近些年来，现代工业发展迅速，推动着人类的进步。但是，随之而来的环境污染尤其是水污染问题也变得格外突出。为了解决这个问题，人们开发了多种方法。其中，半导体材料以其优异的光催化降解有机污染物性能受到了越来越多的关注。然而，传统的半导体材料，如二氧化钛(TiO₂)、氧化锌(ZnO)等，禁带宽度较大，导致其只在紫外光范围内产生响应，因此，它们的应用前景受到了极大的限制。近期，包括钨酸铋(Bi₂WO₆)在内的具有窄禁带宽度的新型光催化剂成为了研究的热点，因为这些光催化剂可以在紫外光和可见光区域同时产生响应。 Bi₂WO₆是一种最简单的Aurivillius型氧化物，其禁带宽度约为2.7 eV，可以吸收波长在450nm以内的可见光，因此，可以在可见光照射下催化降解有机污染物，有效地提高对太阳光的利用效率。 本论文以Bi₂WO₆为研究对象，首先研究了Bi₂WO₆的形貌调控及其影响因素，并探究了形貌对其光催化性能的影响；其次研究了外界条件(如γ射线辐射)对Bi₂WO₆晶体结构及其光催化性能的影响；最后通过不同的实验方法，制备出两种具有良好光催化性能的Bi₂WO₆复合材料，用于提高Bi₂WO₆的催化降解性能。本论文以Bi₂WO₆为研究主线，其主要研究内容和成果如下： 一、以Bi(NO₃)₃·5H₂O和Na₂WO₄·2H₂O为前驱体，聚乙烯基吡咯烷酮(PVP)为稳定剂，通过简单的水热法制备出Bi₂WO₆晶体材料。研究发现，调节PVP的浓度和分子量可以制备出具有不同形貌的Bi₂WO₆。XRD和HRTEM研究结果表明，PVP的添加不会改变Bi₂WO₆的晶体结构，但PVP在初始形成的Bi₂WO₆纳米片上的分布会诱导晶体生长，随着PVP浓度的增加，Bi₂WO₆的形貌会有明显的变化。同时，随着PVP分子量的增加，Bi₂WO₆由简单的片状(S-BWO)变为花瓣状(F-BWO)、红细胞型(B-BWO)和圆柱状(SP-BWO)等不同的形貌。具有不同形貌的Bi₂WO₆的光催化性能，则是通过在可见光条件下降解罗丹明B (RhB)来表征。研究结果显示，S-BWO的光催化性能最好，而SP-BWO的光催化性能最差，这主要取决于它们的禁带宽度和比表面积。 二、以磁性四氧化三铁(Fe₃O₄)纳米粒子为核，在其表面生长一层介孔纤维状二氧化硅(F-SiO₂)，形成核壳结构的Fe₃O₄@F-SiO₂粒子，再以Fe₃O₄@F-SiO₂模板，通过水热法制备出Fe₃O₄@Bi₂WO₆纳米粒子。随着介孔Bi₂WO₆壳层的形成，F-SiO₂层因酸蚀效应而消失。因此，我们最终制备了具有高比表面积(127.3㎡／g)的新型核-壳型介孔Fe₃O₄@Bi₂WO₆纳米粒子。可见光催化降解亚甲基蓝(MB)研究结果表明，介孔Fe₃O₄@Bi₂WO₆纳米粒子具有优异的物理吸附和可见光催化性能，对水溶液中MB的总去除率高达98％。此外，介孔Fe₃O₄@Bi₂WO₆纳米粒子可以很容易地通过磁分离而循环使用，并且在五次循环催化后仍保持较高的光催化活性。 三、以Bi₂WO₆材料为目标物质，探究γ射线对其晶体结构和光催化性能的影响。研究发现，当吸收剂量达到507kGy(5.28kGy·h⁻¹，96h)时，Bi₂WO₆粉末的颜色发生了转变，由淡黄色变为浅蓝色。XRD分析结果显示，随着吸收剂量的增加，Bi₂WO₆的(113)晶面的特征峰向高角度发生了微弱的转移，由28.37°转移至28.45°，证明了Bi₂WO₆晶体结构的微弱变化，而这种变化是由于Bi₂WO₆晶体在γ射线的作用下产生了氧空位缺陷，通过XPS分析也得到了确认。不同吸收剂量的Bi₂WO₆在可见光照射下降解MB结果表明，随着吸收剂量的增加， Bi₂WO₆的光催化活性相应增加。三次循环催化后，Bi₂WO₆的光催化性能仍保持在较高的水平，说明拥有氧空位的Bi₂WO₆具有很好的稳定性和循环催化性能。 四、以3，4-乙烯二氧噻吩(EDOT)为单体，Bi₂WO₆为基体材料，以γ射线辐射氮气饱和的水溶液产生的·OH和H₂O₂为引发剂，引发EDOT单体聚合，制备了Bi₂WO₆／PEDOT复合材料。紫外可见光谱分析结果表明，经PEDOT掺杂后，复合材料对光的吸收由450 nm提升至700 nm左右，这大大提高了Bi₂WO₆对太阳光的利用效率。光催化降解MB实验表明，PEDOT的掺杂可以有效提高Bi₂WO₆的光催化性能，且随着PEDOT含量的增加，其催化性能也相应提高。 关键词：钨酸铋；介孔核壳结构；聚(3，4-乙烯二氧噻吩)；γ-射线；光催化降解

In recent years, the rapid development of modern industry has promoted the progress of humanity. However, the ensuing problems of environmental pollution, especially water pollution, have also become even more prominent. In order to solve this problem, people have developed a variety of methods. Among them, semiconductor materials attracted more and more attention due to their excellent photocatalytic performance on the degradation of organic pollutants. Nevertheless, conventional semiconductor materials such as TiO₂, ZnO can only respond in the ultraviolet region due to their large band gaps. Therefore, their application prospects have been greatly limited. Recently, novel photocatalysts with narrow band gaps including bismuth tungstate (Bi₂WO₆) have become a research hotspot because they can respond both in the ultraviolet and visible light region. Bi₂WO₆ is one of the simplest Aurivillius type oxides with a band gap of about 2.7 eV, which can absorb visible light at wavelengths up to 450 nm. Therefore, it can photocatalyze the degradation of organic pollutants under visible light irradiation and effectively improve the utilization efficiency of sunlight. In this dissertation. Bi₂WO₆, was firstly used as the research object to study the preparation and influential factors of Bi₂WO₆ with different morphologies, the effect of morphology on the photocatalytic performance of Bi₂WO₆ was also explored. Secondly, the influence of external conditions (such as gamma ray radiation) on the crystal structure and photocatalytic performance of Bi₂WO₆ was studied. Finally, the composites combined Bi₂WO₆ with other functional materials were prepared to improve their photocatalytic performance. In this dissertation, Bi₂WO₆ is the main line of research, and its main research contents and achievements are as follows: 1.Bi₂WO₆ crystal materials were prepared by simple hydrothermal method using Bi(N0₃)₃·5H₂O and Na₂WO₄2H₂O as precursors and PVP as stabilizer. It was found that Bi₂WO₆ with different morphologies can be prepared by simply adjusting the concentration and molecular weight of PVR XRD and HRTEM results show that the addition of PVP does not change the crystal structure of Bi₂WO₆. However, the distribution of PVP on the initially formed Bi₂WO₆ nanosheets induces crystal growth. With the increase of PVP concentration, the morphology of Bi₂WO₆ changes significantly. Meanwhile, the morphology of Bi₂WO₆ varied from simple sheet-like (S-BWO) to some complicated morphologies, including flower-like (F-BWO), red blood cell-like (B-BWO), and square-pillar-like (SP-BWO) with the increase of the molecular weight of PVP. The photocatalytic performances of Bi₂WO₆ with various morphologies on the decomposition of RhB under visible light irradiation reveal that S-BWO has the best photocatalytic performance, while SP-BWO has the worst. This depends mainly on their band gaps and specific surface areas. 2.Fe₃O₄ nanoparticles were first modified by a fibrous hierarchically mesoporous silica layer (F-SiO₂). After that, a mesoporous Bi₂WO₆ shell was grown in situ through hydrothermal reaction. Along with the formation of mesoporous Bi₂WO₆ shell, the intermediate F-SiO₂ layer faded away by the acid etching effect. As a result, novel spherical core-shell mesoporous Fe₃O₄@Bi₂WO₆ nanoparticles with a high BET surface area of 127.3 m²/g were fabricated. The photocatalytic performance of the Fe₃O₄@Bi₂WO₆ nanoparticles on the decomposition of methylene blue (MB) under visible light had been investigated. The results show that the mesoporous Fe₃O₄@Bi₂WO₆ nanoparticles combine the excellent physisorption and visible-light photocatalytic performance on the decomposition of MB so that the total removal ratio oi'MB from the solution can be achieved as high as 98%. Furthermore, the mesoporous Fe₃O₄@Bi₂WO₆ nanoparticles can be easily recycled through magnetic separation, and maintain high photocatalytic activity after five cycles. 3.Bi₂WO₆ powders were first used as target substance to investigate the influence of gamma ray on its crystal structure and photocatalytic performance. It is found that the color of Bi₂WO₆ powders changed from light yellow to light blue when the absorbed dose reaches 507 kGy (5.28 kGy·h⁻¹ 96 h), indicating the change of physical property of Bi₂WO₆. The XRD spectra of the irradiated Bi₂WO₆ nanocrystals show the characteristic 2θ of (113) plane shifts slightly from 28.37° to 28.45° with the increase of the absorbed dose, confirming the change in the crystal structure of Bi₂WO₆. And the change is originated from the generation of oxygen vacancies which can be confirmed by XPS spectra. The photocatalytic performances of Bi₂WO₆ with different absorbed doses on the decomposition of MB under visible light irradiation reveal that the photocatalytic activity of Bi₂WO₆ increased correspondingly with the increase of absorbed doses. After three cycles of photocatalysis, the photocatalytic performance of Bi₂WO₆ remains at a high level, indicating that Bi₂WO₆ with oxygen vacancies has good stability and cyclic photocatalytic performance. 4.The Bi₂WO₆/PED0T composites were prepared by γ-ray radiation method using EDOT as the monomer and Bi₂WO₆ as the matrix material. The formation of PEDOT nanoparticles is related with the strong oxidative atmosphere in the nitrogen saturated aqueous solution under the irradiation of γ-ray. UV-vis diffuse reflectance spectra results showed that after the doping of PEDOT, the absorption of light by the Bi₂WO₆/PED0Tcomposites increased from 450 nm to 700 nm, which greatly improves the utilization efficiency of sunlight. The photoeatalytic performances of Bi₂WO₆/PEDOT composites on the decomposition of MB under visible light irradiation showed that the doping of PEDOT can effectively improve the photoeatalytic performance of Bi₂WO₆ and the photocatalytic performance increased accordingly with the increase of the content of PEDOT. Keywords: Bismuth tungstate; Mesoporous core-shell structure; Poly (3,4-ethylenedioxythiophene); γ-ray; Photocatalytic degradation