Pratima Chauhan

Surface Functionalization of TiO2 with Plant Extracts and their Combined Antimicrobial Activities Against E. faecalis and E. Coli

Abstract : The aim of this study is to enhance the antibacterial activity of TiO 2 by pure plant extracts of Bauhinia variegata and Tinospora. cordifolia by making a composite of plant extract and TiO 2 . Plant extracts, TiO 2 and plant extracts/TiO 2 composites were investigated against two bacterial strain Enterococcus faecalis and Escherichia coli . X-ray diffraction investigations have confirmed the presence of TiO 2 nanoparticles in the plant extract/TiO 2 nanocomposites. UV-visible investigations have shown an enhanced photocatalytic activity of plant extract/TiO 2 nanocomposites compared to that of pure TiO 2 and pure plant extract. Plant extract/TiO 2 nanocomposites have shown various level of antibacterial activity on different test microorganisms. The highest antibacterial potentiality expressed in terms of zone of inhibition (ZOI) in mm was exhibited by the aqueous extract of Bauhinia variegata /TiO 2 (45 mm against Enterococcus faecalis and 30 mm against Escherichia coli ) and benzene extract of Tinospora cordifolia /TiO 2 (26 mm) nanocomposites. This is the first study on these types of bio-nano composite materials and it serves as basis for further research on these types of composite materials as a potent antibacterial agent.

Effect of Indium Doping and Annealing on Photoconducting Property of Wurtzite type CdS

In this paper we observed the effect of doping and annealing on the dark current and anomalous photoconducting behavior of hexagonal wurtzite CdS, synthesized by solid state reaction method. Undoped CdS sample shows higher anomalous behavior in photoconductivity as well as contains larger dark current of 19 nA. With the doping of Indium in CdS, dark current decreases from 19 nA to 1 nA but the anomalous behavior is not completely removed. While, after annealing at 150°C for four hour, indium doped CdS sample shows good switching property with rise and decay time of 360 ± 10 & 322 ± 6 seconds respectively. The anomalous photoconducting behavior is completely removed from annealed sample. X-ray diffraction patterns confirm the existence of hexagonal wurtzite phase of indium doped and undoped CdS samples while energy dispersion X-ray spectrum exhibits the elemental presence of cadmium, indium & sulfur in the indium doped sample. UV-Visible absorption spectra show the blue shift in absorption edge on indium doping from 475 nm to 425 nm in comparison to undoped sample. Photoluminescence spectra confirm the indium doping and reveal that annealed CdS sample has lesser defects among other samples due to which annealed sample has best switching performance.

Gas sensing performance of nano zinc oxide sensors

We report nano Zinc Oxide (ZnO) synthesized by sol-gel method possessing the crystallite size which varies from 25.17 nm to 47.27 nm. The Scanning electron microscope (SEM) image confirms the uniform distribution of nanograins with high porosity. The Energy dispersion X-ray (EDAX) spectrum gives the atomic composition of Zn and O in ZnO powders and confirms the formation of nano ZnO particles. These factors reveals that Nano ZnO based gas sensors are highly sensitive to Ammonia gas (NH3) at room temperature, indicating the maximum response 86.8% at 800 ppm with fast response time and recovery time of 36 sec and 23 sec respectively.

Fungicidal activity of silver nanoparticles against Alternaria brassicicola

This work highlighted the fungicidal properties of silver nanoparticles against Alternaria brassicicola. Alternaria brassicicola causes Black spot of Cauliflower, radish, cabbage, kale which results in sever agricultural loss. We treat the synthesised silver nanoparticles (AgNPs) of 10, 25, 50, 100 and 110 ppm concentrations against Alternaria brassicicola on PDA containing Petri dish. We calculated inhibitory rate (%) in order to evaluate the antifungal efficacy of silver nanoparticles against pathogens. Treatment with 100ppm AgNPs resulted in maximum inhibition of Alternaria brassicicola i.e.92.2%. 110ppm of AgNPS also shows the same result, therefore 100ppm AgNPs was treated as optimize concentration. AgNPs effectively inhibited the growth of a Alternaria brassicicola, which suggests that AgNPs could be used as fungicide in plant disease management. Further research and development are necessary to translate this technology into plant disease management strategies.

Study of pressure induced phase transformation in CTAB capped CdS nanoparticles

Effect of high pressure on as prepared 20mM CTAB capped CdS nanoparticles (size ~4nm) has been analyzed in this paper. Raman scattering has been used to observe the phase transition pressure. X-ray diffraction pattern is used for structural characterization. Raman scattering predicts the phase transition occur from mixed cubical phase to rock salt phase above 6.6 GPa. One of the representative XRD pattern at 9.7 GPa confirms the existence of rock salt phase above 6.6 GPa.

Preparation of silver nanoparticles at low temperature

Silver from ancient time is used as antimicrobial agent in the bulk form but now with the advancement in nanotechnology silver in the form of nanoparticles shown potential effect against microbes which make us easy to fight with many diseases plants and animals. In this work silver nanoparticles were synthesized by chemical routes using sodium borohydride as reducing agent at low temperature. The particles were characterized through UV-Visible spectroscopy as well as X-Ray Diffraction. The UV-visible spectra of silver nanoparticles exhibited absorption at 425 cm; the crystallite size of the particles is between 19nm to 39nm. EDAX graph shows two peaks of silver and oxygen. Water absorbed by silver nanoparticles was removed by the calcinations.