Co-reporter:Akshay Kokil, Ambata M. Poe, Youngju Bae, Andrea M. Della Pelle, Paul J. Homnick, Paul M. Lahti, Jayant Kumar, and S. Thayumanavan
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 13) pp:9920
Publication Date(Web):June 19, 2014
DOI:10.1021/am5021759
Polymer solar cells fabricated in air under ambient conditions are of significant current interest, because of the implications in practicality of such devices. However, only moderate performance has been obtained for the air-processed devices. Here, we report that enhanced short circuit current density (JSC) and open circuit voltage (VOC) in air-processed poly(3-hexylthiophene) (P3HT)-based solar cells can be obtained by using a series of donor–acceptor dyes as the third component in the device. Power conversion efficiencies up to 4.6% were obtained upon addition of the dyes which are comparable to high-performance P3HT solar cells fabricated in controlled environments. Multilayer planar solar cells containing interlayers of the donor–acceptor dyes, revealed that along with infrared sensitization, an energy level cascade architecture and Förster resonance energy transfer could contribute to the enhanced performance.Keywords: bulk heterojunction solar cells; donor−acceptor dyes; planar multilayer solar cells; polymer solar cells
Co-reporter:Soumitra Satapathi, Hardeep Singh Gill, Sriya Das, Lian Li, Lynne Samuelson, Micah J. Green, Jayant Kumar
Applied Surface Science 2014 Volume 314() pp:638-641
Publication Date(Web):30 September 2014
DOI:10.1016/j.apsusc.2014.07.003
Abstract
Dye-sensitized solar cells (DSSCs) were fabricated using photoanodes made from graphene–TiO2 nanocomposites. The dependence of the size of graphene sheets on the cell performance was investigated. The experimental results indicated that cells loaded with the smaller graphene sheets yielded larger enhancement. The smaller graphene sheets improved the dye adsorption, leading to higher conversion efficiency. The DSSC incorporated with graphene sheets of 184 nm exhibited the largest enhancement in efficiency (∼49%) as compared to the cell without graphene.
Co-reporter:A. Kumar, P. Doradla, M. Narkhede, L. Li, L. A. Samuelson, R. H. Giles and J. Kumar
RSC Advances 2014 vol. 4(Issue 69) pp:36671-36674
Publication Date(Web):06 Aug 2014
DOI:10.1039/C4RA04923C
We report an easy and simple approach for making silver nanotubes (NTs) using electrospinning. Silver nanoparticles were first deposited on an electrospun polymer nanofiber template by dip-coating in aqueous medium. Subsequently, selective dissolution of the polymer core led to the formation of silver NTs. Average diameter of the NTs was 250 nm and wall thickness was about 50 nm. This method allows the synthesis of a large quantity of silver NTs with high yield. Wall thickness and porosity of the NTs could be readily tuned by varying the dipping time and concentration of the metal precursor. The approach developed is very general and could be used for fabricating NTs of a variety of noble metals, bi-metals and metal oxides.
Co-reporter:Preeti Yadav, Soumitra Satapathi, Meena Kumari, Akanksha Chaturvedi, Lian Li, Lynne A. Samuelson, Jayant Kumar, Sunil K. Sharma
Journal of Photochemistry and Photobiology A: Chemistry 2014 280() pp: 39-45
Publication Date(Web):15 April 2014
DOI:10.1016/j.jphotochem.2014.02.005
•Two-photon (TP) active 4-dimethylaminocinnamoyl coumarins were synthesized.•Strong TPF was observed for each of the compounds.•These coumarins exhibited considerable Stokes shifts and moderate fluorescence quantum efficiencies.•These coumarins have the potential to be used in the development of a biological imaging probe.A series of two-photon (TP) active 4-dimethylaminocinnamoyl coumarins were synthesized. These compounds exhibit red shift in absorption and considerable Stokes shift in emission spectra in comparison to the parent coumarin. Large TP absorption cross-sections were measured for all the coumarins in dilute solutions. A correlation between the chemical structure and TP characteristics was established. TP confocal microscopy revealed that these coumarin derivatives can be internalized by cancer cells rendering them a potential candidate as a label in TP confocal imaging.A series of two-photon (TP) active 4-dimethylaminocinnamoyl coumarins were synthesized that exhibit considerable Stokes shift in emission and can be internalized by cancer cells rendering them a potential candidate as a label in TP confocal imaging.Download full-size image
Co-reporter:Joshna Chittigori, Abhishek Kumar, Lian Li, Sammaiah Thota, Akshay Kokil, Lynne A. Samuelson, Daniel J. Sandman, Jayant Kumar
Tetrahedron 2014 70(4) pp: 991-995
Publication Date(Web):
DOI:10.1016/j.tet.2013.11.071
Co-reporter:Akshay Kokil, J. Matthew Chudomel, Paul J. Homnick, Paul M. Lahti and Jayant Kumar
RSC Advances 2013 vol. 3(Issue 36) pp:15626-15629
Publication Date(Web):12 Jul 2013
DOI:10.1039/C3RA40986D
A new strategy was developed for improving basic dye sensitized solar cell (DSSC) performance, using push–pull organic triarylamines with tunable frontier energy levels as additives in the DSSC electron shuttling electrolyte solution. A significant improvement in the device performance was observed and attributed to improved dye regeneration and hole transport.
Co-reporter:Dr. Akshay Kokil;J. Matthew Chudomel;Dr. Boqian Yang; Michael D. Barnes; Paul M. Lahti; Jayant Kumar
ChemPhysChem 2013 Volume 14( Issue 16) pp:3682-3686
Publication Date(Web):
DOI:10.1002/cphc.201300667
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:Akshay Kokil;Ke Yang
Journal of Polymer Science Part B: Polymer Physics 2012 Volume 50( Issue 15) pp:1130-1144
Publication Date(Web):
DOI:10.1002/polb.23103
Abstract
The charge transport characteristics of organic semiconductors are one of the key attributes that impacts the performance of organic electronic and optoelectronic devices in which they are utilized. For improved performance in organic photovoltaic cells, light-emitting diodes, and field-effect transistors (FETs), efficient transport of the charge carriers within the organic semiconductor is especially critical. Characterization of charge transport in these organic semiconductors is important both from scientific and technological perspectives. In this review, we shall mainly discuss the techniques for measuring the charge carrier mobility and not the theoretical underpinnings of the mechanism of charge transport. Mobility measurements in organic semiconductors and particularly in conjugated polymers, using space-charge-limited current, time of flight, carrier extraction by linearly increasing voltage, double injection, FETs, and impedance spectroscopy are discussed. The relative merits, as well as limitations for each of these techniques are reviewed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
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:Soumitra Satapathi, Lian Li, Abhishek Kumar, Haibin Huo, Robinson Anandakathir, Mengyan Shen, Lynne A. Samuelson, Jayant Kumar
Optics Communications 2011 Volume 284(Issue 14) pp:3612-3614
Publication Date(Web):1 July 2011
DOI:10.1016/j.optcom.2011.03.048
Two-photon-induced fluorescence from a soluble polythiophene containing urethane side groups has been investigated using femto-second laser pulses at 800 nm. Strong two-photon fluorescence was measured in polymer solution. The quadratic dependence of the fluorescence on the excitation laser intensity confirmed the two-photon process. The measured two-photon absorption cross-section is larger as compared to those of other reported polythiophenes. This polymer can be readily hydrolyzed to yield a water soluble polythiophene which could be useful in biological imaging.Research highlights► Two-photon-induced fluorescence from a soluble fluorescent polythiophene was studied using femto-second laser pulse at 800 nm. ► The two-photon-absorption cross section was calculated to be higher than other reported soluble polythiophenes. ► This polythiophene can be readily hydrolyzed to make it water soluble and used as a two-photon fluorescent probe.
Co-reporter:Abhishek Kumar, Mukesh K. Pandey, Robinson Anandakathir, Ravi Mosurkal, Virinder S. Parmar, Arthur C. Watterson, Jayant Kumar
Sensors and Actuators B: Chemical 2010 Volume 147(Issue 1) pp:105-110
Publication Date(Web):18 May 2010
DOI:10.1016/j.snb.2010.02.004
Coumarins comprise a very large class of phenolic compounds and are well known for their optical properties. Co-polymers of 4,8-dimethylcoumarins with poly(ethylene glycol) (PEG) and polydimethylsiloxane (PDMS) have been synthesized using Candida antarctica lipase as a catalyst under solventless condition. These co-polymers can be coated as thin films without significant aggregation of the chromophores. The low Tg of PEG and PDMS may facilitate porous structure in solid thin films which allows quencher molecules to easily diffuse in and out of these films. Fluorescence quenching of these co-polymers containing 4,8-dimethylcoumarin and their response to electron-deficient aromatic compounds, 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), have been investigated in both solution and thin film. The response of these polymeric sensors is promising and can easily detect DNT and TNT at few parts per billion levels.
Co-reporter:Bon-Cheol Ku;Dae Kyom Kim;Jun Seok Lee;Alexre Blumstein;Lynne A. Samuelson
Polymer Composites 2009 Volume 30( Issue 12) pp:1817-1824
Publication Date(Web):
DOI:10.1002/pc.20754
Abstract
Water-soluble single-walled carbon nanotube-polyacetylene [SWNT-PA, SWNT-P(2EPy-MeTf)] nanocomposites have been synthesized by using the surface initiated “grafting-from” method. The FT-IR spectra confirmed the formation of an amide bond between the functionalized SWNTs and the initiator, 4-(2-Aminoethyl) pyridine, to polymerize N-Methyl-2-ethynlypyridinium triflate (2EPy-MeTf). UV-vis spectroscopy indicated that the degree of polymerization of P(2EPy-MeTf) in the SWNT-polyacetylene composites is 15, based on the Lewis-Calvin equation. The SWNT-polyacetylene composites have been characterized by TGA, AFM, and TEM. From TGA analysis, the loading of SWNTs in the SWNT grafted ionic polyacetylenes is estimated to be 22%. AFM and TEM images clearly showed that the nanotube is wrapped with the PA. The SWNT-polyacetylene composites displayed high water solubility (8 mg/ml). The room temperature electrical conductivity of the doped SWNT-polyacetylene composites was found to be in the range of 10−3 to 10−4 S/cm, an order of magnitude of increase over neat P(2EPy-MeTf) and a two order of magnitude increase over Dendrimer-polyacetylen composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Co-reporter:Seong-Cheol Kim;James Whitten
Macromolecular Research 2009 Volume 17( Issue 9) pp:631-637
Publication Date(Web):2009 September
DOI:10.1007/BF03218921
This study examined the unique self-doping behavior of carboxylated polyaniline (PCA). The selfdoped PCA was synthesized using an environmentally benign enzymatic polymerization method with cationic surfactants. XPS showed that HCl-doped PCA contained approximately 34% of protonated amines but selfdoped PCA contained 9.6% of the doped form of nitrogen at pH 4. FTIR and elemental analysis showed that although the PCA was doped with the proton of strong acids at low pH via the protonation of amines, the selfdoping mechanism of PCA at pH > 4 was mainly due to hydrogen bonding between the carboxylic acid group and amine group.
Co-reporter:PilHo Huh, Fadong Yan, Lian Li, Myunghwan Kim, Ravi Mosurkal, Lynne A. Samuelson and Jayant Kumar
Journal of Materials Chemistry A 2008 vol. 18(Issue 6) pp:637-639
Publication Date(Web):04 Jan 2008
DOI:10.1039/B715334A
A simple and low cost methodology for fabricating one and two dimensional periodic ZnO nanostructures utilizing surface relief patterns on azopolymer films as templates is demonstrated.
Co-reporter:Bon-Cheol Ku, Dong Wook Kim, Diane Steeves, Ramaswamy Nagarajan, Alexandre Blumstein, Jayant Kumar, Philip W. Gibson, Jo An Ratto, Lynne A. Samuelson
Composites Science and Technology 2008 Volume 68(15–16) pp:3215-3219
Publication Date(Web):December 2008
DOI:10.1016/j.compscitech.2008.08.009
Nanocomposite films consisting of amphiphilic ionic polyacetylenes (P2EPy-R) and layered aluminosilicates (saponite) have been prepared through electrostatic layer-by-layer assembly. The water vapor barrier properties of the nanocomposite films coated on Nafion™ film have been studied. The Nafion film coated with poly(N-octadecyl-2-ethynylpyridinium bromide) (P2EPy-C18) and aluminosilicates showed 22 times higher diffusion resistance to water vapor and 95% reduction in water vapor permeability when compared with the pristine Nafion control film. The X-ray diffraction data, UV–vis absorption spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM) suggest a strong tendency of micellization of P2EPy-C18 polymer and ordered structure on the surface of aluminosilicate nanosheets compared to short alkyl side chains, C12, C6, and C0. The micellized and ordered structure of P2EPy-C18 between aluminosilicate could explain the improved hydrophobic barrier properties of P2EPy-C18/aluminosilicate nanocomposites.
Co-reporter:Dongwook Kim;Joonsuk Lee;Seong-Cheol Kim;Ke Yang;Yanping Wang;Ferdino F. Bruno and;Lynne A. Samuelson
Macromolecular Rapid Communications 2007 Volume 28(Issue 12) pp:1356-1360
Publication Date(Web):6 JUN 2007
DOI:10.1002/marc.200700133
Self-doped sulfonated polyaniline (PSA) has been synthesized on the surface of micellar nanoparticles made from positively charged surfactants by biocatalysis. The conformation forced by the electrostatic charge interactions between the positively charged micelle and the negatively charged PSA increases the conductivity of the PSA by three orders of magnitude. The pure PSA recovered from ion exchange, however, shows quite similar electrical properties compared with sulfonated polyanilines reported earlier. The increased conductivity of PSA complexes is as a result of the increased charge carrier concentration caused by a certain conformational locking.
Co-reporter:M. Kim;B. Kang;S. Yang;L. A. Samuelson;C. Drew;J. Kumar
Advanced Materials 2006 Volume 18(Issue 12) pp:1622-1626
Publication Date(Web):21 JUN 2006
DOI:10.1002/adma.200502690
Fabrication of a periodic array of anatase wires/dots (see figure) is demonstrated using simple laboratory equipment without the use of high vacuum or chemical vapor deposition. Nanoparticles of TiO2 are selectively confined in the troughs of microstructured surface-relief patterns on polymer films using electrostatic layer-by-layer deposition. Nanopatterning and sintering of anatase is achieved by pyrolyzing the polymer films in air.
Co-reporter:Yanping Wang, Ke Yang, Xiaoyu Wang, Ramaswamy Nagarajan, Lynne A. Samuelson, Jayant Kumar
Organic Electronics 2006 Volume 7(Issue 6) pp:546-550
Publication Date(Web):December 2006
DOI:10.1016/j.orgel.2006.07.013
Solid state dye-sensitized solar cells were fabricated using polydiacetylene as the hole transport material. The polydiacetylene was incorporated into the nanoporous TiO2 film by solution casting of an amphiphilic diacetylene and subsequent in situ polymerization. Polydiacetylenes as prepared via solid state polymerization are crystalline, exhibiting high charge carrier mobility. Our preliminary experiments demonstrated a short-circuit current density of 3.73 mA/cm2 and an overall power conversion efficiency of 0.62% under AM 1.5 illumination (100 mW/cm2).
Co-reporter:M. Kim;R. Nagarajan;J. H. Snook;L. A. Samuelson;J. Kumar
Advanced Materials 2005 Volume 17(Issue 5) pp:
Publication Date(Web):3 MAR 2005
DOI:10.1002/adma.200400693
Fabrication of homogeneous, flexible, polymeric, dielectric Bragg gratings is demonstrated. The Bragg grating is assembled on a poly(ethylene terephthalate) film using polymeric colloidal microspheres of polystyrene (PS) and poly(methyl methacrylate) (PMMA) (see Figure). The microspheres are stacked successively with precise control at the nanometer scale and the gratings, free of metal and other inorganic materials, cover a relatively large area.
Co-reporter:S. Yang;K. Yang;L. Niu;R. Nagarajan;S. Bian;A. K. Jain;J. Kumar
Advanced Materials 2004 Volume 16(Issue 8) pp:
Publication Date(Web):26 APR 2004
DOI:10.1002/adma.200306537
Co-reporter:Ravi Mosurkal, Jin-An He, Ke Yang, Lynne A. Samuelson, Jayant Kumar
Journal of Photochemistry and Photobiology A: Chemistry 2004 Volume 168(Issue 3) pp:191-196
Publication Date(Web):1 December 2004
DOI:10.1016/j.jphotochem.2004.05.004
We have carried out a study on a number of organic dyes to identify photosensitizers for dye-sensitized photovoltaic applications with well matched redox potentials and good absorption characteristics. Triphenylmethyne, anthraquinone and xanthene dyes with catechol groups were chosen as the most promising dyes for fabrication of nanocrystalline TiO2 based dye-sensitized photovoltaic (DSPV) cells using a liquid electrolyte. From our study, a xanthene dye, 9-phenyl-2,3,7-trihydroxy-6-fluorone is found to be efficient photosensitizer in DSPV cells compared to other dyes when a liquid electrolyte is used. Redox potentials, absorption and photovoltaic properties of these dyes are presented. Two possible ways of electron transfer, namely direct charge transfer via formation of strong charge transfer complexes and the conventional excited state electron injection through the HOMO–LUMO energy level matching are discussed.
Co-reporter:Amarjeet Kaur, Mario J. Cazeca, Sandip K. Sengupta, Jayant Kumar, Sukant K. Tripathy
Synthetic Metals 2002 Volume 126(2–3) pp:283-288
Publication Date(Web):14 February 2002
DOI:10.1016/S0379-6779(01)00570-7
The electroluminescence behavior of polymeric light emitting diodes based on poly[2-(3-thienyl)ethanol-n-butoxy carbonyl-methylurethane] (PURET) as an emitting layer has been studied. The organic layer has been doped with varying concentrations of 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) dye. On addition of a very small amount of the dye, a voltage tunable multicolor emission with enhanced luminance ∼1000 cd/m2 has been observed. The mechanism of conduction responsible for color tuning has been explored.
Co-reporter:Ke Yang, Jayant Kumar, Dong-Chan Lee, Daniel J. Sandman, Sukant K. Tripathy
Optics Communications 2002 Volume 201(1–3) pp:197-206
Publication Date(Web):1 January 2002
DOI:10.1016/S0030-4018(01)01646-7
The fifth-order electroabsorption spectroscopy is performed on a spin-coated polydiacetylene film, poly[Bis-p-chlorocinnamate of 10,12-Docosadiyn-1,22-diol] (PDA-ClCin-22). The fifth-order spectrum is composed of the response of linearly allowed transitions and the response of a two-photon state. These responses are consistent with our previously proposed model. The fifth-order spectrum has better resolution than the linear and third-order spectrum, and it reveals more detailed structures.
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:PilHo Huh, Fadong Yan, Lian Li, Myunghwan Kim, Ravi Mosurkal, Lynne A. Samuelson and Jayant Kumar
Journal of Materials Chemistry A 2008 - vol. 18(Issue 6) pp:NaN639-639
Publication Date(Web):2008/01/04
DOI:10.1039/B715334A
A simple and low cost methodology for fabricating one and two dimensional periodic ZnO nanostructures utilizing surface relief patterns on azopolymer films as templates is demonstrated.
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
![Poly[bis(3-dodecyl-2-thienyl)-2,2'-dithiophene-5,5'-diyl]](http://img.cochemist.com/ccimg/827400/827343-06-6.png)
![Poly[bis(3-dodecyl-2-thienyl)-2,2'-dithiophene-5,5'-diyl]](http://img.cochemist.com/ccimg/827400/827343-06-6_b.png)
