Transformation of Silver Nanospheres into Nanobelts and Triangular Nanoplates through a Thermal Process

Silver has been prepared as triangular nanoplates with sharp corners and thin nanobelts by refluxing an aqueous dispersion of spherical colloids of silver with an average diameter of 3.5 nm. The spherical colloids of silver were, in turn, generated by reducing silver nitrate with sodium borohydride in the presence of poly(vinyl pyrrolidone) (PVP) and sodium citrate. Our studies indicate that the light present in an ordinary chemical laboratory was sufficiently strong to transform some spherical nanoparticles into small triangular nanoplates. Refluxing provided the driving force to facilitate the Ostwald ripening process−growth of these plate-like seeds at the expense of spherical nanoparticles. In addition, refluxing might also selectively disrupt the organic layers on the surfaces of the small triangular nanoplates, driving these plates to assemble into thin nanobelts due to the strong dipole−dipole interaction between adjacent plates. These nanostructures of silver with unique planar shapes might find use in areas that include photonics, optoelectronics, and optical sensing.