The Synthesis Conditions Influence on Silver Nanostructures Formation Under the Effect of Electromagnetic Radiation

Abstract

In the present work the influence of the synthesis conditions, particularly the effect of used surrounding media on the silver nanostructures formation with various spatial configuration under the effect of the visible electromagnetic radiation has been studied. Silver nanoparticles were synthesized by photostimulated reduction of silver ions from the silver nitrate water solution in aqueous medium and in water yeast extract. The modification of the configuration of resulting nanoobjects was carried out by irradiating the testing samples with red, green, and blue photon flows under the similar conditions. For this task the unique devise with three isolated cells for irradiating silver colloids under the room temperature was developed. The parameters of obtained silver nanostructures were characterized by spectrophotometry and their optical properties have been researched. For the obtained silver colloids the polydispersity indexes were also determined. Besides, the changes in morphology were confirmed by transmission electron microscopy. The shift of the absorption spectra of the testing colloids to the long-wavelength spectral region and their splitting in some cases after irradiation by different wavelength has been showed. For nanoparticles synthesized in the distilled water after irradiating by red, green, and blue photon flows the additional absorption peaks appeared in the longer-wavelength spectral region. Moreover, the colloidal solutions changed the colors after the electromagnetic radiation effect. This indicates the change in nanostructures shapes. The formation of triangular nanoprisms under the influence of red and green photon flows and formation of decahedral nanostructures under the influence of blue light was found. It has been shown that this method can be successfully used to obtain the large silver nanostructures in aqueous solution of the known spatial and optical parameters. The absorption spectrum of the silver nanostructures obtained in water yeast extract shows one clearly expressed peak. But, after irradiation of this colloid with red and green light, the absorption curves are very close in shape to the initial one. Only under the blue light irradiation an additional weak absorption peak can be observed at the wavelength of 523 nm, which might indicates a partial change in the nanostructures shapes. It has been shown that the use of water yeast extract as a surrounding medium for the synthesis of nanoparticles with different spatial morphology minimizes the photoinduced effect of the shape transformation, which was observed in pure aqueous colloids. The effectiveness and the ability to use of different surrounding media for the silver nanoparticles synthesis by photostimulated reduction for obtaining nanostructures with the predetermined spatial parameters and to shift their absorption peaks to the visible and near infrared spectral region has been shown.Ref. 17, fig. 7, tabl. 1.