Changes in Spectral Properties of Aqueous Silver Sols Induced by Complexation on the Surface of Nanoparticles

The interaction of Ag+ ions existing on the surface of silver nanoparticles with complexing agents, such as ammonia, ammonium thiocyanate, and sodium thiosulfate, has been studied. Both the presence of complexing agents in the initial reaction mixture and their introduction into preliminarily synthesized sols of silver nanoparticles lead to a small shift of the absorption maximum toward long wavelengths and its considerable broadening. In both cases, there is a correlation of the absorption band width with the logarithm of formation constants of corresponding silver complexes. This can be evidence of analogous chemical processes that occur on the surface of nanoparticles. The surface complexation is of interest both for a fundamental understanding of the interaction nature and in the applied aspect for the determination of complexing agents in aqueous systems.