【作者】 韩冬梅；

【导师】 李效玉；

【作者基本信息】 北京化工大学 ， 材料学， 2009， 博士

【摘要】 Ⅱ-Ⅳ族纳米晶是一种特殊的半导体纳米微粒,由于量子尺寸效应的影响,可通过调节纳米晶的尺寸、晶体结构和化学组成来调控它的光学性能。因此,通过化学方法合成纳米晶,对其晶体结构、表面结构与材料本身的性能之间的关系加以研究成为研究热点。论文开展了溶胶凝胶法、水热法、微波法制备Ⅱ-Ⅳ族及过渡金属掺杂纳米材料和性能的研究,对纳米材料的形貌、结构以及与光学性能的关系进行了深入研究,并对纳米晶体的形成机理进行了探讨。论文的主要工作和贡献如下:论文以α-环糊精为稳定剂,在水相中直接制备CdSe-CdS纳米粒子。与传统的有机荧光材料相比,CdSe纳米晶因其具有的激发光波范围宽、发射光谱宽度窄、荧光强度高、稳定性好等特点而成为最有应用前景的新型生物探针。目前,高效的量子探针都是在有机合成体系（TOP/HAD/TOPO）中制得。由于生物识别和检测的环境是水相的,因此上述方法得到的纳米晶尚需进一步转移至水相。此过程带来了量子探针的发光性能和稳定性的破坏。因此,人们试图探索直接在水溶液中合成纳米CdSe。环糊精的独特的“内疏水、外亲水”的分子结构,可以与范围极其广泛的各类客体通过分子间的相互作用形成主—客体关系。以环糊精为稳定剂,已成功制备了金属如Ag、半导体纳米粒子如ZnS等纳米粒子。论文通过两步法,首先制备核层CdSe,进而在其表面沉积壳层CdS壳层材料,对反应进程中纳米粒子的形貌和光学性能、生长机理进行了研究。结果表明,制备的CdSe-CdS为近球形粒子,平均直径约15 nm,为六方晶系的单晶结构,无明显的晶格缺陷。在核层和壳层的反应过程中,均发现随着反应时间的增加,粒子长大,相应的紫外吸收光谱向长波方向移动;当增加Cd/Se的比例,纳米晶的荧光强度提高,且荧光发射峰逐渐变窄。达到了可通过控制反应时间和前躯体配比制备不同粒径和粒度分布的荧光纳米材料的目的。以α-环糊精为稳定剂,水热法一步完成了ZnSe及Mn掺杂ZnSe纳米线的制备,对制得的纳米线的形貌、结构和光学性能进行了研究。CdSe的性质使其成为最有前景的探针材料,但它的生物安全性一直是其生物应用的瓶颈。近年来多个研究小组开展了过渡金属掺杂的半导体材料的研究,有望替代CdSe成为新型的荧光标记物,如Mn、Cu、Co掺杂的ZnS、ZnSe等。研究结果发现,ZnSe及Mn掺杂ZnSe纳米线均属闪锌矿型,Mn掺杂ZnSe的纳米线有微量的纤锌矿型晶体存在。ZnSe纳米线的平均直径约为90 nm;长约在1.5μm～3.5μm之间;Mn掺杂的ZnSe纳米线平均直径约为80 nm;平均长度约在2μm～3μm之间,呈结晶完好的立方晶系单晶结构。Mn植入ZnSe晶格,引起了带隙能的减小,导致紫外吸收的红移。发射谱图上在432nm和580 nm分别有两个发射峰,分别归属于ZnSe缺陷发射和锰的⁴T₁→⁶A₁发射。掺杂比例的改变对产物的光学性能影响很大。此方面的研究未见报道。微波加热是很有前途的体加热方法,具有加热速度快,选择性加热等优点。微波环境下可得到传统的加热方式不同结构和性质的纳米材料。论文研究了利用微波加热法制备ZnSe及Mn、Co掺杂ZnSe纳米材料,并分别对形貌、结构和性能的关系进行了探索。结果表明,制得的ZnSe纳米粒子均为纤锌矿型晶体。选择不同的有机胺配体可调节粒子的粒径大小;随微波功率的变化,粒子可由均匀的球形变成了近似的米粒形状进而生长成为棒状粒子。随着辐照时间的延长,晶体长大或定向生长,相应的荧光光谱和紫外吸收光谱均向长波方向移动。此方面的研究未见报道。微波法合成的Mn、Co掺杂的纳米ZnSe粒子的研究结果表明,Mn离子掺杂的纳米ZnSe粒子的颜色显橙色,为200～500 nm的球形粒子,表面平整,为单晶ZnSe的纤锌矿结构,荧光光谱中出现位于433 nm,487 nm,530 nm三个发射峰;Co离子掺杂的纳米ZnSe粒子的颜色显绿色,为约500 nm的球形粒子,表面平整光滑,形成单晶ZnSe的纤锌矿结构,晶体生长过程中有少量的晶格位错。荧光光谱中出现位于486 nm,527 nm的两个发射峰。Co掺杂的ZnSe纳米粒子随可见光下的钝化时间增加而发射峰强度增强。此方面的研究未见报道。更多还原

【Abstract】 Ⅱ-Ⅳnanocrystals,as a class of special semiconductor nanomaterials, have the similar regularity of atomic arrangement with crystals.As a result of quantum size effects,their optical and electrical properties strongly depend on the size of nanocrystals,the surface structure,crystal structure and the performance of nanocrystals have attracted more attentions.In this paper,Ⅱ-Ⅳsemiconductors and their doped nanomaterials were synthsizied with colloidal method and studied the relationship between the morphology,structure of materials and the optical properties.Main points as follows:α-Cyclodextrin modified CdSe/CdS nanoparticles were successfully synthesized with hydrothermal method.Techniques of AFM,TEM,EDS, FTIR,UV-vis absorbance and photoluminescence spectra were used to characterize the morphology,composition and optical characteristic of the synthesized nanoparticles.The effects of precursor ratios,reaction times and the light stability of the nanoparticles were investigated.The results showed that the as-synthesized nanoparticles were dot-shaped and their average size was 15 nm,had hexagonal single crystal structure.The red shift in both absorption and fluorescence emission spectra of CdSe/CdS nanoparticles are resulted from the presence of the CdS shell.The obvious defects in the lattice and the boundary between CdSe and CdS were not observed.The sizes and size distributions can be adjusted by precursor ratios and reation times respectively by the presence ofα-Cyclodextrin.ZnSe nanoparticles were prepared using alkylamines as ligating solvent by microwave-irradiation method.The differences of morphologies in the effect of alkylamines and microwave variables were investigated.The results show that there is an inverse relationship between the size of nanoparticles and the length of the alkylamine.The average sizes were increased with the duration of irradiation time. Microwave irradiation power affects the sizes and shapes of ZnSe materials because of the movement and polarization of amine molecules under the rapidly changing electric field of the microwave reactor.Mn- Co- doped ZnSe nanoparticles were prepared by microwave-irradiation method.The effects of different doped transition metals and the dope amount on the morphology and optical properties were investigated.The results showed that the Mn- doped ZnSe nanoparticles were orange powder and the average size was 200-500 nm. They had structured surface and single crystal wurtzite structure.Three emission peaks,433 nm,487 nm,530 nm,were detected in the photoluminescence spectrum.Co- doped ZnSe nanoparticles were yellow-green powder and the average size was 500 nm.They had structured surface and single crystal wurtzite structure.Two emission peaks,486 nm,527 nm,were detected in the photoluminescence spectrum.Mn-doped ZnSe nanowires were prepared by hydrothermal method usingα-cyclodextrins as stabilizer and zinc acetate,manganese acetate and Na₂SeSO₃ aqueous solution as precursor.The as-prepared Mn-doped ZnSe nanowires were all typically single well-crystallized structure and had zinc blende structure.The average length of the nanowires was about 2-3 um and average diameter was 80 nm.Experimental results showed that a sharp absorption band appeared at 360 nm in the UV-vis absorbance spectra of Mn-doped ZnSe nanowires.The corresponding photoluminescence spectrum with 350 nm excitation showed signs of two distinct emission bands centered at 432 and 580 nm.更多还原