Persistent phosphors are luminescent sources based on crystalline materials doped with rare-earth or transition metal cations able to produce light after the excitation source vanishes. Although known for centuries, these materials gained renewed interest after the discovery of Eu²⁺,RE³⁺ co-doped aluminates and silicates in the late 1990s due to their unprecedented afterglow properties. In contrast, persistent nanophosphors have emerged only recently as a nanoscale alternative to their bulk counterparts, offering exciting opportunities of particular relevance for in vivo imaging, optical data storage, or unconventional light generation. However, taking advantage of the avenues opened by nanoscience demands developing new synthetic strategies that allow precise control of the morphology, surface, and defect chemistry of the nanomaterials, along with a profound understanding of the physical mechanisms occurring in the nanoscale. Besides, advanced physicochemical characterization is required to assess persistent luminescence in a quantitative manner, which allows strict comparison among different persistent nanophosphors, aiming to propel their applicability. Herein, we revisit the main phenomena that determine the emission properties of persistent nanoparticles, discuss the most promising preparation and characterization protocols, highlight recent achievements, and elaborate on the challenges ahead.

中文翻译：

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持久发光纳米粒子：闪耀未来的挑战和机遇

持久性磷光体是基于掺杂稀土或过渡金属阳离子的晶体材料的发光源，能够在激发源消失后产生光。尽管这些材料已有数百年的历史，但在 1990 年代后期发现 Eu ²⁺、RE ³⁺共掺杂铝酸盐和硅酸盐后，由于其前所未有的余辉特性，这些材料重新引起了人们的兴趣。相比之下，持久性纳米磷光体最近才出现，作为其大量对应物的纳米级替代品，提供了与体内特别相关的令人兴奋的机会成像、光学数据存储或非常规光生成。然而，利用纳米科学开辟的途径需要开发新的合成策略，以精确控制纳米材料的形态、表面和缺陷化学，同时深入了解纳米尺度中发生的物理机制。此外，需要先进的物理化学表征来定量评估持久发光，这允许对不同持久性纳米磷光体进行严格比较，以提高它们的适用性。在此，我们重新审视决定持久性纳米粒子发射特性的主要现象，讨论最有希望的制备和表征协议，突出最近的成就，并阐述未来的挑战。