Ferrocene-derivatized ordered mesoporous carbon as high performance counter electrodes for dye-sensitized solar cells

Ramasamy, E.,Lee, J. Pergamon Press ; Elsevier Science Ltd 2010 Carbon Vol.48 No.13

Ferrocene-derivatized large pore size mesocellular carbon foam (Fe-MCF-C) has been synthesized using divinylbenzene as a carbon source and mesocellular silica foam as a hard template. Cyclic voltammetric studies demonstrate a relatively faster electron transfer rate of Fe-MCF-C in K<SUB>3</SUB>Fe(CN)<SUB>6</SUB>/1M KNO<SUB>3</SUB> solution, as compared with pristine mesocellular carbon foam (MCF-C). Such an enhanced electrochemical property is beneficial for improving the cathodic reduction of tri-iodide in dye-sensitized solar cells (DSSCs). Under 1 sun illumination (100mWcm<SUP>-2</SUP>, AM 1.5G), Fe-MCF-C counter electrode based DSSC shows an energy conversion efficiency of 7.89%, which is 12% higher than that of solar cell based on pristine MCF-C counter electrode.

Large-pore sized mesoporous carbon electrocatalyst for efficient dye-sensitized solar cells

Ramasamy, Easwaramoorthi,Lee, Jinwoo Royal Society of Chemistry 2010 Chemical communications Vol.46 No.12

<P>A counter-electrode comprised of large-pore sized mesoporous carbon exhibits low charge transfer resistance in iodide/triiodide redox electrolyte, thus liquid and quasi-solid dye sensitized solar cells show 8.18% and 3.61% solar to electric energy conversion efficiency, respectively.</P> <P>Graphic Abstract</P><P>A counter-electrode comprised of large-pore sized mesoporous carbon exhibits low charge transfer resistance in iodide/triiodide redox electrolyte, thus liquid and quasi-solid dye sensitized solar cells show 8.18% and 3.61% solar to electric energy conversion efficiency, respectively. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b920916f'> </P>

Soft-Template Simple Synthesis of Ordered Mesoporous Titanium Nitride-Carbon Nanocomposite for High Performance Dye-Sensitized Solar Cell Counter Electrodes

Ramasamy, Easwaramoorthi,Jo, Changshin,Anthonysamy, Arockiam,Jeong, Inyoung,Kim, Jin Kon,Lee, Jinwoo American Chemical Society 2012 Chemistry of materials Vol.24 No.9

<P>Ordered mesoporous titanium nitride-carbon (denoted as OM TiN-C) nanocomposite with high surface area (389 m<SUP>2</SUP> g<SUP>–1</SUP>) and uniform hexagonal mesopores (ca. 5.5 nm) was facilely synthesized via the soft-template method. As a structure-directing agent, Pluronic F127 triblock copolymer formed an ordered structure with inorganic precursors, resol polymer, and prehydrolyzed TiCl<SUB>4</SUB>, followed by a successive heating at 700 °C under nitrogen and ammonia flow. In this study, the amorphous carbon within the parent OM TiO<SUB>2</SUB>-C acted as a rigid support, preventing structural collapse during the conversion process of TiO<SUB>2</SUB> nanocrystals to TiN nanocrystals. The OM TiN-C was then successfully applied as counter electrode material in dye-sensitized solar cells (DSCs). The organic electrolyte disulfide/thiolate (T<SUB>2</SUB>/T<SUP>–</SUP>) was introduced to study the electrocatalytic property of the OM TiN-C nanocomposite. Because of the existence of TiN nanocrystals and the defect sites of the amorphous carbon, the DSCs using OM TiN-C as a counter electrode showed 6.71% energy conversion efficiency (platinum counter electrode DSCs: 3.32%) in the organic electrolyte system (T<SUB>2</SUB>/T<SUP>–</SUP>). Furthermore, the OM TiN-C counter electrode based DSCs showed an energy conversion efficiency of 8.41%, whereas the DSCs using platinum as a counter electrode showed a conversion efficiency of only 8.0% in an iodide electrolyte system. The superior performance of OM TiN-C counter electrode resulted from the low charge transfer resistance, enhanced electrical conductivity, and abundance of active sites of the OM TiN-C nanocomposite. Moreover, OM TiN-C counter electrode showed better chemical stability in organic electrolyte compared with the platinum counter electrode.</P><P>Ordered mesoporous titanium nitride-carbon (OM TiN-C) nanocomposites were synthesized, for the first time, using a simple soft-template method. The iodine-free organic electrolyte dye-sensitized solar cells using OM TiN-C nanocomposite counter electrodes exhibited high efficiency (6.71%), that is, a performance 2-fold greater than that of conventional Pt counter electrode DSCs (fill factor: 0.33, efficiency: 3.32%).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2012/cmatex.2012.24.issue-9/cm203672g/production/images/medium/cm-2011-03672g_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm203672g'>ACS Electronic Supporting Info</A></P>

Magnetic, optical gold nanorods for recyclable photothermal ablation of bacteria

Ramasamy, Mohankandhasamy,Lee, Su Seong,Yi, Dong Kee,Kim, Kwangmeyung The Royal Society of Chemistry 2014 Journal of materials chemistry. B, Materials for b Vol.2 No.8

Solution synthesis of GeS and GeSe nanosheets for high-sensitivity photodetectors

Ramasamy, Parthiban,Kwak, Dohyun,Lim, Da-Hye,Ra, Hyun-Soo,Lee, Jong-Soo The Royal Society of Chemistry 2016 Journal of Materials Chemistry C Vol.4 No.3

<▼1><P>High-sensitivity photodetectors are reported using solution synthesized GeS and GeSe nanosheets.</P></▼1><▼2><P>We report the synthesis of 2D nanosheets of GeS and GeSe by facile solution based approaches. The synthesized nanosheets are single-crystalline in nature with lateral dimensions in micrometers. Band structures calculated from DFT calculations predicted a direct bandgap value of 1.67 and 1.37 eV for GeS and GeSe, respectively. The experimental bandgap values (GeS, <I>E</I>g = 1.6 eV and GeSe, <I>E</I>g = 1.2 eV) determined from optical measurements are slightly smaller than the predicted ones. Photoresponse measurements of GeS and GeSe nanosheets revealed that the nanosheets are extremely photoresponsive toward the incident light and exhibit a high photoresponsivity of up to 173 and 870 A W<SUP>−1</SUP> under a 405 nm laser diode, respectively. These values are several orders of magnitude higher than those of previous reports for graphene and many other metal chalcogenide nanosheet photodetectors. In addition, the photodetectors show a fast photoresponse time and a specific detectivity on the order of 10<SUP>13</SUP> Jones. These results show that both the GeS and GeSe nanosheets are promising narrow bandgap semiconductors for high performance photodetectors.</P></▼2>

Recent Nanotechnology Approaches for Prevention and Treatment of Biofilm-Associated Infections on Medical Devices

Ramasamy, Mohankandhasamy,Lee, Jintae Hindawi Publishing Corporation 2016 BioMed research international Vol.2016 No.-

<P>Bacterial colonization in the form of biofilms on surfaces causes persistent infections and is an issue of considerable concern to healthcare providers. There is an urgent need for novel antimicrobial or antibiofilm surfaces and biomedical devices that provide protection against biofilm formation and planktonic pathogens, including antibiotic resistant strains. In this context, recent developments in the material science and engineering fields and steady progress in the nanotechnology field have created opportunities to design new biomaterials and surfaces with anti-infective, antifouling, bactericidal, and antibiofilm properties. Here we review a number of the recently developed nanotechnology-based biomaterials and explain underlying strategies used to make antibiofilm surfaces. </P>

Direct one-pot synthesis of cinnamaldehyde immobilized on gold nanoparticles and their antibiofilm properties

Ramasamy, Mohankandhasamy,Lee, Jin-Hyung,Lee, Jintae Elsevier 2017 Colloids and surfaces. B, Biointerfaces Vol.160 No.-

<P><B>Abstract</B></P> <P>The objective of the present study was to develop a one-pot strategy to synthesis gold nanoparticle complexes using cinnamaldehyde, a potent antibiofilm agent which in its free form, exhibits high volatility and unstable nature. Hence, we developed cinnamaldehyde gold nanoparticles (CGNPs) in a single step to overcome the limitations of free cinnamaldehyde. Furthermore, reduction abilities of cinnamaldehyde under different experimental conditions, that is, varying precursor concentrations of cinnamaldehyde and gold, metal salts, pH, temperature, and light sources, were investigated. UV–vis spectroscopy, transmission electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and dynamic light-scattering measurements revealed that heat influenced the nanoparticle formation in the presence of cinnamaldehyde, and as produced cinnamaldehyde immobilized on gold nanoparticles were spherical, monodispersed, and stable by surface charge. CGNPs containing 0.01% cinnamaldehyde by weight exhibited effective biofilm inhibition of up to >80% against Gram positive bacteria (methicillin-sensitive and -resistant strains of <I>Staphylococcus aureus,</I> MSSA and MRSA, respectively) and Gram negative (<I>Escherichia coli</I> and <I>Pseudomonas aeruginosa</I>) and a fungus <I>Candida albicans</I>. In addition, CGNPs attenuated the virulence of <I>C. albicans</I> by inhibiting hyphae formation. Based on observations of their antibiofilm effects and confocal microscopy findings, CGNPs caused biofilm damage by direct contact. Thus, cinnamaldehyde appears to be a promising reduction material for the eco-friendly, one-pot synthesis of CGNPs with excellent antibiofilm activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> One-pot, cinnamaldehyde gold nanoparticle complexes (CGNPs) were produced. </LI> <LI> Heat plays predominant role in metal salt reduction with cinnamaldehyde. </LI> <LI> CGNPs exhibited antibiofilm activity against pathogens including fungi. </LI> <LI> Cinnamaldehyde is a potent reductant for nanoparticle synthesis. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Electrochemical Atomic Layer Deposition of CuIn_(1-x)Ga_xSe₂ on Mo Substrate

Ramasamy, Mukunthan,Jung, Chan-Yong,Yeon, Yu-Beom,Lee, Chi-Woo The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.14

<P>The chalcopyrite CuIn(1-x)GaxSe2 (CIGS) thin films were grown on Mo substrate by electrochemical atomic layer deposition (E-ALD) of superlattice sequencing 2InSe/2GaSe/1CuSe, recently developed on model Au surface by Stickney and coworkers (J. Electrochem. Soc. 161, D141 (2014)). The cyclic voltammetry studies were conducted on copper, selenium, indium and gallium on molybdenum substrate and CIGS films were grown by different numbers of superlattice sequencing. The deposited films were examined for phase and microstructure formations by X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning tunneling microscopy (STM) and energy dispersive spectroscopy (EDS). The XRD pattern corresponded to those of chalcopyrite crystalline phase of CIGS and the crystallite size increased with the number of cycles or periods of whole superlattice sequencing increased. The SEM and STM results were in line with those of XRD by showing that the particle size increased as the number of E-ALD cycles increased. The EDS results revealed the CIGS with near stoichiometry. Finally, the deposited E-ALD films were shown to be photoelectrochemically active with p-type conductivity. (c) The Author(s) 2017. Published by ECS. All rights reserved.</P>

β-Amyloid induces nuclear protease-mediated lamin fragmentation independent of caspase activation

Ramasamy, V.S.,Islam, Md.I.,Haque, Md.A.,Shin, S.Y.,Park, I.S. Elsevier Biomedical Press 2016 Biochimica et biophysica acta, Molecular cell rese Vol.1863 No.6

β-Amyloid (Aβ), a hallmark peptide of Alzheimer's disease, induces both caspase-dependent apoptosis and non-apoptotic cell death. In this study, we examined caspase-independent non-apoptotic cell death preceding caspase activation in Aβ42-treated cells. We first determined the optimal treatment conditions for inducing cell death without caspase activation and selected a double-treatment method involving the incubation of cells with Aβ42 for 4 and 6h (4+6h sample). We observed that levels of lamin A (LA) and lamin B (LB) were reduced in the 4+6h samples. This reduction was decreased by treatment with suc-AAPF-CMK, an inhibitor of nuclear scaffold (NS) protease, but not by treatment with z-VAD-FMK, a pan-caspase inhibitor. In addition, suc-AAPF-CMK decreased the changes in nuclear morphology observed in cells in the 4+6h samples, which were different from nuclear fragmentation observed in STS-treated cells. Furthermore, suc-AAPF-CMK inhibited cell death in the 4+6h samples. LA and LB fragmentation occurred in the isolated nuclei and was also inhibited by suc-AAPF-CMK. Together, these data indicated that the fragmentation of LA and LB in the Aβ42-treated cells was induced by an NS protease, whose identity is not clearly determined yet. A correlation between Aβ42 toxicity and the lamin fragmentation by NS protease suggests that inhibition of the protease could be an effective method for controlling the pathological process of AD.

Polyunsaturated fatty acid-based targeted nanotherapeutics to enhance the therapeutic efficacy of docetaxel

Ramasamy, Thiruganesh,Sundaramoorthy, Pasupathi,Ruttala, Hima Bindu,Choi, Yongjoo,Shin, Woo Hyun,Jeong, Jee-Heon,Ku, Sae Kwang,Choi, Han-Gon,Kim, Hwan Mook,Yong, Chul Soon,Kim, Jong Oh Informa Healthcare 2017 DRUG DELIVERY Vol. No.