Roles of Chloride Anions in the Shape Evolution of Anisotropic Silver Nanostructures in Poly(vinylpyrrolidone) (PVP)-Assisted Polyol Process

Abstract

Abstract The roles of Cl− ions on the shape evolution of various silver (Ag) nanostructures including cubes, triangular bipyramids, and rods/wires in AgNO3/poly(vinylpyrrolidone) (PVP)/ethylene glycol (EG) solution have been investigated by changing the concentration of added NaCl, the reaction solution temperature, and the temperature of injection of NaCl to the original AgNO3/PVP/EG solution under oil-bath heating. The addition of different amounts of NaCl could tune morphologies and sizes of the final products from spheres via cubes to rods/wires. Reaction temperature decided the reduction power and the yield of bipyramids increased with decreasing the reaction temperature from 198 to 120 °C. Changing the solution temperature at which NaCl was introduced into the solution could effectively influence the yields of different Ag structures by adjusting the ratios of Ag and AgCl seeds formed in the solution. We found that AgCl could be an important precursor for the formation of the Ag cubes and bipyramids. The roles of Cl− anions for the evolution of various Ag nanostructures have been discussed by taking account of the formation of AgCl as seeds, selective adsorption of Cl− on {100} facets of Ag nanoparticles, and oxidative etching of the Ag particles by Cl−/O2.