Enhanced photocatalytic activity of metal coated ZnO nanowires.

A simple, facile and template free route has been described for the synthesis of ZnO nanowires. The morphology and structure of ZnO nanowires have been tuned by deposing silver and gold onto the surface of ZnO nanowire and this has been done by adding AgNO(3) and HAuCl(4) to aqueous suspension of ZnO. Our synthesized Ag and Au coated ZnO nanoparticles show different emissive property than the native ZnO nanowires. The photocatalytic degradation of Methylene Blue is also evaluated using ZnO and Ag and Au coated ZnO nanowires. It has been observed that Ag coated ZnO nano-needles exhibits significantly enhanced photocatalytic efficiency compare to ZnO nanowire and Au coated ZnO nano-leaves. Fluorescence spectra and surface structure of the samples with their photocatalytic activity indicates that surface deposited metal serves as an electron sinks to enhance the separation of photoinduced electrons from holes, leading to the formation of OH and it enhances their photocatalytic efficiency.

Synthesis of worm like silver nanoparticles in methyl cellulose polymeric matrix and its catalytic activity.

A facile one step method for the synthesis of wormlike silver nanoparticles has been carried out in methyl cellulose matrix. Synthesis is based on the reduction of AgNO3 by sodium borohydride (NaBH4) in aqueous methyl cellulose (MC). Synthesized nanoparticles are mostly mono disperse in size and their aggregation is controlled by varying the concentration of AgNO3. Silver nanoparticles are analyzed using transmission electron microscope (TEM), UV-vis spectroscopy and X-ray diffraction (XRD) technique. It has been found that the concentration of AgNO3 has a significant effect on the morphology of Ag nanostructures. Worm like nanostructures showed excellent catalytic activity in the borohydride reduction of p-nitrophenol compared to spherical shaped nanoparticles.

Aqueous-Phase Synthesis of Silver Nanodiscs and Nanorods in Methyl Cellulose Matrix: Photophysical Study and Simulation of UV-Vis Extinction Spectra Using DDA Method.

We present a very simple and effective way for the synthesis of tunable coloured silver sols having different morphologies. The procedure is based on the seed-mediated growth approach where methyl cellulose (MC) has been used as soft-template in the growth solution. Nanostructures of varying morphologies as well as colour of the silver sols are controlled by altering the concentration of citrate in the growth solution. Similar to the polymers in the solution, citrate ions also dynamically adsorbed on the growing silver nanoparticles and promote one (1-D) and two-dimensional (2-D) growth of nanoparticles. Silver nanostructures are characterized using UV-vis and HR-TEM spectroscopic study. Simulation of the UV-vis extinction spectra of our synthesized silver nanostructures has been carried out using discrete dipole approximation (DDA) method.

DFT based computational study on the excited state intramolecular proton transfer processes in o-hydroxybenzaldehyde.

Potential energy (PE) curves for the intramolecular proton transfer in the ground (GSIPT) and excited (ESIPT) states of o-hydroxybenzaldehyde (OHBA) were studied using DFT-B3LYP/6-31G(d) and TD-DFT-B3LYP/6-31G(d) level of theory, respectively. Our calculations suggest the non-viability of ground state intramolecular proton transfer in this compound. Excited states PE calculations support the ESIPT process in OHBA. The contour PE diagram and the variation of oscillator strength along the proton transfer co-ordinate support the dual emission in OHBA. Our calculations also support the experimental observations of Nagaoka et al. [S. Nagaoka, U. Nagashima, N. Ohta, M. Fujita, T. Takemura, J. Phys. Chem. 92 (1988) 166], i.e. normal emission of the title compound comes from S(2) state and the red-shifted proton transfer band appears from the S(1) state. ESIPT process has also been explained in terms of HOMO and LUMO electron density of the enol and keto tautomer of OHBA and from the potential energy surfaces.