Synthesis of Stable Silver Nanoparticles with Antimicrobial Activities in Room-temperature Ionic Liquids

Stable silver nanoparticles was successfully synthesized by chemical reduction of silver nitrate in an ionic liquid, 1-n-butyl-3-methylimidazolium tetrafluoroborate([BMIM]center dot BF4) at room temperature. Results of UV-Vis diffuse reflectance spectroscopy show as-prepared Ag nanoparticles exhibit a typical emission peak at 400-430 nm. By varying the reaction temperature and the precursor concentration, the size and the shape of the silver nanoparticles could be easily controlled under mild conditions. Analyses of transmission electron micrographs, X-ray diffraction pattern and X-ray photoelectron spectrum further reveal that the silver nanoparticles were coated incompletely by [BMIM]center dot BF4. Microbial experiments indicate that as-prepared silver nanoparticles show a wide spectrum of antimicrobial activities and have better antimicrobial activities to Pseudomonas aeruginosa than silver nitrate with the same concentration of silver.