The work is devoted to the development of scientific and methodological approaches for the obtaining of hybrid organomineral film coatings based on SiO2-polyelectrolyte modified with analytical reagents by sol-gel method and practical recommendations for their application in chemical analysis as sensitive elements of optical and voltammetric sensors. Analytical reagents are immobilized in hybrid films by electrostatic and specific intermolecular interactions with encapsulated strong polyelectrolyte (PE). Stable, uniform film coatings with improved chemical and analytical characteristics are obtained by controlling the composition of silica sol, the nature and concentration of PE and structure-directed templates. The role of intermolecular interactions in the ion exchange mechanism of sorption of dyes of different classes by SiO2-PE films is established.
Micro- and mesoporous hybrid SiO2-PE films with improved structural and mechanical properties are obtained using nonionic surfactants as structuring templates. Rational control of film porosity is achieved by regulating the nature and micellar concentration of nonionic surfactant in SiO2 sol. The affinity of SiO2-PE films to organic analytical reagents is maximum under the conditions of matching the pore sizes of the film and the adsorbate molecule, which is realized in an increase in sorption capacity and a reduction in sorption equilibrium time by 2-3 times due to the “guest-host” effect. Hybrid mesoporous films modified analytical reagents are characterized by improved selectivity, sensitivity and stability of the analytical signal.
There were developed the conditions for obtaining of 17 types of new sensitive elements of optical and voltammetric sensors based on modified with analytical reagents SiO2-PE films. They were used in sorption-spectrophotometric, sorption-luminescent and voltammetric procedures for the determination of Fe (II), Zn (II), Al (III), Mo (VI), NO3-, formaldehyde, tetracycline, purine bases in environmental, biological, pharmaceutical, cosmetic objects and food. In terms of metrological characteristics, the developed methods are not inferior to those in homogeneous systems, are characterized by better selectivity, minimal sample preparation, reduced reagent consumption and detection limit of 0.1-1.0 MPC of the analyte.
A general approach has been developed for encapsulating proteins in SiO2 films on the surface of the electrodes by the method of electroinduced deposition. The main factors for regulating the electroanalytical characteristics of biocomposite SiO2-protein films have been defined, including variation of sol composition, time and value of the potential applied to the working electrode.
The addition of cationic CTAB and nanoparticles of Au, Pt, MnO2, CuO, nanodiamonds or carbon nanotubes into the biocomposite film increases the sensitivity, expands the concentration intervals of analytes determination, improves the selectivity and reproducibility of the analytical signal of modified electrodes. The stability of encapsulated in the film SiO2 enzymes increases 6-8 times compared with solutions. There are developed the sensitive elements of biosensors for voltammetric and amperometric determination of dissolved oxygen, hydrogen peroxide, glucose, choline, sorbitol, sucrose, maltose, streptomycin using electrodes modified SiO2-protein-nanoparticle biocomposite films. The developed electrodes can be used for "on-site" and "in-vitro" analysis.
