A Nonstationarity of silver hydrosols formation and changes of nanoparticles shape after «freezing»

Among the other elements the dispersed silver holds a special place because of its protective biocidal effect and specific physicochemical characteristics depending on the particle size and shape. Absorption spectra of silver hydrosols were monitored in processes of Ag nanoparticles (Ag-NPs) formation due to reducing reaction of Ag+ ions by tannin with AgNO3 or Ag2SO4 as precursors. The dependence of the optical absorption on the wavelength in the long-wavelength range of plasmon spectra has been analyzed in framework of Mie theory by an original method. Several parameters may be estimated, such as the volume fraction of NPs (NV), the effective concentration of conduction electrons (Ne), and the damping factor of the metal electron plasma vibrations (?). The changes in ? are the most interesting because ? includes surfaces' defects of metallic nanoparticles. It was found that in case of AgNO3 precursor the increase of NV leads to ? decrease with oscillations for both parameters when the reaction Ag+n?Ag0n proceeds. Low temperature treatment of the stable silver particles (10 nm in diameter) undergo aggregation (rearrangement) because silver NPs surface becomes defective. At 77 K changes in NV and ? may be explained by tunnel mechanism of surface defects formation. These defects include mobile small surface clusters H+(H2O)n and OH-(H2O)n. We compare the influences of precursor and Ag-NPs concentration on NV and ? parameters before and after freezing. © NANOCON 2018 - Conference Proceedings, 10th Anniversary International Conference on Nanomaterials - Research and Application. All rights reserved.