures for the packing of π-conjugated organic molecules to structures relevant for photovoltaic devices is also discussed.
Co-reporter:G. Nagarjuna, Serkan Yurt, Kedar G. Jadhav, and D. Venkataraman
Macromolecules 2010 Volume 43(Issue 19) pp:8045-8050
Publication Date(Web):September 20, 2010
DOI:10.1021/ma101657e
π-Conjugated moieties are often attached to conjugated polymers to systematically alter their electronic properties. Herein, we report the synthesis and properties of a thiophene polymer bearing a triazole moiety in the third position. Through NMR-based quenching studies, we show that the placement of the triazole moiety alters reaction pathway of the Ni(0)-mediated Grignard metathesis polymerization possibly through chelation. When compared with a triazole on the main chain, the pendant triazole moiety acts as an electron donor and lowers the band gap of the polymer. The triazole moiety also does not hinder the packing of the conjugated backbone. We also show that the fluorescence of this polymer is quenched with PCBM, indicating its potential as a candidate for organic photovoltaic devices.
Co-reporter:Travis L. Benanti, Antranig Kalaydjian and D. Venkataraman
Macromolecules 2008 Volume 41(Issue 22) pp:8312-8315
Publication Date(Web):October 28, 2008
DOI:10.1021/ma801798p
Co-reporter:M. Zhang;L. Yang;S. Yurt;M. J. Misner;J.-T. Chen;E. B. Coughlin;D. Venkataraman;T. P. Russell
Advanced Materials 2007 Volume 19(Issue 12) pp:1571-1576
Publication Date(Web):15 MAY 2007
DOI:10.1002/adma.200602461
A cleavable trityl ether juncture is introduced between polystyrene (PS) and poly(ethylene oxide) (PEO), and thus highly ordered nanoporous thin films have been prepared from self-assembled PS-b-PEO diblock copolymers, via the removal of PEO from solvent-annealed PS-b-PEO thin films in a simple two or one-step process. When patterned substrates are used, addressable nanopore arrays with a high degree of lateral order and a well-defined lattice orientation can be readily produced (see figure).
Co-reporter:Travis L. Benanti, Pranorm Saejueng and D. Venkataraman
Chemical Communications 2007 (Issue 7) pp:692-694
Publication Date(Web):16 Nov 2006
DOI:10.1039/B610565C
We report a general strategy for the spontaneous segregation of electron-rich and electron-poor π-conjugated moieties using mutually phobic aliphatic fluorocarbon–hydrocarbon interactions.
Co-reporter:Uche K. Anyanwu and D. Venkataraman
Green Chemistry 2005 vol. 7(Issue 6) pp:424-425
Publication Date(Web):22 Apr 2005
DOI:10.1039/B501826A
Soxhlet-dialysis is used to facilitate the recovery and reuse of a PEG-supported titanium-salen catalyst for the asymmetric silylcyanation of benzaldehyde—up to five times without any loss in activity or enantioselectivity.
Co-reporter:Jason E. Field, Marianny Y. Combariza, Richard W. Vachet and D. Venkataraman
Chemical Communications 2002 (Issue 19) pp:2260-2261
Publication Date(Web):10 Sep 2002
DOI:10.1039/B207026J
Triphenylamine ortho-tricarboxylic acid (1) has been synthesized and the crystal structure reported. This molecule is shown to spontaneously self-assemble into a hydrogen-bonded tetrahedron. Furthermore, Electrospray Ionization Mass Spectroscopy shows evidence for the stability of such aggregates from an ethanol/water solution.
Co-reporter:Jason E. Field and D. Venkataraman
Chemical Communications 2002 (Issue 4) pp:306-307
Publication Date(Web):28 Mar 2002
DOI:10.1039/B110049A
ortho-Substituted phenyl amines form supramolecular helices or zig-zag structures, depending on the conformation of the carboxylic acid substituents — which can be controlled by an intramolecular hydrogen-bonding interaction.
Co-reporter:G. Nagarjuna, Akshay Kokil, Jayant Kumar and D. Venkataraman
Journal of Materials Chemistry A 2012 - vol. 22(Issue 31) pp:
Publication Date(Web):
DOI:10.1039/C2JM32217J
Co-reporter:Sravan K. Surampudi, Harik R. Patel, G. Nagarjuna and D. Venkataraman
Chemical Communications 2013 - vol. 49(Issue 68) pp:NaN7521-7521
Publication Date(Web):2013/06/26
DOI:10.1039/C3CC43797C
We show that ultrasound-induced mechanical force isomerizes an azobenzene centered within a poly(methyl acrylate) polymer from cis to trans configuration without cleaving the azo bond. The isomerization rate was not altered by the polarity of the solvent indicating that the isomerization occurs through a non-polar, inversion transition state.
Co-reporter:Dipankar Basak, Craig Versek, Daniel T. Toscano, Scott Christensen, Mark T. Tuominen and D. Venkataraman
Chemical Communications 2012 - vol. 48(Issue 47) pp:NaN5924-5924
Publication Date(Web):2012/04/18
DOI:10.1039/C2CC31283B
In this communication, we introduce squaric acid derivatives as anhydrous proton conductors. We report the synthesis, characterization and proton conductivities of four squaric acid derivatives. The anhydrous proton conductivity of one of the derivatives was 2.3 × 10−3 S cm−1 at 110 °C, comparable to the conductivity of molten 1H-1,2,3-triazole or 1H-imidazole.
Co-reporter:Dipankar Basak, Scott Christensen, Sravan K. Surampudi, Craig Versek, Daniel T. Toscano, Mark T. Tuominen, Ryan C. Hayward and D. Venkataraman
Chemical Communications 2011 - vol. 47(Issue 19) pp:NaN5568-5568
Publication Date(Web):2011/04/11
DOI:10.1039/C1CC10509D
In this communication, we show that liquid crystalline phases lower the activation energy barrier for proton transport. The liquid crystalline phases were obtained using a triphenylene core with alkyl chains bearing a triazole moiety at their termini.
Co-reporter:Travis L. Benanti, Pranorm Saejueng and D. Venkataraman
Chemical Communications 2007(Issue 7) pp:
Publication Date(Web):
DOI:10.1039/B610565C
Co-reporter:Xi Yu, Serkan Eymur, Vijay Singh, Boqian Yang, Murat Tonga, Amarnath Bheemaraju, Graeme Cooke, Chandramouleeswaran Subramani, Dhandapani Venkataraman, Robert J. Stanley and Vincent M. Rotello
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 19) pp:NaN6754-6754
Publication Date(Web):2012/03/20
DOI:10.1039/C2CP40073A
A donor–acceptor dyad model system using a flavin moiety as a photo-active acceptor has been synthesized for an energy and photo-induced electron transfer study. The photophysical investigations of the dyad revealed a multi-path energy and electron transfer process with a very high transfer efficiency. The photo-activity of flavin was believed to play an important role in the process, implying the potential application of flavin as a novel acceptor molecule for photovoltaics.
Co-reporter:G. Nagarjuna, Abhishek Kumar, Akshay Kokil, Kedar G. Jadhav, Serkan Yurt, Jayant Kumar and D. Venkataraman
Journal of Materials Chemistry A 2011 - vol. 21(Issue 41) pp:NaN16602-16602
Publication Date(Web):2011/09/20
DOI:10.1039/C1JM12949J
Optical sensing, via fluorescence quenching, of nitroaromatic vapours using polythiophenes has received limited attention due to their rather low sensory response. We hypothesized that a dipolar 1,2,3-triazole moiety can enhance the interaction of DNT and TNT with the polymer in thin films and bulky side chains can decrease the chain packing in thin films resulting in enhanced analyte diffusion. Herein we show that thin films of thiophene-based polymers containing 1,2,3-triazole with appropriate alkyl side chains show enhanced fluorescence quenching in the presence of nitroaromatic vapours.
Co-reporter:Dipankar Basak, Craig Versek, Jacob A. Harvey, Scott Christensen, Jibben Hillen, Scott M. Auerbach, Mark T. Tuominen and D. Venkataraman
Journal of Materials Chemistry A 2012 - vol. 22(Issue 38) pp:NaN20417-20417
Publication Date(Web):2012/08/13
DOI:10.1039/C2JM32835F
What is the impact of mixing two proton-conducting heterocycles on proton conductivity? Herein we answer this question through our investigations on two linear rod-like compounds 2-(4-(dodecyloxy)phenyl)-1H-imidazole (4) and 5-(4-(dodecyloxy)phenyl)-1H-1,2,3-triazole (10). We have found that mixtures of molecules 4 and 10 at certain compositions show enhanced proton conductivity compared to their pure components. We attribute the increased conductivity in these materials to the increased charge density due to facile co-ionization and increased mobility due to the incorporation of long alkyl chains, which prevent crystallization of protogenic groups while maintaining the required hydrogen bonded network. Our results suggest a new strategy for enhancing intrinsic proton conductivity in heterocyclic systems.
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![Benzo[g]pteridine-2,4(3H,10H)-dione,7,8-dimethyl-10-(2-methylpropyl)-](http://img.cochemist.com/ccimg/163700/163657-00-9.png)
![Benzo[g]pteridine-2,4(3H,10H)-dione,7,8-dimethyl-10-(2-methylpropyl)-](http://img.cochemist.com/ccimg/163700/163657-00-9_b.png)
