Poly(arylene piperidine) Quaternary Ammonium Salts Promoting Stable Long-Lived Room-Temperature Phosphorescence in Aqueous Environment

Elucidating the mechanism behind the significant changes in photoluminescence behavior after powder compression into a tablet

Nonconventional luminogens have great potential for applications in fields like anti-counterfeiting encryption. But so far, the photoluminescence quantum yield (PLQY) of most of these powders is still relatively low and the persistent room temperature phosphorescence (p-RTP) emission is relatively weak. To improve their PLQY and p-RTP, pressing the powder into tablets has been preliminarily proven to be an effective method, but the specific mechanism has not been fully elucidated yet. Here, D-(+)-cellobiose has been chosen as the representative to study the problem. The results showed that the PLQY and p-RTP lifetimes of the tablet of D-(+)-cellobiose were improved compared to those of the powder. Using the mechanism of clustering-triggered emission (CTE) and theoretical calculations, it has been demonstrated that the enhanced molecular interactions after compression are the key reason, which result in the formation of cluster emission centers with stronger emission capabilities. And the combination of the powder and tablet has been proven to have application potential for advanced anti-counterfeiting encryption. The above results not only provide possible references for understanding the emission mechanism of small molecules and cellulose based emission materials, but also promote the process of more intuitive observation of emission centers for explaining emission mechanisms.

Cycloolefin Copolymers With a Multiply Rigid Structure for Protecting Triplet Exciton From Thermo- and Moisture-Quenching

Polymeric room temperature phosphorescence (RTP) materials have been well developed and utilized in various fields. However, their fast thermo- and moisture-quenching behavior highly limit their applications in certain harsh environments. Therefore, the preparation of materials with thermo- and moisture-resistant phosphorescence is greatly attractive. Compared with common water-soluble polymers, cycloolefin copolymers (COC) show outstanding hydrophobicity and higher rigidity, even at elevated temperatures, being as a promising candidate to prepare phosphorescence materials with suppressed thermo- and moisture-quenching behavior. Herein, a type of COC bearing hydroxyl, ester, and adamantanyl side groups is synthesized. After dispersing various phosphors into this matrix, the resultant composites exhibit full-color RTP with lifetimes of 249-590 ms. Their luminescence does not show obvious quenching in water, acid, alkalinous, reductive, and oxidative environments. In the presence of both rigid COC matrix and rigid phosphors, the corresponding composite displays high-temperature phosphorescence performance. Even at 378 K, the composite can emit phosphorescence with a lifetime of 40-98 ms. The applications of these COC-based composites for imaging, information encryption, and anti-counterfeiting are thus explored.

Disturbance-Triggered Instant Crystallization Activating Bioinspired Emissive Gels

Many marine organisms feature sensitive sensory-perceptual systems to sense the surrounding environment and respond to disturbance with intense bioluminescence. However, it remains a great challenge to develop artificial materials that can sense external disturbance and simultaneously activate intense luminescence, although such materials are attractive for visual sensing and intelligent displays. Herein, we present a new class of bioinspired smart gels constructed by integrating hydrophilic polymeric networks, metastable supersaturated salt and fluorophores containing heterogenic atoms. Upon external disturbance, the composite gels undergo an instant and reversible soft-rigid state transition, simultaneously turning on intense fluorescence and activating ultralong afterglow emission with a maximum lifetime of 877.15 ms. The experimental results and molecular dynamics simulations reveal that the disturbance-induced luminescence mainly results from the geometrical confinement of aggregated fluorophores and enhanced molecular interactions to immensely suppress the non-radiative dissipation. Given their versatile and sensitive disturbance-responsiveness, dynamic interactive painting and 3D smart optical displays are demonstrated. This study paves a new avenue to achieve disturbance-sensing soft materials and promotes the development of smart visual sensors and interactive optical displays.

Organic dopant cyclization and significantly improved RTP properties

The internal rotation of triplet-generating molecules is detrimental to room temperature phosphorescence (RTP) radiation, and this rotation is usually mitigated by doping into rigid microenvironments. The chemical locking of internal rotation units in advance should be an effective strategy but is rarely studied in comparison. Herein, a triplet-generating molecule with two rotatable phenyls (DIA) was designed, synthesized, and then cyclized using two types of bonding bridges. We found that DIA/PMMA film shows little observable RTP afterglow despite a 148 ms lifetime, whereas carbon bridge cyclized DIA (CDIA) and oxygen bridge cyclized DIA (ODIA) emitted green and blue ultralong RTP in PMMA film, with lifetimes of 2146 ms and 2656 ms, respectively, demonstrating the potent role of pre-locking of internal rotation units in promoting RTP. Benefiting from the good spectral overlap between the RTP emissions of dopants and the absorption of perylene red (PR) in PMMA film, the almost complete triplet-to-singlet Förster resonance energy transfer was achieved under trace doping (0.1%), providing red room temperature afterglow materials with lifetimes of 1567-1800 ms. Preliminary applications of blue, green, and red afterglow materials in optical encryption and anti-counterfeiting are demonstrated. This work not only develops new triplet-generating and -radiating molecules but also introduces an effective molecular strategy for achieving ultralong RTP polymers.

Supramolecular Assembly of Hydrogen-Bonded Organic Frameworks with Carbon Dots: Realizing Ultralong Aqueous Room-Temperature Phosphorescence for Anticounterfeiting

Room-temperature phosphorescent carbon dots (RTP-CDs) have received increasing attention due to their excellent optical properties and potential applications. Nevertheless, the realization of RTP-CDs in aqueous solutions remains a considerable challenge due to the water-molecule- and oxygen-induced deactivation of the triplet excitons, which leads to phosphorescence quenching. In this study, ultralong phosphorescence in water was achieved by in situ self-assembly of CDs encapsulated in a rigid hydrogen-bonded organic framework (HOF). The phosphorescence lifetime reaches an impressive 956.96 ms and exhibits long-lasting optical and structural stability in water for more than 90 days. The composite material not only has ultralong luminescence life and excellent luminescence stability but also has two-color phosphorescence emission, as well as excellent antiphotobleaching and phosphorescence stability in aqueous solution, which can solve the current problem that RTP is easily burst out by water and moisture. In addition, this study introduced a fluorescent dye based on the triplet-singlet Förster resonance energy transfer system (TS-FRET) to fine-tune the afterglow properties. This work will inspire the design of RTP systems with dual phosphor light sources and provide new strategies for the development of smart RTP materials in water.

Color-Tunable Room-Temperature Phosphorescence from Non-Aromatic-Polymer-Involved Charge Transfer

Polymeric room-temperature phosphorescence (RTP) materials especially multicolor RTP systems hold great promise in concrete applications. A key feature in these applications is a triplet charge transfer transition. Aromatic electron donors and electron acceptors are often essential to ensure persistent RTP. There is much interest in fabricating non-aromatic charge-transfer-mediated RTP materials and it still remains a formidable challenge to achieve color-tunable RTP via charge transfer. Herein, a charge-transfer-mediated RTP material by embedding quinoline derivatives within a non-aromatic polymer matrix such as polyacrylamide (PAM) or polyvinyl alcohol (PVA) is developed. Through-space charge transfer (TSCT) is achieved upon alkali- or heat treatment to realize a long phosphorescence lifetime of up to 629.90 ms, high phosphorescence quantum yield of up to 20.51%, and a green-to-blue afterglow for more than 20 s at room temperature. This color-tunable RTP emerges from a nonaromatic polymer to single phosphor charge transfer that has rarely been reported before. This finding suggests that an effective and simple approach can deliver new color-tunable RTP materials for applications including multicolor display, information encryption, and gas detection.

Employing racemization strategies to simultaneously enhance the quantum yield, lifetime, and water stability of room-temperature phosphorescent materials

Room temperature phosphorescence (RTP) materials are increasingly recognized for their superior luminescent properties, which are pivotal in applications such as anti-counterfeiting, information storage, and optoelectronics. Despite this, the sensitivity of most RTP systems to humidity presents a significant challenge in achieving durable RTP performance in aqueous environments. This study proposes a strategy to enhance organic room-temperature phosphorescence through racemization. By incorporating external racemates of various chiral phosphors-NDBD-Ph, NDBD-Ph-Ph, NDBD-CH3, and NDBD-O-CH3-into a polyacrylonitrile (PAN) matrix, we significantly enhance the RTP properties (quantum yield, lifetime, and afterglow-time) of the resultant films. This enhancement can be attributed to the increased density of racemic molecules in the matrix and the increased spin-orbit coupling (SOC), facilitating the development of a long-lasting polymer RTP system in water. Notably, the racemic rac-NDBD-Ph@PAN film exhibits a persistent bright turquoise afterglow, even after immersion in water for a month. Furthermore, for the first time, we achieved an enhanced green to cyan RTP response to pH variations under both acidic and alkaline conditions (pH = 2-12), with the maximum phosphorescence emission intensity increasing up to threefold. The remarkable water stability, reversible response characteristics, and enhanced phosphorescence properties of this system offer promising potential for dynamic information encryption in aqueous environments.

Achieving Efficient Dark Blue Room-Temperature Phosphorescence with Ultra-Wide Range Tunable-Lifetime

Tunable-lifetime room-temperature phosphorescence (RTP) materials have been widely studied due to their broad applications. However, only few reports have achieved wide-range lifetime modulation. In this work, ultra-wide range tunable-lifetime efficient dark blue RTP materials were realized by doping methyl benzoate derivatives into polyvinyl alcohol (PVA) matrix. The phosphorescence lifetimes of the doped films can be increased from 32.8 ms to 1925.8 ms. Such wide range of phosphorescence lifetime modulation is extremely rare in current reports. Moreover, the phosphorescence emission of the methyl 4-hydroxybenzoate-doped film is located in the dark blue region and the phosphorescence quantum yield reaches as high as 15.4 %, which broadens their applications in organic optoelectronic information. Further studies demonstrated that the reason for the tunable lifetime was that the magnitude of the electron-donating ability of the substituent group modulates the HOMO-LUMO and singlet-triplet energy gap of methyl benzoate derivatives, as well as the ability to non-covalent interactions with PVA. Moreover, the potential applications of luminescent displays and optical anti-counterfeiting of these high-performance dark blue RTP materials have been conducted.

Urea-formaldehyde resin room temperature phosphorescent material with ultra-long afterglow and adjustable phosphorescence performance

Organic room-temperature phosphorescence materials have attracted extensive attention, but their development is limited by the stability and processibility. Herein, based on the on-line derivatization strategy, we report the urea-formaldehyde room-temperature phosphorescence materials which are constructed by polycondensation of aromatic diamines with urea and formaldehyde. Excitingly, urea-formaldehyde room-temperature phosphorescence materials achieve phosphor lifetime up to 3326 ms. There may be two ways to enhance phosphorescence performance, one is that the polycondensation of aromatic diamine with urea and formaldehyde promotes spin-orbit coupling, and another is that the imidazole derivatives derived from the condensation of aromatic o-diamine with formaldehyde maintains low levels of energy level difference and spin-orbit coupling, thus achieving ultra-long afterglow. Surprisingly, urea-formaldehyde room-temperature phosphorescence materials exhibit tunable phosphorescence emission in electrostatic field. Accordingly, 1,4-phenylenediamine, urea, and formaldehyde are copolymerized and self-assembled into phosphorescence microspheres with different electrostatic potential strengths. By mixing 1 wt% 1,4-phenylenediamine polycondensation microspheres with 1,4-phenylenediamine free microspheres, phosphor lifetime of the composite could be regulated from 27 ms to 123 ms. Moreover, vulcanization process enables precise shaping of urea-formaldehyde room-temperature phosphorescence materials. This work not only demonstrates that urea-formaldehyde room-temperature phosphorescence materials are promising candidates for organic phosphors, but also exhibits the phenomenon of electrostatically regulated phosphorescence.

Unique Visualization Growth Process of Long-Lived Room Temperature Phosphorescence in Polymer System

Recently, embedding organic phosphors into the polyvinyl alcohol (PVA) matrix has emerged as a convenient strategy to obtain efficient long-lived room temperature phosphorescence (RTP) via forming strong intermolecular hydrogen bonds with organic phosphors to minimize nonradiative relaxations. Regrettably, it is discovered that PVA is unable to trigger RTP emission when a novel functional phosphor THBE containing six extended biphenyl formaldehyde arms is doped into PVA matrix. Surprisingly, the excellent long-lived RTP emission can be easily obtained by doping THBE into PVA analogs, poly(vinyl alcohol-co-ethylene) (PVA-co-PE). The unique visualization growth process (i.e., white streak generation) of long-lived RTP is observed by UV light-driven aggregation of functional molecules THBE in PVA-co-PE matrix. The phosphorescent intensity of the luminescent film is enhanced by 55 times, from 729 to 40,785 a.u., and its phosphorescence lifetime is increased by 38 times, from 37.08 to 1415.41 ms. Due to the dynamically reversible RTP performance, as well as the permeability, flexibility, and wrinkle-free properties of the luminescent film, it can be utilized to create cutting-edge information storage devices.

Mechanical Stretch α-Cyclodextrin Pseudopolyrotaxane Elastomer with Reversible Phosphorescence Behavior

Polyethylene glycol chains in two terminals of the naphthalene functional group are threaded into α-cyclodextrin cavities to form the pseudopolyrotaxane (NPR), which not only effectively induces the phosphorescence of the naphthalene functional group by the cyclodextrin macrocycle confinement, but also provides interfacial hydrogen bonding assembly function between polyhydroxy groups of cyclodextrin and waterborne polyurethane (WPU) chains to construct elastomers. The introduction of NPR endows the elastomer with enhanced mechanical properties and excellent room temperature phosphorescent (RTP) emission (phosphorescence remains in water, acid, alkali, and organic solvents, even at 160 °C high temperatures). Especially, the reversible mechanically responsive room temperature phosphorescence behavior (phosphorescence intensity increased three times under 200% strain) can be observed in the mechanical stretch and recover process, owing to strain-induced microstructural changes further inhibiting the non-radiative transition and the vibration of NPR. Therefore, changing the phosphorescence behavior of supramolecular elastomers through mechanical stretching provides a new approach for supramolecular luminescent materials.

Dynamic Transition between Monomer and Excimer Phosphorescence in Organic Near-Infrared Phosphorescent Crystals

Achieving efficient near-infrared room-temperature phosphorescence of purely organic phosphors remains scarce and challenging due to strong nonradiative decay. Additionally, the investigation of triplet excimer phosphorescence is rarely reported, despite the fact that excimer, a special emitter commonly formed in crystals with strong π-π interactions, can efficiently change the fluorescent properties of compounds. Herein, a series of dithienopyrrole derivatives with low triplet energy levels and stable triplet states, exhibiting persistent near-infrared room-temperature phosphorescence, is developed. Via the modification of halogen atoms, the crystals display tunable emissions of monomers from 645 to 702 nm, with a maximum lifetime of 3.68 ms under ambient conditions. Notably, excimer phosphorescence can be switched on at low temperatures, enabled by noncovalent interactions rigidifying the matrix and stabilizing triplet excimer. Unprecedentedly, the dynamic transition process is captured between the monomer and excimer phosphorescence with temperature variations, revealing that the unstable triplet excimers in crystals with a tendency to dissociate can result in the effective quench of room-temperature phosphorescence. Excited state transitions across varying environments are elucidated, interpreting the structural dynamics of the triplet excimer and demonstrating strategies for devising novel near-infrared phosphors.

Stable and ultralong room-temperature phosphorescent copolymers with excellent adhesion, resistance, and toughness

Developing stable room-temperature phosphorescence (RTP) emission without being affected by moisture and mechanical force remains a great challenge for purely organic systems, due to their triplet states sensitive to the infinitesimal motion of phosphors and the oxygen quencher. We report a kind of highly robust phosphorescent systems, by doping a rigid phosphor into a copolymer (polyvinyl butyral resin) matrix with a balance of mutually exclusive features, including a rigidly hydrophilic hydrogen bond network and elastically hydrophobic constituent. Impressively, these RTP polymeric films have superior adhesive ability on various surfaces and showed reversible photoactivated RTP with lifetimes up to 5.82 seconds, which can be used as in situ modulated anticounterfeit labels. They can maintain a bright afterglow for over 25.0 seconds under various practical conditions, such as storage in refrigerators, soaking in natural water for a month, or even being subjected to strong collisions and impacts. These findings provide deep insights for developing stable ultralong RTP materials with desirable comprehensive performance.

Enabling Highly Robust Full-Color Ultralong Room-Temperature Phosphorescence and Stable White Organic Afterglow from Polycyclic Aromatic Hydrocarbons

In this work, full-color and stable white organic afterglow materials with outstanding water, organic solvents, and temperature resistances have been developed for the first time by embedding the selected polycyclic aromatic hydrocarbons into melamine-formaldehyde polymer via solution polymerization. The afterglow quantum yields and lifetimes of the resulting polymer films were up to 22.7 % and 4.83 s, respectively, under ambient conditions. For the coronene-doped sample, its afterglow color could be linearly tuned between yellow and blue by adjusting the temperature, and it could still emit an intense blue afterglow with a lifetime of 0.68 s at 440 K. Moreover, the films showed a bright and stable white afterglow at 370 K with a lifetime of 2.80 s and maintained an excellent afterglow performance after soaking in water and organic solvents for more than 150 days. In addition, the application potential of the polymer films in information encryption and anti-counterfeiting was also demonstrated.

Intermolecular donor-acceptor stacking to suppress triplet exciton diffusion for long-persistent organic room-temperature phosphorescence

Controlling triplet states is crucial to improve the efficiency and lifetime of organic room temperature phosphorescence (ORTP). Although the intrinsic factors from intramolecular radiative and non-radiative decay have been intensively investigated, the extrinsic factors that affect triplet exciton quenching are rarely reported. Diffusion to the defect sites inside the crystal or at the crystal surface may bring about quenching of triplet exciton. Here, the phosphorescence lifetime is found to have a negative correlation with the triplet exciton diffusion coefficient based on the density functional theory (DFT)/time-dependent density functional theory (TD-DFT) calculations on a series of ORTP materials. For systems with a weak charge transfer (CT) characteristic, close π-π stacking will lead to strong triplet coupling and fast triplet exciton diffusion in most cases, which is detrimental to the phosphorescence lifetime. Notably, for intramolcular donor-acceptor (D-A) type systems with a CT characteristic, intermolecular D-A stacking results in ultra-small triplet coupling, thus contributing to slow triplet diffusion and long phosphorescence lifetime. These findings shed some light on molecular design toward high-efficiency long persistent ORTP.

A general supramolecular strategy for fabricating full-color-tunable thermally activated delayed fluorescence materials

Developing a facile and feasible strategy to fabricate thermally activated delayed fluorescence materials exhibiting full-color tunability remains an appealing yet challenging task. In this work, a general supramolecular strategy for fabricating thermally activated delayed fluorescence materials is proposed. Consequently, a series of host-guest cocrystals are prepared by electron-donating calix[3]acridan and various electron-withdrawing guests. Owing to the through-space charge transfer mediated by multiple noncovalent interactions, these cocrystals all display efficient thermally activated delayed fluorescence. Especially, by delicately modulating the electron-withdrawing ability of the guest molecules, the emission colors of these cocrystals can be continuously tuned from blue (440 nm) to red (610 nm). Meanwhile, high photoluminescence quantum yields of up to 87% is achieved. This research not only provides an alternative and general strategy for the fabrication of thermally activated delayed fluorescence materials, but also establishes a reliable supramolecular protocol toward the design of advanced luminescent materials.

Water/Light Multiregulated Supramolecular Polypseudorotaxane Gel with Switchable Room-Temperature Phosphorescence

Water/light regulated room-temperature phosphorescence (RTP) of polypseudorotaxane supramolecular gel is constructed by threading the poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) chain with the bromoaromatic aldehyde into mono-(6-ethylenediamine-6-deoxygenated)-β-cyclodextrin (ECD) cavities and further assembling with negatively charged Laponite XLG (CNS) and diarylethene derivative (DAE) through electrostatic interaction. This hydrogel exhibits significant blue fluorescence emission; instead, after lyophilization to xerogel, the system exhibits both blue fluorescence and yellow RTP based on the rigid network structure of the xerogel, which restricts the vibration of the phosphor and suppresses the nonradiative relaxation process. Interestingly, the addition of excess ECDs to the gel system can enhance the RTP emission. Furthermore, the reversible luminescence behavior can be adjusted by the photoresponsive isomerism of DAE and humidity. This polypseudorotaxane supramolecular gel system provides a novel strategy for constructing tunable RTP materials.

Visible Light-Activated Ultralong-Lived Triplet Excitons of Carbon Dots for White-Light Manipulated Anti-Counterfeiting

Room temperature phosphorescence (RTP) has emerged as an interesting but rare phenomenon with multiple potential applications in anti-counterfeiting, optoelectronic devices, and biosensing. Nevertheless, the pursuit of ultralong lifetimes of RTP under visible light excitation presents a significant challenge. Here, new phosphorescent materials that can be excited by visible light with record-long lifetimes are demonstrated, realized through embedding nitrogen doped carbon dots (N-CDs) into a poly(vinyl alcohol) (PVA) film. The RTP lifetime of the N-CDs@PVA film is remarkably extended to 2.1 s excited by 420 nm, representing the highest recorded value for visible light-excited phosphorescent materials. Theoretical and experimental studies reveal that the robust hydrogen bonding interactions can effectively reduce the non-radiative decay rate and radiative transition rate of triplet excitons, thus dramatically prolong the phosphorescence lifetime. Notably, the RTP emission of N-CDs@PVA film can also be activated by easily accessible low-power white-light-emitting diode. More significantly, the practical applications of the N-CDs@PVA film in state-of-the-art anti-counterfeiting security and optical information storage domains are further demonstrated. This research offers exciting opportunities for utilizing visible light-activated ultralong-lived RTP systems in a wide range of promising applications.

Achieving Colorful Ultralong Organic Room-Temperature Phosphorescence by Precise Modification of Nitrogen Atoms on Phosphorescence Units

We successfully tune ultralong organic room-temperature phosphorescence (UORTP) by a simple strategy of precisely modifying nitrogen atoms on Phosphorescence Units, and colorful ultralong phosphorescence can be achieved. We for the first time investigate the structure-function relationship between phosphorescence properties and molecular structures of Phosphorescence Units. With BCz and BCz-1 as comparison, eight new Phosphorescence Units were synthesized by introducing one or two nitrogen atoms to the naphthalene moiety. For all the 10 Phosphorescence Units, their room-temperature ultralong phosphorescence in the PMMA film should be assigned to monomer phosphorescence from intrinsic T1 decay. For Phosphorescence Units series I (BCz, NBCz-1, NBCz-2, NBCz-3, NBCz-4, NBCz-5, and NBCz-6), introducing one nitrogen atom to the naphthalene moiety can significantly affect the phosphorescence properties of Phosphorescence Units, and the effect is quite complicated. For modification on the inner ring, the T1 energy level of NBCz-1 decreases, and the red shift of UORTP occurs while the T1 energy level of NBCz-2 increases and the blue shift of UORTP happens. For modification on the outer ring, no phosphorescence color change is observed for NBCz-3 and NBCz-4, but their phosphorescence lifetimes vary notably due to different intersystem crossing efficiencies; as the modification site approaches the central five-member ring, the T1 energy levels of NBCz-5 and NBCz-6 decrease, and their UORTP red shifts dramatically. For Phosphorescence Units series II (BCz, 2NBCz, BCz-1, and 2NBCz-1), introducing two nitrogen atoms to the outer six-member ring reduces energy level of T1 excitons and leads to incredible red shift of UORTP for BCz and 2NBCz while surprisingly energy levels of T1 excitons rise and UORTP blue shifts for BCz-1 and 2NBCz-1. Under the condition of proper modification sites, it is true that the more the additional nitrogen atoms, the more red-shifted the ultralong phosphorescence. This study may expand our knowledge of organic phosphorescence and lay the foundation for its future applications.

Recent advances in the design of afterglow materials: mechanisms, structural regulation strategies and applications

Afterglow materials are attracting widespread attention owing to their distinctive and long-lived optical emission properties which create exciting opportunities in various fields. Recent research has led to the discovery of many new afterglow materials featuring high photoluminescence quantum yields (PLQY) and lifetimes of up to several hours under ambient conditions. Afterglow materials are typically categorized according to their luminescence mechanism, such as long-persistent luminescence (LPL), room temperature phosphorescence (RTP), or thermally activated delayed fluorescence (TADF). Through rational design and novel synthetic strategies to modulate spin-orbit coupling (SOC) and populate triplet exciton states (T1), luminophores with long lifetimes and bright afterglow characteristics can be realized. Initial research towards afterglow materials focused mainly on pure inorganic materials, many of which possessed inherent disadvantages such as metal toxicity or low energy emissions. In recent years, organic-inorganic hybrid afterglow materials (OIHAMs) have been developed with high PLQY and long lifetimes. These hybrid materials exploit the tunable structure and easy processing of organic molecules, as well as enhanced SOC and intersystem crossing (ISC) processes involving heavy atom dopants, to achieve excellent afterglow performance. In this review, we begin by briefly discussing the structure and composition of inorganic and organic-inorganic hybrid afterglow materials, including strategies for regulating their lifetime, PLQY and luminescence wavelength. The specific advantages of organic-inorganic hybrid afterglow materials, including low manufacturing costs, diverse molecular/electronic structures, tunable structures and optical properties, and compatibility with a variety of substrates, are emphasized. Subsequently, we discuss in detail the fundamental mechanisms used by afterglow materials, their classification, design principles, and end applications (including sensing, anticounterfeiting, and photoelectric devices, among others). Finally, existing challenges and promising future directions are discussed, laying a platform for the design of afterglow materials for specific applications.

Stepwise taming of triplet excitons via multiple confinements in intrinsic polymers for long-lived room-temperature phosphorescence

Polymeric materials exhibiting room temperature phosphorescence (RTP) show a promising application potential. However, the conventional ways of preparing such materials are mainly focused on doping, which may suffer from phase separation, poor compatibility, and lack of effective methods to promote intersystem crossing and suppress the nonradiative deactivation rates. Herein, we present an intrinsically polymeric RTP system producing long-lived phosphorescence, high quantum yields and multiple colors by stepwise structural confinement to tame triplet excitons. In this strategy, the performance of the materials is improved in two aspects simultaneously: the phosphorescence lifetime of one polymer (9VA-B) increased more than 4 orders of magnitude, and the maximum phosphorescence quantum yield reached 16.04% in halogen-free polymers. Moreover, crack detection is realized by penetrating steam through the materials exposed to humid surroundings as a special quenching effect, and the information storage is carried out by employing the Morse code and the variations in lifetimes. This study provides a different strategy for constructing intrinsically polymeric RTP materials toward targeted applications.

Large-Scale Preparation for Multicolor Stimulus-Responsive Room-Temperature Phosphorescence Paper via Cellulose Heterogeneous Reaction

The large-scale preparation of sustainable room-temperature phosphorescence (RTP) materials, particularly those with stimulus-response properties, is attractive but remains challenging. This study develops a facile heterogeneous B─O covalent bonding strategy to anchor arylboronic acid chromophores to cellulose chains using pure water as a solvent, resulting in multicolor RTP cellulose. The rigid environment provided by the B─O covalent bonds and hydrogen bonds promotes the triplet population and suppresses quenching, leading to an excellent lifetime of 1.42 s for the target RTP cellulose. By increasing the degree of chromophore conjugation, the afterglow colors can be tuned from blue to green and then to red. Motivated by this finding, a papermaking production line is built to convert paper pulp reacted with an arylboronic acid additive into multicolor RTP paper on a large scale. Furthermore, the RTP paper is sensitive to water because of the destruction of hydrogen bonds, and the stimuli-response can be repeated in response to water/heat stimuli. The RTP paper can be folded into 3D afterglow origami handicrafts and anti-counterfeiting packing boxes or used for stimulus-responsive information encryption. This success paves the way for the development of large-scale, eco-friendly, and practical stimuli-responsive RTP materials.

UV-Curing-Enhanced Organic Long-Persistent Luminescence Materials

Amorphous organic long-persistent luminescence materials (OLPLMs) can realize simpler solution processing and large-area uniform luminescence, where the luminescent properties are significantly influenced by the rigid environment. However, research on utilizing the rigidity to promote long-persistent luminescence (LPL) properties of amorphous OLPLMs is still relatively rare due to the lack of an unambiguous and effective strategy to construct the rigid environment. Here, a universal strategy is proposed to enhance the LPL performance of organic host-guest doping systems by UV curing, which utilizes the rigid environment constructed by UV curing to promote the interaction between host and guest, thus inducing a generation of materials with highly efficient LPL performance. This solution-processable, large-area, and "easy-to-realize" material fabrication strategy can make amorphous OLPLMs show broader application prospects in some fields, such as anti-counterfeiting, nondestructive detection, and pattern marking or indication.

Hydrogen bonds and space restriction promoting long-lived room-temperature phosphorescence and its application for white light-emitting diodes

Achieving the long-lived and strong room-temperature phosphorescence (RTP) is challengeable but desirable, especially for the enhanced phosphorescence and metal-free nanomaterials. Herein, we initially synthesized the green-fluorescence carbon dots (pm-CDs), and further obtained the composite of pm-CDs@DCDA with a long RTP lifetime of 1.01 s through embedding pm-CDs in dicyandiamide (DCDA). And the bright and long-lived afterglow of pm-CDs@DCDA with 365 nm of UV light excitation was observed by the naked eyes for more than 17 s either emerging as the dry solid or in water. Importantly, the phosphorescence intensity and lifetime of pm-CDs@DCDA were remarkably promoted owing to the intermolecular hydrogen bonds and the rigid environment, hence facilitating the intersystem crossing (ISC) process and restricting the non-radiative transition of triplet excitons. Taking advantage of the superior solid-state luminescence of pm-CDs@DCDA, we further innovatively prepared the white light-emitting diodes (WLEDs) with the tunable color temperatures by regulating the mass of pm-CDs@DCDA coated on the chips. This proposed study originally employed DCDA as a matrix to separate and immobilize pm-CDs, which built up a new avenue to improve the RTP property and offered a promising application in WLEDs.

Photoinduced Radical Persistent Luminescence in Semialiphatic Polyimide System with Temperature and Humidity Resistance

Organic persistent luminescence (pL) systems with photoresponsive dynamic features have valuable applications in the fields of data encryption, anticounterfeiting, and bioimaging. Photoinduced radical luminescent materials have a unique luminous mechanism with the potential to achieve dynamic pL. It is extremely challenging to obtain radical pL under ambient conditions; on account of it, it is unstable in air. Herein, a new semialiphatic polyimide-based polymer (A0) is developed, which can achieve dynamic pL through reversible conversion of radical under photoexcitation. A "joint-donor-spacer-acceptor" molecular design strategy is applied to effectively modulate the intramolecular charge-transfer and charge-transfer complex interactions, resulting in effective protection of the radical generated under photoirradiation. Meanwhile, polyimide-based polymers of A1-A4 are obtained by doping different amine-containing fluorescent dyes to modulate the dynamic afterglow color from green to red via the triplet to singlet Förster resonance energy-transfer pathway. Notably, benefiting from the structural characteristics of the polyimide-based polymer, A0-A4 have excellent processability, thermal stability, and mechanical properties and can be applied directly in extreme environments such as high temperatures and humidity.

Rationally Designed Matrix-Free Carbon Dots with Wavelength-Tunable Room-Temperature Phosphorescence

We report the rational design of the matrix-free carbon dots (C-dots) with long wavelength and wavelength-tunable room-temperature phosphorescence (RTP). Taking advantage of microwave-assisted heating treatment, three RTP C-dots in boric acid (BA) composites are synthesized by using diethylenetriaminepentakis (methylphosphonic acid) as a multiple-sites crosslink agent, a moderately acid catalyst and P source; phenylenediamines (either o-PD, m-PD, or p-PD, respectively) as building block while BA as a carbonization-retardant matrix. After the water-soluble BA matrix is removed by dialysis, three matrix-free C-dots are obtained with RTP emission at 540, 550 and 570 nm under an excitation wavelength of 365 nm. Alterations of RTP emission of three matrix-free C-dots are ascribed to the difference in their particle size and band gap from n-π* transition. Furthermore, the application of three matrix-free C-dots are successfully performed in information encryption and decryption.