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ZnO模板离子交换合成纳米异质结
Fabrication of Heterostructures by Ion Exchange Using ZnO Template
【作者】 王琰；
【导师】 杜希文；
【作者基本信息】 天津大学 ， 材料学， 2014， 硕士
【摘要】 离子交换是一种通用的合成方法，可用于设计产物的形貌、成分、结构，该方法扩大了纳米材料的种类和范围。气相离子交换反应具有温度高、结晶性良好的特点；液相离子交换条件温和、操作简便。ZnO纳米材料是一种液相易得的、环境友好型的材料，可采用ZnO纳米材料为模板通过离子交换反应制备得到一维、二维的异质结纳米结构。本文的工作主要围绕ZnO纳米材料为基底进行离子交换方面的研究。气相阴离子交换制备ZnO/ZnSe异质结纳米棒及其光学性能。首次系统研究了ZnO纳米线在Se气氛下的阴离子交换过程，考察了温度、Se源量、反应时间参数对于交换反应的影响。研究发现最低交换反应温度为500°C；Se源的用量影响最终ZnO/ZnSe异质结纳米棒的形貌和壳层厚度；对比了不同直径ZnO纳米线在同样反应条件下的不同反应机制，较细的ZnO模板能得到纤锌矿ZnSe纳米棒，较粗的ZnO纳米棒模板不能完全转化得到ZnO/ZnSe核壳结构纳米棒。同时考察了阴离子交换过程中ZnO/ZnSe异质结纳米线产物发光性能的变化规律：随交换时间延长可见区（505nm）发光减弱，该发光来源于Zn空位缺陷。ZnO/ZnSe异质结纳米线模板气相阳离子交换制备ZnO/ZnSe/PbSe。首次通过两步气相阳离子交换方法制备得到了ZnO/ZnSe/PbSe异质结纳米线，且形貌保持良好，PbSe结晶性良好，通过调节温度及反应时间参数即可实现ZnSe向PbSe的完全转变，为下一步组装固态太阳能电池准备了基础材料。两步液相离子交换制备二维ZnO/CdSe纳米片层结构。首次使用ZnO纳米片层结构为离子交换模板通过两步液相离子交换成功制备出ZnO/CdSe异质结纳米片层结构。对比了不同液相硒化浓度及Cd离子交换的浓度的影响，发现浓度太低则不能发生反应。因纳米片层结构本身具有很大的表面积以及II型半导体能带结构，在光催化方面有一定的应用前景。
【Abstract】 Ion exchange is a versatile method to engineer nanomaterials. It can be used tocontrol the morphologies, composition and structure of nanomaterial, especially somenon-equilibrium nanostructures. Ion exchange in the gas phase can produce highcrystallined nanomaterials, and ion exchange in solution is very facile and simple. Onthe other hand, ZnO nanomaterial can be obtained in aqueous solution easily and it isan environmental friendly material which can be used as template for ion exchange,resulting in1-D and2-D heterostructures base on ZnO nanomaterial. The main resultsare as follows:Firstly, we fabricated ZnO/ZnSe heterostructures by gas phase anion exchange inSe vapor. We systematically investigated the influence of temperature, Seconcentration, reaction time on the formation of ZnO/ZnSe heterostructures. Thelowest reaction temperature was determined as500°C, and the amount of Se powderaffects the morphology and shell thicknes of the final ZnO/ZnSe heterostructures. Wealso studied the relationship of the diamater of the start ZnO nanorods with finalproducts, and found that pure ZnSe and ZnO/ZnSe heterostructures can be generatedby using thin or thick ZnO nanorods as templates, respectively. It is proposed that theanion exchange proceeds as a result of outdiffusion of ZnO. We also found thatintense light emission of ZnO/ZnSe heterostructures at505nm orgininates from Znvacany during anion exchange reaction.Secondly, we successfully fabricated ZnO/ZnSe/PbSe heterostructures by gas phasecation exchange using ZnO/ZnSe heterostructures as a template. And it is possible totansform ZnSe layer into PbSe completely by adjusting reaction temperature and time.The as-obtained products are well-crystallined and promising nanomaterials insolid-state solar cells.Thirdly, we constructed a two-dimensional ZnO/CdSe heterostructure nanosheetusing ZnO nanosheet as a template. ZnO/CdSe heterostructure nanosheets possesshuge specific surface and own a type-II band structure, which is promosing forphotocatalysis application.