激光诱导的稀土纳米粒子的上转换发光由于具有独特的光学效应, 多年来一直受到人们的广泛研究。其中, 溶剂对纳米粒子表面效应的影响是该类材料在实际应用中面临的一个普遍问题, 传统的分析方法对溶剂的作用难以给出定量化的分析结果。针对这一困难, 本文利用Monte Carlo计算模拟方法, 从离子-离子相互作用的微观层面上重构出宏观的上转换发光现象, 进而分别给出了纳米粒子表面效应在4种不同的水相溶剂: 水、甲醇、乙醇和N,N-二甲基甲酰胺(DMF)中的定量化分析结果。稳态和动力学光谱测试结果均表明, 溶剂水中的上转换纳米粒子表面猝灭速率最高, 甲醇和乙醇中次之, DMF中最低, 这可归因于溶剂中羟基基团及其活性对于上转换纳米粒子表面猝灭效应的影响。进一步, 通过计算模拟获得了NaYF4∶20%Yb, 2%Er上转换纳米粒子中, Yb3+激发态(2F5/2)表面猝灭速率的定量化数值, 分别为: 25×104 s-1(DMF)、1×105 s-1(甲醇和乙醇)、5×105 s-1(水)。

Laser-induced upconversion luminescence of lanthanide-doped nanoparticles has attracted great interest from researchers for many years due to its unique optical properties. The influence of solvents on the surfaces of these nanoparticles is a common problem in practical applications of these materials. However, traditional analysis methods are incapable of quantifying the influences of solvents. In response to this difficulty, we used a Monte Carlo simulation to reconstruct macroscopic upconversion luminescence at the microscopic level of ion-ion interaction. Then, we succeeded in obtaining quantified analysis results of the surface effects from four different aqueous solvents, which were water, methanol, ethanol and N,N-dimethylformamide(DMF). Both steady-state and dynamic spectra results show that the surface quenching rate of the upconversion nanoparticles in the highest to the lowest order of the four solvents are water, methanol, ethanol and DMF, which is attributed to the hydroxyl group and its activity. The computational simulation results show that the surface quenching rates of the Yb3+ excited state(2F5/2) in NaYF4∶20%Yb,2%Er upconversion nanoparticles in the four solvents are 25×104 s-1(DMF), 1×105 s-1(methanol and ethanol) and 5×105 s-1(water), which confirms our hypothesis.