ИСТИНА

Nanocrystalline materials based on tin oxide are widely used as sensitive materials for gas sensors. To increase the sensitivity and improve the selectivity of materials based on semiconductor oxides, researchers synthesize nanocomposites using various dopants. Nowadays, chemical methods for the synthesis from the liquid phase are actively used for receiving functional materials based on tin oxide. During the process of the synthesis the dopants allocate in a complex way between the surface and the volume and main functions of the materials are changing: magnitude of electrical conductivity and reactivity. In this regard, the investigation of methods for determining the composition of the materials obtained in various ways is of exceptional importance for the establishment of the relationship "the conditions of synthesis - functional properties.” At the same time, one of the problems is the absence of standard reference materials for advanced samples. Gold, cobalt and chromium oxides were studied as modifiers. The systems with chromium are still not characterized enough; as the described sensory properties contradict one another. An approach to the determination of Au, Co and Cr modifiers on the surface and in the volume is suggested for advanced materials based on tin oxide by ICP-MS. For transference of gold and cobalt from the surface to the solution, the samples were treated with a mixture of acids (HNO 3 , HCl 1:3). For the selection of reagent for the dilution of chromium (that is presumably in the form of mixed oxides), HNO3, aqua regia, NH 3aq, EDTA and a solution of KSCN in NH 3aq were investigated on the surface of tin dioxide. It was shown that the use of KSCN allowed washing off chromium completely from the surface without dissolving the tin. To determine Au, Co in the volume of SnO 2 , the acid decomposition conditions (HNO3, HCl, HF) of the samples were chosen by means of an autoclave in a microwave oven. It has been found that gold and part of cobalt are situated on the surface of SnO2, while some cobalt is distributed in the volume of the material by ICPMS. According to the obtained data, 20% of chromium is on the surface of the material, 80% -distributed in the volume. And at the same time, the distribution of chromium on the surface and in the volume of SnO2 does not depend on the amount introduced in the synthesis. The results of the distribution of the dopants are used to select the synthesis and for the establishment of the connection of "the conditions of synthesis - functional properties.” The obtained results of the determination of the total composition of materials in solutions by the ISP-MS method were used to verify the validation of analysis of samples without decomposition by high resolution continuous source electrothermal atomic absorption spectrometry and by Xray fluorescence. Suspensions of the samples were used to inject into the atomizer. It was determined that glycerin and carboxymethylcellulose are effective stabilizers (stability is up to 30 minutes), however, the use of glycerin is complicated due to the selection of a viscous solution and the spreading of a drop on the surface of a graphite furnace.