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Krishnamoorthy, Karthikeyan,M. S. P., Sudhakaran,Pazhamalai, Parthiban,Mariappan, Vimal Kumar,Mok, Young Sun,Kim, Sang-Jae The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.32
<P>The dry reforming of methane (DRM) using CO2 for the production of syngas (H2 and CO) has received increasing attention for reducing global CO2 emissions. The main drawback of DRM reactions is the limited reusability of the spent catalyst due to carbon deposition on its surface. Thus, designing an appropriate catalytic system is adequate to achieve increased syngas production with low carbon deposition, and developing smart strategies to reuse the carbon deposited spent catalyst is highly desirable. In this work, two dimensional siloxene sheet (silicon analog of graphene oxide) coated nickel foam is examined as a novel catalyst for the DRM reaction. The siloxene/Ni foam catalyst demonstrated superior catalytic performance in terms of conversion efficiencies (for CH4 and CO2) and syngas production (H2 and CO) with a high H2/CO ratio of 1.5. Further, the carbon deposited siloxene/Ni spent catalyst recovered after the DRM reaction was effectively re-utilized as electrodes for a symmetric supercapacitor (SSC) using an organic electrolyte. The fabricated SSC (using the spent catalyst as electrodes) delivered a high device capacitance (24.65 F g<SUP>−1</SUP>), high energy density (30.81 Wh kg<SUP>−1</SUP>), and high-power density (15 625 W kg<SUP>−1</SUP>) with a long cycle life. Considering that the estimated carbon cost for developing a supercapacitor electrode is about $15 per kilogram, our strategy to effectively reutilize the recovered carbon deposited spent catalyst for energy storage applications might be a promising and economical approach for utilization of the spent catalyst.</P>
Titanium carbide sheet based high performance wire type solid state supercapacitors
Krishnamoorthy, Karthikeyan,Pazhamalai, Parthiban,Sahoo, Surjit,Kim, Sang-Jae Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.12
<P>Two dimensional sheets based on transition metal carbides have attracted much attention in electrochemical energy storage sectors. In this work, we demonstrated the fabrication and performance of titanium carbide based wire type supercapacitors (WSCs) towards next generation energy storage devices. The layered titanium carbide sheets were prepared<I>via</I>selective extraction of Al from the precursor Ti2AlC using hydrofluoric acid and are extensively characterized using X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform-infrared spectroscopy, and laser Raman spectral analyses, respectively. The X-ray photoelectron spectroscopy studies confirmed the presence of oxygen and fluorinated functional groups attached on the surface of titanium carbide. The electrochemical studies of the fabricated titanium carbide WSC devices showed ideal capacitive properties with a specific length capacitance of 3.09 mF cm<SUP>−1</SUP>(gravimetric capacitance of about 4.64 F g<SUP>−1</SUP>), and specific energy density of about 210 nW h cm<SUP>−1</SUP>(in length) or 315 mW h kg<SUP>−1</SUP>(in gravimetric) with excellent cycling stability. Further, a detailed examination of the capacitive and charge-transfer behavior of titanium carbide WSCs has been investigated<I>via</I>electrochemical impedance analysis using Nyquist and Bode plots. Additionally, we have also demonstrated the practical application of the titanium carbide WSCs, highlighting the path for their huge potential in energy storage and management sectors.</P>
Ruthenium sulfide nanoparticles as a new pseudocapacitive material for supercapacitor
Krishnamoorthy, Karthikeyan,Pazhamalai, Parthiban,Kim, Sang Jae Pergamon Press 2017 Electrochimica Acta Vol. No.
<P><B>Abstract</B></P> <P>Transition metal chalcogenides received much attention as high performance electrode materials for energy storage devices during this decade. In this article, we demonstrated the sonochemical preparation of cubic RuS<SUB>2</SUB> nanoparticles with average size in the range of 20nm and investigated their supercapacitive properties in detail using cyclic voltammetry, charge-discharge analysis and electrochemical impedance spectroscopy, respectively. The RuS<SUB>2</SUB> electrode delivered a specific capacitance of 85Fg<SUP>−1</SUP> at a constant discharge current density of 0.5mAcm<SUP>−1</SUP> using a three electrode configuration. The RuS<SUB>2</SUB> symmetric supercapacitor device delivered a specific capacitance of 17Fg<SUP>−1</SUP> and excellent cyclic stability of about 96.15% capacitance retention over 5000 cycles. The electrochemical impedance spectroscopy (Nyquist and Bode) analysis together with the frequency dependent capacitance (real and imaginary) studies confirmed the ideal capacitive nature of the RuS<SUB>2</SUB> supercapacitor. The experimental findings ensure the potential application of RuS<SUB>2</SUB> nanoparticles as a novel electrode material for electrochemical energy storage devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> RuS<SUB>2</SUB> nanoparticles were prepared via sonochemical approach. </LI> <LI> RuS<SUB>2</SUB> based symmetric supercapacitor (SC) device was fabricated. </LI> <LI> Symmetric RuS<SUB>2</SUB> SC device delivered a specific capacitance of 17Fg<SUP>−1</SUP>. </LI> <LI> The RuS<SUB>2</SUB> SC device possesses capacitance retention of about 96.15% over 5000 cycles. </LI> </UL> </P>
Antibacterial Efficiency of Graphene Nanosheets against Pathogenic Bacteria via Lipid Peroxidation
Krishnamoorthy, Karthikeyan,Veerapandian, Murugan,Zhang, Ling-He,Yun, Kyusik,Kim, Sang Jae American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.32
<P>Graphene nanosheets are highly recognized for their utility toward the development of biomedical device applications. The present study investigated the antibacterial efficiency of graphene nanosheets against four types of pathogenic bacteria. Graphene nanosheets are synthesized by a hydrothermal approach (under alkaline conditions using hydrazine hydrate). UV–vis and X-ray diffraction show a maximum absorbance at 267 nm and appearance of new broad diffraction peak at 26°, which ensures the reduction of graphene oxide into graphene nanosheets. Stretching and bending vibrations of C–C bonds, chemical states, disorder, and defects associated with the graphene nanosheets are evaluated in comparison with graphene oxide. The minimum inhibitory concentration (MIC) of graphene nanosheets against pathogenic bacteria was evaluated by a microdilution method. MICs such as 1 μg/mL (against <I>Escherichia coli</I> and <I>Salmonella typhimurium</I>), 8 μg/mL (against <I>Enterococcus faecalis</I>), and 4 μg/mL (against <I>Bacillus subtilis</I>) suggest that graphene nanosheets have predominant antibacterial activity compared to the standard antibiotic, kanamycin. Measurement of free radical modulation activity of graphene nanosheets suggested the involvement of reactive oxygen species in antibacterial properties.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-32/jp3047054/production/images/medium/jp-2012-047054_0008.gif'></P>
Krishnamoorthy, Karthikeyan,Mariappan, Vimal Kumar,Pazhamalai, Parthiban,Sahoo, Surjit,Kim, Sang-Jae Elsevier 2019 Nano energy Vol.59 No.-
<P><B>Abstract</B></P> <P>The development of functional materials towards mechanical energy harvesting applications is rapidly increasing during this decade. In this study, we are reporting the mechanical energy harvesting properties of free-standing carbyne-enriched carbon film (prepared via dehydrohalogenation of PVDF). Physico-chemical characterizations such as X-ray diffraction, Fourier-transformed infrared spectroscopy, X-ray photoelectron spectroscopy, <SUP>13</SUP>C NMR spectroscopy, and laser Raman spectral analyses confirmed the formation of the carbyne-enriched carbon film. The Raman mapping analysis revealed the homogeneous distribution of cumulenic (β-carbyne) networks in carbonoid matrix of the prepared film. The mechanical energy harvesting properties of carbyne-enriched carbon film have been examined under various applied compressive forces. The carbyne-enriched carbon film based energy harvester generates a peak to peak voltage of 6.48 V using a periodic force of 0.2 N, and the output voltage is directly proportional to the levels of applied compressive force. The carbyne-enriched carbon film based energy harvester possesses an instantaneous power density of about 72 nW cm<SUP>−2</SUP> with excellent electromechanical stability. These experimental findings ensure the use of carbyne-enriched carbon film as a mechanical energy harvester for the first time, which can create new insights towards the development of carbon-based mechanical energy harvesters.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dehydrohalogenation of PVDF into carbyne-enriched carbon film is obtained. </LI> <LI> Spectroscopic studies confirmed the conversion of PVDF carbyne-enriched carbon film. </LI> <LI> Raman mapping revealed the homogenous distribution of cumulene in the prepared film. </LI> <LI> Carbyne-enriched carbon film is explored as a novel mechanical energy-harvester. </LI> <LI> Mechanism of energy harvesting properties of carbyne-enriched carbon is discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Mechanistic investigation on the toxicity of MgO nanoparticles toward cancer cells
Krishnamoorthy, Karthikeyan,Moon, Jeong Yong,Hyun, Ho Bong,Cho, Somi Kim,Kim, Sang-Jae The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.47
<P>Magnesium oxide nanoparticles (MgO NPs) are increasingly recognized for their applications in cancer therapy such as nano-cryosurgery and hyperthermia. The present study investigated the cytotoxic effects of magnesium oxide nanoparticles (MgO NPs) against normal lung fibroblast cells and different types of cancerous cells. MgO NPs exhibited a preferential ability to kill cancerous cells such as HeLa, AGS and SNU-16 cells. A detailed study has been undertaken to investigate the mechanism of cell death occurring in cancer cells (AGS cells) by the analysis of morphological changes, western blot analysis and flow cytometry measurements. Western blot analysis measurements suggested the role of apoptosis in cell death due to MgO exposure. MgO NPs enhanced ultrasound-induced lipid peroxidation in the liposomal membrane. Flow cytometry measurements using H<SUB>2</SUB>DCFDA showed that the toxicity of MgO NPs is attributed to the generation of reactive oxygen species, which further results in the induction of apoptosis in cancer cells. Our experimental results suggested the potential utility of MgO NPs in the treatment of cancer.</P> <P>Graphic Abstract</P><P>MgO nanoparticles exhibit an ability to kill cancer cells by inducing apoptosis through reactive oxygen species. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm35087d'> </P>