COMPUTER QUANTUM-CHEMICAL MODELING OF THE INTERACTION OF SELENIUM NANOPARTICLES WITH QUATERNARY AMMONIUM COMPOUNDS

Abstract

In this paper, a computer quantum-chemical simulation of the interaction of selenium nanoparticles with quaternary ammonium compounds was carried out, in which models of molecular complexes, electron density distribution, as well as higher populated and lower free molecular orbitals were obtained. For the presented molecular systems, the total energy of the molecular complex E, the difference in the energy of the quaternary ammonium compound molecule and the system «quaternary ammonium compound-selenium nanoparticles» ΔE, the energy of the highest occupied molecular orbital EHOMO, the energy of the lowest unoccupied molecular orbital ELUMO, and the chemical rigidity of the system η were calculated. As a result of data analysis, it was found that the interaction of selenium nanoparticles with quaternary ammonium compounds is energetically advantageous (ΔE > 11991 kcal/mol). The optimal system of interaction of selenium nanoparticles with quaternary ammonium compounds is the «cetyltrimethylammonium chloride-selenium nanoparticles» system, which is due to the highest value of the energy difference (ΔE = 11991,79 kcal/mol). Based on the analysis of the obtained models of molecular systems, it was found that when a quaternary ammonium compound interacts with selenium nanoparticles, the electron density is shifted and new molecular orbitals are formed, which indicate formation of a chemical interaction between the molecules. Next, IR spectroscopy of selenium nanoparticles stabilized with cetyltrimethylammonium chloride was performed. Based on the data obtained, it is found that there is a decrease in the intensity of the bands, in comparison with the IR spectrum of cetyltrimethylammonium chloride, in the regions from 2851 to 3026 cm-1 and from 1265 to 1377 cm-1, characteristic of the CH2 and CH3 groups, which indicates the presence of cetyltrimethylammonium chloride molecules oriented with the hydrophobic side to selenium particles on their surface. After that, the morphology of selenium particles was studied using the transmission electron microscopy method. As a result of the analysis of transmission electron microscopy images, the formation the layer of the quaternary ammonium compound on the surface of selenium particles with a diameter of 25 to 60 nm was confirmed.