Selective gas sensing response from different loading of Ag in sol–gel mesoporous titania powders

Bare and Ag loaded TiO2 (0.05, 0.5, and 5.0 mol% Ag) powders prepared by sol–gel process have been used for the detection of ethanol, LPG, acetone and toluene gases. These materials were well characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) specific surface area analysis techniques. Specific surface area increased with increasing Ag loading in these mesoporous materials. A thorough TEM/HRTEM investigation with X-ray maps of the modified particles shows the extent of TiO2 surface coverage by Ag nanoparticles. From the comparative study of the sensor response of Ag–TiO2 powders for various gases, it is observed that each Ag loading resulted in the highest response towards a particular gas or in other words, every gas responded best towards a particular Ag loading of the sensor material, i.e. 0.05 mol% Ag–TiO2 sensor showed highest response towards ethanol, 0.5 mol% Ag–TiO2 sensor showed best response towards toluene, whereas, bare TiO2 proved to be the best sensor for both acetone and LPG gases. This establishes that Ag loading is not required for detection of acetone and LPG gases. On the basis of detailed materials characterization, a mechanism for the gas sensing response of each analyte has been discussed.