Browsing by Author "Kriti Sharma"

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Experimental and density functional theoretical study of the effects of chemical vapours on the vibrational spectra of nickel phthalocyanine thin films
(2011) G.S.S. Saini; Sukh Dev Dogra; Kriti Sharma; Sukhwinder Singh; S.K. Tripathi; Vasant Sathe; Ranjan K. Singh
We report the effects of chemical vapours on the Raman and infrared absorption spectra of α crystalline nickel phthalocyanine thin films. Transmission electron micrograph of the thin films suggests presence of nano-sized particles of nickel phthalocyanine in the thin film. Some vibrational bands show changes in their positions and/or intensities on exposure of thin films with chemical vapours. These changes have been interpreted on the basis of interactions of the vapours molecule with the central nickel ion and other peripheral atoms of the phthalocyanine ring. Density functional theory (DFT) calculations have been carried out to determine the probable geometric structures of the complexes of vapour and phthalocyanine molecules. Calculated geometric structures show in-plane and out-of-plane distortions in the phthalocyanine molecule. Calculations further suggest charge transfer between vapour and phthalocyanine molecules. © 2011 Elsevier B.V. ALl Rights Reserved.
Influence of carbon nanotubes reinforcement on the structural feature and bioactivity of SiO2–Al2O3–MgO–K2CO3–CaO–MgF2 bioglass
(Springer Science and Business Media Deutschland GmbH, 2021) Shweta; Chandkiram Gautam; Krishna Kishor Dey; Manasi Ghosh; Ravi Prakash; Kriti Sharma; Divya Singh
Various glass compositions were synthesized using a melt-quenching technique doped with different concentrations of carbon nanotubes (CNTs) from 0.1 to 0.7% in the glassy system SiO2–Al2O3–MgO–K2CO3–CaO–MgF2. Density was determined by employing a liquid displacement method. Several physical parameters such as molar volume (Vm), oxygen molar volume (Vo) were calculated and found to be decreases from 36.49 ± 0.729 to 24.28 ± 0.485 × 10–6 m3/mol, and 21.86 ± 0.437 to 14.60 ± 0.292 × 10–6 m3/mol, respectively. However, density and oxygen packing density (OPD) increases from 1.99 ± 0.099 to 2.98 ± 0.149 × 103 kg/m3 and 45.74 ± 0.914 to 68.49 ± 1.369 × 10–3 kg-atom/l with increasing content of CNT. In the present study, reinforcement effects of CNTs were explained using several spectroscopic techniques like Fourier transform infrared, ultraviolet–visible (UV–Vis), Raman, and nuclear magnetic resonance (NMR) spectroscopy, respectively. Based on Tauc plots of the UV–Vis spectra, the energy band gap was determined and their values decreased from 6.95 to 6.23 × 10–19 J which is owing to the formation of non-bridging oxygen (NBO) in the glassy matrix. Contact angle measurements were also performed to check the wettability of the glasses and their values increased with CNT % from 18.14° to 77.8°. 29Si-MAS-NMR spectroscopic study revealed the random distribution of two different cations, Ca 2 + and Mg 2 + within the glasses which lead to structural and topological frustration. To check the cell viability, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and alkaline phosphatase assay were also performed. Owing to outstanding stability in various fluids like saline water, distilled water, and hydrochloric acid, the fabricated glasses exhibited functional activities with an adequate proliferation of rat calverail osteoblast cells. Consequently, based on the various characterization techniques such as mechanical, tribological, and biological activities, the fabricated bioactive glasses can be used for biomedical and multifunctional applications. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.