Spectroscopic characteristics of colloidal solutions of metal nanoparticles

Abstract

Nanoparticles are finding more and more practical applications in various fields of human activity, including veterinary and medicine. Due to the fact that the effectiveness of activity of colloidal solutions of nanoparticles is directly related to the state of aggregation of nanosized particles, it is urgent to use fast and convenient methods for assessing the physicochemical characteristics of such preparations. Nanoparticles have unique optical properties that depend on their size and shape. They can be determined by the refractive index of the light on the surface of the nanoparticles in a phenomenon known as plasmon resonance, which makes UV-Vis spectroscopy a valuable tool for studying and evaluating the characteristics of nanomaterials. Goal of the study is to study the optical characteristics of several samples of colloids of nanoparticles of noble metals (silver) and bioelements (copper, silicon dioxide) in order to determine the possibility of further application of UV-Vis spectroscopy for evaluation of activity and stability of colloidal solutions of nanoparticles. Commercial preparations based on nanoparticles of noble metals (silver) or bioelements (copper, silicon dioxide) in working dilutions recommended by manufacturers were used to study optical characteristics of the colloidal solutions. Optical density and absorption spectra were determined at the wavelengths (nm): 300-800 nm. The f plasmon surface resonance has been found in all test preparations, while all of them exhibited obvious nonlinear optical properties. The most pronounced plasma resonance peak is found in the colloidal solution of silver nanoparticles within a wavelength of 420 nm. In the case of a colloidal solution of copper nanoparticles, the peak of plasmon resonance was less pronounced and had a red shift (peak at 560 nm). In the colloidal solution of silicon silica, the plasmon resonance was less pronounced than other test preparations, being shifted to the blue side of the spectrum (360 nm).