Amrita Center for Nanosciences and Molecular Medicine

Cochin, India

Amrita Center for Nanosciences and Molecular Medicine

Cochin, India
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Ranjusha R.,Amrita Center for Nanosciences and Molecular Medicine | Prathibha V.,Amrita Center for Nanosciences and Molecular Medicine | Ramakrishna S.,National University of Singapore | Sreekumaran Nair A.,Amrita Center for Nanosciences and Molecular Medicine | And 7 more authors.
Scripta Materialia | Year: 2013

The present study investigates a novel approach by which MnO2 nanoparticle and camphoric carbon nanobead blends are coated on Ti-foils for rechargeable energy storage applications. Depending on the amount of nanocarbon blended onto the MnO2 nanoflake system, these thin film nanocomposite electrodes can exhibit a specific mass capacitance value as high as 1020 F g-1. It has been shown that electrodes based on such a composite system can allow significant room for improvement in the cyclic stability of a rechargeable electrode system.© 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Ranjusha R.,Amrita Center for Nanosciences and Molecular Medicine | Sreekumaran Nair A.,Amrita Center for Nanosciences and Molecular Medicine | Ramakrishna S.,National University of Singapore | Anjali P.,Amrita Center for Nanosciences and Molecular Medicine | And 6 more authors.
Journal of Materials Chemistry | Year: 2012

The present study demonstrates a novel approach by which titanium foils coated with MnO2 nanowires can be processed into a high surface area electrode for rechargeable energy storage applications. A detailed study has been performed to elucidate how surface morphology and redox reaction behaviors underlying these electrodes impact the cyclic and capacitive behavior of the electrode. These nanowires were synthesized hydrothermally and exhibited an aspect ratio in the order of 102. BET analysis revealed that these MnO2 nanowires show a high surface area of 44 m2 g -1. From the analysis of the relevant electrochemical parameters, an intrinsic correlation between the capacitance, internal resistance and the surface morphology has been deduced and explained on the basis of relative contributions from the faradic properties of the MnO2 in different electrolytes. Depending on the type of surface morphology incorporated, these thin film nanowire electrodes exhibited specific mass capacitance value as high as 1050 F g-1 and 750 F g-1 measured from cyclic voltammetry and charge-discharge curves respectively. It has been shown that electrodes based on such nanowires can allow significant room for improvement in the cyclic stability of a hybrid supercapacitor/battery system. Further, a working model supercapacitor in cylindrical form is also shown exhibiting a capacitance of 10 F. © 2012 The Royal Society of Chemistry.


Zhu P.,National University of Singapore | Reddy M.V.,National University of Singapore | Wu Y.,National University of Singapore | Peng S.,National University of Singapore | And 6 more authors.
Chemical Communications | Year: 2012

Mesoporous SnO 2 agglomerates with hierarchical structures and a high surface area were fabricated through a molten salt method. The SnO 2 demonstrated high photoelectric conversion efficiencies of 3.05% and 6.23% (with TiCl 4 treatment) in dye-sensitized solar cells, which are attributed to its dual functionality of providing high dye-loading and efficient light scattering. © 2012 The Royal Society of Chemistry.


Mini P.A.,Amrita Center for Nanosciences and Molecular Medicine | Balakrishnan A.,Amrita Center for Nanosciences and Molecular Medicine | Nair S.V.,Amrita Center for Nanosciences and Molecular Medicine | Subramanian K.R.V.,Amrita Center for Nanosciences and Molecular Medicine
Chemical Communications | Year: 2011

We report on the development and characterization of high performance supercapacitor electrodes synthesized using electrophoretic deposition of graphene, upon which the poly(pyrrole)-layer was electropolymerised. The highly capacitive electrode had a specific capacitance of 1510 F g-1, area capacitance of 151 mF cm-2 and volume capacitance of 151 F cm -3 at 10 mV s-1. © 2011 The Royal Society of Chemistry.


Lekha P.,Amrita Center for Nanosciences and Molecular Medicine | Balakrishnan A.,Amrita Center for Nanosciences and Molecular Medicine | Subramanian K.R.V.,Amrita Center for Nanosciences and Molecular Medicine | Nair S.V.,Amrita Center for Nanosciences and Molecular Medicine
Materials Chemistry and Physics | Year: 2013

In this present study, we demonstrate the size dependent charge transfer from CdTe quantum dots (QDs) into TiO2 substrate and relate this charge transfer to the actual behavior of a CdTe sensitized solar cell. CdTe QDs was synthesized using mercaptopropionic acid as the capping agent. The conduction band offset for TiO2 and CdTe QDs indicates thermodynamically favorable band edge positions for smaller QDs for the electron-transfer at the QD-TiO2 interface. Time-resolved emission studies were carried out for CdTe QD on glass and CdTe QD on TiO2 substrates. Results on the quenching of QD luminescence, which relates to the transfer kinetics of electrons from the QD to the TiO2 film, showed that at the smaller QD sizes the transfer kinetics are much more rapid than at the larger sizes. I-V characteristics of quantum dot sensitized solar cells (QDSSC) with different sized QDs were also investigated indicating higher current densities at smaller QD sizes consistent with the charge transfer results. The maximum injection rate constant and photocurrent were obtained for 2.5 nm CdTe QDs. We have been able to construct a solar cell with reasonable characteristics (Voc = 0.8 V, Jsc = 1 mA cm-2, FF = 60%, η = 0.5%)© 2013 Elsevier B.V. All rights reserved.


Ranjusha R.,Amrita Center for Nanosciences and Molecular Medicine | Sajesh K.M.,Amrita Center for Nanosciences and Molecular Medicine | Roshny S.,Amrita Center for Nanosciences and Molecular Medicine | Lakshmi V.,Amrita Center for Nanosciences and Molecular Medicine | And 7 more authors.
Microporous and Mesoporous Materials | Year: 2014

The present study investigates in detail the synthesis and characterization of PEDOT: PSS/MnO2 hybrid sponge electrodes for supercapacitor/ battery applications. These hybrid sponges were prepared using freeze drying technique and showed hierarchical pores ranging from micron to nanometric size. Scanning electron microscopy-energy dispersive X-ray showed uniform dispersion of MnO2 along the PEDOT: PSS matrix. Thermo gravimetric-differential thermal analysis showed higher thermal stability for these hybrid constructs compared to PEDOT: PSS sponges. From the electrochemical studies, an intrinsic correlation between overall specific capacitance, morphology and weight percentage of MnO2 in the PEDOT: PSS matrix has been defined and explained in KOH electrolyte system. High cyclic stability was observed at the end of 2000 cycles for these hybrid sponges with less than 5 % capacitance fading. These sponges exhibit mass specific capacitance values as high as 10688 F g-1 which was found to be 35% higher compare to PEDOT: PSS sponges as obtained from Weibull statistics. The application of these electrodes was explored in a fully functional asymmetric coin cell unit where an energy and power density of 200 mWh kg-1 and 6.4 kW kg-1, was obtained, respectively. © 2013 Elsevier B.V. All rights reserved.


Anish Madhavan A.,Amrita Center for Nanosciences and Molecular Medicine | Kalluri S.,Amrita Center for Nanosciences and Molecular Medicine | Chacko D.K.,Amrita Center for Nanosciences and Molecular Medicine | Arun T.A.,Amrita Center for Nanosciences and Molecular Medicine | And 5 more authors.
RSC Advances | Year: 2012

The present study reports the electrospinning of TiO2-graphene composite nanofibers to develop conductive nano-fiber mats using polyvinylpyrrolidone as a carrier solution. This carrier solution was sublimated at 450 °C to attain a complete conducting continuous nanofibrous network. It was observed during the annealing that as the graphene content was increased to 1 wt% the continuous fiber morphology was lost. Annealing did not have any impact on the fiber diameter (∼150 nm) or morphology as the graphene content was maintained between 0.0-0.7 wt%. The surface porosity of these samples was found be in the range of 45-48%. The presence of graphene in TiO2 nanofibers was confirmed using Raman spectroscopy. Photoluminescence spectroscopy showed excitonic intensity to be lower in graphene-TiO2 samples indicating that the recombination of photo-induced electrons and holes in TiO2 can be effectively inhibited in the composite nanofibers. Fluorescence spectroscopy was used to confirm this phenomenon where blue and quenched emissions were observed for the electrospun TiO2 nanofibers and composite fibers, respectively. Conductivity measurements showed the mean specific conductance values obtained for TiO2-graphene composites to be about two times higher values than that of the electrospun TiO2 fibers. Assembling these TiO2-graphene fiber composites as photoanodes in dye sensitized solar cells, an efficiency of 7.6% was attained. © 2012 The Royal Society of Chemistry.


Nandhini R.,Amrita Center for Nanosciences and Molecular Medicine | Mini P.A.,Amrita Center for Nanosciences and Molecular Medicine | Avinash B.,Amrita Center for Nanosciences and Molecular Medicine | Nair S.V.,Amrita Center for Nanosciences and Molecular Medicine | Subramanian K.R.V.,Amrita Center for Nanosciences and Molecular Medicine
Materials Letters | Year: 2012

In this letter, we report on the process of preparation of a high performance supercapacitor electrode using activated carbon of nanoscale size (<100 nm). The activated carbon was processed by high-energy ball milling of graphite followed by activation treatments with nitric acid and sulphuric acid. The activated carbon was coated on titanium substrates using electrophoretic deposition and subjected to a post-deposition annealing treatment at 100°C. The electrophoretically deposited thin film layer has adequate porosity with ultrafine pores (pores with diameter ranging from 20 Å to 100 Å) that constitute majority of number of pores (>95%) and hence maximally contribute to the surface area of the carbon for charge storage purposes. The designed supercapacitor electrode with nanoscale activated carbon not only has excellent storage capacity (specific capacitance of 1071 F g -1 and area capacitance of 0.48 F cm -2) but also good control of discharge when used as a power source. The above process used by us is a cost-effective and novel technique, which expands the application of activated carbon for high performance supercapacitor electrodes by achieving the desired performance. © 2012 Elsevier B.V.


Sebastian S.T.,Amrita Center for Nanosciences and Molecular Medicine | Jagan R.S.,Amrita Center for Nanosciences and Molecular Medicine | Rajagoplan R.,Amrita Center for Nanosciences and Molecular Medicine | Paravannoor A.,Amrita Center for Nanosciences and Molecular Medicine | And 4 more authors.
RSC Advances | Year: 2014

Camphoric carbon wrapped NiS powders have been profitably exploited to fabricate high surface area electrodes for Li storage. The NiS morphology showed a network of interconnected nanoscale units with rod like profiles which terminated into needle-like apexes spanning diameters of about 50-80 nm. These particles were pyrolyzed using a camphoric solution to form a carbon sheath wrapping. These carbon functionalized NiS powders were processed into high-surface-area cathodes for a fully functional coin cell unit. A detailed study was performed to elucidate the effect of carbon content on the performance of these coin cells. BET surface area analysis revealed that these carbon sheathed NiS could exhibit a high surface area of 32 m2 g -1 compared to pristine powders which exhibited surface area values of 20 m2 g-1. From the analysis of relevant electrochemical parameters, an intrinsic correlation between the specific capacity, internal resistance and temperature has been deduced. Relative contributions of capacitive and diffusion-controlled processes underlying these thin-film electrodes have been mathematically modeled. These thin-film electrodes exhibited specific capacity values as high as 500 mA h g-1 as determined from charge discharge curves. The present study shows that this functional material can provide the advantages of simple processing technique, low cost, and scalability. © The Royal Society of Chemistry 2014.


Anjusree G.S.,Amrita Center for Nanosciences and Molecular Medicine | Nair A.S.,Amrita Center for Nanosciences and Molecular Medicine | Nair S.V.,Amrita Center for Nanosciences and Molecular Medicine | Vadukumpully S.,Amrita Center for Nanosciences and Molecular Medicine
RSC Advances | Year: 2013

Two dimensional (2D) nanostructures such as graphene have been attracting increasing research interest in the recent past due to their superior material properties. Herein, we report a facile and scalable method for the production of a few layered graphene sheets and the synthesis of TiO2 nanoparticles on the surface of the prepared graphene sheets using a single step hydrothermal method. The composites prepared with different graphene loading were assessed for their photocatalytic degradation ability under visible light and in dye sensitized solar cells (DSC). The results showed that the average thickness of the obtained graphene sheets was 1.1 nm and the TiO2 nanoparticles were uniformly dispersed on the surface of the graphene. In the photodegradation of methyl orange (MO), the photoactivity of the composite (with 10 wt% graphene loading) was found to be three times better than bare TiO 2 nanoparticles. This increased activity is due to the synergistic effects of TiO2 nanoparticles and graphene sheets. For DSC, composites with 0.7 wt% graphene loading showed a maximum efficiency of 4.26%, 25% higher than without graphene. © The Royal Society of Chemistry 2013.

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