Recent Progress in Inorganic Afterglow Materials: Mechanisms, Persistent Luminescent Properties, Modulating Methods, and Bioimaging Applications

Abstract

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.202202382.the stored excitation energy in energy traps, which can be released by thermal stimulation. [2] Obviously, the process is very different from the real-time excited fluorescence (FL). Usually, the excitation source can be X-ray, ultraviolet (UV), and visible (Vis) light, and there is no need for continuous external light irradiation, while the PL may locate in UV, Vis, or near-infrared (NIR) spectral regions. [3] Especially, Vis emissions are easy to be modulated for colorful light, and NIR emissions in the biological window (≈650-1800 nm) offer deep tissue penetration and prevented autofluorescence. [3a,4] According to the outstanding luminescent properties, enormous opportunities in diverse application fields have been discovered, mainly including long-lasting tumor optical imaging and therapy, [5] security and anti-counterfeiting, [6] optical information and data storage, [7] photocatalysis, [8] fingerprint recognition, [6c] analysis and sensing, [1c,4a,9] as well as the potential applications of synaptic plasticity [10] and light-emitting diodes. [11] Retrieved from Web of Science, > 6800 articles by tracing the themes "afterglow" or "persistent luminescence" or "longlasting luminescence" have been published during the last decade (i.e., ≈2012-2022). Diverse categories of persistent luminescent materials have been developed, such as organic materials, [12] carbon dots, [13] metal-organic frameworks, [14] doped inorganic crystals et al. [2,15] Among them, organic afterglow materials, usually named as organic room temperature phosphorescence materials have recently drawn extensive attention due to the advantage of sustainable resources, low cost, and safety. [16] Based on the composition, organic afterglow materials can be mainly divided into organic small molecules, polymers, and organic-inorganic hybrids, which are normally related to the radiative transition from the lowest excited triplet state (T 1 ) to the ground state (S 0 ). Thus, methods for enhancing the intersystem crossing (ISC) rate are reasonable for realizing highly efficient afterglow, such as introducing heavy atoms, paramagnetic molecules, aromatic carbonyls, heteroatoms, and crystal engineering. [17] Recently, organic room-temperature phosphorescence with a high quantum yield above 56% and long afterglow lifetime longer than 22 s has been achieved by using suitable inorganic framework. [18] Additionally, color-tunable

Molecular substrates for the construction of afterglow imaging probes in disease diagnosis and treatment

“…Inorganic afterglow imaging agents usually contain rare-earth metal ions, transition metal ions, or some main group metal ions with a highly conductive structure. 14,15 Upon light irradiation, electrons can be promoted from the valence band (VB) to the conduction band (CB), which can be further captured by electron traps or tunnelled to emitters. These electrons can stay in the traps and emitters in an excited state for a very long period of time and then slowly escape to the ground state after certain stimulations, eventually generating persistent luminescence lasting for hours or even days (Scheme 1(d)).…”

“…These electrons can stay in the traps and emitters in an excited state for a very long period of time and then slowly escape to the ground state after certain stimulations, eventually generating persistent luminescence lasting for hours or even days (Scheme 1(d)). 14 However, the use of inorganic materials in biomedical applications can be compromised due to the potential leakage of toxic heavy metal ions and limited targeting capability toward specific molecules. 16 In contrast, the organic afterglow imaging agents show high biocompatibility and molecule-level specificity because organic afterglow substrates have high structural diversity that can be caged by a biomarker-responsive moiety to achieve activatable afterglow emission.…”

High-Pressure Near-Infrared Luminescence Studies of Fe3+-Activated LiGaO2

“…Consequently, it is highly regarded as a promising phosphor material for fluorescent lamps in plant growth applications. − Apart from its optical properties, solid β-LiGaO 2 also demonstrates intriguing mechanical characteristics such as elasticity and piezoelectricity . β-LiGaO 2 has also found applications as a ceramic tritium breeder material in experimental fusion reactors. , It serves as a lattice-matched substrate for the growth of GaN, InN, and ZnO and as a solid gallium precursor source material for bulk GaN crystal growth. , Recent studies have indicated the applicability of these ceramic phosphors in various biological fields due to their biocompatible nature and promising NIR luminescence properties when doped with transition-metal elements. , Iron (Fe 3+ ) is an efficient transition-metal dopant for achieving the NIR luminescence and persistent luminescence in LiGaO 2 . − …”

Near‐Infrared Persistent Phosphor‐Mediated Smart Sensing Light‐Emitting Diodes for Advanced Driver Assistance Systems

“…However, defects have an “angelic effect” in other optical applications such as photocatalysis, optical storage, and anti‐counterfeiting. [ 7 ] These defects can capture the photo‐excited electrons emitted upon applying an external force field. Therefore, defect‐mediated materials can be engineered as optical sensors to solve the key issues in bio‐sensing, [ 8 ] light communication, [ 9 ] development of advanced driver assistance systems (ADAS), [ 10 ] augmented reality (AR) [ 11 ] and virtual reality (VR) technology, [ 12 ] machine vision, [ 13 ] and intelligent security.…”