Abstract
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.
Highlights
Smart utilization of light-generating tools enabled the extension of social and economic activities when sunlight did not reach, being the development of light-emitting materials and devices that are both efficient and environmentally friendly the cornerstone of lighting technologies nowadays
We provide some keys to study these phenomena and to understand the way in which they are altered in the nanoscale, which determine the distinct features of persistent luminescence nanoparticles (PLNPs)
Charge de-trapping can be triggered by light, leading to optically stimulated luminescence (OSL) after charge recombination on the active cation and due to charge redistribution within traps. This optical stimulation is getting increased attention in the community. It may bring about new opportunities for the application of PLNPs, as near infrared (NIR) stimulation enables the redistribution of charges from deep traps toward efficient traps for room temperature Pers
Summary
Smart utilization of light-generating tools enabled the extension of social and economic activities when sunlight did not reach, being the development of light-emitting materials and devices that are both efficient and environmentally friendly the cornerstone of lighting technologies nowadays. Coming out of this successful use as indoor safety signs, persistent phosphors have been proposed for jogging and cycling paths,[36] or even for road markings.[37] limited storage capacity combined with a reduction of the release rate associated with temperature drop at night prevent the usage of these materials for outdoor applications.[38] In addition to their applicative concern, bulk persistent phosphors retain purely scientific interest from a fundamental point of view since they allow studying the effect of variations in the chemical composition on the optical properties in a simple way.[30] we refer the reader to recent review articles authored by Li et al and by Poelman et al for in-depth discussions on these materials.[39,40].
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