Long persistent phosphors—from fundamentals to applications

Abstract

Owing to the unique mechanism of photoelectron storage and release, long persistent phosphorescence, also called long persistent luminescence or long lasting afterglow/phosphorescence, plays a pivotal role in the areas of spectroscopy, photochemistry, photonics and materials science. In recent years, more research has focused on the manipulation of the morphology, operational wavebands and persistent duration of long persistent phosphors (LPPs). These desired achievements stimulated the growing interest in designing bio-labels, photocatalysts, optical sensors, detectors and photonic devices. In this review, we present multidisciplinary research on synthetic methods, afterglow mechanisms, characterization techniques, materials system, and applications of LPPs. First, we introduce the recent developments in LPPs for the synthesis of nanoparticles from the aspects of particle sizes, monodispersity and homogeneity based on the urgent application of bio-imaging. In the later sections, we present the possible mechanisms, which involve the variation of trap distribution during the trapping and de-trapping process, complicated photo-ionization reaction of trap site levels and impurity centers together with their corresponding migration kinetics of carriers. Meanwhile, we emphasize the characterization techniques of defects, used to qualitatively or quantitatively describe the types, concentrations and depths of the traps. This review article also highlights the recent advances in suggested LPPs materials with a focus on the LPPs' hosts and optically active centers as well as their control, tuning and intrinsic links. We further discuss the classification of LPPs based on the different emission and excitation wavebands from the ultraviolet to the near-infrared region along with an overview of the activation mode of afterglow. Afterwards, we provide an exhibition of new products towards diverse application fields, including solar energy utilization, bio-imaging, diagnosis, and photocatalysts. Finally, we summarize the current achievements, discuss the problems and provide suggestions for potential future directions in the aforementioned parts.

Lu2CaMg2(Si1−xGex)3O12:Ce3+solid-solution phosphors: bandgap engineering for blue-light activated afterglow applicable to AC-LED

“…ultraviolet or X-ray). 16,20 Unlike that, the PersL excitation spectrum in Fig. 4d demonstrates the efficient activation of PersL in LCMSGO:Ce…”

“…[6][7][8][9] Recently, this approach was revealed as applicable for phosphors (an insulator in nature) as well, endowing them with PersL properties, [10][11][12][13][14][15] which opens up a brand-new perspective for exploring novel phosphorescent materials that are highly desirable in security signs, night displays, optical storage media, etc. [16][17][18][19][20] PersL is an interesting phenomenon whereby luminescence from an active center still lasts for a long period after ceasing the excitation. 16 However, there is some complex and profound physics behind the PersL mechanism, including excitation, delocalization, migration, storage, release, and recombination of charge carriers, which casts a veil of mystery over it.…”

“…[16][17][18][19][20] PersL is an interesting phenomenon whereby luminescence from an active center still lasts for a long period after ceasing the excitation. 16 However, there is some complex and profound physics behind the PersL mechanism, including excitation, delocalization, migration, storage, release, and recombination of charge carriers, which casts a veil of mystery over it. Especially, the trap properties (including the species, depth, concentration and distribution) that determine PersL behavior in a host are difficult to be identified and modulated.…”

Rare earth based nanostructured materials: synthesis, functionalization, properties and bioimaging and biosensing applications

“…As mentioned above, excitation and emissions in the NIR are of particular interest, since they are located in the biological windows in which the absorption and self-fluorescence of many biological tissues are avoided [257]. Moreover, deeper penetration depth into biological tissues, better image contrast and reduced phototoxicity and photobleaching are observed [258].…”

“…The energy band engineering model ( Figure 13C) Figure 13D) [283]. However, it should be taken into account that there is no universal mechanism that explains the persistent luminescence and this is still an open topic in the scientific community [257,283,287]. Eu 2+ is the lanthanide cation most commonly used for persistent luminescence [288].…”