Stabilization of Silver Nanoparticles with Copolymers of Maleic Acid

摘要

Silver nanoparticles are obtained by reducing AgNO_3 with sodium borohydride in an aqueous solution in the presence of maleic acid copolymers with ethylene, N-vinylpyrrolidone, or styrene, as well as their octadecylamide group-containing hydrophobized derivatives, as dispersants. The influence of the struc- tural features of the dicarboxylic acid copolymers on the silver nanoparticle formation process and the con- ditions for producing sols containing spherical nanoparticles with sizes of 1.5-3.5 nm (according to the data of transmission electron microscopy) are determined. It is shown that, at the equimolar copolymer/silver cat- ion ratio, the morphology of resulting silver nanoparticles weakly depends on the nature of comonomers of maleic acid and the presence of hydrophobic fragments, which play an auxiliary role in the stabilization of dispersions of nanoparticles by increasing their stability with respect to ionic strength and oxidation. Evolu- tion of the particle sizes in the system is monitored beginning with copolymer solutions to silver sols by the methods of light scattering, transmission electron microscopy, and atomic force microscopy. According to the light scattering data, copolymers and their complexes with silver ions in solutions are partly aggregated at concentrations corresponding to the conditions of nanosilver synthesis. Silver sols are shown to contain sta- bilized nanoparticles, which represent core-polyelectrolyte corona-type micelles and micellar clusters with polyelectrolyte coronas.