【作者】 王岚；

【导师】 孙秀冬；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2010， 博士

【摘要】 半导体纳米晶体(量子点)由于其半径小于或接近于激子玻尔半径,具有特有的量子尺寸效应和表面效应,使其在高效太阳能电池、量子点激光器、生物标签以及发光二极管等方面具有极大的研发吸引力和应用前景。其中II-VI族CdSe纳米晶体作为一种重要的半导体纳米材料因其具有优良的可见光区荧光发射性质引起了人们极大的兴趣。探求一种安全、无污染、成本低、操作简单、重复性好的制备高质量纳米晶体的合成路线成为许多学者的关注的重点。基于无膦制备CdSe纳米晶体的路线,本文采用绿色、低成本、可操作性强的合成技术合成出CdSe、ZnSe两种II-VI族半导体纳米晶体,并对其光学性质、晶体结构及形貌进行了表征。基于前人提出的油酸-液体石蜡体系制备CdSe纳米晶体的合成路线在开放的条件下(空气中)合成出CdSe纳米晶体,并对制备的CdSe纳米晶体的紫外-可见光吸收谱、光致发光谱、粉末X射线衍射谱及透射电子显微镜等进行了表征。通过与在N2气中合成结果的对比,分析了该路线在空气中合成CdSe纳米晶体的可行性。采用硬脂酸作为Cd的配体,提出了一种新的CdSe纳米晶体的绿色无膦合成体系——硬脂酸-液体石蜡体系,并分别在N2及在空气中合成出CdSe纳米晶体。分析、讨论了在不同的生长环境、不同的反应温度下纳米晶体的质量,还对测试溶剂对测试结果的影响进行了研究。结果表明硬脂酸-液体石蜡合成体系更适合在较低的温度下制备CdSe纳米晶体,并且在空气中合成的CdSe纳米晶体的质量不亚于在N2气中的合成结果。分别选择油酸及硬脂酸作为Cd的配体,对其在空气中、生长温度为230℃条件下的合成结果进行了对比。结果表明硬脂酸为配体合成的CdSe纳米晶体具有更小的Stocks频移及半高宽,更高的荧光量子产率和更好的结晶度。研究中还发现,无论是油酸还是硬脂酸作为Cd的配体,在较低的合成温度下(220℃-260℃)合成的CdSe纳米晶体均为在三辛基氧化膦-三辛基膦合成路线中不常见的立方相结构。研究了表面活性剂十六胺(HDA)对液体石蜡反应体系中CdSe纳米晶体合成的影响,同时还对实验的可重复性进行了研究。结果表明,在合成体系中加入十六胺可加速纳米晶体的成核过程,降低其生长速度,获得尺寸小的晶粒,同时可提高晶体的单分散性及荧光量子产率,并且实验的可重复性好。通过研究十六胺的注入方式对合成结果的影响,发现将十六胺加入到Cd前驱体中制备的CdSe纳米晶体的质量优于将十六胺加入到Se前驱体中制备的纳米晶体。提出了利用月桂酸在液体石蜡中进行另一种可替代有毒的CdSe纳米晶体作为生物荧光标记物的ZnSe纳米晶体的绿色合成路线。对比了多种从反应基质中分离ZnSe纳米晶体的方法,成功地合成出单分散性好、尺寸可调的ZnSe纳米晶体。虽然实验的可重复性不是很理想,但是为ZnSe纳米晶体的绿色合成开辟了一条新途径。更多还原

【Abstract】 Colloidal semiconductor nanocrystals (quantum dots) show quantum confinement effects due to the size of them on the order of the Bohr radius and hence have attracted broad attention in recent years for usage in a variety of applications such as solar cell, lasers, biological labels and light-emitting diodes. Among the colloidal semiconductor nanocrystals, II-VI CdSe has shown almost full range visible light emission within a reasonable size range and attracted a great deal of interest. It is important to develop safe, low-cost, green, fast, and mass-production routes for the synthesis of CdSe NCs with high quality. Here, we present a much cheaper and greener non- tri-n-octylphosphine (TOP)-based route for the syntheses of CdSe and ZnSe nanocrystals. The optical properties, structures and appearances of CdSe nanocrystals were charactered. The main contents are listed below:Based on oleic acid - paraffin liquid route, CdSe nanocrystals were prepared in open air. The CdSe nanocrystals were charactered by UV-vis absorption and photoluminescence (PL) spectroscopy, powder X-ray diffraction (P-XRD) and transmission electron microscopy (TEM). The data obtained in air were compared with those obtained under N2. The feasibility to synthesize CdSe nanocrystals in air was discussed.Using stearic acid as ligand, a new, green, non-TOP system -was proposed. CdSe nanocrystals were synthesized under N2 and in air respectively. The quality of CdSe nanocrystals prepared at different conditions and temperatures, and the effects of different testing solvents were investigated. The results show that CdSe nanocrystals are suitable to be synthesized at lower growth temperature in stearic acid - paraffin liquid system and the quality of CdSe nanocrystals prepared in air is as better as that obtained under N2. Choosing oleic acid and stearic acid as ligands, the data obtained at 230℃growth temperatures in air were compared. The results show that the CdSe nanocrystals prepared by stearic acid ligands have smaller Stokes shift, narrower full widths at half-maximum, higher photoluminescence quantum efficiency and crystallinity. The results also show CdSe nanocrystals in the less common zinc blende crystal structure in TOPO (tri-n-octylphosphine oxide)-TOP routes have been obtained in the systems with oleic acid or stearic acid ligands at lower growth temperatures (220℃-260℃).The effects of surfactant n-hexadecylamine (HDA) on the synthesis of CdSe nanocrystals and the reproducibility of the synthesis in liquid paraffin system were investigated. The results show that the nucleation rates are faster and the growth rates are slower in presence of hexadecylamine and the use of hexadecylamine generally can produce highly homogeneous CdSe NCs with higher photoluminescence quantum efficiency and smaller sizes and the system is reproducible. The study on the effects of injection ways of hexadecylamine shows that higher quality CdSe NCs can be obtained by adding HDA to Cd precursor rather than to Se precursor.A green route using dodecanoic acid to synthesize ZnSe nanocrystals who will replace toxic, biological labeling CdSe nanocrystals in liquid paraffin matrix is proposed. Highly homogeneous and size-tunable ZnSe nanocrystals were finally obtained by comparing different methods to separate ZnSe nanocrystals from the reaction mixture. Although reproducibility of experiment is not well enough, it provides a new approach to the green synthesis of ZnSe nanocrystals.更多还原