Evolution of Electronic State and Properties of Silver Nanoparticles during Their Formation in Aqueous Solution

Abstract

The electron density of a nanoparticle is a very important characteristic of the properties of a material. This paper describes the formation of silver nanoparticles (NPs) and the variation in the electronic state of an NP’s surface upon the reduction in Ag+ ions with oxalate ions, induced by UV irradiation. The calculations were based on optical spectrophotometry data. The NPs were characterized using Transmission electron microscopy and Dynamic light scattering. As ~10 nm nanoparticles are formed, the localized surface plasmon resonance (LSPR) band increases in intensity, decreases in width, and shifts to the UV region from 402 to 383 nm. The interband transitions (IBT) band (≤250 nm) increases in intensity, with the band shape and position remaining unchanged. The change in the shape and position of the LSPR band of silver nanoparticles in the course of their formation is attributable to an increasing concentration of free electrons in the particles as a result of a reduction in Ag+ ions on the surface and electron injection by radicals. The ζ-potential of colloids increases with an increase in electron density in silver nuclei. A quantitative relationship between this shift and electron density on the surface was derived on the basis of the Mie–Drude theory. The observed blue shift (19 nm) corresponds to an approximately 10% increase in the concentration of electrons in silver nanoparticles.

Photochemical Synthesis of Silver Hydrosol Stabilized by Carbonate Ions and Study of Its Bactericidal Impact on Escherichia coli: Direct and Indirect Effects

“…Please note that regarding the time of stability, both types of hydrosols are suitable for conducting expreriments on studying the antibacterial activity of silver on the Escherichia coli cells (48 h). The results of optical detection of the dissolution of silver nanoparticles in the Adkins M culture medium by monitoring the decrease in intensity of the interband electronic transition at 250 nm, which reflects the Ag 0 concentration in the nanoparticle [22], are in good agreement with the results of analysis of Ag + ions released to the solution. Indeed, after 24 and 48 h, the concentration of the dissolved metal in 1 × 10 −4 mol L −1 Ag 0 was approximately 14 and 25%, respectively, according to the results of optical measurement and 13 and 24.3%, respectively, according to IPC determination of Ag + ions.…”

“…Therefore, it is important to prepare stable hydrosols composed of nanoparticles of moderate size containing no toxic impurities and stable in biological media. Previously, we developed a method for the synthesis of stable silver particles of moderate size complying with the green chemistry principles [21][22][23][24]. The method includes UV-induced reduction of Ag + ions with C 2 O 4 2− oxalate ions.…”

“…Solutions were irradiated by a pulse xenon lamp with the total radiation flux intensity I UV = 6.0 × 10 20 quantum/s (alpha-05, Melitta, Moscow, Russia). A detailed description of the synthesis and mechanism of formation of silver NPs was reported in our previous publications [22][23][24].…”

In situ green synthesis of lysozyme/silver nanoparticles sol and their antimicrobial properties

“…Based on the Mie scattering theory, the ultraviolet absorption peak of spherical AgNPs sol was detected in the band at about 390–430 nm. 39,40 A strong surface plasmon resonance absorption peak was detected at 406 nm (Fig. 1(b)), 40 manifesting that AgNPs were formed during the reaction.…”

“…The UV absorption peak was relatively sharper, with the half-peak width of 80-90 nm, signifying the narrow particle size distribution of the generated AgNPs. 39 Moreover, the absorption peak intensity of AgNPs strengthened with the increase in reaction time. This was mainly due to the fact that more reducing free radicals were produced in the sol with the continuation of UV irradiation time, and the reduction rate of Ag + ions was enhanced.…”