【作者】 徐丹；

【导师】 张明喆； 陈海勇；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2008， 硕士

【摘要】 本文介绍了使用注射剂瓶作为装置,在常温常压下用缓慢化学沉淀法制备低维ZnS结构。通过XRD确定样品的成分结构-立方闪锌矿ZnS。TEM中观察样品是球状粒子,粒径在2.6nm至5.0nm之间,电子衍射与XRD吻合,并证明是多晶。通过紫外-可见吸收谱线移动监测纳米粒子尺寸大小变化。此方法可以用来制备不同尺寸的纳米材料。谱线的移动,带隙的变大（3.7eV到5.3eV）体现了量子效应。研究ZnS纳米粒子表面的修饰:可以通过将样品浸没在不同浓度的溶液使其裸露的表面生长更为缓慢,从而精细控制其尺寸;十二硫醇的表面修饰使表观光学带隙减小了0.4eV,体现了介电限域效应。研究0.02、0.06mol/l反应试剂制得的ZnS纳米粒子的发光性质,用209nm的光激发,在421nm附近和340-363nm有发光峰,其中421nm是带隙发光;340-363nm是表面缺陷发光。研究了掺入5%ZnS:Eu³⁺的发光,荧光谱中611nm认为是Eu3+的7F2和5D0能级的电偶跃迁,由于次跃迁对发光中心对称性非常敏感验证了ZnS纳米粒子属于具有对称性的立方晶系。另外将实验装置小瓶换成两个试管,延长反应时间以制备ZnS纳米棒,通过TEM观察棒长约1μm,宽200nm。使用缓慢沉淀法的小瓶和试管装置制备了立方晶系的硫化铬（CdS）、硫化铅（PbS）、单斜晶系三硫化二钇（Y2S3）纳米管和硫化银（Ag2S）纳米簇,研究此方法在制备纳米材料的适用性。制备溶度积更低的PbS粒子粒径在11-14nm之间,还制备出了直径15nm的Y2S3管和直径在111-258nm的Ag2S棒组成的簇。更多还原

【Abstract】 Nano-science is an important part of the 21st century science and technology industrial revolution. In recent years, the properties of the bandgap broaden for the quantum effect and the dielectric confinement effect make nanomaterials a popular science.Ⅱ-Ⅵsemiconductor nanocrystalshave been intensively investigated as a luminescent material. An important groupⅡ-Ⅵsemiconductor, zinc sulfide (ZnS)has a wide bandgap energy of≈3.7 eV (at 300K), andhas been considered as the most promising material for ultraviolet-light-emitting diodes and injection lasers, phosphors in cathode-ray tube and flat-panel displays, thin-film electroluminescence, and IR windows. Nanostructures can significantly change the emitting mechanism of the material (such as the restrictions on the movement of the exciton, changing of the energy transport means, etc.). People expect that ZnS nanostructure can excite UV light and laser light efficiently, which can apply in computer storage and nano-middleweight optoelectronic intergration. Therefore, the preparation of ZnS nanostructures and the study of ZnS Luminescent Mechanism are significant.In this paper, we introduce a slow chemical precipitation method, by which controllable size of the zero-dimensional ZnS nanoparticles can be prepared at normal temperature and pressure. XRD was used to determine the composition of samples - sphalerite cubic ZnS. TEM microscope observations investigate the morphology of sample. They are spherical particles, and the particle size is 2.6nm to 5.0nm. Selected-Area Electron diffraction and XRD prove them to be polycrystalline. We monitor the changes of nanoparticle size by the shift of UV-vis Spectra and PL. This method can be used to prepare different size of nano-materials. In the appropriate reagent concentration range (0.01-0.06mol/l), the lower of the concentration, the bigger of the particle size. We explain the growth mechanism through the changes of absorption of UV-vis with the ratio of 1:1 by different concentrations of two reagent with the extension of reaction time, with reaction process, distribution of Zn、S ions and ZnS monomer in reagent region. And we explain why the UV-vis of thehigh concentration of the reagents samplehas the reverse phenomenon; the spectrum of lower concentration of reagenthas no such phenomenon. The decreasing of particle size is propitious to narrow particle size distribution. The UV spectra of sample at concentration of 0.06mol/l reagent reacting 8h shows clear peak, proves fine monodisperse. The shift of spectrum and broaden of band gap (3.7eV to 5.3eV) embodies the quantum effect. Through surface-capped, we can good control the particle size and reduce bandgap arising from dielectric confinement effect. We study the photoluminescence spectra of ZnS nanoparticles prepared with the reaction concentration of 0.02、0.06mol/l reagent , using an excitation wavelength of 290nm. The emission can be divided into two regions: 340-363nm and 421nm. The 421nm is attributed to the band edge luminescence whereas 340-363nm is surface defects luminescence. The emission of Eu3+ ions doped ZnS is 611nm for 7F2- 5D0 transition of Eu3+ ions. For the transition is sensitive to the symmetry of luminescent centers, it prove that ZnS nanoparticles is a cubic crystal system with symmetry.however, we get a 580nm luminescence peak with 514nm laser excitation. The reason for that phenomenon may be Eu3+ ions absorbed the energy that release by the luminescence transition of ZnS. In addition, we also do research on the preparation and characterization of ZnS nanorods. We change the bottle to two tubes; extend the reaction time to prepare about 11μm long, 200nm wide rods. Electron diffraction showed diffraction rings and superlattice diffraction spots. The diffraction rings are the rings of ZnS nanoparticles, the reason for the formation of superlattice diffraction spots maybe attribute to the elements of ZnS/ZnO alternately growth. We can do research on the one-dimensional structure on the basis of bar of ZnS. We use slowly chemical precipitation method to prepare a cubic crystal chromium sulfide (CdS), lead sulfide (PbS), monoclinic three sulfide two yttrium (Y2S3) nano-tubes and silver sulfide (Ag2S) nanocluster, which prove the application of this method in the preparation of the nanomaterials. The solubility of CdS is lower than ZnS, so the UV spectra of CdS withdraw for many times. The TEM shows the diameter of PbS is between 11-14nm. This method has not been found to be a suitable experimental method to control the size of PbS. We also prepared Y2S3 (diameter of 15nm) nanotubes and Ag2S (diameter of 111-258nm) nanoclusters.We prepared a controllable size of zero-dimensional ZnS nanoparticles and one-dimensional nanorod structures, using UV - absorption spectra to monitor the particle size of different reaction time, reflects the quantum effect. We explain the growth mechanism and the luminescent properties. And this method can be potentially extended to the preparing of PbS, CdS, Ag2S, and other sulfides one-dimensional structure. The slow precipitation method is easy to operate and low cost, it is an effective way to prepare nanomaterials.更多还原