ИСТИНА

Effect of active sites of nanocrystalline tin(IV), tungsten(VI), and zinc-indium oxides on sensing behavior to CO and ammonia is analyzed. The oxides were synthesized by aqueous deposition routes, and subsequently modified by catalytic (Pd, Ru) and/or adsorptive (In, SO4) additives. Surface sites and gas-solid interaction were investigated by HRTEM, EDX-mapping, FTIR, probe molecule methods, sensing test and DRIFT spectroscopy. CO sensitivity of ZnO(In) increased with the dopant amount, in agreement with DFT-predicted catalytic activity of In(III) in CO oxidation. The largest catalytic effect favoring CO detection down to 1 ppm at room temperature was shown for Pd-modified sensors. Gas-solid interaction route in such systems was controlled by CO chemisorption on Pd-clusters irrespective of the supporting matrix. The sensitivity of SnO2/SO4 and WO3 to ammonia was improved by increasing surface acidity. The largest NH3 sensitivity was observed for the materials with modified by Ru clusters, which provide catalytic oxidation of target molecules. Surface acidity in the latter case should not be too strong for not to deactivate the adsorbed ammonia species.