| Energy shortage, environmental pollution and ecological damage were the maincrises we are faced with the development of industry. Among them, environmentalpollution is close to our healthy which need to pay more attention to. Currently, thewater and air pollution were always naturally pushed out to environment which putour life in tremendous danger. As a thermal sensitivity and photosensitivity material,semiconductor has been widely used in decomposing organic dyes and detecting toxicgas. Besides the wide band gap, the major limitation to achieve high photocatalyticactivity and gas sensing performance in semiconductor is the quick recombination ofcharge carriers. Hence, over the past decades, a number of efforts have been attractedto solving these problems. On the other hand, graphene flourishes due to its highconductivity, large surface area, and high transparency since2004. Graphene caneffectively improve the transfer efficiency of electron and prevent nanoparticles fromaggregation. Therefore, loaded on graphene can effectively improve thephotocatalytic activity and gas sensing performance of semiconductor.The main research topic is to improve the photocalytic and gas sensingperformance of semiconductors.(1) Firstly, spindle-like mesoporous maghemite nanoparticles (MMNs) have beenfabricated via a glucose-assisted hydrothermal and calcination process by using β-FeOOH nano-spindles as the precursor. The phase purity, morphology, structureand surface area of MMNs were investigated by X-ray diffraction, X-rayphotoelectron spectroscopy, transmission electron microscopy, high-resolutiontransmission electron microscopy and Brunauer-Emmett-Teller analysis. The resultsdemonstrated that MMNs preserved a good individual dispersion and had a uniformmorphology of about150nm in length and50nm in width. These nanoparticles wereused as gas sensors and exhibited high responses for many reducing gases, includingethanol, acetone, ethyl acetate, benzene, etc. Specifically, the gas response (Ra/Rg) of MMNs to1000ppm acetone was about217. Moreover, the MMNs-based sensor alsoshowed a good selectivity and long-term stability under various ambient environments.The superior gas sensing properties of MMNs may be due to their large surface area(86.9m2g-1) and special crystal structure. Additionally, the MMNs were loaded onthe rGO sheets. The composites showed enhanced gas sensing performance thanMMNs.(2) Secondly, reduced graphene oxide (rGO)-zinc oxide (ZnO) composites weresynthesized by a two-step hydrolysis-calcination method, using graphene oxide andZn(Ac)2as precursors. The structure and morphology of as-prepared samples werecharacterized by thermogravimetric analysis, X-ray diffraction, Fourier transformsinfrared spectroscopy and transmission electron microscopy. It was shown that thewell-dispersed ZnO nanoparticles (NPs) were deposited on rGO homogeneously. Sofar as ZnO NPs with different diameters were synthesized in the varied samples, theZnO NPs with an average diameter of around10nm which was obtained at theheating temperature of300oC for4h exhibited higher photocatalytic activity thanothers. The relatively low amount of rGO-ZnO composites (5mg) demonstratedenhanced photocatalytic activity to decompose methyl orange (MO,40mg L-1)efficiently under low-power ultraviolet light. Furthermore, rGO-ZnO compositesexhibited high sensitivity, and the response can be achieved50.09to1000ppmacetone. In addition, the ultraviolet light-induced photocatalytic mechanism as well asgas sensing mechanism was also discussed. Both rGO and crystallinity playedimportant roles in improving photocatalytic activity and gas sensing property.(3) Finally, TiO2/MoS2/GO composites were synthesized used coprecipitationmethod in different ratio of Ti to Mo. Among different composites, the stack of MoS2layers whose morphology does not change will alleviate with the increase of TiO2.The XRD results show that the TiO2NPs were effectively loaded on the MoS2/GO films and embed in the MoS2layers. The composites show photocatalyticperformance. |
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