Tuning Microstructures Of Semiconductor Materials For Gas Sensing And Photocatalysis

Semiconductor industry plays an important role in technology-based sectors of society,and thus semiconductor materials have become one of the most influential materials inmodern electronic information industry and high-tech areas. Because of their uniqueoptoelectronic conversion characteristics, gas sensing and photocatalytic properties,semiconductor materials have been widely used in manufacturing various kinds of electroniccomponents, such as light-emitting diodes, gas sensors, solar cells, etc. More importantly,semiconductor materials possess regulated function, providing great potential in thedevelopment of new types of functional materials or products, and have become the researchfocus of modern materials science. So far, many domestic and foreign research workers arecommitted to the controllable synthesis and optimization of semiconductor functionalmaterials. It has been demonstrated that, designing and optimizing macro-functions ofsemiconductor materials can be realized by microstructure-regulating. Therefore, furtherstudying and clarifying the microstructure-regulating mechanism of semiconductor materialsis the key issue, and the theoretical basis of designing high-performance functional materialsor products. This dissertation focuses on the controlled preparation and modification of NiO,In2O3and BiOI materials, and the microstructure-regulating of gas sensing and photocatalyticproperties. The details are summarized as follows:(1) Ni1-xFexO (x=00.05) nanoplatelets were synthesized by a facile hydrothermalprocess. The crystal structure, morphology and composition of the as-prepared samples werecharacterized by XRD, SEM and XPS. The gas sensing properties of the as-preparedNi1-xFexO sensors, such as the optimal composition and working temperature, sensitivity anddetection range were systematically investigated. Finally, the influence of Fe-dopant and itsfunctional mechanism were discussed.(2) Urchin-like InOOH microspheres were successfully prepared in glycol/watermixtures by a convenient and controllable method. Such experimental parameters as solventsand additives on the composition and morphology of the urchin-like InOOH microsphereswere discussed in details. The growth mechanism of the urchin-like InOOH microspheres wasinvestigated and proposed by a time-evolution process. Furthermore, by controlling theannealing temperature under ambient pressure of the as-prepared urchin-like InOOHprecursor, rhombohedral corundum-type indium oxide (rh-In2O3), cubic bixbyite-type indiumoxide (c-In2O3) and mixed phases of rh-In2O3and c-In2O3products were obtained, respectively. Finally, the influence of phase composition and its functional mechanism on thegas sensing properties of the prepared In2O3sensors were systematically investigated.(3) Based on the idea of structural similarity of bismuth-containing materials and p-nheterojunction, Bi2O2CO3/BiOI microspheres were fabricated through a facile partial anionexchange method with the assistance of sodium citrate between urea and BiOI flower-likemicrospheres, which were prepared by a low-temperature chemical bath method. The contentof Bi2O2CO3in the composites was regulated by modulating the amount of urea as a precursor,which would decompose to generate CO32-in the hydrothermal process. In addition, theimpacts of urea and sodium citrate on mediating the morphology and composition werediscussed in details, and the formation process of Bi2O2CO3/BiOI heterojunctionmicrospheres was proposed. Furthermore, the influence of component ratio on photocatalyticactivity and the mechanism for improved photocatalytic performance were systematicallyinvestigated. The present strategy is expected to be extended to synthesize otherbismuth-containing heterostructured visible-light-driven photocatalysts with controllablestructures.