Nanocomposites SnO(2)/SiO(2):SiO(2) Impact on the Active Centers and Conductivity Mechanism

This paper is focused on the effect of the stabilizing component SiO(2) on the type and concentration of active sites in SnO(2)/SiO(2) nanocomposites compared with nanocrystalline SnO(2). Previously, we found that SnO(2)/SiO(2) nanocomposites show better sensor characteristics in CO detection (lower detection limit, higher sensor response, and shorter response time) compared to pure SnO(2) in humid air conditions. Nanocomposites SnO(2)/SiO(2) synthesized using the hydrothermal method were characterized by low temperature nitrogen adsorption, XRD, energy dispersive X-ray spectroscopy (EDX), thermo-programmed reduction with hydrogen (TPR-H(2)), IR-, and electron-paramagnetic resonance (EPR)-spectroscopy methods. The electrophysical properties of SnO(2) and SnO(2)/SiO(2) nanocomposites were studied depending on the oxygen partial pressure in the temperature range of 200–400 °C. The introduction of SiO(2) results in an increase in the concentration of paramagnetic centers Sn(3+) and the amount of surface hydroxyl groups and chemisorbed oxygen and leads to a decrease in the negative charge on chemisorbed oxygen species. The temperature dependences of the conductivity of SnO(2) and SnO(2)/SiO(2) nanocomposites are linearized in Mott coordinates, which may indicate the contribution of the hopping mechanism with a variable hopping distance over local states.