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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: Rhodamin 6G (Rh6G) functionalized Au nanoparticles (AuNPs) are being used as efficient fluorescence probe for selective sensing of heavy metal ions. It has been observed that the quenching of fluorescence of Rh6G in presence of AuNPs takes place through fluorescence resonance energy transfer (FRET). Recovery of fluorescence of Rh6G emission in presence of Hg (II) in AuNPs–Rh6G coupled system has been explained as the increasing affinity of heavy metal ions to form shell and thereby reduced the FRET rate. In presence of heavy metal ions such as Hg (II), Rh6G molecules are released from the AuNPs surface and the fluorescence of Rh6G is restored. The modulation of photoluminescence quenching efficiency of Rh6G–AuNPs in the presence of Hg (II) ions can achieve a large turn on fluorescence enhancement. Our experiment using marcapto propanoic acid (MPA) caped AuNPs show much less fluorescence enhancement in presence of Hg2+ compares to tri sodium citrate (TSC) stabilized AuNPs. [Copyright &y& Elsevier]