Abstract: Ag nanoparitcles were prepared via Ultrasound-assisted Membrane Reaction(UAMR) method. The key issue of the method is to control precisely the injection speed of the reactants by pulseless pump to make the nanoparticles of Ag with small size and narrow size distribution. The size and morphology of silver nanoparticles were characterized with Transmission Electron Microscope(TEM) and UV-Vis spectrum. The experiment results show that the size of Ag nanoparticles prepared via UAMR method was smaller than that via Ultrasound-assisted Dropping Reaction(UADR) method. The size of 80% Ag nanoparticles prepared via UAMR was ranged from 3 nm to 5 nm with the mean particle size 4.7 nm and considerable narrow size distribution. The Ag hydrosol fabricated via UAMR method was very stable at room temperature, even within three months.

Key words: Silver, Nanoparticles, Ultrasound-assisted membrane reaction(UAMR)