Oxythermography as a method of assessment of modification of a nanoparticles surface of silicon dioxide by organic compounds

Abstract

Functionalized colloidal particles of silicon dioxide are widely used in modern science and various industries. The increased interest of researchers in modified nanoparticles is explained by the presence of their unique physical and chemical properties. The properties of the described systems depend on the composition, structure and density of the surface grafted layer, as well as on the particle size. Particles with a modified surface are increasingly used as chemical catalysts, biosensors, stationary phases in chromatography, polymer fillers, biological and medical preparations. During the modification, it is necessary to control the chemical process on a solid surface. There are several approaches for the analysis of nanoparticles with grafted surface structures [3]. In this work, thermal oxidation spectroscopy-oxythermography was used for the first time to determine the quality of inoculation of 3 - aminopropyltriethoxysilane (APTES) [4]. The peculiarity of the chosen method is that the formation of an analytical signal is carried out due to the oxidation of organic matter in the air stream. Thus, when using an oxythermograph, a change (decrease) in the oxygen content in the air stream coming out of the high-temperature reactor was recorded during the programmed oxidation of a chemically grafted modifier on the surface of SiO2 nanoparticles. This method has a number of advantages. For example, when using air as an oxidizing medium, no consumable reagents are required, and the analysis itself does not require much time. The purpose of this work was to study the possibility of using the oxythermography method in the analysis of the kinetics of chemisorption of 3-aminopropyltriethoxysilane on the surface of silica nanoparticles [1]. Silicon dioxide nanoparticles were obtained by the Stober-Fink-Bohn method [6]. The choice of 3-aminopropyltriethoxysilane as a modifier is due to the presence of amino groups in its molecule, which can easily be protonated by changing the charge of the silica surface. To select the optimal conditions for modifying the surface of SiO2 particles, the kinetics of this process was studied using various methods: microelectrophoresis with zeta potential determination and oxythermography. A quantitative assessment of the chemisorption of the modifier was also carried out by oxithermography.