Preparation And Characterization Of Ag And Au Nanomaterials By Sonochemical And Sonoelectrochemical Methods

Preparation of nano-structured materials is one important component parts of nano-scale science and technology research. The structure prepared by nano-particles assembly has witnessed tremendous growth from expectation to nano-structured materials by chemical method.The purposes of this dissertation are to study the preparation of Ag nano-particles, Au nano-particles and Au assembly membrane by sono-chemical and sono-electrochemical preparation technique. By means of modern characterization methods with TEM, SAED, SEM, SPM, XRD and UV-vis, the influencing factors, growth mechanism and related properties of these metal nano-materials have been investigated.In the ultrasonic field, stable Silver colloids have been produced by the reduction of AgNO₃ with the protection of PVP using KBH4 and N2H4·H2O as reductants. For the first time, the main effective factors on morphology of silver nano-particles, such as distribution of the ultrasonic field, ultrasonic time and ultrasonic power, are studied. The results indicate that the factors such as distribution of the ultrasonic field, ultrasonic time, ultrasonic power and the species of reductant make great impact on morphology of silver nano-particles. The size of silver nano-particles decreases with the ultrasonic power and ultrasonic time increasing. Ag nano-particles prepared in the standing wave field grow following a certain direction. The standing wave field is propitious to form hexagonal and spherical-like silver nano-particles. Well-dispersed spherical silver nano-particles are easily synthesized in the diffusion field. The stability of silver colloid becomes better after ultrasonic treatment. For example, precipitation is not found after several weeks deposited of silver colloid with ultrasonic treatment 180min. The silver nanoparticles are big spherical-like and hexagonal without ultrasonic. Well-dispersed spherical silver particles with the mean size of about 20nm have been prepared after ultrasonic treatment. Spherical, spherical-like and hexagonal silver nano-particles are prepared with the change of reductants.Stable and well-dispersed gold colloids have been prepared by the reduction of HAuCl4 with sodium citrate and tannin as reductants in the ultrasonic field. The spindle gold particles were prepared firstly in the standing wave field. The resultsindicate that ultrasonic field distribution and power influence morphology of gold nano-particles strongly. The average aspect ratio decreases with the ultrasonic power increase. Mono-dispersed spherical gold nano-particles with the size of 25nm are synthesized in the diffusion wave field.In the present time, gold colloids prepared by the two phases method and the citrate deoxidization method can usually be used to assembly nano-structure materials. The ultrasound field was firstly introduced into the preparation of Au nano-particles. The assembly of Au nano-particles on different substrate such as mica, Si and glass were investigatedShaped silver nano-particles with sphere, wire and dendrite were prepared by sono-electrochemical deposition from an aqueous solution of AgNO3 in the presence of ethylenediaminetetraacetic acid disodium salt (EDTA) and polyvinylpyrrolidone (PVP). The main effective factors on morphology of silver nano-particles and absorption spectrum, such as ultrasonic time and ultrasonic power, are studied. The effect of supersonic field on silver nano-particles prepared by sono-electrochemistry method was firstly discussed with the static polarization curves.