Synthesis and Photodynamic Properties of Colloidal Silver Solutions

This work presents the results of research the electromagnetic radiation influence on the change in the geometric shape of spherical silver nanoparticles, obtained by method of photostimulated recovery of Ag ions from salt solution (AgNO3). Сrystalline sodium citrate (Na3C6H5O7) was used to recover Ag by anions of citrate acid. Due to adsorption on the surface of silver nanoparticles and creating electrostatic barrier that prevents aggregation of silver nanoparticles, sodium citrate was also used as a stabilizer.

Using light for the controlled synthesis and shape changing of silver nanoparticles are very perspective. Light can significantly affect on the formation and growth of nanoparticles. This work show, that using of photon fluxes is an effective way to modifying the spatial shape of nanoparticles, since nanoobjects have the ability to absorb a certain wavelength. This allows shifting the working range of wavelengths to the longer-wavelength region of the spectrum.

The research of the light influence on silver nanoparticles was carried out by irradiating silver colloids by LED-diodes with power 1W and wavelengths 525 nm, 465 nm and 623 nm during 6 days under similar conditions. It is shown that an additional absorption peak has appeared on the absorption spectra for all samples, irradiating by different wavelengths. This is linked to a partial change in the geometrical shape of the nanoparticles.

The theoretical prediction of the size of silver nanoparticles and the plasmon resonance peak position on the spectral scale were carried out by principle of the dipole equivalence. The comparison of the calculated dependences of the absorption coefficient of synthesized silver nanoparticles from the wavelength with the experimental ones was carried out.