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Prasanth R.,Pondicherry University | Gopinath D.,Amrita Center for Nanosciences
Applied Physics Letters

Development of a therapeutic drugs based on nanoparticles requires a better understanding of the mechanism of selective cyto-toxic effects of nanopaticles over cancer cells. Scanning electrochemical microscopy provides opportunity to measure the real time chemical process at cell proximity in the presence of nanoparticle. Herein, the respiration process in nasopharyngeal cancer cells is investigated with the help of scanning electrochemical microscopy. The cell viability has been tested with MTT assay. The results show that ZnO nanoparticles have time and dose dependent effect in nasopharyngeal cancer cells and the cell respiration rate decreases with time. © 2013 American Institute of Physics. Source

Sivakumar N.,University of Madras | Sivakumar N.,Amrita Center for Nanosciences
Materials Chemistry and Physics

In the present study, nanostructured manganese zinc ferrite of 11 nm grain size was synthesized by co-precipitation technique and subsequently suitably heat treated to obtain higher grain sizes. The plot of temperature dependence of dc conductivity shows the semiconducting nature of samples. The observed changes in the electrical conductivity have been attributed with the influence of structural ordering upon annealing. The observed decrease in conductivity when the grain size is increased from 11 to 69 nm upon annealing is clearly due to the structural ordering which is evident from FESEM. © 2012 Elsevier B.V. All rights reserved. Source

Anjali P.,Amrita Center for Nanosciences | Sonia T.S.,Amrita Center for Nanosciences | Shakir I.,King Saud University | Nair S.V.,Amrita Center for Nanosciences | Balakrishnan A.,Amrita Center for Nanosciences
Journal of Alloys and Compounds

The present study demonstrates a novel approach by which 'bulk nanostructured' NiO micro bouquets can be processed into a high surface area electrode for supercapacitor applications. A detailed study has been performed to elucidate the impact of porosity and redox reactions on the electrochemical behavior. The spheres were synthesized using a soft template technique. An intrinsic correlation between the surface area, capacitance and the internal resistance has been deduced and explained on the basis of relative contributions from the faradic properties of NiO. These NiO spheres exhibited specific mass capacitance values as high as 1950 F g-1. Further, coin cells employing these rechargeable electrodes were also demonstrated which exhibits energy and power densities of 17 W h kg-1and 24 kW kg-1. It has been shown that these electrodes based on such bulk nanostructures can allow significant room for high performance supercapacitor devices. © 2014 Elsevier B.V. All rights reserved. Source

Paravannoor A.,Amrita Center for Nanosciences | Ranjusha R.,Amrita Center for Nanosciences | Asha A.M.,Amrita Center for Nanosciences | Vani R.,Amrita Center for Nanosciences | And 6 more authors.
Chemical Engineering Journal

Nanowires of NiO were successfully synthesized using a simple hydrothermal route. The nanowires were characterized for phase composition and morphology by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques, respectively. XRD analysis showed that the powders produced were of high purity cubic NiO phase. Selected area electron diffraction (SAED) analysis during TEM showed the growth direction of NiO nanowires in (100), while exhibiting an average diameter of ∼ 65nm. BET analysis showed these nanowires exhibiting a surface area of 153.2m2/g. These nanowires were electrophoretically deposited on titanium foils as thin layer (∼5μm thickness) and were studied for their capacitive behavior as electrodes for supercapacitor applications. Image analysis and atomic force microscopy (AFM) studies revealed the thin film coating to be highly porous (>50%). Cyclic voltammetry (CV) studies on these electrodes exhibited a specific mass capacitance of 750F/g with 12% capacitance fade at the end of 1000 cycles. The present study elucidates how NiO surface morphology and OH- adsorption/desorption behaviors underlying these electrodes impact the chemical and structural stability performance. © 2013 Elsevier B.V. Source

Ranjusha R.,Amrita Center for Nanosciences | Lekha P.,Amrita Center for Nanosciences | Subramanian K.R.V.,Amrita Center for Nanosciences | Shantikumar V.N.,Amrita Center for Nanosciences | Balakrishnan A.,Amrita Center for Nanosciences
Journal of Materials Science and Technology

Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy (SEM) showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a large area. X-ray diffraction (XRD) of ZNT layer showed substantially higher intensity for the (0002) diffraction peak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements of the ZNT layer showed an average thickness of ~7 μm. Diameter size distribution (DSD) analysis showed that ZNTs exhibited a narrow diameter size distribution in the range of 65-120 nm and centered at ~75 nm. The photoluminescence (PL) spectrum measurement showed violet and blue luminescence peaks that were centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet (UV) spectroscopy showed major absorbance peak at ~348 nm, exhibiting an increase in energy gap value of 3.4 eV. By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximum of incident photon-to-electron conversion efficiency in a visible region located at 520-550 nm range. © 2011 The Chinese Society for Metals. Source

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