Development of the Metal Nanoparticle Synthesis Method by Means of the Hydrothermal Technique
Noritsugu KOMETANI, Takeshi TERANISHI and Yoshiro YONEZAWA
Abstract:Two different types of the high-temperature high-pressure reactor systems with one-line or two-line flow paths have been developed to examine the hydrothermal syntheses of metal nanoparticles. For the two-line reactor system, two kinds of reaction solutions could be quickly mixed at the Y-shaped junction inside the reactor under high-temperature high-pressure conditions. The aqueous solutions containing 1.5 mM silver nitrate, 30 wt% polyvinylpyrrolidone and three different kinds of reducing agents (trisodium citrate, ethanol or acetone) were reacted at T = 200-350°C and P = 40 MPa by the one-line reactor system. The finest silver nanoparticles with average diameter of about 15 nm were obtained when trisodium citrate was used as the reducing agent. The bimetallic nanoparticles composed of silver and platinum have been synthesized with the one-line reactor system by using the mixed solution of silver nitrate and dihydrogen hexachloroplatinate(IV) as the starting material. The optical absorption spectra of the obtained bimetallic nanoparticles in the aqueous solutions indicated the spontaneous formation of the platinum-core silver-shell structure. It was demonstrated that smaller Ag nanoparticles with narrower size distribution could be synthesized when the two-line reactor system was used instead of the one-way reactor system under nearly identical experimental conditions. Key Words:Silver nanoparticle, Composite nanoparticle, Hydrothermal synthesis, Subcritical Water, Reactor