发光粉量子产率是指发光粉对光量子的利用率，常使用发射光与激发光的强度比描述量子产率。本文合成的铕掺杂稀土发光粉和铈铽共掺杂发光粉，具备稳定的物理和化学性质、高发射光纯度等特点，因此具有十分广泛的应用场景。发光粉可作为多模态成像剂：在分子成像领域，发光粉可用于组织、器官、病灶的可视化等成像。在CT成像领域，发光粉可以作为CT造影剂。本文将发光粉合成与元启发式算法相结合，利用元启发式算法优化发光粉量子产率，并对发光粉的应用场景进行探索与拓展。具体工作如下：

1、将遗传算法应用于铕掺杂稀土发光粉优化。使用MATLAB实现遗传算法过程，使用水热共沉淀法合成铕掺杂稀土发光粉。采用十进制编码方式对发光粉编码，实现遗传算法与发光粉合成过程的结合。测试发光粉细胞毒性，对发光粉进行光学成像、CT成像研究，将稀土发光粉用于指纹识别领域。共沉淀法有如下特点：(1)实验周期短，能够实现短时间批量合成样品。(2)合成的发光粉颗粒具有分布均匀，粒径小等优点。(3)反应过程及条件容易掌控，合成样品更加稳定。基于以上特点，共沉淀法更适合作为算法指导优化的发光粉合成方法。

2、将多种算法应用于铈铽共掺杂发光粉优化。实现粒子群算法和模拟退火算法过程，调整遗传算法参数。将算法与铈铽共掺杂发光粉合成过程结合。通过各算法优化结果分析比较，探究不同算法对发光粉优化的特点：(1)遗传算法优化速度快，迭代至第三代出现最优发光粉，表明该算法适合快速优化。(2)粒子群算法优化过程更平稳，随着迭代次数增加，发光粉优化效果愈佳，该算法适合在更多的迭代次数下寻找高性能发光粉。(3)模拟退火算法对发光粉没有明显优化效果，表明经典模拟退火算法不适用于发光粉优化。

3、对模拟退火算法进行改进，并将改进后算法用于铈铽共掺杂发光粉优化。针对模拟退火算法优化效果不佳的问题进行分析改进。发现模拟退火算法的编码生成方式过于简单，不适用于发光粉优化。利用全局编码信息，改进编码生成方式。实现改进模拟退火算法对铈铽共掺杂发光粉优化。改进后算法优化效果显著优于改进前模拟退火算法。对样品进行分析，得出样品发光强度与铈铽浓度关系。发光粉样品与四苯乙烯具有波长250-300nm的共同激发区，稀土发光粉热稳定性好而四苯乙烯受热易失效，基于以上特性构造出一种特殊的发光二维码。

本论文工作获得了国家自然科学基金(No. 81801744 )的资助。

The quantum yield of phosphors refers to the utilization of photons. Researchers usually use the intensity ratio of emitted light to excited light to describe quantum yield. Eu³⁺ doped phosphors and Ce/Tb codoped phosphors synthesized in this article have stable physical and chemical properties and narrow emission bands, so they have a very wide range of application scenarios. The phosphors can be used as dual-modal imaging agent. For example, in the field of molecular imaging, the phosphors are used for visualization of tissues, organs and lesions. In the field of CT imaging, phosphors are used as CT agent. In this thesis, this research combined the synthesis of phosphors with the meta-heuristics algorithm, optimized the quantum yield of phosphors by meta-heuristics algorithm and expanded the application scenarios of phosphors. The main contributions of our work are as following:

 

1. This research used the genetic algorithm to optimize the Eu³⁺ doped phosphor, used the MATLAB to realize the process of genetic algorithms and applied the hydrothermal co-precipitation method to synthesize Eu³⁺ doped phosphors. The combination of genetic algorithm and phosphor synthesis process was realized by decimal coding. This research tested the cytotoxicity of phosphors, studied the optical imaging and CT imaging of phosphors, and applied the rare earth phosphors to fingerprint identification. There are some characteristics of the co-precipitation method. First, the experimental period is short, and the sample could be synthesized in short time. Second, the synthesized phosphors have the advantages of uniform distribution and small particle size. Third, the process and conditions of reactions are easy to control, and the products are stable. Based on the above characteristics, co-precipitation method is suitable for the optimization of phosphor synthesis.

 

2. This research used multiple algorithms to optimize Ce/Tb co-doped phosphors, realized the process of particle swarm optimization and simulated annealing algorithm, adjusted the parameters of genetic algorithm, combined the algorithm with the process of Ce-Tb co-doped phosphors. By comparing the optimization results of different algorithms, this research explored the characteristics of different algorithms for optimization of phosphors and got the following conclusions. Firstly, the genetic algorithm has high searching speed. The optimal generation of phosphors occurred in the third generation, which indicates that this algorithm is suitable for rapid optimization. Secondly, the particle swarm optimization algorithm is stable. With the increase of iteration times, the optimization effect of phosphors was better. This algorithm is suitable for searching high performance phosphors at more iterations. Thirdly, the simulated annealing algorithm had no obvious effect on the luminescent powder, which shows that the classical simulated annealing algorithm is not suitable for the optimization of phosphors.

 

3. This research improved the simulated annealing algorithm, and the improved algorithm was applied to optimize the Ce-Tb co-doped phosphors. For the poor optimization effect of simulated annealing algorithm, this research analyzed and improved it. This research found that the encoding method of simulated annealing algorithm was too simple to apply to the optimization of phosphors, so this research used the global coding information to improve new coding generation way. The improved algorithm was significantly better than the original simulated annealing algorithm. by analyzing the samples, this reaserch obtained the relationship between the luminescence intensity and the concentration of Ce/Tb. The sample of phosphors and TPE have a shared excitation region in 250-300 nm. Phosphors have good thermal stability but TPE have poor thermal stability. Based on the above characteristics, this research constructed a special improved QR code.

 

This work is supported by the National Science Fund of China (Grant NO. 81801744).

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