L. P. Golovkova

Role of surface nature of functional silicas in adsorption of monocarboxylic and bile acids

The chemical modification of silica surfaces by nitrogen-containing organic reagents (γ-aminopropyltriethoxysilane, imidazole, or N-vinyl-2-pyrrolidone) and also with hexamethyl disilazane and hydrocarbon oligomers was proposed to enhance the adsorptive capacity of silica with respect to monocarboxylic and bile acids. The calculation of the content of protonated and deprotonated groups on the surfaces of synthesized organosilicas with distinguished basicity of functional groups was performed using the program GRFIT for the model of a diffuse layer. The contribution of hydrophobic and electrostatic interactions to the adsorption of organic acids was revealed. It has been established that the maximum of organic acid adsorption coincides with the pH at which the curve of increasing concentration of the anion of an organic acid and the curve of decreasing concentration of the protonated functional groups of aminopropyl silica are intercrossed.

Adsorption of components of nucleic acids on a titanium dioxide surface

The adsorption of heterocyclic nucleic acid bases and nucleosides at titanium dioxide-aqueous electrolyte solution interface has been studied. Equilibrium constants have been calculated for the acid-base reactions of the surface hydroxyl groups of titanium dioxide and the formation of surface complexes with biomolecules.

Adsorption of organic acids on a cerium dioxide surface

Adsorption of organic acids from aqueous solutions on a cerium dioxide surface has been quantitatively studied in terms of the theory of complexation at interfaces. Potentiometric titration data have been used to calculate the equilibrium constants of acid-base reactions of surface hydroxyl groups of cerium dioxide. The study of adsorption of organic acids on a cerium dioxide surface from aqueous solutions as depending on pH has allowed us to calculate surface complexation constants complexation constants.

Adsorption of biogenic amines on albumin-modified silica surface

The adsorption of biogenic amines, tryptamine and tyramine, from aqueous solutions on the surface of finely dispersed silica modified by the adsorption of bovine serum albumin is studied depending on pH and adsorbate concentration. Silica surface modification with albumin is shown to widen the pH range of amine adsorption from aqueous solutions.

Spectroscopic study of biogenic amine complexes formed at fumed silica surface.

The structure and stability of biogenic amine complexes formed at the fumed silica surface were studied by UV-, IR-spectroscopy and TPD MS techniques. It was found that surface complexes are formed due to electrostatic interactions between amine cations and ionized silanol groups. The mechanism of thermal transformations of surface complexes is proposed. Kinetic parameters of thermal reactions at the fumed silica surface have been calculated.

Adsorption complexes of acridine diaminoderivatives on silica surface

The adsorption of acridine diaminoderivatives on the surface of finely dispersed silica from aqueous solutions is studied in relation to pH, ionic strength, and adsorbate concentration. The stability constants of the surface complexes of acridine derivatives with unionized and dissociated silanol groups of silica are calculated within the framework of the electrostatic model of surface complexation (the basic Stern model). Dimerization of all examined compounds in aqueous solutions is taken into account. It is established that, in the case of acridine dyes (orange and yellow), complexes containing both monomeric and dimeric forms of these compounds are formed on silica surface. The selection in favor of one of the possible sets of the constants, which quantitatively characterize the equilibria of the reactions, results from the analysis of the adsorption isotherms of examined diaminoacridines.

Ternary surface complexes in silica-Ni2+ ions-2,2′-dipyridyl systems

The adsorption of complexes of nickel ions with an organic base (2,2′-dipyridyl) at an interface between silica and an aqueous electrolyte solution has been considered in terms of the theory of complexation. It has been shown that, on the silica surface, ternary complexes are formed, in which nickel ions are bonded to silanol groups. The equilibrium constants of the reactions of ternary surface complex formation have been calculated from the adsorption curves describing the pH dependences of nickel ion and dipyridyl adsorption.

Interaction of nucleobases with proflavine on silica surface

The adsorption of purine and pyrimidine nucleobases from aqueous solutions on silica surface modified by preliminary adsorption of proflavine has been studied as depending on pH and adsorbate concentration. It has been shown that the bases interact with proflavine, the molecules of which are attached to neutral silanol groups of silica via hydrogen bonds. The equilibrium constants of the complexation reactions between the bases and adsorbed proflavine have been calculated.