Wide-Range Color-Tunable Organic Phosphorescence Materials for Printable and Writable Security Inks

Crosslink-Enhanced Emission-Dominated Design Strategy for Constructing Self-Protective Carbonized Polymer Dots With Near-Infrared Room-Temperature Phosphorescence

Self-protective carbonized polymer dots (CPDs) with advantageous crosslinked nano-structures have attracted considerable attention in metal-free room temperature phosphorescence (RTP) materials, whereas their RTP emissions are still limited to short wavelength. Expanding their RTP emissions to Near-Infrared (NIR) range is attractive but suffers from the difficulties in constructing narrow energy levels and inhibiting intense non-radiative decay. Herein, a crosslink-enhanced emission (CEE)-dominated construction strategy was proposed, achieving desired NIR RTP (710 nm) in self-protective CPDs for the first time. Structural factors, i.e., crosslinking (covalent-bond CEE), conjugation (conjugated amine with bridging N-H and C=C group), and steric hindrance (confined-domain CEE), were confirmed indispensable for triggering NIR RTP emission in CPDs. Contrast experiments and theoretical calculations further revealed the rationality of the design strategy originating from CEE in terms of promoting the narrow energy level emission of triplet excitons and inhibiting the non-radiative quenching. This work not only firstly achieves NIR RTP in self-protective CPDs but also helps understand the origin of NIR RTP to further guide the synthesis of diverse CPDs with efficient long-wavelength RTP emission.

Sergeant-and-Soldier Effect in an Organic Room-Temperature Phosphorescent Host-Guest System

Host-guest systems have emerged as an efficient strategy for promoting organic room temperature phosphorescence (RTP). Despite the advantages of doping guest molecules into a host matrix, the complexity of these systems and the lack of techniques to visualize host-guest interactions at the molecular scale pose significant challenges in understanding the underlying mechanisms. Here, a novel host-guest RTP system is developed by incorporating low concentrations (1-10 mol%) of TPP-4C-BI (guest) into crystalline TPP-4C-Cz (host). Utilizing structural isomerism, the guest molecules are regularly incorporated into the host crystal lattice, resulting in phosphorescence quantum yields almost ten times higher than the pure compounds. The system enabled resolution of the molecular packing of the single crystal through X-ray diffraction, providing unprecedented visualization of host-guest interactions. A "sergeant-and-soldier" effect, where the minority dopant molecules (sergeants) significantly influence the packing arrangement of the host molecules (soldiers), enhances RTP is identified. Further analyses revealed that due to the host molecule's inefficient phosphorescence pathway, its long-lived dark triplets are channeled to the guest via triplet-triplet energy transfer (TTET), allowing the excited energy to radiatively decay more efficiently. These insights advance the understanding of RTP mechanisms and offer practical implications for designing high-efficiency phosphorescent materials.

Triplet Energy Gap-Regulated Room Temperature Phosphorescence in Host-Guest Doped Systems

The organic room temperature phosphorescence (RTP) materials via host-guest doped method receive considerable attention in the fields of optoelectronics, bioimaging, and information encryption. Despite many host-guest doped materials with excellent RTP properties have been developed, their luminous mechanism is still limited. Here, a series of host-guest doped materials, using benzophenone as the host and quinone compounds as the guests, were constructed to investigate the effect of the triplet energy gap (ΔET) between the host and guest on triplet states population. The guest's triplet state is proposed to be a "triplet energy reservoir", gathering the triplet excitons to emit RTP when ΔET is large and returning triplet excitons to the host when ΔET is small. By combining the results of steady-state and delayed emission spectra, time-resolved transient absorption spectra, and theoretical calculations, a bidirectional energy transfer process is proved, which are triplet-triplet energy transfer and reverse triplet-triplet energy transfer processes. The thermal equilibrium of these two energy transfer processes can be regulated by the ΔET and temperature. The potential applications of these RTP properties are also realized in data encryption and anti-counterfeiting. This work provides valuable insight into the design of host-guest doped materials based on energy transfer mechanisms.

Dimethylene-Cyclopropanide Units as Building Blocks for Fluorescence Dyes

Many organic dyes are fluorescent in solution. In the solid state, however, quenching processes often dominate, hampering material science applications such as light filters, light-emitting devices, or coding tags. We show that the dimethylene-cyclopropanide scaffold can be used to form two structurally different types of chromophores, which feature fluorescence quantum yields up to 0.66 in dimethyl sulfoxide and 0.53 in solids. The increased fluorescence in the solid state for compounds bearing malonate substituents instead of dicyanomethide ones is rationalized by the induced twist between the planes of the cyclopropanide core and a pyridine ligand.

Room-temperature phosphorescence and aggregation behavior in chiral heavy-atom-free organic molecules

Purely organic room temperature phosphorescence materials (RTP) have attracted much attention recently, but most of them are substituted with heavy atoms to enhance the intersystem crossing (ISC), which requires complicated design and synthesis. Herein, we report four chiral heavy-atom-free small molecules which integrate properties of aggregation and long-lifetime room temperature phosphorescence. The phosphorescence lifetime of synthesized chiral molecules is measured to be 150 ms, and the phosphorescence quantum yield reaches 15 % at room temperature. The twisted chiral conformation of four molecules not only affect aggregation photoluminescence properties but also can synergistically stabilize triplet exciton in the triplet excited states for excellent ISC efficiency. This strategy enriches the application fields of chiral aggregated long-lifetime room temperature phosphorescent materials.

Simplifying complexity: integrating color science for predictable full-color and on-demand persistent luminescence using industrial disperse dyes

Developing color-tunable ultralong room temperature phosphorescence (RTP) materials with variable afterglow is essential for applications in displays, sensors, information encryption, and optoelectronic devices. However, designing full-color ultralong RTP for persistent luminescence remains a significant challenge. Here, we propose a straightforward strategy to achieve predictable full-color afterglow using readily available disperse dyes in polymeric systems, via the phosphorescence resonance energy transfer (PRET) process. We incorporated the unconventional luminophore tetraacetylethylenediamine (TAED) into polyurethane (PU) to create a polymer host with green afterglow. By adding three typical disperse dyes as guests, we achieved a modulated afterglow covering the full visible light spectrum. Leveraging PRET processes between TAED and the disperse dyes, we achieved a prediction accuracy of 88.89% for afterglow color, surpassing well-developed coloration dye systems. This work thus introduces a novel method to obtain easily predictable ultralong RTP emission and establishes an on-demand design strategy for constructing disperse dye-based full-color afterglow, effectively linking fundamental color science to practical customization.

Xylan-based full-color room temperature phosphorescence materials enabled by imine chemistry

Developing sustainable matrix and efficient bonding mode for preparing room temperature phosphorescence (RTP) materials with full-color afterglows is attractive but still challenging. Here, xylan, a hemicellulose by-product from the paper mill, is used to construct full-color RTP materials based on imine bonds. Xylan is oxidation by periodate to introduce aldehyde groups to increase reaction sites; aromatic amines with different π conjugations can be readily anchored to dialdehyde xylan (DAX) by imine chemistry. The dual rigid environments were constructed by hydrogen bonding and imine covalent bonding, which can facilitate the triplet population and suppress non-radiative transitions, thus the xylan derivatives display satisfactory RTP performances. As the degree of conjugation of the chromophore increases, the afterglow colors can be changed from blue to green, yellow, and then to red. Thus, such a universal, facile, and eco-friendly strategy can be used to fabricate full-color RTP materials, which show a bright future in information encryption and advanced anti-counterfeiting. These results unambiguously state that the biodegradable paper mill waste-based RTP materials are convincingly expected to replace and surpass petroleum polymer-based counterparts.

Visualizing Triplet Energy Transfer in Organic Near-Infrared Phosphorescent Host-Guest Materials

Limited by the energy gap law, purely organic materials with efficient near-infrared room temperature phosphorescence are rare and difficult to achieve. Additionally, the exciton transition process among different emitting species in host-guest phosphorescent materials remains elusive, presenting a significant academic challenge. Herein, using a modular nonbonding orbital-π bridge-nonbonding orbital (n-π-n) molecular design strategy, we develop a series of heavy atom-free phosphors. Systematic modification of the π-conjugated cores enables the construction of a library with tunable near-infrared phosphorescence from 655 to 710 nm. These phosphors exhibit excellent performance under ambient conditions when dispersed into a 4-bromobenzophenone host matrix, achieving an extended lifetime of 11.25 ms and a maximum phosphorescence efficiency of 4.2 %. Notably, by eliminating the interference from host phosphorescence, the exciton transition process in hybrid materials can be visualized under various excitation conditions. Spectroscopic analysis reveals that the improved phosphorescent performance of the guest originates from the triplet-triplet energy transfer of abundant triplet excitons generated independently by the host, rather than from enhanced intersystem crossing efficiency between the guest singlet state and the host triplet state. The findings provide in-depth insights into constructing novel near-infrared phosphors and exploring emission mechanisms of host-guest materials.

Dual-Mechanism Design Strategy for High-Efficiency and Long-Lived Organic Afterglow Materials

Organic room-temperature phosphorescence (RTP) and afterglow materials hold great potential for various applications, but there remain inherent trade-offs between the afterglow efficiency and the lifetime. Here, we propose a dual-mechanism design strategy, leveraging the RTP or thermally activated delayed fluorescence (TADF) mechanism for a high afterglow efficiency and the organic long-persistent luminescence (OLPL) mechanism for a prolonged afterglow duration. The intramolecular charge transfer (ICT)-type difluoroboron β-diketonate molecules with a large S1 dipole moment are doped as the luminescent component into the organic matrix with a large dipole moment, and a series of TADF-type afterglow materials can be achieved with an afterglow efficiency of up to 88.7% and an afterglow lifetime of 200 ms. To prolong the afterglow duration, an electron donor is introduced as the third component to generate traps and facilitate charge separation. The obtained materials exhibit a dual afterglow mechanism, first exhibiting a TADF/RTP afterglow with an afterglow efficiency of up to 50.9%, followed by an hours-long OLPL afterglow emission with an afterglow efficiency of up to 13.1%. Further investigations reveal that an appropriate heavy-atom effect can facilitate the intersystem crossing process, which can promote the charge separation process and thus improve the OLPL afterglow performance. Additionally, rare-earth upconversion materials are introduced into OLPL materials to enable their near-infrared excitation properties, showcasing their potential applications in bioimaging.

Time-Dependent Color-Changing Room-Temperature Phosphorescence Materials with Mutual Achievement between Guest and Host Molecules

Host-guest doping strategy has gradually become the mainstream in constructing organic room-temperature phosphorescence (RTP) materials. The two-component doped system typically emits monochromatic phosphorescence dominated by the guest molecule, which also means that the intrinsic phosphorescence emission of the host molecule is not well utilized. In this work, a time-dependent color-changing RTP material is constructed based on host-guest doped system, in which the initial yellow phosphorescence stems from the isoquinoline-pyrazole guest and the final cyan phosphorescence originates from the intrinsic emission of the polymer host. The phenomenon of the strong interaction between host and guest molecules leading to their respective intrinsic phosphorescence provides new design inspiration for designing and developing two-component doped materials with RTP properties of color variation over time.

Intersystem crossing in a dibenzofuran-based room temperature phosphorescent luminophore investigated by non-adiabatic dynamics

The use of phosphorescent luminophores is highly beneficial in diverse high-technological and biological applications. Yet, because of the formally forbidden character of intersystem crossing, the use of heavy metals or atoms is usually necessary to achieve high quantum yields. This choice imposes serious constraints in terms of high device cost and inherent toxicity. In this contribution we resort to density functional based surface hopping non-adiabatic dynamics of a potential organic luminophore intended for room-temperature applications. We confirm that intersystem crossing is operative in a ps time-scale without requiring the activation of large-scale movements, thus confirming the suitability of the El Sayed-based strategy for the rational design of fully organic phosphorescent emitters.

Polymer-Based Room-Temperature Phosphorescence Materials Exhibiting Emission Lifetimes up to 4.6 s Under Ambient Conditions

The long-emission-lifetime nature of room-temperature phosphorescence (RTP) materials lays the foundation of their applications in diverse areas. Despite the advantage of mechanical property, processability and solvent dispersity, the emission lifetimes of polymer-based room-temperature phosphorescence materials remain not particularly long because of the labile nature of organic triplet excited states under ambient conditions. Specifically, ambient phosphorescence lifetime (τP) longer than 2 s and even 4 s have rarely been reported in polymer systems. Here, luminescent compounds with small phosphorescence rate on the order of approximately 10-1 s-1 are designed, ethylene-vinyl alcohol copolymer (EVOH) as polymer matrix and antioxidant 1010 to protect organic triplets are employed, and ultralong phosphorescence lifetime up to 4.6 s under ambient conditions by short-term and low-power excitation are achieved. The resultant materials exhibit high afterglow brightness, long afterglow duration, excellent processability into large area thin films, high transparency and thermal stability, which display promising anticounterfeiting and data encryption functions.

Carbon Dots-Inked Paper with Single/Two-Photon Excited Dual-Mode Thermochromic Afterglow for Advanced Dynamic Information Encryption

Achieving thermochromic afterglow (TCAG) in a single material for advanced information encryption remains a significant challenge. Herein, TCAG in carbon dots (CDs)-inked paper (CDs@Paper) is achieved by tuning the temperature-dependent dual-mode afterglow of room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). The CDs are synthesized through thermal treatment of levofloxacin in melting boric acid with postpurification via dialysis. CDs@Paper exhibit both TCAG and excitation-dependent afterglow color properties. The TCAG of CDs@Paper exhibits dynamic color changes from blue at high temperatures to yellow at low temperatures by adjusting the proportion of the temperature-dependent TADF and phosphorescence. Notably, two-photon afterglow in CDs-based afterglow materials and time-dependent two-photon afterglow colors are achieved for the first time. Moreover, leveraging the opposite emission responses of phosphorescence and TADF to temperature, CDs@Paper demonstrate TCAG with temperature-sensing capabilities across a wide temperature range. Furthermore, a CDs@Paper-based 3D code containing color and temperature information is successfully developed for advanced dynamic information encryption.

Excellent Persistent Near-Infrared Room Temperature Phosphorescence from Highly Efficient Host-Guest Systems

Organic near-infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal-to-background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy-gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten-folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host-guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs.

Multicolor Photochemical Printing Inside Polymer Matrices for Advanced Photonic Anticounterfeiting

Conventional security inks, generally directly printed on the data page surface, are vulnerable to counterfeiters, thereby raising the risk of chemical structural deciphering. In fact, polymer film-based data pages with customized patterns embedded within polymer matrix, rather than printed on the surface, emerge as a promising solution. Therefore, the key lies in developing fluorophores offering light dose-controlled fluorescent color inside polymer matrices. Though conventional fluorophores often suffer from photobleaching and uncontrolled photoreactions, disqualifying them for this purpose. Herein a diphenanthridinylfumaronitrile-based phototransformers (trans-D5) that undergoes photoisomerization and subsequent photocyclization during photopolymerization of the precursor, successively producing cis- and cyclo-D5 with stepwise redshifted solid-state emissions is developed. The resulting cyclo-D5 exhibits up to 172 nm emission redshift in rigidifying polymer matrices, while trans-D5 experiences a slightly blueshifted emission (≈28 nm), cis-D5 undergoes a modest redshift (≈14 nm). The markedly different rigidochromic behaviors of three D5 molecules within polymer matrices enable multicolor photochemical printing with a broad hue ranging from 38 to 10 via an anticlockwise direction in Munsell color space, yielding indecipherable fluorescent patterns in polymer films. This work provides a new method for document protection and implements advanced security features that are unattainable with conventional inks.

Multimode Stimuli-Responsive Room-Temperature Phosphorescence Achieved by Doping Butterfly-like Fluorogens into Crystalline Small-Molecular Hosts

Materials with stimuli-responsive purely organic room-temperature phosphorescence (RTP) exempt from exquisite molecular design and complex preparation are highly desirable but still relatively rare. Moreover, most of them work in a single switching mode. Herein, we employ a versatile host-guest-doped strategy to facilely construct efficient RTP systems with multimode stimuli-responsiveness without ingenious molecular design. By conveniently doping butterfly-like guests, namely, N,N'-diphenyl-dihydrodibenzo[a,c]phenazines (DPACs), featured with vibration-induced emission into the small-molecular hosts via various methods, RTP systems with finely tunable photophysical properties are readily obtained. Through systematic mechanistic studies and with the aid of a series of control experiments, we unveil the critical role of the host crystallinity in achieving efficient RTP. By virtue of the inherent environmental sensitivity of both RTP and fluorescence of the DPACs, our systems exhibit multiple-stimuli-responsiveness with the luminescence not only switching between the fluorescence and phosphorescence but also continuously changing in the fluorescence color. Advanced dynamic anticounterfeiting and multilevel information encryption is thereby realized.

Narrowband Organic/Inorganic Hybrid Afterglow Materials

Narrowband afterglow materials display interesting functions in high-quality anti-counterfeiting and multiplexed bioimaging. However, there is still a limited exploration of these afterglow materials, especially for those with a full width at half maxima (FWHM) around 30 nm. Here, we report the fabrication of narrowband organic/inorganic hybrid afterglow materials via energy transfer technology. Coronene (Cor) with a long phosphorescence feature and broad phosphorescence band is selected as the donor for energy transfer, and inorganic quantum dots (QDs) of CdSe/ZnS with a narrowband emission are used as acceptors. Upon doping into the organic matrix, the resultant three-component materials exhibit a narrowband afterglow with an afterglow lifetime of approximately 3.4 s and an FWHM of 31 nm. The afterglow wavelength of the afterglow materials can be controlled by the QDs. This work based on organic/inorganic hybrids provides a facile approach for developing multicolor and narrowband afterglow materials, as well as opens a new way for expanding the features of organic afterglow for multifunctional applications. It is expected to rely on narrowband afterglow emitters to solve the "spectrum congestion" problem of high-density information storage in optical anti-counterfeiting and information encryption.

Finely manipulating room temperature phosphorescence by dynamic lanthanide coordination toward multi-level information security

Room temperature phosphorescence materials have garnered significant attention due to their unique optical properties and promising applications. However, it remains a great challenge to finely manipulate phosphorescent properties to achieve desirable phosphorescent performance on demand. Here, we show a feasible strategy to finely manipulate organic phosphorescent performance by introducing dynamic lanthanide coordination. The organic phosphors of terpyridine phenylboronic acids possessing excellent coordination ability are covalently embedded into a polyvinyl alcohol matrix, leading to ultralong organic room temperature phosphorescence with a lifetime of up to 0.629 s. Notably, such phosphorescent performance, including intensity and lifetime, can be well controlled by varying the lanthanide dopant. Relying on the excellent modulable performance of these lanthanide-manipulated phosphorescence films, multi-level information encryption including attacker-misleading and spatial-time-resolved applications is successfully demonstrated with greatly improved security level. This work opens an avenue for finely manipulating phosphorescent properties to meet versatile uses in optical applications.

Delayed room temperature phosphorescence enabled by phosphines

Organic ultralong room-temperature phosphorescence (RTP) usually emerges instantly and immediately decays after excitation removal. Here we report a new delayed RTP that is postponed by dozens of milliseconds after excitation removal and decays in two steps including an initial increase in intensity followed by subsequent decrease in intensity. The delayed RTP is achieved through introduction of phosphines into carbazole emitters. In contrast to the rapid energy transfer from single-molecular triplet states (T1) to stabilized triplet states (Tn*) of instant RTP systems, phosphine groups insert their intermediate states (TM) between carbazole-originated T1 and Tn* of carbazole-phosphine hybrids. In addition to markedly increasing emission lifetimes by ten folds, since TM → Tn* transition require >30 milliseconds, RTP is thereby postponed by dozens of milliseconds. The emission character of carbazole-phosphine hybrids can be used to reveal information through combining instant and delayed RTP, realizing multi-level time resolution for advanced information, biological and optoelectronic applications.

Isostructural doping for organic persistent mechanoluminescence

Mechanoluminescence, featuring light emission triggered by mechanical stimuli, holds immense promise for diverse applications. However, most organic Mechanoluminescence materials suffer from short-lived luminescence, limiting their practical applications. Herein, we report isostructural doping as a valuable strategy to address this challenge. By strategically modifying the host matrices with specific functional groups and simultaneously engineering guest molecules with structurally analogous features for isostructural doping, we have successfully achieved diverse multicolor and high-efficiency persistent mechanoluminescence materials with ultralong lifetimes. The underlying persistent mechanoluminescence mechanism and the universality of the isostructural doping strategy are also clearly elucidated and verified. Moreover, stress sensing devices are fabricated to show their promising prospects in high-resolution optical storage, pressure-sensitive displays, and stress monitoring. This work may facilitate the development of highly efficient organic persistent mechanoluminescence materials, expanding the horizons of next-generation smart luminescent technologies.

Visible-light-excited robust room-temperature phosphorescence of dimeric single-component luminophores in the amorphous state

Organic room temperature phosphorescence (RTP) has significant potential in various applications of information storage, anti-counterfeiting, and bio-imaging. However, achieving robust organic RTP emission of the single-component system is challenging to overcome the restriction of the crystalline state or other rigid environments with cautious treatment. Herein, we report a single-component system with robust persistent RTP emission in various aggregated forms, such as crystal, fine powder, and even amorphous states. Our experimental data reveal that the vigorous RTP emissions rely on their tight dimers based on strong and large-overlap π-π interactions between polycyclic aromatic hydrocarbon (PAH) groups. The dimer structure can offer not only excitons in low energy levels for visible-light excited red long-lived RTP but also suppression of the nonradiative decays even in an amorphous state for good resistance of RTP to heat (up to 70 °C) or water. Furthermore, we demonstrate the water-dispersible nanoparticle with persistent RTP over 600 nm and a lifetime of 0.22 s for visible-light excited cellular and in-vivo imaging, prepared through the common microemulsion approach without overcaution for nanocrystal formation.

3-Ethynyltriimidazo[1,2-a:1',2'-c:1″,2″-e][1,3,5]triazine Dual Short- and Long-Lived Emissions with Crystallization-Enhanced Feature: Role of Hydrogen Bonds and π-π Interactions

Organic room temperature phosphorescent (ORTP) materials with stimuli-responsive, multicomponent emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with an ethynyl group, TT-CCH, is isolated and investigated. The compound possesses crystallization-enhanced emission (CEE) comprising dual fluorescence and dual phosphorescence of both molecular and supramolecular origin with aggregation-induced components highly sensitive to grinding. The mechanisms involved in the emissions have been disclosed thanks to combined structural, spectroscopic and computational investigations. In particular, strong CH⋯N hydrogen bonds are deemed responsible, for the first time in the TT family, together with frequently observed π⋯π stacking interactions, for the aggregated fluorescence and phosphorescence.

Multilevel Information Encryption Based on Thermochromic Perovskite Microcapsules via Orthogonal Photic and Thermal Stimuli Responses

Increasing modal variations of stimulus-responsive materials ensure the high capacity and confidentiality of information storage and encryption systems that are crucial to information security. Herein, thermochromic perovskite microcapsules (TPMs) with dual-variable and quadruple-modal reversible properties are designed and prepared on the original oil-in-fluorine (O/F) emulsion system. The TPMs respond to the orthogonal variations of external UV and thermal stimuli in four reversible switchable modes and exhibit excellent thermal, air, and water stability due to the protection of perovskites by the core-shell structure. Benefiting from the high-density information storage TPMs, multiple information encryptions and decryptions are demonstrated. Moreover, a set of devices are assembled for a multilevel information encryption system. By taking advantage of TPMs as a "private key" for decryption, the signal can be identified as the corresponding binary ASCII code and converted to the real message. The results demonstrate a breakthrough in high-density information storage materials as well as a multilevel information encryption system based on switchable quadruple-modal TPMs.

Blue-Shifted and Broadened Fluorescence Enhancement by Visible and Mode-Selective Infrared Double Excitations

Mode-selective vibrational excitations to modify the electronic states of fluorescein dianion in methanol solutions are carried out with a femtosecond visible pulse synchronized with a tunable high-power, narrow-band picosecond infrared (IR) pulse. In this work, simultaneous intensity enhancement, peak blueshift, and line width broadening of fluorescence are observed in the visible/IR double resonance experiments. Comprehensive investigations on the modulation mechanism with scanning the vibrational excitation frequencies, tuning the time delay between the two excitation pulses, theoretical calculations, and nonlinear and linear spectroscopic measurements suggest that the fluorescence intensity enhancement is caused by the increase of the Franck-Condon factor induced by the vibrational excitations at the electronic ground state. Various enhancement effects are observed as vibrations initially excited by the IR photons relax to populate the vibrational modes of lower frequencies. The peak blueshift and line width broadening are caused by both increasing the Franck-Condon factors among different subensembles because of IR pre-excitation and the long-lived processes induced by the initial IR excitation. The results demonstrate that the fluorescence from the visible/IR double resonance experiments is not a simple sum frequency effect, and vibrational relaxations can produce profound effects modifying luminescence.

Rapid room-temperature phosphorescence chiral recognition of natural amino acids

Chiral recognition of amino acids is very important in both chemical and life sciences. Although chiral recognition with luminescence has many advantages such as being inexpensive, it is usually slow and lacks generality as the recognition module relies on structural complementarity. Here, we show that one single molecular-solid sensor, L-phenylalanine derived benzamide, can manifest the structural difference between the natural, left-handed amino acid and its right-handed counterpart via the difference of room-temperature phosphorescence (RTP) irrespective of the specific chemical structure. To realize rapid and reliable sensing, the doped samples are obtained as nanocrystals from evaporation of the tetrahydrofuran solutions, which allows for efficient triplet-triplet energy transfer to the chiral analytes generated in situ from chiral amino acids. The results show that L-analytes induce strong RTP, whereas the unnatural D-analytes produce barely any afterglow. The method expands the scope of luminescence chiral sensing by lessening the requirement for specific molecular structures.

Multi-colour room-temperature phosphorescence from fused-ring compounds for dynamic anti-counterfeiting applications

We present a facile strategy to achieve purely organic multi-colour room-temperature phosphorescence (RTP) films by doping typical fused-ring compounds into a poly(vinyl alcohol) matrix. Such RTP films demonstrate inherent RTP emission ranging from green to red with a long lifetime and high quantum yield (QY) (lifetime: ∼0.56 ms, QY: ∼35.4%). We further exploit such high-performance RTP films for dynamic information encryption.

Sunlight-Activated Hour-Long Afterglow from Transparent and Flexible Polymers

Afterglow materials featuring long emission durations ranging from milliseconds to hours have garnered increasing interest owing to their potential applications in sensing, bioimaging, and anti-counterfeiting. Unfortunately, polymeric materials rarely exhibit afterglow properties under ambient conditions because of the rapid nonradiative decay rate of triplet excitons. In this study, hour-long afterglow (HLA) polymer films are fabricated using a facile molecular doping strategy. Flexible and transparent polymer films emitted a bright afterglow lasting over 11 h at room temperature in air, which is one of the best performances among the organic afterglow materials reported to date. Intriguingly, HLA polymer films can be activated by sunlight, and their cyan afterglow in air can be readily observed by the naked eye. Moreover, the HLA color of the polymer films could be tuned from cyan to red through the Förster resonance energy transfer mechanism. Their application in flexible displays and information storage has also been demonstrated. With remarkable advantages, including an hour-long and bright afterglow, tunable afterglow colors, superior flexibility and transparency, and ease of fabrication, the HLA polymer paves the way for the practical application of afterglow materials in the engineering sector.

High-Resolution Afterglow Patterning Using Cooperative Vapo- and Photo-Stimulation

Bright afterglow room-temperature phosphorescence (RTP) soon after ceasing excitation is a promising technique for greatly increasing anti-counterfeiting capabilities. The development of a process for rapid high-resolution afterglow patterning of crystalline materials can improve both high-speed fabrication of anti-counterfeiting afterglow media and stable afterglow readout compared with those achieved with amorphous materials. Here, the high-resolution afterglow patterning of crystalline materials via cooperative organic vapo- and photo-stimulation is reported. A single crystal of (S)-(-)-2,2'-bis(diphenylphosphino)-5,5',6,6',7,7'8,8'-octahydro-1,1'-binaphthyl [(S)-H8-BINAP] doped with (S)-(-)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(S)-BINAP] shows green afterglow RTP. Crystals of (S)-BINAP-doped (S)-H8-BINAP changed to an amorphous state with no afterglow capability on weak continuous photoirradiation under dichloromethane (DCM) vapor. Photoirradiation induced oxidation of the (S)-H8-BINAP host molecule in the crystal. The oxidized (S)-H8-BINAP forms on the crystal surface strongly interacted with DCM molecules, which induces melting of the (S)-BINAP-doped (S)-H8-BINAP crystal and trigger formation of an amorphous state without an afterglow capability. High-resolution afterglow patterning of the crystalline film is rapidly achieved by using cooperative organic vapo- and photo-stimulation. In addition to the benefit of rapid afterglow patterning, the formed afterglow images of the crystalline film can be repeatedly read out under ambient conditions without DCM vapor.

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.

Recent progress in ion-regulated organic room-temperature phosphorescence

Organic room-temperature phosphorescence (RTP) materials have attracted considerable attention for their extended afterglow at ambient conditions, eco-friendliness, and wide-ranging applications in bio-imaging, data storage, security inks, and emergency illumination. Significant advancements have been achieved in recent years in developing highly efficient RTP materials by manipulating the intermolecular interactions. In this perspective, we have summarized recent advances in ion-regulated organic RTP materials based on the roles and interactions of ions, including the ion-π interactions, electrostatic interactions, and coordinate interactions. Subsequently, the current challenges and prospects of utilizing ionic interactions for inducing and modulating the phosphorescent properties are presented. It is anticipated that this perspective will provide basic guidelines for fabricating novel ionic RTP materials and further extend their application potential.

ε-Polylysine organic ultra-long room-temperature phosphorescent materials based on phosphorescent molecule doping

Achieving long-lived room-temperature phosphorescence from pure organic amorphous polymers is attractive, and afterglow materials with colour-tunable and multiple-stimuli-responsive afterglow are particularly important, but only few materials with these characteristics have been reported so far. Herein, a facile and general method is reported to construct a series of ε-polylysine (ε-PL)-based afterglow materials with tunable colour (from blue to red) and long life. By doping guest molecules into ε-PL to obtain composite materials, the polymer matrix provides a rigid environment for luminescent groups, resulting in amorphous polymers with different RTPs. In this system, the materials even have impressive humidity-stimulated responses, and the phosphorescence emission exhibits excitation-dependent and time-dependent properties. The humidity-responsive afterglow is caused by the destruction of hydrogen bonds and quenching of triplet excitons. The time-dependent afterglow should stem from the formation of diversified RTP emissive species with comparable but different lifetimes. 9,10-diaminophene has Ex-De properties in the film doping state. With the change of excitation wavelength (254 nm to 365 nm), the emission wavelength shifts from 461 nm to 530 nm, accompanied by the change of emission colour from blue to green. In addition, the phosphorescence life of the film is the longest, up to 2504.7 ms, and the afterglow lasts up to 15 s, which is conducive to its applications in anti-counterfeiting and information encryption.

Photochemically and Thermally Programmed Optical Multi-States from a Single Diacetylene-Functionalized Cyanostilbene Luminogen

To develop advanced optical systems, many scientists have endeavored to create smart optical materials which can tune their photophysical properties by changing molecular states. However, optical multi-states are obtained usually by mixing many dyes or stacking multi-layered structures. Here, multiple molecular states are tried to be generated with a single dye. In order to achieve the goal, a diacetylene-functionalized cyanostilbene luminogen (DACSM) is newly synthesized by covalently connecting diacetylene and cyanostilbene molecular functions. Photochemical reaction of cyanostilbene and topochemical polymerization of diacetylene can change the molecular state of DACSM. By thermal stimulations and the photochemical reaction, the conformation of polymerized DACSM is further tuned. The synergetic molecular cooperation of cyanostilbene and diacetylene generates multiple molecular states of DACSM. Utilizing the optical multi-states achieved from the newly developed DACSM, switchable optical patterns and smart secret codes are successfully demonstrated.

Steerable mass transport in a photoresponsive system for advanced anticounterfeiting

Numerous anticounterfeiting platforms using photoresponsive materials have been designed to improve information security, enabling applications in anticounterfeiting technology. However, fabricating sophisticated micro/nanostructures using bidirectional mass transport to achieve advanced anticounterfeiting remains challenging. Here, we propose one strategy to achieve steerable mass transport in a photoresponsive system with the assistance of solvent vapor at room temperature. Upon optimizing the host-guest ratio and the width of photoisomerized areas, wettability gradient is acquired just photo-patterning once, then bidirectional mass transport is realized due to the competition of mass transport induced by surface energy gradient of the material itself and flow of the solvent on the film surface with wettability gradient. Taking advantage of the interaction between solvent and film surface with wettability gradient, this bidirectional polymer flow has been successfully applied in multi-mode anticounterfeiting. This work paves a promising avenue toward high-level information storage in soft materials, demonstrating the potential applications in anticounterfeiting.

Achieving Ultralong Room-Temperature Phosphorescence in Covalent Organic Framework System

The combination of room-temperature phosphorescence (RTP) and covalent organic frameworks (COFs) would give rise to a new class of functional materials with sensing and responsive properties. However, such organic materials have been rarely reported, especially for those with long phosphorescence lifetimes. Here we report the incorporation of RTP emitters into COFs either via chemical decoration or noncovalent doping to achieve ultralong RTP in a COF system. The RTP emitters are designed with small phosphorescence rates and consequently exhibit ultralong phosphorescence lifetimes when nonradiative decay and oxygen quenching are suppressed in COF system. The RTP-COF materials have been found to possess oxygen sensing properties with large response of phosphorescence lifetimes.

Twofold rigidity activates ultralong organic high-temperature phosphorescence

A strategy is pioneered for achieving high-temperature phosphorescence using planar rigid molecules as guests and rigid polymers as host matrix. The planar rigid configuration can resist the thermal vibration of the guest at high temperatures, and the rigidity of the matrix further enhances the high-temperature resistance of the guest. The doped materials exhibit an afterglow of 40 s at 293 K, 20 s at 373 K, 6 s at 413 K, and a 1 s afterglow at 433 K. The experimental results indicate that as the rotational ability of the groups connected to the guests gradually increases, the high-temperature phosphorescence performance of the doped materials gradually decreases. In addition, utilizing the property of doped materials that can emit phosphorescence at high temperatures and in high smoke, the attempt is made to use organic phosphorescence materials to identify rescue workers and trapped personnel in fires.

Stimuli-fluorochromic smart organic materials

Smart materials based on stimuli-fluorochromic π-conjugated solids (SFCSs) have aroused significant interest due to their versatile and exciting properties, leading to advanced applications. In this review, we highlight the recent developments in SFCS-based smart materials, expanding beyond organometallic compounds and light-responsive organic luminescent materials, with a discussion on the design strategies, exciting properties and stimuli-fluorochromic mechanisms along with their potential applications in the exciting fields of encryption, sensors, data storage, display, green printing, etc. The review comprehensively covers single-component and multi-component SFCSs as well as their stimuli-fluorochromic behaviors under external stimuli. We also provide insights into current achievements, limitations, and major challenges as well as future opportunities, aiming to inspire further investigation in this field in the near future. We expect this review to inspire more innovative research on SFCSs and their advanced applications so as to promote further development of smart materials and devices.

Wide-Range Color-Tunable Organic Scintillators for X-Ray Imaging Through Host-Guest Doping

With the increasing demands of X-ray detection and medical diagnosis, organic scintillators with intense and tunable X-ray excited emission have been becoming important. To guarantee the X-ray absorption, heavy atoms were widely added in reported organic scintillators, which led to emission quenching. In this work, we propose a new strategy to realize organic scintillators through the host-guest doping strategy. Then the X-ray absorption centers (host) and emission centers (guest) are separated. Under X-ray excitation, these materials displayed intense and readily tunable emissions ranging from green (520 nm) to near infrared (NIR) regions (682 nm). Besides, the relationship between the X-ray absorption and spatial arrangement of the heavy atoms in the host matrix was also revealed. The potential application of these wide-range color tunable organic host-guest scintillators in X-ray imaging were demonstrated. This work provides a new feasible strategy for constructing high-performance organic scintillators with tunable luminescence properties.

Chaperone Mimetic Strategy for Achieving Organic Room-Temperature Phosphorescence based on Confined Supramolecular Assembly

The development of organic materials that deliver room-temperature phosphorescence (RTP) is highly interesting for potential applications such as anticounterfeiting, optoelectronic devices, and bioimaging. Herein, a molecular chaperone strategy for controlling isolated chromophores to achieve high-performance RTP is demonstrated. Systematic experiments coupled with theoretical evidence reveal that the host plays a similar role as a molecular chaperone that anchors the chromophores for limited nonradiative decay and directs the proper conformation of guests for enhanced intersystem crossing through noncovalent interactions. For deduction of structure-property relationships, various structure-related descriptors that correlate with the RTP performance are identified, thus offering the possibility to quantitatively design and predict the phosphorescent behaviors of these systems. Furthermore, application in thermal printing is well realized for these RTP materials. The present work discloses an effective strategy for efficient construction of organic RTP materials, delivering a modular model which is expected to help expand the diversity of desirable RTP systems.

Naphthyl Substituted Impurities Induce Efficient Room Temperature Phosphorescence

Accidentally, it was found that triphenylamine (TPA) from commercial sources shows ultralong yellow-green room temperature phosphorescence (RTP) like commercial carbazole, which however disappears for lab-synthesized TPA with high purity. Herein, we for the first time identify the impurity types that cause RTP of commercial TPA, which are two N, N-diphenyl-naphthylamine isomers. Due to similar molecular polarity and very trace amount (≈0.8 ‰, molar ratio), these naphthyl substituted impurities can be easily overlooked. We further show that even at an extremely low amount (1000000 : 1, mass ratio) of impurities, RTP emission is still generated, attributed to the triplet-to-triplet energy transfer mechanism. Notably, this doping strategy is also applicable to the triphenylphosphine and benzophenone host systems, of which strong RTP emission can be activated by simply doping the corresponding naphthyl substituted analogues into them. This work therefore provides a general and efficient host/guest strategy toward high performance and diverse organic RTP materials.

Dopant-Matrix Afterglow Systems: Manipulation of Room-Temperature Phosphorescence/Thermally Activated Delayed Fluorescence Afterglow Mechanism via Mismatch/Match of Intermolecular Charge Transfer between Dopants and Matrices

Dopant-matrix organic afterglow materials exhibit ease of fabrication and intriguing functions in diverse fields. However, a deep and comprehensive understanding of their photophysical behaviors remains elusive. Here we report manipulation of a room-temperature phosphorescence/thermally activated delayed fluorescence (RTP/TADF) afterglow mechanism via the mismatch/match of intermolecular charge transfer between dopants and matrices. When dispersed in inert crystalline matrices, the luminescent dopants show RTP lifetimes up to 2 s. Interestingly, when suitable organic matrices are selected, the resultant dopant-matrix materials display a TADF-type afterglow under ambient conditions due to the formation of dopant-matrix intermolecular charge transfer complexes. Detailed studies reveal that reverse intersystem crossing from dopants' T1 states to charge transfer complexes' S1 states, which features a moderate kRISC of 101-102 s-1, is responsible for the emergence of a TADF-type organic afterglow in rigid crystalline matrices. Such less reported delicate photophysics reveals a new aspect of the excited state property in dopant-matrix afterglow systems.

A near-infrared fluorescent probe with remarkably large stokes shift for specifical imaging of peroxynitrite fluctuations in Hela cells

Peroxynitrite (ONOO-), an endogenous reactive nitrogen species, plays an important role in maintaining intracellular homeostasis. Abnormal levels of ONOO- in cells could cause protein oxidation which is confirmed that related with Alzheimer's diseases, so accurate monitoring of ONOO- in cells is crucial. Herein, a novel fluorescent probe (XPC) based on dicyanomethylene-4H-benzothiopyran was developed by regulating its intramolecular charge transfer (ICT) effect to detect ONOO-. Once reaction with ONOO-, the fluorescence of XPC was turned on and the emission wavelength could reach up to 750 nm. Furthermore, XPC exhibited satisfactory performances for ONOO- such as large Stokes shift (200 nm), good sensitivity (Limit of detection = 13 nM), high selectivity to ONOO- over other a reactive nitrogen species (RNS)/reactive oxygen species (ROS). More importantly, XPC was successfully applied for monitoring the fluctuations of ONOO- in living cells.

Excitation wavelength-dependent multi-coloured and white-light emissive pyrene-based hydrazones: suppression of Kasha's rule

Multi-coloured and white-light emissions from pyrene-based hydrazones are described. They exhibit excitation wavelength-dependent emissions in solution due to the suppression of Kasha's rule. Interestingly, in dimethylformamide, 1-3 emit light that covers all the regions of primary colours as a function of excitation wavelength, and 1 and 2 emit white light (λex = 420 nm) in isopropanol.

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.

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.

Thermal annealing promoted room temperature phosphorescence: motion models and internal mechanism

Thermal annealing has been proven to be an efficient method to optimize the device performance of organic and polymeric opto-electronic materials. However, no detailed information of aggregate structures was obtained for a deeper understanding of what happens during thermal annealing. Herein, through modulation of molecular configurations by tunable linkage positions, and the amplified amplitudes of molecular motions by incorporation of additional methylene units, accurate changes of aggregated structures upon thermal annealing have been achieved, accompanying with the 'turn-on' room temperature phosphorescence (RTP) response by about 4800- and 177-fold increase of lifetimes. The stretching and swing motion models have been proposed, which afforded an efficient way to investigate the science of dynamic aggregation in depth.

Room-temperature phosphorescent materials derived from natural resources

Room-temperature phosphorescent (RTP) materials have enormous potential in many different areas. Additionally, the conversion of natural resources to RTP materials has attracted considerable attention. Owing to their inherent luminescent properties, natural materials can be efficiently converted into sustainable RTP materials. However, to date, only a few reviews have focused on this area of endeavour. Motivated by this lack of coverage, in this Review, we address this shortcoming and introduce the types of natural resource available for the preparation of RTP materials. We mainly focus on the inherent advantages of natural resources for RTP materials, strategies for activating and enhancing the RTP properties of the natural resources as well as the potential applications of these RTP materials. In addition, we discuss future challenges and opportunities in this area of research.

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.

Mn2+ and Sb3+ Codoped Cs2ZnCl4 Metal Halide with Excitation-Wavelength-Dependent Emission for Fluorescence Anticounterfeiting

In recent years, there has been a growing demand for luminescence anticounterfeiting materials that possess the properties of environmentally friendly, single-component, and multimode fluorescence. Among the materials explored, the low dimensional metal halides have gained wide attention because of unique characteristics including low toxicity, simple synthesis, good stability, and so on. Here, we synthesized Mn2+ and Sb3+ codoped Cs2ZnCl4 single crystals by a facile hydrothermal method. Under 365 nm excitation, the codoped compound exhibits dual-band emissions at 530 and 730 nm. However, under 316 nm excitation, the compound only shows one emission band from 500 to 850 nm peaking at 730 nm, while under 460 nm excitation, the emission from 500 to 650 nm with an emission peak at 530 nm can be observed. Based on the study of the photoluminescence mechanism, the green and red emissions originate from the Mn2+ located in the tetrahedron and self-trapped exciton emission of [SbCl4]- clusters, respectively. Due to the zero-dimensional structure of the Cs2ZnCl4 host, there is minimal energy transfer between these dopants. Consequently, the luminous ratios of the two emissions can be independently regulated. Except by tuning the dopant concentrations, the Cs2ZnCl4:Mn2+, Sb3+ demonstrates excitation-wavelength-dependent properties, which could emit more than two colors with the change of excitation wavelength. As a result, multimode anticounterfeiting based on Cs2ZnCl4:Mn2+, Sb3+ crystals has been designed, which aligns with the requirements of environmentally friendly, single-component, and multimode fluorescence properties.

Room-Temperature Multiple Phosphorescence from Functionalized Corannulenes: Temperature Sensing and Afterglow Organic Light-Emitting Diode

Corannulene-derived materials have been extensively explored in energy storage and solar cells, however, are rarely documented as emitters in light-emitting sensors and organic light-emitting diodes (OLEDs), due to low exciton utilization. Here, we report a family of multi-donor and acceptor (multi-D-A) motifs, TCzPhCor, TDMACPhCor, and TPXZPhCor, using corannulene as the acceptor and carbazole (Cz), 9,10-dihydro-9,10-dimethylacridine (DMAC), and phenoxazine (PXZ) as the donor, respectively. By decorating corannulene with different donors, multiple phosphorescence is realized. Theoretical and photophysical investigations reveal that TCzPhCor shows room-temperature phosphorescence (RTP) from the lowest-lying T1 ; however, for TDMACPhCor, dual RTP originating from a higher-lying T1 (T1 H ) and a lower-lying T1 (T1 L ) can be observed, while for TPXZPhCor, T1 H -dominated RTP occurs resulting from a stabilized high-energy T1 geometry. Benefiting from the high-temperature sensitivity of TPXZPhCor, high color-resolution temperature sensing is achieved. Besides, due to degenerate S1 and T1 H states of TPXZPhCor, the first corannulene-based solution-processed afterglow OLEDs is investigated. The afterglow OLED with TPXZPhCor shows a maximum external quantum efficiency (EQEmax ) and a luminance (Lmax ) of 3.3 % and 5167 cd m-2 , respectively, which is one of the most efficient afterglow RTP OLEDs reported to date.

A narrow-band deep-blue MRTADF-type organic afterglow emitter

We report a multi-resonant thermally activated delayed fluorescent (MRTADF) afterglow emitter with unprecedented long emission lifetime > 100 ms, full-width at half-maximum < 40 nm, and deep-blue emission color of CIEy at 0.048. Such emitters remain rarely achieved and would show potential applications in multiplexed bioimaging and high-density information encryption.