Kaustav Bhattacharjee

Self-sacrificial template directed hydrothermal route to kesterite-Cu2ZnSnS4 microspheres and study of their photo response properties

In this work, a self-sacrificial template directed hydrothermal route to synthesize Cu2ZnSnS4 (CZTS) 3D-hierarchical microspheres in the presence of citric acid is reported. The phase purity and morphology of the as-synthesized product were optimised. Citric acid plays a key role in reducing the chance of phase segregation and at the same time it helps in the formation of the 3D structure by affecting the crystal growth process. A time dependent growth study of the microspheres has been performed and a possible growth mechanism is proposed. UV-Vis absorption analysis shows that the material has a strong absorption in the visible range with a direct band gap of 1.45 eV. The photoelectric response of the sample has also been studied which shows significant photo current for the sample fabricated into thin films. Thus the as synthesized CZTS microspheres are an optimum candidate for use as an absorber layer in solar cell devices.

pH responsive cylindrical MSN for oral delivery of insulin-design, fabrication and evaluation.

Abstract Objective: The objective of the present study was to develop novel PMV [poly (methacrylic acid-co-vinyl triethoxylsilane)]-coated mesoporous silica nanoparticles (MSN) with improved hypoglycemic effect for oral insulin (INS) delivery. Methods: MSN was synthesized under acidic condition using Pluronic® P 123 and Tetra ethoxy orthosilane. Surfactant was removed by calcination. Calcined MSN was coated with pH sensitive polymer PMV. Cytotoxicity of this coated MSN was evaluated by MTT assay using CHO-K1 cell line. Different MSN samples were characterized with BET surface area analyzer, FESEM, TEM, FT-IR, XRD, TG-DTA. In vivo study was performed using male rats. Pharmacokinetic study was conducted using HPLC. Results and discussion: Highest surface area (304.3921 m2/g) was observed in case of calcined sample. Adsorption pore width of final coated sample was highest (64.7844 nm) compared with others. No noticeable cytotoxicity was observed for this coated support. The entrapment efficiency of insulin was found to be 39.39%. In vitro studies were done at different pH using Franz-diffusion cell. Results showed significant release at pH 7.4. Cumulative drug release over a period of 6 h was more than 48% at this systemic pH. Effect of this MSN-PMV-INS on blood glucose level was retained for 16 h. This novel formulation has shown 73.10% relative bioavailability of insulin. Conclusion: A novel-coated mesoporous silica support was successfully developed for delivery of insulin through oral route.

Effect of particle size distribution on the structure, hyperfine, and magnetic properties of Ni0.5Zn0.5Fe2O4 nanopowders

Ni0.5Zn0.5Fe2O4 nano powders were synthesized by an auto combustion method and then heat treated at different temperatures in air for a fixed time. As a consequence, a distribution in particle size and strain was incorporated within the specimens, as estimated from the Rietveld refinement analysis of the powder x-ray diffraction data. The changes in the microstructure and crystal structure parameters were carefully extracted through the refinement analysis. Thermal annealing causes increment in the dispersion and mean of the size distribution. Reallocation of cations in the lattice sites occur as a consequence of the heat treatment which was manifested in their altered unit cell length (a), r.m.s. strain (⟨e2⟩1/2), oxygen positional parameter (u), metal-oxygen bond lengths ( ROA and ROB), and the band positions (ν1and ν2) in the vibrational spectroscopy. We also investigate the hyperfine and magnetic properties of the samples using different instrumental techniques (with different operating time scales) l...