Co-reporter:Vikram Singh Raghuwanshi, Robert Wendt, Maeve O’Neill, Miguel Ochmann, Tirtha Som, Robert Fenger, Marie Mohrmann, Armin Hoell, and Klaus Rademann
Journal of Chemical Education April 11, 2017 Volume 94(Issue 4) pp:510-510
Publication Date(Web):March 8, 2017
DOI:10.1021/acs.jchemed.6b00388
We demonstrate here a novel laboratory experiment for the synthesis of gold nanoparticles (AuNPs) by using a low energy gold-sputtering method together with a modern, green, and biofriendly deep eutectic solvent (DES). The strategy is straightforward, economical, ecofriendly, rapid, and clean. It yields uniform AuNPs of 5 nm in diameter with high reproducibility. Moreover, catalytic applications of AuNPs in DES are shown by studying the conversion of p-nitrophenol to p-aminophenol. Systematic in situ UV–vis spectra are recorded during the catalytic reaction. While the experimental procedures are simple, our laboratory experiments can be applied in a variety of settings depending upon how detailed the instructor requires the depth of the analyses. The laboratory experiments described herein were successfully conducted and evaluated by students with a bachelor degree.Keywords: Catalysis; General Public; Graduate Education/Research; Green Chemistry; Hands-On Learning/Manipulatives; High School/Introductory Chemistry; Inorganic Chemistry; Nanotechnology; Spectroscopy;
Co-reporter:Virgil Andrei, Kevin Bethke and Klaus Rademann
Energy & Environmental Science 2016 vol. 9(Issue 5) pp:1528-1532
Publication Date(Web):10 Mar 2016
DOI:10.1039/C6EE00247A
While the field of thermoelectricity continues developing, the academic world is still debating its applicability for wide-scale implementation. The main concerns revolve around its low energy conversion efficiency (5–10%), compared to photovoltaics (up to 46%), and the environmental impact of commonly used materials (e.g. Bi2Te3, PbTe). Although less scrutinized, other fields such as photoelectrochemistry and catalysis have suffered from similar drawbacks. In light of the recent developments, the question arises, if the introduction of hybrid devices combining those renewable energy sources is preferable to the current divided efforts. Several new papers bring arguments in favor of this combined approach, with an efficiency of 16% reported for a triboelectric–thermoelectric–photovoltaic water splitting cell.
Co-reporter:Virgil Andrei, Kevin Bethke and Klaus Rademann
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 16) pp:10700-10707
Publication Date(Web):16 Feb 2016
DOI:10.1039/C5CP06828B
We present a facile alternative to other well known strategies for synthesizing flexible thermoelectric materials. Instead of printing thin active layers on flexible substrates or doping conductive polymers, we produce thermoelectric pastes, using a mixture of graphite, copper(I) oxide and polychlorotrifluoroethene. The Seebeck coefficient of the investigated pastes varies between 10 and 600 μV K−1, while the electrical conductivity spans over an even wider range of 10−4 to 102 S m−1. Here, the influence of phenomena such as percolation on the electrical transport is revealed. The resulting power factor reaches 5.69 × 10−4 ± 0.70 × 10−4 μW m−1 K−2 for the graphite–polymer paste, with an unexpected minimum at a graphite molar fraction of approximately 0.4. The values are comparable to those of the powder mixtures, which are slightly higher, but less precisely tunable. Such compounds are further evaluated for practical applications. The graphite–polymer paste is used to exemplify, how a flexible thermoelectric sensor can be easily manufactured, step by step. Our results represent a proof of principle, that thermoelectric pastes are viable alternatives to current solutions. A further expansion of the scope for the composites can be achieved by using high performance thermoelectric materials and conductive polymers.
Co-reporter:Christian Alexander Schaumberg, Markus Wollgarten and Klaus Rademann
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 27) pp:17934-17938
Publication Date(Web):15 Jun 2015
DOI:10.1039/C5CP01153A
Pulsed laser ablation in liquids (PLAL) is a versatile route to stable colloids without the need for stabilizing agents. The use of suspensions instead of bulk targets further simplifies the experimental set-up and even improves the productivity. However, the utilization of this approach is hindered by limited knowledge about the underlying mechanisms of the nanoparticle formation. We present the synthesis of copper(I) iodide nanoparticles via ns-pulsed laser irradiation of CuI powder suspended in water or ethyl acetate. A thorough study of the nanoparticle size by transmission electron microscopy reveals a log-normal distribution with a mean diameter of 31 nm (±11 nm) in water and 18 nm (±7 nm) in ethyl acetate. The duration of the laser irradiation appears to have only a minor influence on the size distribution. Selected area diffraction and electron energy-loss spectroscopy verify the chemical composition of the generated CuI nanoparticles. While comparable precursors like CuO and Cu3N follow a reductive ablation mechanism, a fragmentation mechanism is found for CuI. With a productivity of 1.7 μg J−1 this pulsed laser fragmentation in liquids (PLFL) proves to be an efficient route to colloidal CuI nanoparticles.
Co-reporter:Thomas Hendel, Maria Wuithschick, Frieder Kettemann, Alexander Birnbaum, Klaus Rademann, and Jörg Polte
Analytical Chemistry 2014 Volume 86(Issue 22) pp:11115
Publication Date(Web):October 7, 2014
DOI:10.1021/ac502053s
This paper studies the UV–vis absorbance of colloidal gold nanoparticles at 400 nm and validates it as a method to determine Au(0) concentrations in colloidal gold solutions. The method is shown to be valid with restrictions depending on the investigated system. The uncertainty of the determined Au(0) concentration can be up to 30%. This deviation is the result of the combined influence of parameters such as particle size, surface modification, or oxidation state. However, quantifying the influence of these parameters enables a much more precise Au(0) determination for specific systems. As an example, the reduction process of the well-known Turkevich method was monitored and the Au(0) concentration was determined with a deviation of less than 5%. Hence, a simple, fast, easy, and cheap in situ method for Au(0) determination is demonstrated that has in the presence of other gold species such as Au(III) an unprecedented accuracy.
Co-reporter:Christian A. Schaumberg, Markus Wollgarten, and Klaus Rademann
The Journal of Physical Chemistry A 2014 Volume 118(Issue 37) pp:8329-8337
Publication Date(Web):May 16, 2014
DOI:10.1021/jp501123y
Pulsed laser ablation in liquids (PLAL) has developed to a convenient and efficient method for the synthesis of colloidal solutions. So far, in most cases, the laser pulse is focused on bulk targets like metal plates. An interesting alternative is the use of suspended μm-sized precursors. This leads to higher production rates and simpler setups. A thorough understanding of the mechanism is essential in order to gain control over the characteristics of the synthesized nanoparticles. Therefore, we investigated the formation of copper colloids by PLAL of CuO, Cu3N, Cu(N3)2, and Cu2C2 powders in organic liquids. Thus, we can compare copper precursors based on elements of the 4th, 5th, and 6th main group. The chemical composition of the resulting nanoparticles is revealed by electron energy loss spectroscopy (EELS). The presented investigations point to a reductive ablation process followed by laser-driven aggregation and coalescence steps instead of a simple fragmentation mechanism.
Co-reporter:Anne Simo, Jörg Polte, Norbert Pfänder, Ulla Vainio, Franziska Emmerling, and Klaus Rademann
Journal of the American Chemical Society 2012 Volume 134(Issue 45) pp:18824-18833
Publication Date(Web):October 25, 2012
DOI:10.1021/ja309034n
In any given matrix control over the final particle size distribution requires a constitutive understanding of the mechanisms and kinetics of the particle evolution. In this contribution we report on the formation mechanism of silver nanoparticles embedded in a soda-lime silicate glass matrix. For the silver ion-exchanged glass it is shown that at temperatures below 410 °C only molecular clusters (diameter <1 nm) are forming which are most likely silver dimers. These clusters grow to nanoparticles (diameter >1 nm) by annealing above this threshold temperature of 410 °C. It is evidenced that the growth and thus the final silver nanoparticle size are determined by matrix-assisted reduction mechanisms. As a consequence, particle growth proceeds after the initial formation of stable clusters by addition of silver monomers which diffuse from the glass matrix. This is in contrast to the widely accepted concept of particle growth in metal–glass systems, in which it is assumed that the nanoparticle formation is predominantly governed by Ostwald ripening processes.
Co-reporter:Tanja Gnutzmann, Klaus Rademann and Franziska Emmerling
Chemical Communications 2012 vol. 48(Issue 11) pp:1638-1640
Publication Date(Web):04 Nov 2011
DOI:10.1039/C1CC16301A
An unusually fast crystallization of the organic glass former nifedipine has been observed. The crystallization process, starting from an amorphous film to crystalline material, was investigated by time resolved Raman microspectroscopy. The crystallization rates of the initially crystallizing metastable β-form are four orders of magnitude higher than those of previous studies.
Co-reporter:Adnan Sarfraz, Anne Simo, Robert Fenger, Wolfgang Christen, Klaus Rademann, Ulrich Panne, and Franziska Emmerling
Crystal Growth & Design 2012 Volume 12(Issue 2) pp:583-588
Publication Date(Web):March 21, 2011
DOI:10.1021/cg101358q
A systematic crystal morphology study on the pharmaceutical model compound caffeine has been conducted on different surfaces: silicon, silver, soda lime glass, and silver subsurface ion-exchanged soda-lime silicate (SIMO) glasses. The morphology of the solid caffeine deposits has been investigated using environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). Needle-shaped caffeine crystals have been observed by drop-casting and also by applying the rapid expansion of supercritical solutions (RESS) technique using supercritical carbon dioxide. The aspect ratio of the crystalline needles typically vary between 10 and 100, but have been observed as large as 500. The XRD data of the RESS products indicate unambiguously the presence of the thermodynamically most stable polymorph of caffeine known as the β-form. Under defined conditions we observe a unique, surface-mediated morphology for caffeine crystals with nearly perfect hexagonal shape. The relative fraction of the hexagons was seen to strongly increase especially when SIMO glasses were used. These hexagons have a distinct upper size limit depending on the solvent and substrate being used. The size distribution analysis of the hexagons yielded an average perimeter of typically 10 μm. The mechanism of the formation process of this new hexagonal motif is explained in terms of the spinodal dewetting of the thin film of caffeine solution on the surface.
Co-reporter:R. Fenger, E. Fertitta, H. Kirmse, A. F. Thünemann and K. Rademann
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 26) pp:9343-9349
Publication Date(Web):02 Apr 2012
DOI:10.1039/C2CP40792B
CTAB-stabilized gold nanoparticles were synthesized by applying the seeding-growth approach in order to gain information about the size dependence of the catalytic reduction of p-nitrophenol to p-aminophenol with sodium borohydride. Five different colloidal solutions of stabilized gold nanoparticles have been characterized by TEM, AFM, UV-Vis, SAXS, and DLS for their particle size distributions. Gold nanoparticles (mean sizes: 3.5, 10, 13, 28, 56 nm diameter) were tested for their catalytic efficiency. Kinetic data were acquired by UV-Vis spectroscopy at different temperatures between 25 and 45 °C. By studying the p-nitrophenol to p-aminophenol reaction kinetics we determined the nanoparticle size which is needed to gain the fastest conversion under ambient conditions in the liquid phase. Unexpectedly, CTAB-stabilized gold nanoparticles with a diameter of 13 nm are most efficient.
Co-reporter:Maria Klimakow, Peter Klobes, Klaus Rademann, Franziska Emmerling
Microporous and Mesoporous Materials 2012 Volume 154() pp:113-118
Publication Date(Web):15 May 2012
DOI:10.1016/j.micromeso.2011.11.039
The compound MOF-14 (Cu3(BTB)2, BTB = 4,4′,4″-benzenetribenzoate) was synthesized by ball milling and characterized by powder X-ray diffraction (XRD). The raw material was activated using an efficient single washing step to ensure a free pore access. Nitrogen adsorption measurements were carried out to determine the specific areas of the samples before and after activation. To interpret the activation process in terms of blocking effects in the micropore channels, NLDFT evaluations (Nonlocal Density Functional Theory) of the MOF-14 nitrogen isotherms were carried out. In connection with the appearance of additional hysteresis loops in the nitrogen isotherms, calculations of the mesopore size distribution were performed using the method of Barret, Joyner, and Halenda (BJH). The results are compared to those of a structurally analogue MOF, namely HKUST-1 (Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylate). This comparison showed notable differences regarding the impact of the activation step on the formation of mesopores and their size distribution.Graphical abstractHighlights► Mechanochemistry is used to synthesize metal–organic frameworks. ► Activation of the raw products leads to enhanced specific surface areas. ► Adsorption isotherms show hysteresis loops. ► Calculation of pore size distributions with BJH and DFT method. ► Comparison of two MOFs shows different influence of the activation on the formation of mesopores.
Co-reporter:Dr. Tirtha Som;Anne Simo;Robert Fenger;Gerald V. Troppenz;Roman Bansen;Norbert Pfänder;Dr. Franziska Emmerling;Dr. Jörg Rappich;Dr. Torsten Boeck; Dr. Klaus Rademann
ChemPhysChem 2012 Volume 13( Issue 8) pp:2162-2169
Publication Date(Web):
DOI:10.1002/cphc.201101009
Abstract
A unique direct electrodeposition technique involving very high current densities, high voltages and high electrolyte concentrations is applied for highly selective mass synthesis of stable, isolable, surfactant-free, single-crystalline Bi hexagons on a Cu wire at room temperature. A formation mechanism of the hexagons is proposed. The morphology, phase purity, and crystallinity of the material are well characterized by FESEM, AFM, TEM, SAED, EDX, XRD, and Raman spectroscopy. The thermal stability of the material under intense electron beam and intense laser light irradiation is studied. The chemical stability of elemental Bi in nitric acid shows different dissolution rates for different morphologies. This effect enables a second way for the selective fabrication of Bi hexagons. Bi hexagons can be oxidized exclusively to α-Bi2O3 hexagons. The Bi hexagons are found to be promising for thermoelectric applications. They are also catalytically active, inducing the reduction of 4-nitrophenol to 4-aminophenol. This electrodeposition methodology has also been demonstrated to be applicable for synthesis of bismuth-based bimetallic hybrid composites for advanced applications.
Co-reporter:Anne Simo;Virginia Joseph;Robert Fenger; Dr. Janina Kneipp; Dr. Klaus Rademann
ChemPhysChem 2011 Volume 12( Issue 9) pp:1683-1688
Publication Date(Web):
DOI:10.1002/cphc.201100098
Abstract
We report on the formation of silver subsurface ion-exchanged metal oxide (silver SIMO) glasses and their surface-enhanced Raman scattering (SERS) activity. The samples were prepared by a combined thermal and chemical three-step methodology and characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), environmental electron scanning microscopy (ESEM), and UV/Vis spectroscopy. This unique method provides SERS substrates with protection against contamination and strong, reliable and reproducible SERS enhancement. The Raman enhancement factors of the long-term stable SIMO glasses were estimated to approximately 107.
Co-reporter:Anne Simo;Virginia Joseph;Robert Fenger; Dr. Janina Kneipp; Dr. Klaus Rademann
ChemPhysChem 2011 Volume 12( Issue 9) pp:
Publication Date(Web):
DOI:10.1002/cphc.201190044
Co-reporter:Maik Eichelbaum
Advanced Functional Materials 2009 Volume 19( Issue 13) pp:2045-2052
Publication Date(Web):
DOI:10.1002/adfm.200801892
Abstract
With the technique of synchrotron X-ray activation, molecule-like, non-plasmonic gold and silver particles in soda-lime silicate glasses can be generated. The luminescence energy transfer between these species and lanthanide(III) ions is studied. As a result, a significant lanthanide luminescence enhancement by a factor of up to 250 under non-resonant UV excitation is observed. The absence of a distinct gold and silver plasmon resonance absorption, respectively, the missing nanoparticle signals in previous SAXS and TEM experiments, the unaltered luminescence lifetime of the lanthanide ions compared to the non-enhanced case, and an excitation maximum at 300–350 nm (equivalent to the absorption range of small noble metal particles) indicate unambiguously that the observed enhancement is due to a classical energy transfer between small noble metal particles and lanthanide ions, and not to a plasmonic field enhancement effect. It is proposed that very small, molecule-like noble metal particles (such as dimers, trimers, and tetramers) first absorb the excitation light, undergo a singlet-triplet intersystem crossing, and finally transfer the energy to an excited multiplet state of adjacent lanthanide(III) ions. X-ray lithographic microstructuring and excitation with a commercial UV LED show the potential of the activated glass samples as bright light-emitting devices with tunable emission colors.
Co-reporter:Maik Eichelbaum Dr.;Janina Kneipp Dr.;Bruno E. Schmidt;Ulrich Panne Dr. Dr.
ChemPhysChem 2008 Volume 9( Issue 15) pp:2163-2167
Publication Date(Web):
DOI:10.1002/cphc.200800417
Co-reporter:Jork Leiterer, Franziska Emmerling, Ulrich Panne, Wolfgang Christen and Klaus Rademann
Langmuir 2008 Volume 24(Issue 15) pp:7970-7978
Publication Date(Web):June 26, 2008
DOI:10.1021/la800768v
Crystallization processes under different conditions are of fundamental interest in chemistry, pharmacy, and medicine. Therefore, we have studied the formation of micro- and nanosized crystals using water−caffeine (1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione) solutions under ambient conditions as a relevant model system. When droplets of an aqueous caffeine solution evaporate and eventually dry on surfaces (glass, polystyrene, and polyester), stable “coffee tabletop” rings with a perimeter of typically 3 mm are formed after 20 to 50 min. Using a micro focus X-ray beam available at the BESSY μSpot-beamline, the fine structure of different caffeine needles can be distinguished. Unexpectedly, both crystal modifications (α- and β-caffeine) are present, but locally separated in these rings. Furthermore, AFM studies reveal the presence of even smaller particles on a nanometer length scale. To eliminate influences of surface irregularities from the crystallization process, acoustic levitation of liquid samples was employed. Such levitated droplets are trapped in a stable position and only surrounded by air. The solvent in an ultrasonically levitated drop evaporates completely, and the resulting crystallization of caffeine was followed in situ by synchrotron X-ray diffraction. In this case, the diffraction pattern is in accordance with pure α-caffeine and does not indicate the formation of the room temperature polymorph β-caffeine. Hence, our investigations open new vistas that may lead to a controlled formation of cocrystals and novel polymorphs of micro- and nanocrystalline materials, which are of relevance for fundamental studies as well as for pharmaceutical and medical applications.
Co-reporter:Maik Eichelbaum;Wilfried Weigel;Bernd Löchel
Gold Bulletin 2007 Volume 40( Issue 4) pp:278-282
Publication Date(Web):2007 December
DOI:10.1007/BF03215600
We describe the microstructuring of gold-ruby glasses with synchrotron radiation. Plasmonic or luminescent microstructures with a lateral width of minimum 5 μm can be written directly into the glasses by implementing X-ray lithography. The technique involves two steps: First, gold containing glass samples are irradiated with synchrotron X-rays through a microstructured mask. And second, subsequent annealing at minimum 500°C induces the growth of gold nanoparticles. The patterned sites are ruby coloured due to the gold surface plasmon resonance of gold nanoparticles. Furthermore we investigated the photoluminescence of the microstructured glass. After synchrotron irradiation a red photoluminescence is observed under UV light excitation. Subsequent annealing for a few minutes at 300°C induces the quenching of the red luminescence. If the irradiated sample is annealed for 5 minutes at a higher temperature of 500°C a bright green light emission is detected. The green photoluminescence decreases after further annealing and finally vanishes. We assume that the origin of the luminescence are silicate hole centres. The technique of generating gold particles with synchrotron X-ray lithography has potential to produce micro-optical devices like optical storage units, photonic crystals, gratings or sensors.
Co-reporter:Maik Eichelbaum Dipl.-Chem. Dr.;Ralf Müller Dr.;Martin Radtke Dr.;Heinrich Riesemeier Dr.;Wolf Görner Dr.
Angewandte Chemie 2005 Volume 117(Issue 48) pp:
Publication Date(Web):31 OCT 2005
DOI:10.1002/ange.200502174
Gold im Glas: Durch eine Aktivierung von Gold-Silicatgläsern mit Synchrotron-Röntgenstrahlung ist es möglich, ortsaufgelöst Goldkationen zu Goldatomen zu reduzieren. Mit einer anschließenden thermischen Behandlung kann man Nanopartikel definierter Größe mit maßgeschneiderten optischen Eigenschaften wachsen lassen und somit chemisch und mechanisch beständige Gläser für integrierte, nanophotonische Anwendungen funktionalisieren (siehe Bild).
Co-reporter:Maik Eichelbaum, Klaus Rademann, Ralf Müller, Martin Radtke, Heinrich Riesemeier,Wolf Görner
Angewandte Chemie International Edition 2005 44(48) pp:7905-7909
Publication Date(Web):
DOI:10.1002/anie.200502174
Co-reporter:R. Fenger, E. Fertitta, H. Kirmse, A. F. Thünemann and K. Rademann
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 26) pp:NaN9349-9349
Publication Date(Web):2012/04/02
DOI:10.1039/C2CP40792B
CTAB-stabilized gold nanoparticles were synthesized by applying the seeding-growth approach in order to gain information about the size dependence of the catalytic reduction of p-nitrophenol to p-aminophenol with sodium borohydride. Five different colloidal solutions of stabilized gold nanoparticles have been characterized by TEM, AFM, UV-Vis, SAXS, and DLS for their particle size distributions. Gold nanoparticles (mean sizes: 3.5, 10, 13, 28, 56 nm diameter) were tested for their catalytic efficiency. Kinetic data were acquired by UV-Vis spectroscopy at different temperatures between 25 and 45 °C. By studying the p-nitrophenol to p-aminophenol reaction kinetics we determined the nanoparticle size which is needed to gain the fastest conversion under ambient conditions in the liquid phase. Unexpectedly, CTAB-stabilized gold nanoparticles with a diameter of 13 nm are most efficient.
Co-reporter:Christian Alexander Schaumberg, Markus Wollgarten and Klaus Rademann
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 27) pp:NaN17938-17938
Publication Date(Web):2015/06/15
DOI:10.1039/C5CP01153A
Pulsed laser ablation in liquids (PLAL) is a versatile route to stable colloids without the need for stabilizing agents. The use of suspensions instead of bulk targets further simplifies the experimental set-up and even improves the productivity. However, the utilization of this approach is hindered by limited knowledge about the underlying mechanisms of the nanoparticle formation. We present the synthesis of copper(I) iodide nanoparticles via ns-pulsed laser irradiation of CuI powder suspended in water or ethyl acetate. A thorough study of the nanoparticle size by transmission electron microscopy reveals a log-normal distribution with a mean diameter of 31 nm (±11 nm) in water and 18 nm (±7 nm) in ethyl acetate. The duration of the laser irradiation appears to have only a minor influence on the size distribution. Selected area diffraction and electron energy-loss spectroscopy verify the chemical composition of the generated CuI nanoparticles. While comparable precursors like CuO and Cu3N follow a reductive ablation mechanism, a fragmentation mechanism is found for CuI. With a productivity of 1.7 μg J−1 this pulsed laser fragmentation in liquids (PLFL) proves to be an efficient route to colloidal CuI nanoparticles.
Co-reporter:Virgil Andrei, Kevin Bethke and Klaus Rademann
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 16) pp:NaN10707-10707
Publication Date(Web):2016/02/16
DOI:10.1039/C5CP06828B
We present a facile alternative to other well known strategies for synthesizing flexible thermoelectric materials. Instead of printing thin active layers on flexible substrates or doping conductive polymers, we produce thermoelectric pastes, using a mixture of graphite, copper(I) oxide and polychlorotrifluoroethene. The Seebeck coefficient of the investigated pastes varies between 10 and 600 μV K−1, while the electrical conductivity spans over an even wider range of 10−4 to 102 S m−1. Here, the influence of phenomena such as percolation on the electrical transport is revealed. The resulting power factor reaches 5.69 × 10−4 ± 0.70 × 10−4 μW m−1 K−2 for the graphite–polymer paste, with an unexpected minimum at a graphite molar fraction of approximately 0.4. The values are comparable to those of the powder mixtures, which are slightly higher, but less precisely tunable. Such compounds are further evaluated for practical applications. The graphite–polymer paste is used to exemplify, how a flexible thermoelectric sensor can be easily manufactured, step by step. Our results represent a proof of principle, that thermoelectric pastes are viable alternatives to current solutions. A further expansion of the scope for the composites can be achieved by using high performance thermoelectric materials and conductive polymers.
Co-reporter:Tanja Gnutzmann, Klaus Rademann and Franziska Emmerling
Chemical Communications 2012 - vol. 48(Issue 11) pp:NaN1640-1640
Publication Date(Web):2011/11/04
DOI:10.1039/C1CC16301A
An unusually fast crystallization of the organic glass former nifedipine has been observed. The crystallization process, starting from an amorphous film to crystalline material, was investigated by time resolved Raman microspectroscopy. The crystallization rates of the initially crystallizing metastable β-form are four orders of magnitude higher than those of previous studies.
