Browsing by Author "Srivastava, S."

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    Electronic structure and simulated STM images of non-honeycomb phosphorene allotropes
    (American Institute of Physics Inc., 2018) Kaur, S.; Kumar, A.; Srivastava, S.; Tankeshwar, K.
    We have investigated the electronic structure and simulated STM images of various non-honeycomb allotropes of phosphorene namely ? - P, ? - P, ? - P and ? - P, within combined density functional theory and Tersoff-Hamman approach. All these allotropes are found to be energetically stable and electronically semiconductingwith bandgap ranging between 0.5-1.2 eV. Simulated STM images show distinctly different features in terms of the topography. Different maximas in the distance-height profile indicates the difference in buckling of atoms in these allotropes. Distinctly different images obtained in this study may be useful to differentiate various allotropes that can serve as fingerprints to identify various allotropes during the synthesis of phosphorene. ? 2018 Author(s).
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    H2 O2 sensing through electrochemically deposited thionine coated ITO thin film
    (CMB Association Publications, 2017) Singh, P.; Srivastava, S.; Singh, S. K.
    Progression and initiation of different diseases including pulmonary diseases, alzheimer’s and tumors are linked with the oxidative stress, an important cause of cell damage. Different antioxidant enzymes are involved in detoxifying reactive oxygen species including hydrogen peroxide (H2O2) that is generated in response to various stimuli and has important role in cell activation & bio-signaling processes. Herein, we developed hydrogen peroxide electrochemical sensor based on horseradish peroxidase (HRP) entrapped polymerized thionine (PTH) film. Electrochemical deposition of thionine (dye) on indium tin oxide (ITO) surface was carried out through chornoamperometry followed by cyclic voltammetry. Deposited thionine thin film obtained was checked for its stability at different scan rates. The PTH-modified electrodes showed linear dependence of peak current with scan rate within the range of 20 to 100 mV s−1. Thionine used as electron transfer mediator between heme site of HRP and electrode. Cyclic voltammetry showed increase in the reduction peak current due to electrocatalytic reduction of H2O2. The sensor detection limit range from 10-1 _ 102 μM and limit of detection was 0.1μM. The proposed sensor has good storage response, cost effective, high sensitivity and wide linear range that could be used for the fabrication of other enzyme based biosensors.
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    Stability and tunable electronic structure of planar phosphorus nanotubes
    (American Institute of Physics, 2019) Singh, S; Kaur, S; Gupta, S.K; Kumar, Ashok; Srivastava, S.
    The stability and electronic properties of planar phosphorous nanotubes with different chirality are investigated within the formulation of density functional theory. Armchair phosphorous nanotube (APNT) is found to be energetically most favorable with very small formation energy (0.08 eV). APNT also possess highest tensile strength (∼2 GPa), among the considered nanotubes. Armchair and helical PNTs are semiconducting while zigzag PNT is metallic in nature. We found that the application of strain and external electric field greatly modifies the electronic band structure of given PNTs. We believe that planar APNT can be realized and its tunable electronic properties may be useful for nanoelectronics. © 2019 Author(s).