Casillas-Rubio Alejandro, Mendez-Gonzalez Diego, Laurenti Marco, Rubio-Retama Jorge, Calderón Oscar G, Melle Sonia
Department of Optics, Complutense University of Madrid, E-28037 Madrid, Spain.
Department of Chemistry in Pharmaceutical Sciences, Complutense University of Madrid, E-28040 Madrid, Spain.
Nanoscale. 2024 Jun 27;16(25):12184-12195. doi: 10.1039/d4nr00718b.
The upconversion luminescence (UCL) lifetime has a wide range of applications, serving as a critical parameter for optimizing the performance of upconversion nanoparticles (UCNPs) in various fields. It is crucial to understand that this lifetime does not directly correlate with the decay time of the emission level; rather, it represents a compilation of all the physical phenomena taking place in the upconversion process. To delve deeper into this, we analyzed the dependence of the UCL lifetime on the excitation pulse width for β-NaYF:Yb,Er nanoparticles. The results revealed a significant increase in the UCL lifetime with both the excitation pulse width and the excitation intensity. The laser fluence was identified as the parameter governing the UCL decay dynamics. We showcased the universality of the pulse-width-dependent UCL lifetime phenomenon by employing UCNPs of various sizes, surface coatings, host matrices, Yb and Er ratios, and dispersing UCNPs in different solvents. Theoretical explanations for the experimental findings were derived through a rate equation analysis. Finally, we discussed the implications of these results in UCNP-FRET (Förster resonance energy transfer)-based applications.
上转换发光（UCL）寿命具有广泛的应用，是优化上转换纳米粒子（UCNPs）在各个领域性能的关键参数。必须明白，这个寿命与发射能级的衰减时间并无直接关联；相反，它代表了上转换过程中发生的所有物理现象的汇总。为了更深入地探究这一点，我们分析了β-NaYF:Yb,Er纳米粒子的UCL寿命对激发脉冲宽度的依赖性。结果表明，UCL寿命随激发脉冲宽度和激发强度均显著增加。激光能量密度被确定为控制UCL衰减动力学的参数。我们通过使用各种尺寸、表面涂层、主体基质、Yb和Er比例的UCNPs，并将UCNPs分散在不同溶剂中，展示了脉冲宽度依赖的UCL寿命现象的普遍性。通过速率方程分析得出了实验结果的理论解释。最后，我们讨论了这些结果在基于UCNP-荧光共振能量转移（FRET）的应用中的意义。
