Highly sensitive and selective volatile organic compound gas sensors based on mesoporous nanocomposite monoliths

Abstract

We introduce the use of highly ordered mesoporous silica/metal oxide (HOM/MO) nanocomposite monoliths for volatile organic compound (VOC) gas sensor applications. Monoliths with various loadings of semiconducting metal oxides (SnO2, ZnO, NiO, CuO, and Fe2O3) were prepared through instant direct-templating method. The dependence of the doping elements and doping levels on the mesoporous structure of monoliths was investigated. The results indicate that the monoliths retained their ordered porous structure at up to 40% doping by SnO2. The high-resolution transmission electron microscopy and scanning transmission electron microscopy images revealed that the SnO2 nanocrystals were homogenously distributed in the matrix of the HOM monoliths up to 40% doping concentration. The gas-sensing properties of the HOM/SnO2 and HOM/ZnO monoliths to acetone, benzene, and ethanol were also investigated. Sensors based on the HOM/SnO2 nanocomposites showed highest sensitivity, selectivity, response rate, and response stability to acetone compared with the others. This finding provides interesting results on the large-scale synthesis of HOM/MO monoliths with the ability to control pore structure and opens a new strategy in the application of mesoporous nanocomposites for gas sensors. In addition, various HOM/MO nanocomposite monoliths are easily synthesized through this method. It expands the potential of HOM/MO nanocomposite monoliths to other applications, such as catalysis and adsorption.