Stable colloidal silver solutions for different applications

The paper presents a method for obtaining of some stable colloidal silver solutions containing 5 ... 100 ppm silver nanoparticles. This method is based on the reduction of aqueous silver nitrate solutions with sodium borohydricle solutions in presence of a steric stabilizing agent (PVP) and an electrostatic stabilizing agent (tri-sodium citrate), being in certain molar ratio. We obtained by this method some high defined colloidal silver solutions having spherical silver nanoparticles with a narrow grain size distribution, depending on the colloidal silver solutions concentrations. The grain size and the shape of the particles were studied by TEM. The mean diameter of the silver nanoparticles, the grain size distribution and the zeta potential were measured by DLS on a nanoparticles size analyzer. The colloidal silver solutions stability was assessed monthly by zeta potential and UV-Vis spectra recording for a time period of six months. The zeta potential of the studied colloidal silver solutions was included in the range of - 44.82 mV and - 31.88 mV. These values proved a high stability of the solutions.