ИСТИНА

Applications of nanoparticles in chemical analysis is very diverse: to enhance a signal in Raman and fluorescence spectroscopy, voltammetry, when developing electrochemical, piezoquartz, immuno- and optical sensors, for increasing sorption ability of materials. In most cases, nanoparticles keep many of their valuable properties in immobilized on solid matrices state. As solid matrices for nanoparticles immobilization one often uses glass, different polymers such as polyvinylpyrrolidone, polyethylene, oligourethanemethacrylate et al. Practically unexplored in this role matrix is polyurethane foam (PUF). Meanwhile, chemical stability, mechanical durability, easiness of separation from a solution, relative cheapness and availability of this polymer could play an essential role while producing new nanocomposites for chemical analysis. In this work the possibility of synthesis of PUF modified with silver nanoparticles (PUF/Ag) is investigated. The potentialities of using destruction/formation of silver nanoparticles processes in PUF matrix for determination of oxidants and reductants are demonstrated. Two ways to obtain PUF/Ag have been suggested. First of them was based on sorption of previously synthesized in water solution silver nanoparticles by PUF. The second one included sorption of silver nitrate by PUF followed by reduction of the silver ions directly in PUF matrix. Due to silver nanoparticles, PUF/Ag had a surface plasmon resonance (SPR) band in diffuse reflectance spectra. Spectral characteristics and optimal conditions of the composite formation have been found. It has been stated that when PUF/Ag getting in touch with hydrochloric acid solution of Fe(III) or dichromate ions, the SPR band disappeared and the color of the samples was changed from yellow to white that seems to be connected with the oxidation of the nanoparticles. On the contrary, formation of the nanoparticles in PUF matrix by the reduction of sorbed silver nitrate with ascorbic acid resulted in appearing SPR band and changing color from white to yellow. These processes were shown can be used for determination of oxidants and reductants. Metrological performance of the determination of Fe(III), dichromate and ascorbic acid using such an approach has been evaluated. The possibility of decreasing the detection limits by varying volume of the solution and content of the nanoparticles or silver ions in PUF matrix has been demonstrated. The technique suggested has been tested for determination of Fe(III) in natural waters and ascorbic acid in vitamin samples. Thus, such a composite material based on PUF and silver nanoparticles seems to be attractive for environmental analysis.