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伽蓝o0

铜虫 (小有名气)

应助: 1 (幼儿园)
金币: 42.8
帖子: 257
在线: 157.1小时
虫号: 2857679
注册: 2013-12-08
性别: GG
专业: 有机分子功能材料化学

[求助] 求助 Introduction翻译

有没有大神帮忙翻译一下。。或者给我一篇现成的化学文献 Introduction翻译+原文。。字数不要太少就好。。。。谢谢了

1. Introduction
Recent development in the area of water treatment gave birth to an improvement of the oxidative and catalytic degradation of organic compounds dissolved in aqueous media. Photocatalysis, known as green technique, offers great potential for complete elimination of toxic chemicals in the environment through its efficiency and broad applicability. Semiconductor metal oxides, such as TiO2, ZnO, ZnS, CdS, Fe2O3 nanoparticles (NPs), have so far been shown to be the most promising materials in this field [1], [2], [3], [4] and [5]. Among these semiconductor metal oxide, ZnO and TiO2 (with wide band gaps of about 3.2 eV and 3.37 eV, respectively) have been recognized as the excellent materials because of their excellent electronic, chemical and optical properties with high photosensitivity and nontoxicity [6], [7] and [8]. However, the rate of electron–hole (e–h) recombination during photocatalytic process limits the application of these materials under UV irradiation [5]. Furthermore, nano-sized particles (having high surface area) are found to be more effective photocatalyst but their recovery from the reaction system is very difficult, which limits their application environmentally (secondary pollution) and economically (loss of catalyst) [9]. Various attempts have been made to address the above mentioned drawback. Doping novel metal into the photocatalyst lattice [10] and [11] and coupling semiconductors [3], [12] and [13] are effective ways to decrease the e–h recombination process whereas providing a fixed surface with sufficient surface area (such as polymeric nanofibers) is the way to increase its durability for repeated use. Our previous work showed that the Ag-loaded TiO2/nylon-6 electrospun mat can prevent the loss of catalyst and can be repeatedly used [9].
Crystalline TiO2 and ZnO, both in the pure form or as a composite, are semiconductor oxides widely used in photocatalytic reactions [14], [15] and [16]. In principle the coupling of TiO2 with ZnO seems useful in order to achieve a more effective e–h pair separation under radiation and, consequently, a higher photodegradation rate. The increase of the lifetime of the photoproduced pairs, due to electron and hole transfer between the TiO2 and ZnO, is invoked in many cases as the key factor for the improvement of the photocatalytic activity. Therefore, incorporating the two materials into an integrated structure is of great significance because the resulting products may possess improved physicochemical properties, which should find applications in variety of fields. But getting such structure in nano scale is still a giant challenge because of the structural complexity and difficulty in controlling the crystal growth of materials. Therefore, the suitable technique and reagents play an important role in the preparation of the photocatalyst. Several methods have been made to fabricate ZnO with TiO2, which needed high temperature, long time, and more reagents [17], [18], [19] and [20].
Here, to exploit the effect of the unique shape of ZnO and incorporation of TiO2 NPs to ZnO flower as well as the photocatalytic activity of hierarchical composite nanostructure, we synthesized ZnO nano flower decorated with TiO2 NPs on their surface. The objective of the present study was to prepare TiO2-doped ZnO flower as a photocatalyst with one-pot hydrothermal method under a short period of time and at low temperature. In this work polycrystalline powders were prepared by supporting TiO2 NPs (Aeroxide P25) (P25 NPs) on the surface of ZnO nano-flower obtained from zinc nitrate hexahydrate during hydrothermal synthesis. Zinc oxide flower not only increase the photocatalytic efficiency by preventing e–h recombination process but also provide a fixed position for TiO2 NPs which can prevent the loss of TiO2 NPs during recovery from the reaction system. The photocatalytic activity as well as recovery of these samples for repeated use was evaluated by degradation of methylene blue (MB) solution under UV-irradiation.

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