RESUMEN
The properties of planar sensors based on tin dioxide and indium oxide used for the determination of acetone vapors have been studied. Sensors based on synthesized SnO2 and In2O3 nanopowders showed high sensitivity to low concentrations of acetone in a humid environment which simulates human exhalation. The addition of a small amount of AuIII ions to hydroxide sols significantly increases the threshold sensitivity and the sensor response in a wide range of acetone concentrations. In2O3-Au sensors have the maximum sensitivity at an operating temperature of 325 °C. The In2O3-Au-sensors reliably record the change in acetone concentration in the concentration range from a minimum of 0.1 to 5 ppm with high accuracy, which is necessary for rapid diagnostics of the condition of patients with diabetes (1.8-5.0 ppm). The high sensitivity of the obtained sensors is explained by the structural features and the surface conditions of oxides and gold nanoparticles, which depend on the sample synthesis conditions.
RESUMEN
The defect structure and phase formation processes occurring in the bulk and on the surface of titanium carbide (TiC) under thermal treatment in different ambient atmospheres (air, hydrogen, vacuum) were characterized using XRD, SEM, EPR, XPS and IR-spectroscopy. The oxidized states of both titanium (TiO2-x ) and carbon, in the form of carbonate-carboxylate structures (O-C[double bond, length as m-dash]O), were found on the surface of untreated TiC. Carbon vacancies were detected as paramagnetic defects in the crystalline lattice of TiC. The heat treatment of TiC in reducing conditions leads to an increase of the electrical conductivity associated with the formation of structural defects. Annealing of TiC in air causes its oxidation with the formation of an anatase-type TiO2 phase. Paramagnetic defects typical of both TiC and TiO2-x were revealed.
