The active sites on the surface of the nanocrystalline metal oxides and specificity of their interactions with nitrogen-containing organic compounds

      The synthesis of several series of nanocrystalline materials based on SnO₂ crystallite size controlled in a range of 5-40 nm waste sol-gel method, followed by drying and annealing in air at temperatures of 300-900 deg. For the synthesis of nanocomposites based on nanocrystalline SnO₂ ( introduction to its structure modifiers ) impregnation techniques were used (including wetness). Selected synthesis methods allow to control the composition and content of the resulting materials used modifiers (SiO₂, Al₂O₃, Cr₂O₃, Nb₂O₅, Au). The resulting nanocomposites were characterized complex techniques - XRD, BET , TPR - H₂, TPD-NH₃. Composition highly sensitive materials identified by elemental analysis, - an X-ray fluorescence spectrometry for total internal reflection. Characterized by electrical and sensory properties of materials.
      Shown that the system SnO₂-SiO₂ method " prishivki " organic precursor to the surface modifier can effectively control the quantitative composition of the resulting samples. It was found that the growth of the content up to 3 % SiO₂ by weight. samples simultaneously with increasing the heat treatment temperature to 700 њ C accompanied by increased sensitivity to touch SB. A similar pattern is typical for the system SnO₂-Al₂O₃, but the optimal annealing temperature is in this case 500 њC . The observed effect , judging by the TPR - H₂ is connected not only with a change in the chemical activity of materials in conjunction with gases, but also a change in their electrophysical parameters .

KEYWORDS
nanocrystalline state , surface chemistry , reactivity , solid, chemisorption , the active center