Preparation of Nanosilver Colloidal Solution by Anodic Dissolution under High DC Voltage

Nanosilver colloidal solution with strong bactericidal effect has been widely applied in numerous fields. Instead of using other known methods, the colloidal solution was prepared by anodic dissolution of silver under high DC voltage in doubly distilled water. Highly pure colloidal solution with particle sizes from 2 to 40 nm and concentrations of up to 700 ppm were obtained. Their low electrical conductivities indicated that these colloidal solutions did not contain free ions. The Zeta potential values ranged from −28.83 to −38.91 mV, in the region of stable colloid systems. Anodic dissolution process followed electrochemical mechanism, where concentrations of the colloidal solutions determined by the weight loss method were less than the values calculated by anodic current according to Faraday’s law. It was also demonstrated that the process included water decomposition with gas evolution at the electrodes and the generated hydrogen took part in reduction reaction to form nano silver particles in the solution.