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Abstract: Metal nanostructures have unusual physicochemical properties and biological activities compared to their bulk parent materials. Thus in recent years a number of physical, chemical and biological techniques were applied for the development of metal nanoparticles (NP). Here we have synthesized silver and gold nanoparticles (AgNPs and AuNPs) by using leaves extracts of Rosa rugosa. Surface plasmon resonance spectra for silver and gold are obtained at 451 and 578nm with brown yellow and pink-red color, respectively. AgNPs and AuNPs vary in size according to different leaves extract and metal concentration used for the synthesis. Different instrumental techniques were applied to characterize the synthesized AgNPs and AuNPs viz. UV–vis, TEM, XRD, FTIR, Zetasizer and EDX. The synthesized NPs were mostly spherical (in case of AgNPs) with some triangular and hexagonal (especially in case of AuNPs) in shapes with an average size of 12 and 11nm for AgNPs and AuNPs, respectively. [Copyright &y& Elsevier]

Abstract: Nanosized ZrO2 and WO3–ZrO2 particles were prepared by solution combustion synthesis using urea as fuel. These materials were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. XRD study indicates the presence of a mixture of tetragonal and monoclinic phases in the synthesized ZrO2 particles. The tetragonal phase content is enhanced in the WO3–ZrO2 nanocomposite oxide. IR study indicates the presence of well-dispersed WO x species grafted on to the surface of the tetragonal ZrO2. TEM analysis of the sample shows the presence of uniform particles with size in the range of 10–25nm. The catalytic activity of the WO3–ZrO2 nanocomposite catalyst was evaluated for the synthesis of coumarins by Pechmann condensation of phenols with β-ketoesters. It was observed that the composite oxide catalyst was highly active for the reaction. Grafting of WO3 species on the surface of ZrO2 has a beneficial effect on the catalytic activity of the WO3–ZrO2 nanocomposite catalyst. [Copyright &y& Elsevier]