Preparation And Characterization Of Ag Colloids Nanoparticles

Due to their volume effect, surface effect, quantum dimension effect and macroscopic quantum tunneling effect, Ag nanoparticles are the prominent candidates for applications in superconduction, electronics, antibacterial actions and catalysis. It is of great importance to know the growth rules of Ag nanocrystal and the factors which influence the growth process in order to get a fast, stable and green way of Ag nanoparticles preparation.There are many methods to prepare Ag nanoparticles domestic and abroad, in which the chemical reduction in liquid phase is the method we often use in present laboratory and industry because of its multiple advantages such as low cost and high efficiency. In this paper, sphere-shaped Ag nanoparticles were prepared using silver nitrate, tannic acid as both reducing agent and protecting agent. The monodispersity and stability of Ag nanoparticles can be well controlled and meets the environment-benign demand.The experiment results show that the average size of Ag nanoparticles is in relation to the temperature and the concentration of silver nitrate and tannic acid. Among them, the concentration of silver nitrate makes the biggest contribution. By means of adjusting the amount of silver nitrate, the size of Ag nanoparticles can be controlled between 20 and 80 nm. The yield of Ag nanoparticles gets higher when the pH is about 7.0. Ultrasonic treatment is helpful to improve the monodispersity and stability of Ag nanoparticles. We found intermittent ultrasonic treatment is more effective compared with continuous treatment.The prepared Ag nanoparticles were characterized by UV-Vis, XRD, FTIR and TEM. It demonstrated that the resulting nanoparticles are spherical, of face-centered structure and well-dispersed. When the average size of Ag nanoparticles gets bigger, the color of Ag colloids gets darker and the UV-Vis spectra gets red-shifted. There could be a coordination bond between the silver atom and the hydroxyl group of tannic acid, which stabilize the Ag nanoparticles in the spatial reticulate structure of tannic acid.