Gold and silver nanoparticles: synthesis, characterization and functional properties

Abstract

This thesis focuses on the shape-controlled metal nanoparticles for functional applications, covering the synthesis, characterization and optical properties. Three parts are mainly involved in this work, including, gold worm-like nanoparticles, silver nanoplates, and silver induced selenium nanowires. The first part focuses on a facile synthesis method for shape control of gold nanoparticles by treating an aqueous solution of chloroauric acid with sodium citrate and poly(vinyl pyrrolidone) (PVP), in which those worm-like nanoparticles were investigated by various advanced experimental characterizations combining density function theory (DFT) calculation. These nanoparticles can be used for optical sensing detection of ions in aqueous system. The second part involves the synthesis, growth, and optical properties of silver nanoplates (triangles and circular discs). Such nanoplates could be synthesized by a self-seeding co-reduction method at ambient conditions. In particular, molecular dynamics simulation is used to quantify the interaction energies between surfactant molecules and different facets of silver crystal. Such molecular information, together with measurements using x-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and ultraviolet–visible (UV–vis) spectroscopy, has proven to be useful for understanding the growth mechanisms of silver nanoplates. The third part focuses on the template of silver nanoparticles for generating trigonal selenium (t-Se) nanowires. This technique exhibits some advantages in fabricating t-Se nanostructures, including no need to use stabilizers and sonichemical process and all operations being proceeded in aqueous media and at room temperature. Particularly it can successfully achieve the transformation from amorphous α-Se to crystalline t-Se in aqueous solution and this method would be useful for generating one-dimensional nanostructures with similar lattice parameter(s). It is considered that the technique for the shape-controlled metal nanoparticles can at least partially, be extended to other nanomaterials for functional applications.