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Here, we report the high yield synthesis of different shaped gold nano particles (AuNPs) through seed mediated growth process in aqueous medium. Shape dependent surface plasmon resonance (SPR) and the gradual shift of longitudinal SPR band are observed with increasing anisotropy of AuNPs. Structural changes during the growth processes are observed by transmission electronic microscopy (TEM). Here, spherical nano seeds are transformed into rice and dendrimer shaped nanoparticles in the subsequent four stage growth processes. Gold nanoparticles have been demonstrated to be very efficient catalysts for the cleavage of N N of sudan-1 and it is investigated by monitoring the reduction of sudan-1 in the presence of excess NaBH 4 . It has been observed that the reaction is first order with respect to the concentration of sudan-1 and the catalytic efficiency of dendrimer shaped AuNPs is higher than the other as synthesized AuNPs. [ABSTRACT FROM AUTHOR]

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1-5 nm) has been done by reducing Ag over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV-Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles. [ABSTRACT FROM AUTHOR]

Present investigation demonstrates a very simple seed-mediated route for the synthesis of silver nanorods in aqueous solution. Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centres to grow nanoparticles to a desired size and shape. Hydroxypropyl methyl cellulose (HPMC) has been used as soft template for one-dimensional growth of silver particles. Morphological, structural and spectral changes that are associated with the seed-mediated growth of the nanoparticles in presence of HPMC are characterized using UV-vis and HR-TEM spectroscopic study. Simulation of UV-vis extinction spectra of our synthesized silver nanorods has been carried out using discrete dipole approximation methodology. The broad red-shifted longitudinal extinction band of green-coloured silver sol has been explained, due to the presence of silver nanorods of different aspect ratios. [ABSTRACT FROM AUTHOR]

Abstract: Here, we report synthesis of star shape gold nanoparticles using seed mediated growth process. Ag+ ions have been used to catalyze the anisotropic growth of gold particles in the growth solution. Star like gold nanoparticles are characterized using UV–vis and TEM study. Excitation of localized surface plasmon of star shaped gold nanoparticles by the visible radiation results broad and intense localized surface plasmon resonance excitation band. Emission spectra of nanostars upon excitation at 230nm and 480nm has been explained due to localized plasmon at the edge of star like particle and the longitudinal mode of these anisotropically grown gold nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Spherical, hexagonal, triangular and bar shaped silver nanostructures have been synthesized at large scale in aqueous media using methyl cellulose (MC) as soft template. Synthesis is based on the reduction of Ag+ by hydrogen at different temperatures. Morphology of particles is mostly spherical at 60°C with an average diameter 4–8nm, whereas hexagonal, triangular and truncated hexagon silver nanostructures are obtained at 80°C. On the other hand bar shaped silver nanoparticles are formed as the reaction is carried out at 90°C. Silver nanoparticles are characterized using UV–Vis and TEM study. Formation of silver nanostructures of variable morphologies has been explained in terms of different shaped template formed by MC at different temperature due to its thermogelation properties. [Copyright &y& Elsevier]

Abstract: Methyl cellulose (MC) capped gold nanoparticles are successfully prepared through a simple route. Synthesis is based on the reduction of aqueous HAuCl4.4H2O by hydrogen gas at 85°C and methyl cellulose has been used as encapsulating agent. Gold nanoparticle so-prepared are characterized by UV–Vis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HR-TEM). Methyl cellulose encapsulated gold hydrosol shows broad surface plasmon resonance (SPR) band with maxima at 537nm along with a broad tail at 635nm. In accordance with the SPR band, HRTEM micrograph shows two broad distributions of particles, most of them are small and spherical and nearly 25% particles are bigger with uneven shapes. [Copyright &y& Elsevier]

Abstract: We report a method to synthesize silver nanoparticles of varying morphologies by a seeding growth approach at room temperature. Seeds are prepared by reducing silver nitrate with sodium borohydride, and trisodium citrate is used as capping agent. This citrate capped seed sol is added to the growth solution containing ascorbic acid, sodium dodecyl sulphate (SDS) and sodium hydroxide. Colour of the growth solution changes from colourless to pink and the surface plasmon resonance (SPR) shows two distinct bands, indicating the formation of anisotropically grown silver nanostructures. Synthesized silver nanoparticles are characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. Silver nanoseeds are spherical in shape with diameter ranges from 8 to 16nm. On the other hand, a mixture of morphologies with shapes like triangular and hexagonal nanoplates, nanorods are obtained in the growth solution. XRD results suggest that the particles are crystalline in nature with face centered cubic (fcc) geometry. [Copyright &y& Elsevier]