【作者】 姜代旬；

【导师】 曹立新；

【作者基本信息】 中国海洋大学 ， 材料物理与化学， 2008， 硕士

【摘要】 在纳米材料科学中,人们对于纳米半导体材料的研究给予了极大的重视。II-VI族化合物半导体纳米材料是现今研究的一个热点,特别是材料的光电物理性质。Mn离子掺杂ZnS(ZnS:Mn)半导体纳米微晶发光材料有广泛的潜在应用前景,引起学术界的极大关注,人们对其发光机理、制备方法、实际应用进行了深入研究。但是它距离应用还有一定距离,制约其走向应用的关键在于表面态的猝灭作用导致其发光效率低下,因此,表面修饰对纳米发光材料走向应用起着重要作用。在众多的表面修饰方法中,核/壳结构是一种十分有效的方法。本课题研究了无机壳层修饰对纳米ZnS:Mn发光性质的影响,目的是减少或消除ZnS:Mn纳米微晶的表面态,提高其发光效率。本论文的主要工作总结如下:1.利用溶剂热法合成了Mn离子掺杂的ZnS球形纳米颗粒及纳米棒,发现在乙二胺与水以等体积比混合作为溶剂时,通过改变锌与硫的物质的量的比可以控制纳米粒子的形貌,当Zn:S=2:1时,得到闪锌矿型的球形纳米颗粒;当Zn:S=1:1时,得到纤维锌矿型的纳米棒;2.成功制备了不同壳层厚度的ZnS:Mn/ZnS,ZnS:Mn/CdS,ZnS:Mn/ZnO,ZnS:Mn/SiO2核/壳结构纳米颗粒和ZnS:Mn/ZnS核/壳结构纳米棒,采用了TEM、XRD、XPS、PL、PLE等测试对样品的晶形、形貌、发光等性质进行了表征。TEM和XPS测试证明了样品的核/壳结构,PL和PLE测试发现:适当厚度的壳层可以有效的提高ZnS:Mn纳米粒子的发光强度,同时有些壳层材料也对ZnS核产生应力,导致激发光谱发生蓝移。具体结论如下:(1)随着ZnS壳层的增厚, ZnS:Mn/ZnS纳米颗粒的Mn离子发光强度出现了先增强后减弱的现象,当壳层厚度达到0.05时(壳与核中Zn2+的物质的量的比,下同),发光效果达到最好,其强度为原来的1.2倍。样品的激发峰位随着壳层的增厚发生了逐渐的红移;(2)在ZnS:Mn纳米颗粒表面包覆CdS壳层后,Mn离子发光出现了降低的现象,并且随着壳层的增厚,发光强度逐渐降低。ZnS的激发峰位随着壳层的增厚发生了逐渐的蓝移,并且在激发光谱中同时出现了合金态的ZnCdS的吸收;(3)随着ZnO壳层的增厚,ZnS:Mn/ZnO纳米颗粒的Mn离子发光强度出现了先增强后减弱的现象,当壳层厚度达到0.1时,发光效果达到最好,其强度几乎达到原来的2倍。包覆ZnO后,样品的激发峰位发生了明显的蓝移;(4)随着SiO2壳层的增厚,ZnS:Mn/SiO2的Mn离子发光强度出现了先增强后减弱的现象,当壳层厚度达到5时,发光效果达到最好,其强度达到原来的3.5倍,并且SiO2对ZnS:Mn纳米颗粒的表面修饰效果要明显优于ZnS,CdS,ZnO对ZnS:Mn纳米颗粒的表面修饰效果。包覆不同厚度的SiO2壳层,样品的激发峰位发生了相同程度的蓝移;(5)随着ZnS壳层的增厚, ZnS:Mn/ZnS纳米棒的Mn离子发光强度出现了先增强后减弱的现象,当壳层厚度达到0.1时,发光效果达到最好,其强度达到原来的1.2倍。包覆ZnS壳层后,样品的激发峰位基本不发生移动。更多还原

【Abstract】 In the nanomaterials science, a great deal of effort has been devoted to the semiconductor nanomarials. Research onⅡ-Ⅵsemiconductor materials is a hotspot nowadays, especially in their optical and electric properties. As a kind of luminescent materials, Mn-doped ZnS nanocrystal has drown considerable interests because of its broad potential application prospect, and the luminescent mechanism, preparation method and practical application have been researched deeply. But the surface states usually act as luminescence quenching centers, causing low luminescent efficiency. There is a large distance for Mn-doped ZnS nanocrystal to application, which was mainly caused by the surface states. Hence, the modification of surface is of crucial importance for the applications of this type of luminescent semiconductor nanomaterials. Among all the surface modification methods, core/shell structure is proved to be a very effective method. This paper focuses on the impact of inorganic shell on luminescent properties of Mn-doped ZnS nanocrystals, which aimed at improving the luminescence efficiency by diminishing or eliminating the surface states. The main work of this paper is listed as follows:1. Mn-doped ZnS spherical nanoparticles and nanorods were synthesized by solvothermal. It was found that the morphology of nanocrystals can be controlled by changing the mole raito of Zn and S, keeping the ethylenediamine and water in 1:1 volume ratio severing as solvent. When the mole ratio of Zn and S was 2:1, spherical nanoparticles were obtained; when the mole ratio of Zn and S was 1:1, nanorods were obtained;2. Core/shell structure ZnS:Mn/ZnS,ZnS:Mn/CdS,ZnS:Mn/ZnO,ZnS:Mn/SiO2 nanoparticles and ZnS:Mn/ZnS nanorods with different shell thicknesses were synthesized. The samples were characterized by TEM, XRD, XPS, PL and PLE. TEM and XPS measurements showed the evidence for the core/shell structure. PL and PLE spectra showed the shell with appropriate thickness can enhance the photoluminescence intensity of ZnS:Mn nanomaterials; at the same time, some kinds of shell materials can bring strain on the ZnS:Mn core, inducing the red shift in PLE spectra. The details are as follows:(1) As the ZnS shell thickened, the Mn emission intensity of ZnS:Mn/ZnS nanoparticles showed an increase followed by a steady decline, which attained its maxium at 0.05 shell thickness. The PLE spectra showed a gradual red shift with ZnS shell thickening.(2) As the CdS shell thickened, the Mn emission intensity of ZnS:Mn/CdS nanoparticles showed a gradual decline. In the PLE spectra, the peak position of ZnS exhibited a progressive blue shift, and the absorbtion of ZnCdS in alloy state can also be observed.(3) As the ZnO shell thickened, the Mn emission intensity of ZnS:Mn/ZnO nanoparticles showed an increase followed by a steady decline, which attained its maxium at 0.1 shell thickness. The PLE spectra showed an obvious blue shift after coating ZnS:Mn nanoparticles with ZnO.(4) As the SiO2 shell thickened, the Mn emission intensity of ZnS:Mn/SiO2 nanoparticles showed an increase followed by a steady decline, which attained its maxium at 5 shell thickness. The PLE spectra showed a same degree of blue shift after coating ZnS:Mn nanoparticles by SiO2 shells of differents.(5) As the ZnS shell thickened, the Mn emission intensity of ZnS:Mn/ZnS nanorods showed an increase followed by a steady decline, which attained its maxium at 0.1 shell thickness. The peak position of PLE spectra kept almost unchaged after coating ZnS:Mn nanorods with ZnS.更多还原