量子点敏化ZnO三维分级结构的制备、表征及其光催化性能研究

In this project, according to the matching of energy levels, some new composite photocatalytic semiconductor materials based on quantum dot-sensitized three-dimensional ZnO hierarchical architecture will be designed. The novel structure is not only helpful to improve catalytic activity and to overcome the agglomeration problem of conventional photocatalyst due to its possessing the high specific surface area and the steric effect of "house of cards" of the hierarchical ZnO architecture, but also helpful to tune the energy band structures of photocatalyst with the size- and component-dependent optical properties of colloidal semiconductor quantum dots (QDs). The synthesis of QDs with different composition, size, surface state, doping and controllable absorption spectra will be explored to extend the spectral response range, increase the photocatalytic efficiency and resistance to photocorrosion for the new composite photocatalyst. The crystal structure, surface condition, geometric shape and surface physical and chemical properties of QDs-sensitized three-dimensional ZnO hierarchical architecture will be studied by using various modern characterization techniques. The various mechanism and influencing factors of the exciton separation, transmission route, mobility and recombination in the hetero-junction structure will be also studied. The photocatalytic activities of the photocatalyst will be evaluated using degradation efficiency of dyeing and printing wastewater under the ultraviolet and visible irradiation, respectively. The photodegradation mechanism will be detailedly studied, and also the parameters of influencing the photocatalytic efficiency will be optimized. The emphasis is on demonstrating the mechanism of interaction and synergetic effect between ZnO and QDs and thus revealing their structure-activity relationship. The project will offer a new idea to develop the Zn-based composite photocatalyst with novel structure and higher efficiency.

本项目拟以能级匹配为原则，设计用量子点敏化ZnO三维分级结构，充分利用ZnO三维分级结构高比表面积、多孔道的表面特性和空间位阻效应，和量子点独特的随尺寸、组分变化的光谱特征，构筑能带结构可调、既具有较高催化活性又能抗团聚的新型ZnO复合半导体光催化剂。从基于拓宽催化剂光谱响应范围、提高催化效率及抗光腐蚀性能的角度出发指导组分、尺寸、表面态、掺杂态等可调的全光谱吸收量子点的合成。运用现代表征技术对量子点敏化的ZnO分级结构的晶体结构、表面状态、形貌等进行表征，测试其表面光物理化学性能，研究异质结体系中激子分离、传输、复合机制及其影响因素。分别在紫外和可见光照射下，考察其降解染料废水的效果，详细研究光催化降解机理和提高催化效率的基本途径，重点阐明ZnO和不同量子点之间的相互作用机制和协同催化效应，揭示纳米材料的微观结构与性能之间的构效关系，为新型高效锌基复合光催化剂的开发研究提供新思路。

通过多组分耦合、多结构协同构筑复合光催化剂，是拓展光催化剂光谱响应范围、提供光催化效率的重要途径。本项目根据构筑量子点敏化ZnO三维分级结构复合材料能带结构要求，发展了合成CdSe量子点的宏量制备方法，获得了吸收光谱恒定、尺寸单一、具有强激子发光的CdSe“幻簇”量子点；设计了一种绿色液相反应体系，合成了二元ZnS、CdS量子点，三元ZnxCd1-xS合金量子点，实现了通过组分调节量子点能带；以单一分子源作壳前驱体，合成了ZnxCd1-xS/ZnS核壳量子点。揭示了量子点的形核生长机理及组分-结构-性能的构效关系。.以锌片、铜片等柔性基片为基底，开展了不同形貌ZnO微纳结构薄膜的制备及其降解有机污染物的光催化性能研究。以Zn片为基底和锌源，采用正丁胺-水热体系原位生长Zn基ZnO纳米线薄膜，改变反应条件调节ZnO致密度及结构中的氧空位浓度，实现了其光催化活性的调节。在反应体系中添加硝酸镧，通过改变La3+浓度，诱导Zn基底ZnO纳米结构形貌按线-锥-棒-碟演化，棒状ZnO因致密度和氧空位浓度高且有更多的（002）极性暴露面，光催化活性最高。.采用两步法合成了Cu基ZnO纳米结构，改变电镀工艺及水热条件，考察了ZnO形核生长过程。控制氨水浓度，获得了紧密堆积的双层对称ZnO三维分级结构；往水热体系中加入微量可溶性金属盐，诱导生成了各种新颖形貌的ZnO分级结构，揭示了水热条件及金属离子的添加对ZnO成核生长的影响机制，ZnO分级结构尺寸、形貌、比表面积和其光催化性能的关系。.采用连续离子层沉积法，以Na2S、Pb(NO3)2为阴、阳离子源，制备了PbS量子点敏化的Zn基ZnO纳米棒复合薄膜。用气态H2S或H2S溶液代替Na2S作硫源，制备了PbS、CdS量子点分别敏化及PbS、CdS共敏化的Cu基ZnO三维分级结构复合薄膜，表征了其结构、组分、形貌及光谱性质，研究了沉积条件对其形貌及可见光降解甲基橙催化效果的影响，研究了复合薄膜的催化机理、催化动力学过程及催化失活机制，揭示了纳米材料的微观结构与性能之间的构效关系。为开发新型高效复合光催化剂的制备方法提供了新思路。