Browsing by Author "Srivastava, S"

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Adsorption of nucleobases on different allotropes of phosphorene
(American Institute of Physics, 2019) Jakhar, M; Kumar, Ashok; Srivastava, S; Parida, P; Tankeshwar, K.
There has been tremendous interest in low-dimensional quantum systems during past two decades, fueled by a constant stream of striking discoveries and also by the potential for, and realization of, new state-of-the-art electronic device architectures. In this paper, our work includes the structural, electronic and optical properties of nucleobase (Adenine(A), Cytosine(C), Guanine(G), Thymine(T)) adsorbed on different allotropes of phosphorene (α, β, γ). From the optical absorption spectra of different nucleobases when adsorbed on the surface of phosphorene, we could optically probe different Nucleobases. As phosphorene shows different spectra for different nucleobases, it behaves as a bio-sensor to detect various nucleobases. © 2019 Author(s).
Energetics and electronic structure of novel hybrid dumbbell monolayers
(American Institute of Physics, 2019) Kaur, S; Singh, J; Kumar, Ashok; Srivastava, S; Tankeshwar, K.
We report three new hybrid monolayers (C6P4, C6N4 and N6P4) of group-IV and group-V elements in dumbbell structure using density functional theory calculations. C6P4, C6N4 possess sp2 as well as sp3 hybridization in their honeycomb dumbbell structure while N6P4 possess only the sp3 hybridization in its non-honeycomb but dumbbell structure. The magnitude of cohesive energy of these hybrid monolayers suggests that C6N4 is the most favorable monolayer to be formed. We found that C6P4 is metallic while C6N4 and N6P4 are semiconductors. Also, we report as a representative case, the systematic structural phase transition from LHD-C to a new phosphorous allotrope which has been suggested to exists in our cohesive energy calculations. The reported monolayers join the family of two dimensional materials and may possess application in nanoelectronic devices. © 2019 Author(s).
Molecular mechanisms of action of epigallocatechin gallate in cancer: Recent trends and advancement
(Academic Press, 2020) Aggarwal, V; Tuli, H.S; Tania, M; Srivastava, S; Ritzer, E.E; Pandey, A; Aggarwal, D; Barwal, T.S; Jain, A; Kaur, G; Sak, K; Varol, M; Bishayee, A.
Epigallocatechin gallate (EGCG), also known as epigallocatechin-3-gallate, is an ester of epigallocatechin and gallic acid. EGCG, abundantly found in tea, is a polyphenolic flavonoid that has the potential to affect human health and disease. EGCG interacts with various recognized cellular targets and inhibits cancer cell proliferation by inducing apoptosis and cell cycle arrest. In addition, scientific evidence has illustrated the promising role of EGCG in inhibiting tumor cell metastasis and angiogenesis. It has also been found that EGCG may reverse drug resistance of cancer cells and could be a promising candidate for synergism studies. The prospective importance of EGCG in cancer treatment is owed to its natural origin, safety, and low cost which presents it as an attractive target for further development of novel cancer therapeutics. A major challenge with EGCG is its low bioavailability which is being targeted for improvement by encapsulating EGCG in nano-sized vehicles for further delivery. However, there are major limitations of the studies on EGCG, including study design, experimental bias, and inconsistent results and reproducibility among different study cohorts. Additionally, it is important to identify specific EGCG pharmacological targets in the tumor-specific signaling pathways for development of novel combined therapeutic treatments with EGCG. The present review highlights the ongoing development to identify cellular and molecular targets of EGCG in cancer. Furthermore, the role of nanotechnology-mediated EGCG combinations and delivery systems will also be discussed. � 2020 Elsevier Ltd
Novel phosphorus-based 2D allotropes with ultra-high mobility
(Institute of Physics Publishing, 2020) Kaur, S; Kumar, A; Srivastava, S; Tankeshwar, K; Pandey, R.
Electronic structure calculations based on density functional theory were performed to investigate structural, mechanical, and electronic properties of phosphorene-based large honeycomb dumbbell (LHD) hybrid structures and a new phosphorene allotrope, referred to as ??-P. The LHD hybrids (i.e., X6P4; X being C or Si or Ge or Sn) and ??-P have significantly higher bandgaps than the corresponding pristine LHD structures, except the case of C6P4, which is metallic. ??-P is found to be a highly flexible p-type material which shows strain-engineered photocatalytic activity in a highly alkaline medium. The carrier mobility of the considered systems is as high as 105 cm2 V-1 s-1 (specifically the electron mobility of LHD structures). The calculated STM images display the surface morphologies of the LHD hybrids and ??-P. The predicted phosphorus-based 2D structures with novel electronic properties may be candidate materials for nanoscale devices. - 2020 IOP Publishing Ltd.
Stability and electronic properties of two dimensional pentagonal layers of palladium chalcogenides
(American Institute of Physics, 2019) Kumar, Ashok; Jakhar, M; Srivastava, S; Tankeshwar, K.
We report structural and electronic properties of pristine and hybrid monolayers/bilayers of Pd chlcogenides within state-of-the-art density functional theory (DFT) calculations. The calculated cohesive energy suggests hybrid systems to be more stable than pristine monolayer/bilayer system. The considered structures show indirect band gap which get reduced on going from monolayer to bilayers. Spin-orbit coupling (SOC) further reduce the bandgap by shifting the band edges towards Fermi level. The reduction in band gap of hybrid bilayers is more pronounced which is attributed to the electronegativity difference between chalcogen S/Se atoms and greater charge redistribution between the layers. We believe that our theoretical study will add more 2D materials in the fascinating class of new 2D family and may guide the experimentalists to realize them for various future nano-electronic applications. © 2019 Author(s).