Mesostructure And Framework Composition Manipulation Of Ordered Mesoporous Indium Oxide For Gas Sensors

Highly sensitive gas sensors have attracted extensive attention because of their prominent roles in the areas of environmental monitoring, industrial production. The researching and development of the gas sensors has been more and more important. Preparation of sensitive materials with excellent sensitive properties is the core of building gas sensor. Ordered mesoporous metal oxides are highly promising candidates for gas sensing materials because of their unique properties, such as regular and adjustable pore size, high surface area, large pore volume, diversified composition and mesostructure, well-controlled morphology. In this paper, a series of ordered mesoporous indium oxides and their metal ion doped solid solution counterparts with tunable textual parameters were successfully synthesized by using two kinds of ordered mesoporous silica MCM-48 and KIT-6 with same double-gyroid mesoporous structure but different pore sizes as hard templates and the application of materials on detecting toxic gases (such as HCHO、C6H6、CH3COCH3) of these indium oxide based specimes was also investigated:1. Ordered mesoporous indium oxide with large specific surface area (-300 cm2/g) and ultrathin frameworks (～3nm) was firstly and successfully synthesized through the nanocasting route by using indium nitrate hydrate as precursors and ordered mesoporous silica MCM-48 with cubic laid symmetry as hard template. Only 20% of the pore volume of MCM-48 could be filled by indium nitrate precursors, whereas ordered mesoporous silica KIT-6 with the same laid symmetry but larger mesopores could contain about 100% the pore volume of precursors. Increasing the amount of indium nitrate precursors would result in some bulk indium oxide byproducts and thus decrease the specific surface area and pore volume. The resultant ordered mesoporous indium oxide specimens exhibits high and fast response to formaldehyde (HCHO), where the response for 46 ppm of HCHO is up to 110 and the response and recovery time is 7 and 15 s, respectively. The loss of specific surface area resulting from bulk indium oxide byproduct could result in the decrease of gas sensing properties.2. Ordered mesoporous indium oxide based solid solution containing different doping metal ions (such as La, Ce, Er) were successfully synthesized through the above-mentioned method by using indium nitrate hydrate and other metal salts as mixed precursors. Ordered mesoporous La-doped indium oxide templated from MCM-48 exhibits higher response than those without doping La ions, whose response towards 46 ppm of HCHO is up to 1900 at the optimized La/In of 0.05. On the contrary, those ordered mesoporous La-doped indium oxide templated from KIT-6 exhibits a maxtium response towards 46 ppm of HCHO at the La/In of 0.1, about 375.Moreover, ordered mesoporous Er-doped indium oxide templated from KIT-6 exhibits a higher response towards 46 ppm of HCHO at the Er/In of 0.1 than those doped La ions, about 760.