Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemical vapour deposition using the b-diketonate complex, vanadyl acetylacetonate, as the precursor. It is found that nearly monophasic, monoclinic VO 2 (M) films are formed in the narrow temperature range 475-520 uC, films formed outside this range comprising significant proportions of other vanadium oxide phases beside VO 2 (M). The microstructure of these well-crystallized films varies significantly with temperature in this range. Films grown at 475 uC are dense and have a very strong (200) orientation. At 520 uC, films are somewhat porous, and display little preferred orientation. Film microstructure influences the semiconductor-metal transition noticeably. Films deposited at 475 uC have a large change in resistance at 66 uC, and display a small temperature hysteresis in the transition. The transition temperature in films grown at 520 uC is higher (72 uC), whereas the change in resistance is smaller and the hysteresis larger. An attempt has been made to understand the unusual microstructure of VO 2 films grown on glass substrates. The variation in the phase transition characteristics is interpreted in terms of the observed film microstructure. The thermal properties of the CVD precursor are also reported.

Silver nanospheres (AgNS) with SPR band ∼417 nm was synthesized by Green synthesis, using a pre‐hydrolysed liquor (PHL) of Nilgiri wood without any pretreatment. The synthesis was carried out at room temperature and was complete within three hours. The reduction and stabilization of silver is brought about by hemicelluloses present in the pre‐hydrolysed liquor. Electrochemical oxidation of nitrite on glassy carbon electrode (GCE) modified with the AgNS in 0.1 M phosphate buffer solution (PBS) of pH 7.0 was found to occur at 0.86 V with respect to Ag/AgCl. Electrochemical sensing experiments with AgNS/GCE showed a linear range of detection between 0.1 to 8 μM, with detection limit of 0.031 μM and a sensitivity of 580 μA mM−1cm−2.

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The preparation of advanced nanomaterials with unique functions from the bio-renewable (natural resources) materials is considered as one of the environmentally friendly and cost effective approaches. In this report, we demonstrate on the synthesis of carbon nanospheres with tunable diameters (30-40 nm) and controlled morphology with a pore size ∼2.0 nm from biorenewable carbon rich Areca nut and their applications in the electrochemical sensing of nitrite. The obtained carbon nanospehres exhibit good linear range (0.2 to 400 μM) for electrocatalytic oxidation of nitrite, are able to detect low levels of nitrite with high sensitivity (28.91 mA/ μM/cm 2 ) and are found to have better sensing capability than other porous carbon based electrocatalysts. This excellent electrocatalytic performance of carbon nanospheres toward oxidation of nitrite may be arising from synergistic effect between its high porosity, surface area and the catalytic effect of the carbon surface due to the presence of surface functional groups. The carbon nanosphere based sensor is also succesfully used for the real time sensing of nitrite from sea and lake water.

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