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The physical and chemical properties of materials are greatly influenced by the state of their surface layers. In turn, the characteristics of the surface depend, for example, on the processes of absorption from a gas medium. In this study, by in situ measurements, the surface layers of polycrystalline silver exposed to external activated oxygen from different sources are investigated. For sources of activated oxygen, water vapor at a temperature of 1073 K and an ion source that makes it possible to obtain an oxygen ion beam with the energy 100–300 eV (5 μA/cm2) are used. It is established that, after treatment, the composition of AgO and Ag2O in the surface layers of silver includes, apart from atomic oxygen, molecular oxygen and silver in the zero-valence state. From estimates of the ratio between the intensities of spectroscopy peaks related to silver and oxygen components, it can be concluded that there exist associative forms of oxygen in the surface layers of silver. An increase in Ag 3d5/2–Ag 3d3/2 spin–orbit splitting is detected, which suggests that there are oxidized silver nanoparticles on the surface. [ABSTRACT FROM AUTHOR]

Background: Knowledge about silver nanoparticles in soils is limited even if soils are a critical pathway for their environmental fate. In this paper, speciation results have been acquired using a silver ion selective electrode in three different soils. Results: Soil organic matter and pH were the most important soil properties controlling the occurrence of silver ions in soils. In acidic soils, more free silver ions are available while in the presence of organic matter, ions were tightly bound in complexes. The evolution of the chemical speciation of the silver nanoparticles in soils was followed over six months. Conclusion: During the first few hours, there appeared to be a strong sorption of the silver with soil ligands, whereas over time, silver ions were released, the final concentration being approximately 10 times higher than at the beginning. Ag release was associated with either the oxidation of the nanoparticles or a dissociation of adsorbed silver from the soil surfaces. [ABSTRACT FROM AUTHOR]

The correlation between the chemical nature of capping agents used to prepare colloidal silver dispersions and kinetic characteristics of the process of oxidation of the dispersed phase (spherical silver nanoparticles, 2–50 nm in diameter) by hydrogen peroxide was studied for the first time. The well-pronounced correlation between the oxidative dissolution rate and the biological activity of silver dispersions was revealed with respect to the inhibition of the growth of the Saccharomyces cerevisiae yeast. The biological activity of nanosilver dispersions was found to be primarily controlled by the rate of generation of silver ions while the chemical nature of the capping agent defined the rate of generation of silver ions, thus showing an effective way to control the biological action of medications based on silver nanoparticles by varying the nature of the capping agent. [ABSTRACT FROM AUTHOR]