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In₂O₃ and metal-doped (Ni or Ce) In₂O₃ mesoporous three-dimensional (3D) nanospheres arrays were synthesized via nanocasting using mesoporous silica as hard templates. Effects of Ni or Ce doping on the structure, optical and gas-sensing properties of the In₂O₃ nanospheres were investigated. Both the undoped and the doped In₂O₃ nanospheres showed single-phase structure without any impurity. The nanospheres were about 20nm in size and they stacked closely to form rigid 3D mesoporous structure. A change in the value of optical band gap was observed upon metal doping. The room temperature photo luminescence behavior also showed some differences between pure and doped In₂O₃. Compared with pure In₂O₃ nanospheres, the metal-doped In₂O₃ exhibited superior response, fast recovery and good selectivity to ethanol. The enhanced gas-sensing properties might be related to the doping of metal ion and its effective contribution towards the oxygen vacancies, conductivity and crystallite size of the grains.

A mesoporous silica bearing uniformly distributed copper oxide nanoparticles (CuO@mesoporous SiO₂) was prepared through silica nanocasting copper metal organic frameworks (MOFs) followed by calcination. The nanocasting filled the micropores of MOFs with silica and then, the calcination removed the organic linker in MOFs and converted copper metal ions into CuO particles, resulting in the CuO@mesoporous SiO₂ architecture. The characterization results indicated that the final product basically maintained the original MOF morphology and the mesoporous silica effectively prevented the aggregation of nanoparticles. In addition, the CuO@mesoporous SiO₂ exhibited a superior activity for catalyzing the oxidation of styrene, which could be attributed to the fact that the dispersed CuO particles in mesoporous silica provided more accessible catalytic sites and better stability. This work provides a new strategy to prepare nanoparticles@mesoporous silica with adjustable morphology structure, which has a promising potential in the field of heterogeneous catalysis.

Carbon nanotube (CNT) and mesoporous TiO₂ composite (CNT/meso-TiO₂) was synthesized by a nanocasting method using CNT-implanted mesoporous silica material as the template. The CNT was successfully incorporated within a mesoporous TiO₂ particle, and the CNT/meso-TiO₂ composite obtained exhibits a high surface area and well-established mesoporosity. Moreover, the composite material exhibits much lower electric resistance than those of mesoporous TiO₂ only and physical mixture of CNT and mesoporous TiO₂, which probably due to the large interface area and strong junction between the implanted CNT and TiO₂ framework in the composite.