稀土和氧离子掺杂的ZnS量子点的制备与性能研究

As a new type of luminescent materials, ZnS quantum dots (QDs) have become the foucus owing to their unique optical properties and wide application prospect in many fields. Appropriate doping in QDs can improve evidently their optical properties, and then make them widely be applied. This program will synthesize the ZnS QDs doped only with rare earth (RE) ions and codoped with RE and oxygen ions by solid-state method, and characterize their performances. In order to optimize the synthesis route, the effects of the synthesis conditions on the crystal structure, the suface structure, defects, the morphology, the particle size, the dispersion and optical properties of doped ZnS QDs and the corresponding mechasims will be researched. The doped sites of RE and oxygen ions in ZnS QDs with different doping concentrations will be studied using the Topas software, site-selective excitation and emission spectra at low temperature and the theoretical calculation, and then the influences of the crystral instructure, the suface structure, defects, the doped concentrations and sites of oxygen and RE ions, and the kind of RE ions on the optical properties of QDs and the corresponding mechanisms will be discussed. Accordingly, the optimal doped concentrations of oxygen and RE ions will be obtained to prepare the ZnS QDs with excellent optical properties. Finally, the rule of the energy obsorption, transfer and emitting of both ZnS QDs doped with RE ions and codoped with oxygen and RE ions will be explored. This program will provide the theoretical and practical basis for the synthesis, the doping and the study on the mechanisms of the effects of oxygen and RE ions on the optical properties of QDs. Therefore, it has important theoretical significance and practical application value.

ZnS量子点作为一种新型发光材料，因其独特的光学特性和在众多领域的广阔应用前景而成为研究的热点。适当掺杂能使量子点光电性能明显提高，从而使其得到广泛应用。本项目采用固相法合成稀土（RE）离子单掺及RE和氧离子共掺的ZnS量子点，表征其性能，研究合成条件对其晶体结构、表面结构、缺陷、形貌、粒度、分散性及光学性能的影响及机理，以优化合成方案。利用Topas软件、低温格位选择发光谱和理论计算研究不同掺杂浓度下RE和氧离子的掺杂位置，探讨晶体结构、表面结构、缺陷、RE和氧离子的掺杂位置、浓度及RE种类对量子点光学性能的影响及机理，确定RE和氧离子掺杂浓度的最佳值，制备出光学性能优良的量子点，探索RE离子单掺及RE和氧离子共掺的ZnS量子点能量吸收、传递及发射的规律特征。本课题将为量子点的合成、掺杂、及RE和氧离子对量子点光学性能影响的机理研究提供理论与实践基础，具有重要的理论意义和实际应用价值。

量子点与传统的荧光粉相比具有多种优势，ZnS量子点因其优良的物化性质而备受瞩目。稀土金属由于具有独特的最外层电子结构，已成为各种发光粉体材料掺杂体系研究的重点。目前对稀土离子（RE3+）掺杂的ZnS量子点的研究，取得了许多重要成果，但RE3+的掺杂位置仍有争议，量子点的发光效率及亮度还需进一步提高。阴离子掺杂可有效提高ZnS材料的发光性能，但目前对阴离子掺杂ZnS量子点的研究较少。我们针对这些问题进行了深入研究。首先研究了O2-的掺杂对ZnS纳米粒子性能的影响，优化了合成条件，在本课题范围内，确定了最佳的掺杂浓度，O2-的掺杂使ZnS纳米粒子的发光强度提高了8倍。利用退火和表面活性剂进一步提高了ZnS:O纳米粒子的发光性能。退火和使用PEG后，样品的发光强度分别提高了3倍和7倍。接着，我们研究了其他阴离子如卤素离子的掺杂对ZnS量子点性能的影响，结果表明：卤素粒子的掺杂均能显著提高ZnS纳米粒子的发光性能，且卤素离子的半径越小，对ZnS纳米粒子发光强度的提高越显著，F-的掺杂使ZnS的发光强度提高了9倍。同时采用Cl-和O2-的共掺的方法进一步提高了ZnS纳米粒子的发光强度。首次采用固相法合成了ZnO:S纳米粒子及ZnS/ZnO:S纳米粒子异质结，其发光强度分别约为ZnO纳米粒子的6倍和25倍。低温固相法具有对设备和工艺过程的要求不高、生产成本较低、操作相对简单的特点，用该法合成的ZnO:S/ZnS纳米粒子异质结适用于蓝色发光器件的规模化工业生产，具有广阔的应用前景。首次采用固相法合成了Tb3+/Eu3+和O2-共掺的ZnS纳米粒子，在464nm激发下，ZnS:Eu,O量子点发黄光，色坐标为(0.514, 0.475)，色纯度良好，且色温较低（为2419K），适用于白光发光二极管器件的规模化工业生产，市场前景广阔。用固相法合成了Ba3YB3O9:Eu荧光粉，探讨了不同波长激发下样品的发光机理，为稀土在ZnS量子点中的掺杂位置研究提供了思路。采用熔液法合成了Er3+/Yb3+掺杂的NaYF4纳米晶，研究了合成条件、粒径和形貌对发光特性的影响，为分析Re3+掺杂量子点的发光机理提供了参考。