Organic long persistent luminescence

Ultralong room temperature phosphorescence with multicolor afterglow achieved in a harsh polymeric viscous flow state

Polymer-based ultralong room temperature phosphorescence (RTP) is more attractive than that of organic small molecules. However, the intrinsic contradictions between the motion of the chain and the stability of phosphors' triplet excitons make achieving ultralong lifetime in polymeric systems a big challenge. Herein, we have achieved ultralong RTP emission in a polymeric viscous flow state with free chain motion through a facile B-O click reaction among boric acid, polyvinyl alcohol, and hydroxyl silicone oil. The yielded RTP putties (RTPPs) exhibited long lifetimes under ambient conditions (up to 2.39 s), surpassing those of all reported elastic RTP polymers and most glassy RTP polymers. Furthermore, multi-color afterglow can be achieved in RTPPs using the triplet-to-singlet Förster resonance energy transfer strategy. Impressively, utilizing viscous liquid features combined with RTP performance, RTPPs can be easily applied in complex models, handiwork, and anti-counterfeiting. Therefore, this progress, achieving a long phosphorescence lifetime in a viscous flow state, greatly expands the application scope of polymeric RTP materials and further compels a conceptual advance of polymeric RTP.

Long organic persistent luminescence triggered by photo-induced charge-separation for water-resistant information encryption

The long persistent luminescence (LPL) phenomenon in the water environment presents us with a broad blueprint to struggle for a new generation of optical materials. However, the realization of water-resistant LPL remains a formidable challenge due to severe quenching of triplet excitons inflowing media. Here, an electron donor-acceptor system is designed based on a B2O3 host and carbon dot (CD) guest, which exhibits deep-blue LPL with a lasting time of about 21 s to the naked eye. The average LPL lifetime is over 2 s, and the LPL quantum yield is 10.78%. This host-guest system possesses charge-separated states and charge-transferred states triggered by an optical source, which is the foundation for LPL. Importantly, in water environments (HCl, NaOH, electrolyte NaCl, and H2O), the LPL of as-obtained CDs@B2O3 can still remain due to high environmental stability of B2O3. Based on the excellent LPL with ultra-long lifetime and water-resistant feature, the CDs@B2O3 successfully applies in water-resistant information encryption.

Wide-range tunable circularly polarized luminescence in triphenylamine supramolecular polymers via charge-transfer complexation

Circularly polarized luminescence materials with broad color tunability are highly valuable for applications in 3D display and photonic technologies. Here we show that incorporating intermolecular charge-transfer complexation into chiral supramolecular polymers is an efficient strategy to achieve this objective. Adjusting the charge-transfer strength between triphenylamine donors and naphthalenemonoimide acceptors enables tunable circularly polarized luminescence signals across the visible light spectrum. This includes blue-colored emission for the supramolecular donor polymers, as well as green, yellow, orange and red-colored emission for supramolecular donor-acceptor polymers. The donor-acceptor packing modes are further influenced by the presence or absence of acetylene linkages on the triphenylamine donors, resulting in ground- or excited-state charge transfer with varying luminescent lifetimes. Additionally, white-light circularly polarized luminescence is achieved by encapsulating blue- and orange-emitting species into surfactant-based micelles in a compartmentalized manner. Overall, manipulating charge-transfer complexation in supramolecular polymers provides an effective approach to wide-range tunable circularly polarized luminescence materials.

Recent Advances in Thermally Activated Delayed Fluorescence-Based Organic Afterglow Materials

Thermally activated delayed fluorescence (TADF)-based materials are attracting widespread attention for different applications owing to their ability of harvesting both singlet and triplet excitons without noble metals in their structures. As compared to the conventional fluorescence and room-temperature phosphorescence pathways, TADF originates from the reverse intersystem crossing process from the excited triplet state (T1) to the singlet state (S1). Therefore, TADF emitters enabling activated and long lifetime T1 excitons are potential candidates for generating long-lived afterglow emission, an effect that can still be observed for a while by the naked eye after the removal of the excitation light source. Recently, TADF-based organic afterglow materials featuring high photoluminescence quantum yields and long lifetimes above 100 ms under ambient conditions, have emerged for advanced information security, high-contrast biological imaging, optoelectronic devices, and intelligent sensors, whereas the related systematic review is still lacking. Herein, the recent progress in TADF-based organic afterglow materials is summarized and an overview of the photophysical mechanism, design strategies, and the performances for relevant applications is given. In addition, the challenge and perspective of this area are given at the end of the review.

Abnormal Relaxation Behavior of Excited Electrons in the Flat Band of Kagome Compound Nb3Cl8

Carrier dynamics is crucial in semiconductors, and it determines their conductivity, response time, and overall functionality. In flat bands (FBs), carriers with high effective masses are predicted to host unconventional transport properties. The FBs usually overlap with other trivial energy bands, however, making it difficult to accurately distinguish their carrier dynamics. In this paper, we have investigated the flat-band carrier dynamics of excited electrons in Nb3Cl8, which hosts ideal nonoverlapping FBs near the Fermi level. The optical transition between Hubbard bands is abnormally weakened, exhibiting weak interband absorption and its related slow photoresponse with a time constant of ∼120 s, which are associated with flat-band Mottness-induced large electron effective mass and parity-forbidden transitions. Besides, the localized states created by chlorine vacancies also act as trapping centers for carriers with a time constant of ∼600 s, which are similar to those of the compact localized states of the FB, making the relaxation behavior even more extraordinary. The presence and impacts of atomic defects are confirmed experimentally and theoretically. This work has revealed the abnormal flat-band carrier dynamics of Nb3Cl8, which is essential for understanding the optical, electrical, and thermal transport properties of flat-band materials.

Lighting Up Nonemissive Azobenzene Derivatives by Pressure

Pressure-induced emission (PIE) is a compelling phenomenon that can activate luminescence within nonemissive materials. However, PIE in nonemissive organic materials has never been achieved. Herein, we present the first observation of PIE in an organic system, specifically within nonemissive azobenzene derivatives. The emission of 1,2-bis(4-(anthracen-9-yl)phenyl)diazene was activated at 0.52 GPa, primarily driven by local excitation promotion induced by molecular conformational changes. Complete photoisomerization suppression of the molecule was observed at 1.5 GPa, concurrently accelerating the emission enhancement to 3.53 GPa. Differing from the key role of isomerization inhibition in conventional perception, our findings demonstrate that the excited-state constituent is the decisive factor for emission activation, providing a potentially universal approach for high-efficiency azobenzene emission. Additionally, PIE was replicated in the analogue 1,2-bis(4-(9H-carbazol-9-yl)phenyl)diazene, confirming the general applicability of our findings. This work marks a significant breakthrough within the PIE paradigm and paves the novel high-pressure route for crystalline-state photoisomerization investigation.

Long-Wavelength Afterglow Emission with Nearly 100% Efficiency through Space-Confined Energy Transfer in Organic-Carbon Dot Hybrid

Long-wavelength afterglow emitters are crucial for optoelectronics and information security; however, it remains a challenge in achieving high luminescence efficiency due to the lack of effective modulation in electronic coupling and nonradiative transitions of singlet/triplet excitons. Here, we demonstrate an organic-carbon-dot (CD) hybrid system that operates via a space-confined energy transfer strategy to obtain bright afterglow emission centered at 600 nm with near-unity luminescence efficiency. Photophysical characterization and theoretical calculation confirm efficient luminescence can be assigned to the synergistic effect of intermolecular energy transfer from triplet excitons of CDs to singlets of subluminophores and the intense restraint in nonradiative decay losses of singlet/triplet-state excitons via rationally space-confined rigidification and amination modification. By utilizing precursor engineering, yellow and near-infrared afterglow centered at 575 and 680 nm with luminescence efficiencies of 94.4% and 45.9% has been obtained. Lastly, these highly emissive powders enable superior performance in lighting and information security.

X-ray/γ-ray/Ultrasound-Activated Persistent Luminescence Phosphors for Deep Tissue Bioimaging and Therapy

Persistent luminescence phosphors (PLPs) can remain luminescent after excitation ceases and have been widely explored in bioimaging and therapy since 2007. In bioimaging, PLPs can efficiently avoid tissue autofluorescence and light scattering interference by collecting persistent luminescence signals after the end of excitation. Outstanding signal-to-background ratios, high sensitivity, and resolution have been achieved in bioimaging with PLPs. In therapy, PLPs can continuously produce therapeutic molecules such as reactive oxygen species after removing excitation sources, which realizes sustained therapeutic activity after a single dose of light stimulation. However, most PLPs are activated by ultraviolet or visible light, which makes it difficult to reactivate the PLPs in vivo, particularly in deep tissues. In recent years, excitation sources with deep tissue penetration have been explored to activate PLPs, including X-ray, γ-ray, and ultrasound. Researchers found that various inorganic and organic PLPs can be activated by X-ray, γ-ray, and ultrasound, making these PLPs valuable in the imaging and therapy of deep-seated tumors. These X-ray/γ-ray/ultrasound-activated PLPs have not been systematically introduced in previous reviews. In this review, we summarize the recently developed inorganic and organic PLPs that can be activated by X-ray, γ-ray, and ultrasound to produce persistent luminescence. The biomedical applications of these PLPs in deep-tissue bioimaging and therapy are also discussed. This review can provide instructions for the design of PLPs with deep-tissue-renewable persistent luminescence and further promote the applications of PLPs in phototheranostics, noninvasive biosensing devices, and energy harvesting.

Hierarchical Dual-Mode Efficient Tunable Afterglow via J-Aggregates in Single-Phosphor-Doped Polymer

The development of polymer-based persistent luminescence materials with color-tunable organic afterglow and multiple responses is highly desirable for applications in anti-counterfeiting, flexible displays, and data-storage. However, achieving efficient persistent luminescence from a single-phosphor system with multiple responses remains a challenging task. Herein, by doping 9H-pyrido[3,4-b]indole (PI2) into an amorphous polyacrylamide matrix, a hierarchical dual-mode emission system is developed, which exhibits color-tunable afterglow due to excitation-, temperature-, and humidity-dependence. Notably, the coexistence of the isolated state and J-aggregate state of the guest molecule not only provides an excitation-dependent afterglow color, but also leads to a hierarchical temperature-dependent afterglow color resulting from different thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) behaviors of the isolated and aggregated states. The complex responsiveness based on the hierarchical dual-mode emission can serve for security features through inkjet printing and ink-writing. These findings may provide further insight into the regulated persistent luminescence by isolated and aggregated phosphors in doped polymer systems and expand the scope of stimuli-responsive organic afterglow materials for broader applications.

Toward Quantum Noses: Quantum Chemosensing Based on Molecular Qubits in Metal-Organic Frameworks

ConspectusQuantum sensing leverages quantum properties to enhance the sensitivity and resolution of sensors beyond their classical sensing limits. Quantum sensors, such as diamond defect centers, have been developed to detect various physical properties, including magnetic fields and temperature. However, the spins of defects are buried within dense solids, making it difficult for them to strongly interact with molecular analytes. Therefore, nanoporous materials have been implemented in combination with electron spin center of molecules (molecular qubits) to produce quantum chemosensors that can distinguish various chemical substances. Molecular qubits have a uniform structure, and their properties can be precisely controlled by changing their chemical structure. Metal-organic frameworks (MOFs) are suitable for supporting molecular qubits because of their high porosity, structural regularity, and designability. Molecular qubits can be inserted in the MOF structures or adsorbed as guest molecules. The qubits in the MOF can interact with analytes upon exposure, providing an effective and tunable sensing platform.In this Account, we review the recent progress in qubit-MOF hybrids toward the realization of room-temperature quantum chemosensing. Molecular qubits can be introduced in controlled concentrations at targeted positions by exploiting metal ions, ligands, or guests that compose the MOF. Heavy metal-free organic chromophores have several outstanding features as molecular qubits; namely, they can be initialized by light irradiation and exhibit relatively long coherence times of submicroseconds to microseconds, even at room temperature. One detection method involves monitoring the hyperfine interaction between the electron spins of the molecular qubits and the nuclear spins of the analyte incorporated in the pore. There is also an indirect detection method that relies on the motional change in molecular qubits. If the motion of the molecular qubit changes with the adsorption of the analyte, it can be detected as a change in the spin relaxation process. This mechanism is unique to qubits exposed in nanopores, not observed in conventional qubits embedded in dense solids.By maximizing the guest recognition ability of MOFs and the environmental sensitivity of qubits, quantum chemosensing that recognizes specific chemical species in a highly selective and sensitive manner may be possible. It is difficult to distinguish between diverse chemical species by employing only one combination of MOF and qubit, but by creating arrays of different qubit-MOF hybrids, it would become possible to distinguish between various analytes based on pattern recognition. Inspired by the human olfactory mechanism, we propose the use of multiple qubit-MOF hybrids and pattern recognition to identify specific molecules. This system represents a quantum version of olfaction, and thus we propose the concept of a "quantum nose." Quantum noses may be used to recognize biometabolites and biomarkers and enable new medical diagnostic technologies and olfactory digitization.

An Organophosphorescence Probe with Ultralong Lifetime and Intrinsic Tissue Selectivity for Specific Tumor Imaging and Guided Tumor Surgery

Organic phosphorescent materials are excellent candidates for use in tumor imaging. However, a systematic comparison of the effects of the intensity, lifetime, and wavelength of phosphorescent emissions on bioimaging performance has not yet been undertaken. In addition, there have been few reports on organic phosphorescent materials that specifically distinguish tumors from normal tissues. This study addresses these gaps and reveals that longer lifetimes effectively increase the signal intensity, whereas longer wavelengths enhance the penetration depth. Conversely, a strong emission intensity with a short lifetime does not necessarily yield robust imaging signals. Building upon these findings, an organo-phosphorescent material with a lifetime of 0.94 s was designed for tumor imaging. Remarkably, the phosphorescent signals of various organic nanoparticles are nearly extinguished in blood-rich organs because of the quenching effect of iron ions. Moreover, for the first time, we demonstrated that iron ions universally quench the phosphorescence of organic room-temperature phosphorescent materials, which is an inherent property of such substances. Leveraging this property, both the normal liver and hepatitis tissues exhibit negligible phosphorescent signals, whereas liver tumors display intense phosphorescence. Therefore, phosphorescent materials, unlike chemiluminescent or fluorescent materials, can exploit this unique inherent property to selectively distinguish liver tumor tissues from normal tissues without additional modifications or treatments.

Light/X-ray/ultrasound activated delayed photon emission of organic molecular probes for optical imaging: mechanisms, design strategies, and biomedical applications

Conventional optical imaging, particularly fluorescence imaging, often encounters significant background noise due to tissue autofluorescence under real-time light excitation. To address this issue, a novel optical imaging strategy that captures optical signals after light excitation has been developed. This approach relies on molecular probes designed to store photoenergy and release it gradually as photons, resulting in delayed photon emission that minimizes background noise during signal acquisition. These molecular probes undergo various photophysical processes to facilitate delayed photon emission, including (1) charge separation and recombination, (2) generation, stabilization, and conversion of the triplet excitons, and (3) generation and decomposition of chemical traps. Another challenge in optical imaging is the limited tissue penetration depth of light, which severely restricts the efficiency of energy delivery, leading to a reduced penetration depth for delayed photon emission. In contrast, X-ray and ultrasound serve as deep-tissue energy sources that facilitate the conversion of high-energy photons or mechanical waves into the potential energy of excitons or the chemical energy of intermediates. This review highlights recent advancements in organic molecular probes designed for delayed photon emission using various energy sources. We discuss distinct mechanisms, and molecular design strategies, and offer insights into the future development of organic molecular probes for enhanced delayed photon emission.

Achieving Efficient X-ray Scintillation of Purely Organic Phosphorescent Materials by Chromophore Confinement

Scintillators have attracted significant attention due to their wide-ranging applications in both industrial and medical fields. However, one of the ongoing challenges is the efficient utilization of triplet excitons to achieve high radioluminescence efficiency. Here, a series of purely organic phosphors is presented for X-ray scintillation, employing a combined rigid and flexible host-guest doping strategy. The doped crystals exhibit a remarkable maximum phosphorescence efficiency of 99.4% under UV excitation. Furthermore, upon X-ray irradiation, the radioluminescence intensities of the doped phosphors are markedly higher compared to their single-component crystal counterparts. Through systematic investigations, it is demonstrated the crucial role of confining isolated chromophores in enhancing scintillation efficiency. Additionally, a transparent scintillator screen fabricated with the doped phosphor exhibits excellent X-ray imaging performance, achieving a high spatial resolution of 18.0 lp mm-1. This work not only offers valuable insights into suppressing non-radiative transitions of triplet excitons during scintillation but also opens a new avenue for designing highly efficient purely organic phosphorescent scintillators.

Exciton Dissociation and Recombination Afford Narrowband Organic Afterglow Through Efficient FRET

Organic afterglow with long-persistent luminescence (LPL) after photoexcitation is highly attractive, but the realization of narrowband afterglow with small full-width at half-maximum (FWHM) is a huge challenge since it is intrinsically contradictory to the triplet- and solid-state emission nature of organic afterglow. Here, narrow-band, long-lived, and full-color organic LPL is realized by isolating multi-resonant thermally activated delayed fluorescent (MR-TADF) fluorophores in a glassy steroid-type host through a facile melt-cooling treatment. Such prepared host becomes capable of exciton dissociation and recombination (EDR) upon photoirradiation for both long-lived fluorescence and phosphorescence; and, the efficient Förster resonance energy transfer (FRET) from the host to various MR-TADF emitters leads to high-performance LPL, exhibiting small FWHM of 33 nm, long persistent time over 10 s, and facile color-tuning in a wide range from deep-blue to orange (414-600 nm). Moreover, with the extraordinary narrowband LPL and easy processability of the material, centimeter-scale flexible optical waveguide fibers and integrated FWHM/color/lifetime-resolved multilevel encryption/decryption devices have been designed and fabricated. This novel EDR and singlet/triplet-to-singlet FRET strategy to achieve excellent LPL performances illustrates a promising way for constructing flexible organic afterglow with easy preparation methods, shedding valuable scientific insights into the design of narrow-band emission in organic afterglow.

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.

Programmable Persistent Room Temperature Phosphorescence Switches through Wavelength-Selective Photoactivation

Controlling multicolor persistent room-temperature phosphorescence (RTP) through photoirradiation holds fundamental significance but remains a significant challenge. In this study, we engineered a wavelength-selective photoresponsive system utilizing the Förster resonance energy transfer strategy. This system integrates a photoactivated long-lived luminescent material as the energy donor with a fluorescent photoswitch as the energy acceptor, facilitating programmable persistent luminescence switches. Distinct afterglow color states, such as initial nonemissive, green, yellow, and orange, were achieved through irradiation at 400 nm, 365 nm, and 254 nm, respectively. Based on this capability, we established an interacting network for multistate afterglow color switching among these four emissive states. In addition, we demonstrate the potential of this wavelength-selective photoresponsive system in the photo-controlled rewritable printing of multicolor afterglow images on a single thin film. This work represents a substantial step towards the fabrication of sophisticated wavelength-selective photoresponsive systems, potentially revolutionizing applications in optical data storage, security labeling, and smart displays by enabling precise control over photoresponsive behaviors under various photoirradiation wavelengths.

Long-persistent luminescence by host-guest Förster resonance energy transfer

In this study, Förster resonance energy transfer (FRET) is harnessed to construct a novel stimulus-responsive long-persistent luminescence (LPL) system. Two organic molecules, DPSD and DPOD, were initially found to have no afterglow under ambient conditions, but exhibited prolonged afterglow upon friction with paper, showing a significantly promoted transition of triplet excited states. Substituting paper with α-cellulose (the main composition of paper) reveals a novel host-guest long afterglow system and allows for a deeper investigation of the above paper-promoted LPL phenomenon. The activation of the LPL effect was achieved by matrixing these components through a grinding process, capitalizing on the efficient FRET from the host to the guest owing to the appropriate energy level match, and the robust intersystem crossing (ISC) capability of the guest. This model presents a new matrix strategy to achieve efficient LPL by a facile, low cost and easy-to-handle process. Furthermore, we successfully implemented anti-counterfeiting, encryption and decryption, decoration, and water/heat stimulus-responsive applications of the obtained materials. These advancements bring LPL materials one step closer to practical commercialization.

Study on the Influence of Host-Guest Structure and Polymer Introduction on the Afterglow Properties of Doped Crystals

Due to their low cost, good biocompatibility, and ease of structural modification, organic long-persistent luminescence (LPL) materials have garnered significant attention in organic light-emitting diodes, biological imaging, information encryption, and chemical sensing. Efficient charge separation and carrier migration by the host-guest structure or using polymers and crystal to build rigid environments are effective ways of preparing high-performance materials with long-lasting afterglow. In this study, four types of crystalline materials (MODPA: DDF-O, MODPA: DDF-CHO, MODPA: DDF-Br, and MODPA: DDF-TRC) were prepared by a convenient host-guest doping method at room temperature under ambient conditions, i.e., in the presence of oxygen. The first three types exhibited long-lived charge-separated (CS) states and achieved visible LPL emissions with durations over 7, 4, and 2 s, respectively. More surprisingly, for the DDF-O material prepared with PMMA as the polymer substrate, the afterglow time of DDF-O: PMMA was longer than 10 s. The persistent room-temperature phosphorescence effect caused by different CS state generation efficiencies and rigid environment were the main reason for the difference in LPL duration. The fourth crystalline material was without charge separation and exhibited no LPL because it was not a D-A system. The research results indicate that the CS state generation efficiency and a rigid environment are the key factors affecting the LPL properties. This work provides new understandings in designing organic LPL materials.

Light/Force-Responsive Room Temperature Phosphorescence in a Zinc-Organic Coordination Polymer

A zinc-organic hybrid (1) with multifunctional room temperature phosphorescence (RTP) was synthesized. 1 presents light/force-sensitive RTP properties due to the photochromic behavior from gray to light yellow and the transition from crystalline to amorphous state, respectively. Furthermore, inkless printing and information encryption models were successfully constructed to prove their widespread application prospect.

Ultrahigh-Temperature Long-Persistent Luminescence from B2O3-Confined Polycyclic Aromatic Compounds

Organic molecules and polymers have recently been intensively explored for afterglow materials owing to their low cost and flexible design. However, they normally fail to generate long-persistent luminescence at elevated temperatures, mostly due to the fast deactivation of triplet excited states. Here, we report that polycyclic aromatic compounds (PACs) individually confined in a B2O3 crystalloid emit long-persistent luminescence at high temperatures up to 400 °C. This is facilely accomplished by dispersing a series of aromatic derivatives in an aqueous solution of boric acid, followed by drying, melting, and dehydrating. The resulting highly rigid and thermostable B2O3 crystalloid network provides a matched ultrastrong confinement effect and completely restricts the vibration and rotation of the molecularly distributed PACs even at ultrahigh temperatures and thereby prevents the nonradiative dissipation of triplet excitons and promotes the generation of ultrahigh-temperature long-persistent luminescence. The afterglow colors are responsive to both temperature and time, spanning from ultraviolet to near-infrared regions over a wide temperature range, which is substantially modulated by the subtle balance of phosphorescence and thermally activated delayed fluorescence. These features favor the creation of advanced afterglow materials for visual 3D temperature probing, anticounterfeiting, and data encryption in extreme environments.

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.

Pushing Trap-Controlled Persistent Luminescence Materials toward Multi-Responsive Smart Platforms: Recent Advances, Mechanism, and Frontier Applications

Smart stimuli-responsive persistent luminescence materials, combining the various advantages and frontier applications prospects, have gained booming progress in recent years. The trap-controlled property and energy storage capability to respond to external multi-stimulations through diverse luminescence pathways make them attractive in emerging multi-responsive smart platforms. This review aims at the recent advances in trap-controlled luminescence materials for advanced multi-stimuli-responsive smart platforms. The design principles, luminescence mechanisms, and representative stimulations, i.e., thermo-, photo-, mechano-, and X-rays responsiveness, are comprehensively summarized. Various emerging multi-responsive hybrid systems containing trap-controlled luminescence materials are highlighted. Specifically, temperature dependent trapping and de-trapping performance is discussed, from extreme-low temperature to ultra-high temperature conditions. Emerging applications and future perspectives are briefly presented. It is hoped that this review would provide new insights and guidelines for the rational design and performance manipulation of multi-responsive materials for advanced smart platforms.

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.

Highly stable color-tunable organic long-persistent luminescence from a single-component exciplex copolymer for in vitro antibacterial

Developing exciplex-based organic long-persistent luminescence (OLPL) materials with high stability is very important but remains a formidable challenge in a single-component system. Here, we report a facile strategy to achieve highly stable OLPL in an amorphous exciplex copolymer system via through-space charge transfer (TSCT). The copolymer composed of electron donor and acceptor units can not only exhibit effective TSCT for intra/intermolecular exciplex emission but also construct a rigid environment to isolate oxygen and suppress non-radiative decay, thereby enabling stable exciplex-based OLPL emission with color-tunable feature for more than 100 h under ambient conditions. These single-component OLPL copolymers demonstrate robust antibacterial activity against Escherichia coli under visible light irradiation. These results provide a solid example to exploit highly stable exciplex-based OLPL in polymers, shedding light on how the TSCT mechanism may potentially contribute to OLPL in a single-component molecular system and broadening the scope of OLPL applications.

Synchronously Improved Multiple Afterglow and Phosphorescence Efficiencies in 0D Hybrid Zinc Halides With Ultrahigh Anti-Water Stabilities

Zero-dimensional (0D) hybrid metal halides have been emerged as room-temperature phosphorescence (RTP) materials, but synchronous optimization of multiple phosphorescence performance in one structural platform remains less resolved, and stable RTP activity in aqueous medium is also unrealized due to serious instability toward water and oxygen. Herein, we demonstrated a photophysical tuning strategy in a new 0D hybrid zinc halide family of (BTPP)2ZnX4 (BTPP=benzyltriphenylphosphonium, X=Cl and Br). Infrequently, the delicate combination of organic and inorganic species enables this family to display multiple ultralong green afterglow and efficient self-trapped exciton (STE) associated cyan phosphorescence. Compared with inert luminescence of [BTPP]+ cation, incorporation of anionic [ZnX4]2- effectively enhance the spin-orbit coupling effect, which significantly boosts the photoluminescence quantum yield (PLQY) up to 30.66 % and 54.62 % for afterglow and phosphorescence, respectively. Synchronously, the corresponding luminescence lifetime extend to 143.94 ms and 0.308 μs surpassing the indiscernible phosphorescence of [BTPP]X salt. More importantly, this halide family presents robust RTP emission with nearly unattenuated PLQY in water and harsh condition (acid and basic aqueous solution) over half a year. The highly efficient integrated afterglow and STE phosphorescence as well as ultrahigh aqueous state RTP realize multiple anti-counterfeiting applications in wide chemical environments.

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.

Continuous tuning of persistent luminescence wavelength by intermediate-phase engineering in inorganic crystals

Multicolor tuning of persistent luminescence has been extensively studied by deliberately integrating various luminescent units, known as activators or chromophores, into certain host compounds. However, it remains a formidable challenge to fine-tune the persistent luminescence spectra either in organic materials, such as small molecules, polymers, metal-organic complexes and carbon dots, or in doped inorganic crystals. Herein, we present a strategy to delicately control the persistent luminescence wavelength by engineering sub-bandgap donor-acceptor states in a series of single-phase Ca(Sr)ZnOS crystals. The persistent luminescence emission peak can be quasi-linearly tuned across a broad wavelength range (500-630 nm) as a function of Sr/Ca ratio, achieving a precision down to ~5 nm. Theoretical calculations reveal that the persistent luminescence wavelength fine-tuning stems from constantly lowered donor levels accompanying the modified band structure by Sr alloying. Besides, our experimental results show that these crystals exhibit a high initial luminance of 5.36 cd m-2 at 5 sec after charging and a maximum persistent luminescence duration of 6 h. The superior, color-tunable persistent luminescence enables a rapid, programable patterning technique for high-throughput optical encryption.

Critical Aspects and Challenges in the Design of Small Molecules for Electrochemiluminescence (ECL) Application

Electrochemiluminescence (ECL) has gained renewed interest due to the strong parallel development of luminophores in the field of organic light emitting diodes (OLEDs) with which this technique shares several aspects. In this perspective review we discuss the most relevant advances of the past 15 years in the study of organic and organometallic compounds as ECL emitters, by dividing them in three different classes: i) fluorescent emitters, ii) phosphorescent emitters and iii) Thermally Activated Delayed Fluorescence (TADF) emitters; then, water-soluble organic luminophores will be also discussed. We focus on how their design, their photo- and electrochemical properties and, in particular, the nature of the emitter, affect their efficiency in ECL. Regardless of the type of luminophore or the photoluminescence quantum yield (PLQY), the literature converges on the fact that the most determining aspect is the stability of the oxidized/reduced form of the emitter. Even if phosphorescent emitters can show outstanding efficiency, this often requires the absence of oxygen. In the case of TADFs, there is also a strong dependence of photoluminescence both in terms of PLQY and emission energy on the polarity of the media, so compounds, that appear promising in organic solvents, may be very inefficient in aqueous media.

Enhancing the Room-Temperature Phosphorescence Performance by Salinization of Guests

Although the host-guest doped strategy effectively improves the phosphorescence performance of materials and greatly enriches the variety of materials, most of the guests are organic molecules with weak luminescence ability, which leads to the need for further improvement in the phosphorescence performance of doped materials. Herein, by salinization of organic molecules, the luminescence performance of the guests was effectively improved, thereby significantly enhancing the phosphorescence performance of the doped system. A compound 4-(naphthalen-2-yl)quinoline (QL) containing nitrogen atom was synthesized as initial guest, then QL was salted to obtain six organic salt guests containing anions BF4-, PF6-, CF3SO3-, N(CF3SO2)2-, ClO4-, and C4F9SO3-, respectively. Two doped systems were constructed using benzophenone and poly(methyl methacrylate) as the hosts. The phosphorescence quantum yield and phosphorescence lifetime of doped materials with QL as guest were only 4.1%/5.2% and 131 ms/141 ms, while those of doped materials with salinized molecules as guests were improved to 32-39% and 534-625 ms, respectively. The single-crystal structures and theoretical calculations indicated that anions can not only enhance the intermolecular interaction of guests but also increase the spin-orbit coupling constant. This work provides an effective strategy for improving the phosphorescence performance of doped materials.

Enabling Visible-Light-Charged Near-Infrared Persistent Luminescence in Organics by Intermolecular Charge Transfer

Visible light is a universal and user-friendly excitation source; however, its use to generate persistent luminescence (PersL) in materials remains a huge challenge. Herein, the concept of intermolecular charge transfer (xCT) is applied in typical host-guest molecular systems, which allows for a much lower energy requirement for charge separation, thus enabling efficient charging of near-infrared (NIR) PersL in organics by visible light (425-700 nm). Importantly, NIR PersL in organics occurs via the trapping of electrons from charge-transfer aggregates (CTAs) into constructed trap states with trap depths of 0.63-1.17 eV, followed by the detrapping of these electrons by thermal stimulation, resulting in a unique light-storage effect and long-lasting emission up to 4.6 h at room temperature. The xCT absorption range is modulated by changing the electron-donating ability of a series of acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile-based CTAs, and the organic PersL is tuned from 681 to 722 nm. This study on xCT interaction-induced NIR PersL in organic materials provides a major step forward in understanding the underlying luminescence mechanism of organic semiconductors and these findings are expected to promote their applications in optoelectronics, energy storage, and medical diagnosis.

Highly-Polarized Solar-Blind Ultraviolet Organic Photodetectors

Developing high-performance polarization-sensitive ultraviolet photodetectors is crucial for their application in military remote sensing, detection, bio-inspired navigation, and machine vision. However, the significant absorption in the visible light range severely limits the application of polarization-sensitive ultraviolet photodetectors, such as high-quality anti-interference imaging. Here, based on a wide-bandgap organic semiconductor single crystal (trans-1,2-bis(5-phenyldithieno[2,3-b:3',2'-d]thiophen-2-yl)ethene, BPTTE), high-performance polarization-sensitive solar-blind ultraviolet photodetectors with a dichroic ratio close to 4.26 are demonstrated. The strong anisotropy of 2D grown BPTTE single crystals in molecular vibration and optical absorption is characterized by various techniques. Under voltage modulation, stable and efficient detection of polarized light is demonstrated, attributed to the intrinsic anisotropy of transition dipole moment in the bc crystal plane, rather than other factors. Finally, high-contrast polarimetric imaging and anti-interference imaging are successfully demonstrated based on BPTTE single crystal photodetectors, highlighting the potential of organic semiconductors for polarization-sensitive solar-blind ultraviolet photodetectors.

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.

Stepwise Stiffening Chromophore Strategy Realizes a Series of Ultralong Blue Room-Temperature Phosphorescent Materials

Ultralong room-temperature phosphorescent (URTP) materials have attracted wide attention in anti-counterfeiting, optoelectronic display, and bio-imaging due to their special optical properties. However, room-temperature blue phosphorescent materials are very scarce during applications because of the need to simultaneously populate and stabilize high-energy excited states. In this work, a stepwise stiffening chromophore strategy is proposed to suppress non-radiative jump by continuously reducing the internal spin of the chromophore, and successfully developing a series of blue phosphorescent materials. Phosphorescence lifetimes of more than 3 s are achieved, with the longest lifetime reaching 5.44 s and lasting more than 70 s in the naked eye. As far as is know, this is the best result that has been reported. By adjusting the chromophore conjugation, multicolor phosphorescences from cyan to green have been realized. In addition, these chromophores exhibit the same excellent optical properties in urea and polyvinyl alcohmance (PVA). Finally, these materials are successfully applied to luminescent displays.

Circularly Polarized Room Temperature Phosphorescence through Twisting-Induced Helical Structures from Polyvinyl Alcohol-Based Fibers Containing Hydrogen-Bonded Dyes

Room temperature phosphorescence (RTP) materials have garnered significant attention owing to its distinctive optical characteristics and broad range of potential applications. However, the challenge remains in producing RTP materials with more simplicity, versatility, and practicality on a large scale, particularly in achieving chiral signals within a single system. Herein, we show that a straightforward and effective combination of wet spinning and twisting technique enables continuously fabricating RTP fibers with twisting-induced helical chirality. By leveraging the hydrogen bonding interactions between polyvinyl alcohol (PVA) and quinoline derivatives, along with the rigid microenvironment provided by PVA chains, typically, Q-NH2@PVA fiber demonstrates outstanding phosphorescent characteristics with RTP lifetime of 1.08 s and phosphorescence quantum yield of 24.6 %, and the improved tensile strength being 1.7 times than pure PVA fiber (172±5.82 vs 100±5.65 MPa). Impressively, the transformation from RTP to circularly polarized room temperature phosphorescence (CP-RTP) is readily achieved by imparting left- or right-hand helical structure through simply twisting, enabling large-scale production of chiral Q-NH2@PVA fiber with dissymmetry factor of 10-2. Besides, an array of displays and encryption patterns are crafted by weaving or seaming to exemplify the promising applications of these PVA-based fibers with outstanding adaptivity in cutting-edge anti-counterfeiting technology.

Recent strategies for triplet-state emission regulation toward non-lead organic-inorganic metal halides

Organic-inorganic metal halides (OIMHs) have strengthened the development of triplet-state emission materials due to their excellent luminescence performance. Due to the inherent toxicity of lead (Pb) significantly limiting its further advancement, numerous studies have been conducted to regulate triplet-state emission of non-Pb OIMHs, and several feasible strategies have been proposed. However, most of the non-Pb OIMHs reported have a relatively short lifetime or a low luminescence efficiency, not in favor of their application. In this review, we provide a summary of recent reports on the regulation of triplet-state emissions in non-Pb OIMHs to provide benefits for the design of innovative luminescent materials. Our focus is primarily on exploring the internal and external factors that influence the triplet-state emission. Starting from the luminescence mechanism, the current strategies for regulating triplet-state emissions are summarized. Moreover, by manipulating these strategies, it becomes feasible to achieve triplet-state emissions that span a range of colors from blue to red, and even extend into the near-infrared spectrum with high luminescence efficiency, while also increasing their lifetimes. This review not only provides fresh insights into the advancement of triplet-state emissions in OIMHs but also integrates experimental and theoretical perspectives to illuminate the trajectory of future research endeavors.

Ligand Meta-Anchoring Strategy in Metal-Organic Frameworks for Remarkable Promotion of Quantum Yields

Aggregation is a conventional method to enhance the quantum yields (QYs) of pure organic luminophores due to the restriction of intramolecular motions (RIM). However, how to realize RIM in metal-organic frameworks (MOFs) is still unclear and challenging. In this work, the ligand meta-anchoring strategy is first proposed and proved to be an effective and systematic approach to restrict the intramolecular motions of MOFs for the QY improvement. By simply shifting the substituent position in the ligand from para to meta, the QY of the resulting MOF is significantly enhanced by eleven-fold. The value is even higher than that of ligand aggregates, demonstrating the strong RIM effect of this ligand meta-anchoring strategy. The introduction of co-ligand induces the appearance of visible yellow room temperature phosphorescence with a lifetime of 222 ms due to the QY enhancement and the charge transfer between the donor and accepter units. The present work thus broadens the understanding of the RIM mechanism from a new perspective, develops a novel method to realize RIM and expands the applicable objects from pure organic materials to organic-inorganic hybrid materials.

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.

Stepwise Charge/Energy Transfer in MR-TADF Molecule-Doped Exciplex for Ultralong Persistent Luminescence Activated with Visible Light

Organic long-persistent luminescence (OLPL), which relies on energy storage for delayed light emission by the charge separation state, has attracted intense attention in various optical applications. However, charge separation (CS) is efficient only under ultraviolet excitation in most OLPL systems because it requires a driving force from the large energy difference between the local excited (LE) and charge transfer (CT) states. In this study, a multiresonance thermally activated delayed fluorescence (MR-TADF) molecule is incorporated into an exciplex system to achieve efficient OLPL in a composite material activated by visible light via a stepwise charge/energy transfer process. The enhanced absorption of the composite material facilitated a tenfold increase in the duration of the OLPL, which can last for several hours under visible light excitation. The excited state of the MR-TADF molecule tends to charge transfer to the acceptor, followed by energy transfer to the exciplex, which benefits from the small difference between the LE and CT states owing to the inherent CS characteristics of the opposing resonance effect. Afterglow displays of these composite materials are fabricated to demonstrate their considerable potential in encryption patterns and emergency lights, which take advantage of their excellent processability, visible light activation, and tunable luminescence properties.

Edible Long-Afterglow Photoluminescent Materials for Bioimaging

Confining luminophores into modified hydrophilic matrices or polymers is a straightforward and widely used approach for afterglow bioimaging. However, the afterglow quantum yield and lifetime of the related material remain unsatisfactory, severely limiting the using effect especially for deep-tissue time-resolved imaging. This fact largely stems from the dilemma between material biocompatibility and the quenching effect of water environment. Herein an in situ metathesis promoted doping strategy is presented, namely, mixing ≈10-3 weight ratio of organic-emitter multicarboxylates with inorganic salt reactants, followed by metathesis reactions to prepare a series of hydrophilic but water-insoluble organic-inorganic doping afterglow materials. This strategy leads to the formation of edible long-afterglow photoluminescent materials with superior biocompatibility and excellent bioimaging effect. The phosphorescence quantum yield of the materials can reach dozens of percent (the highest case: 66.24%), together with the photoluminescent lifetime lasting for coupes of seconds. Specifically, a long-afterglow barium meal formed by coronene salt emitter and BaSO4 matrix is applied into animal experiments by gavage, and bright stomach afterglow imaging is observed by instruments or mobile phone after ceasing the photoexcitation with deep tissue penetration. This strategy allows a flexible dosage of the materials during bioimaging, facilitating the development of real-time probing and theranostic technology.

Recent advances in circularly polarized luminescence of planar chiral organic compounds

Circularly polarized luminescence (CPL), as an important chiroptical phenomenon, can not only directly characterize excited-state structural information about chiroptical materials but also has great application prospects in 3D optical displays, information storage, biological probes, CPL lasers and so forth. Recently, chiral organic small molecules with CPL have attracted a lot of research interest because of their excellent luminescence efficiency, clear molecular structures, unique flexibility and easy functionalization. Planar chiral organic compounds make up an important class of chiral organic small molecular materials and often have rigid macrocyclic skeletons, which have important research value in the field of chiral supramolecular chemistry (e.g., chiral self-assembly and chiral host-guest chemistry). Therefore, research into planar chiral organic compounds has become a hotspot for CPL. It is time to summarize the recent developments in CPL-active compounds based on planar chirality. In this feature article, we summarize various types of CPL-active compounds based on planar chirality. Meanwhile, we overview recent research in the field of planar chiral CPL-active compounds in terms of optoelectronic devices, asymmetric catalysis, and chiroptical sensing. Finally, we discuss their future research prospects in the field of CPL-active materials. We hope that this review will be helpful to research work related to planar chiral luminescent materials and promote the development of chiral macrocyclic chemistry.

Ratiometric Afterglow Luminescent Imaging of Matrix Metalloproteinase-2 Activity via an Energy Diversion Process

Ratiometric afterglow luminescent (AGL) probes are attractive for in vivo imaging due to their high sensitivity and signal self-calibration function. However, there are currently few ratiometric AGL probes available for imaging enzymatic activity in living organisms. Here, we present an energy diversion (ED) strategy that enables the design of an enzyme-activated ratiometric AGL probe (RAG-RGD) for in vivo afterglow imaging. The ED process provides RAG-RGD with a radiative transition for an 'always on' 520-nm AGL signal (AGL520) and a cascade three-step energy transfer (ET) process for an 'off-on' 710-nm AGL signal (AGL710) in response to a specific enzyme. Using matrix metalloproteinase-2 (MMP-2) as an example, RAG-RGD shows a significant ~11-fold increase in AGL710/AGL520 toward MMP-2. This can sensitively detect U87MG brain tumors through ratiometric afterglow imaging of MMP-2 activity, with a high signal-to-background ratio and deep imaging depth. Furthermore, by utilizing the self-calibration effect of ratiometric imaging, RAG-RGD demonstrated a strong negative correlation between the AGL710/AGL520 value and the size of orthotopic U87MG tumor, enabling accurate monitoring of orthotopic glioma growth in vivo. This ED process may be applied for the design of other enzyme-activated ratiometric afterglow probes for sensitive afterglow imaging.

Full-color, time-valve controllable and Janus-type long-persistent luminescence from all-inorganic halide perovskites

Long persistent luminescence (LPL) has gained considerable attention for the applications in decoration, emergency signage, information encryption and biomedicine. However, recently developed LPL materials - encompassing inorganics, organics and inorganic-organic hybrids - often display monochromatic afterglow with limited functionality. Furthermore, triplet exciton-based phosphors are prone to thermal quenching, significantly restricting their high emission efficiency. Here, we show a straightforward wet-chemistry approach for fabricating multimode LPL materials by introducing both anion (Br-) and cation (Sn2+) doping into hexagonal CsCdCl3 all-inorganic perovskites. This process involves establishing new trapping centers from [CdCl6-nBrn]4- and/or [Sn2-nCdnCl9]5- linker units, disrupting the local symmetry in the host framework. These halide perovskites demonstrate afterglow duration time ( > 2,000 s), nearly full-color coverage, high photoluminescence quantum yield ( ~ 84.47%), and the anti-thermal quenching temperature up to 377 K. Particularly, CsCdCl3:x%Br display temperature-dependent LPL and time-valve controllable time-dependent luminescence, while CsCdCl3:x%Sn exhibit forward and reverse excitation-dependent Janus-type luminescence. Combining both experimental and computational studies, this finding not only introduces a local-symmetry breaking strategy for simultaneously enhancing afterglow lifetime and efficiency, but also provides new insights into the multimode LPL materials with dynamic tunability for applications in luminescence, photonics, high-security anti-counterfeiting and information storage.

Water-Ice Microstructures and Hydration States of Acridinium Iodide Studied by Phosphorescence Spectroscopy

Ice has been suggested to have played a significant role in the origin of life partly owing to its ability to concentrate organic molecules and promote reaction efficiency. However, the techniques for studying organic molecules in ice are absorption-based, which limits the sensitivity of measurements. Here we introduce an emission-based method to study organic molecules in water ice: the phosphorescence displays high sensitivity depending on the hydration state of an organic salt probe, acridinium iodide (ADI). The designed ADI aqueous system exhibits phosphorescence that can be severely perturbed when the temperature is higher than 110 K at a concentration of the order of 10-5 M, indicating changes in hydration for ADI. Using the ADI phosphorescent probe, it is found that the microstructures of water ice, i.e., crystalline vs. glassy, can be strongly dictated by a trace amount (as low as 10-5 M) of water-soluble organic molecules. Consistent with cryoSEM images and temperature-dependent Raman spectral data, the ADI is dehydrated in more crystalline ice and hydrated in more glassy ice. The current investigation serves as a starting point for using more sensitive spectroscopic techniques for studying water-organics interactions at a much lower concentration and wider temperature range.

Hour-Level Persistent Multicolor Phosphorescence Enabled by Carbon Dot-Based Nanocomposites Through a Multi-Confinement-Based Approach

Hour-level persistent room temperature phosphorescence (RTP) phenomena based on multi-confinement carbon dots (CDs) are reported. The CDs-based system reported here (named Si-CDs@B2O3) can be efficiently synthesized by a simple pyrolysis method compared to the established persistent RTP systems. The binding modes of CDs, silica (SiO2), and boron oxide (B2O3) are deduced from a series of characterizations including XRD, FT-IR, and TEM characterization. Further studies show that the formation of covalent bonds between B2O3, SiO2, and CDs play a key role in activating the persistent RTP and preventing its quenching. This is a rare example of a persistent RTP system that exhibits hourly persistent RTP under environmental conditions. Finally, the applications of Si-CDs@B2O3 are demonstrated for anti-counterfeiting, long-duration phosphorescence imaging, and fingerprinting. This synthetic strategy is expected to provide strong technical support for the preparation of persistent RTP CDs and pave the way for the synthesis of persistent RTP CDs in the future.

Efficient intersystem crossing and tunable ultralong organic room-temperature phosphorescence via doping polyvinylpyrrolidone with polyaromatic hydrocarbons

Polymer-based pure organic room-temperature phosphorescent materials have tremendous advantages in applications owing to their low cost, vast resources, and easy processability. However, designing polymer-based room-temperature phosphorescent materials with large Stokes shifts as key requirements in biocompatibility and environmental-friendly performance is still challenging. By generating charge transfer states as the gangplank from singlet excited states to triplet states in doped organic molecules, we find a host molecule (pyrrolidone) that affords charge transfer with doped guest molecules, and excellent polymer-based organic room-temperature phosphorescent materials can be easily fabricated when polymerizing the host molecule. By adding polyaromatic hydrocarbon molecules as electron-donor in polyvinylpyrrolidone, efficient intersystem crossing and tunable phosphorescent from green to near-infrared can be achieved, with maximum phosphorescence wavelength and lifetime up to 757 nm and 3850 ms, respectively. These doped polyvinylpyrrolidone materials have good photoactivation properties, recyclability, advanced data encryption, and anti-counterfeiting. This reported design strategy paves the way for the design of polyvinylpyrrolidone-based room-temperature phosphorescent materials.

Dual-Stimuli-Responsive Modulation Organic Afterglow Based on N─H Proton Migration Mechanism

Organic afterglow materials have significant applications in information security and flexible electronic devices with unique optical properties. It is vital but challenging to develop organic afterglow materials possessing controlled output with multi-stimuli-responsive capacity. Herein, dimethyl terephthalate (DTT) is introduced as a strong proton acceptor. The migration direction of N─H protons on two compounds Hs can be regulated by altering the excitation wavelength (Ex) or amine stimulation, thereby achieving dual-stimuli-responsive afterglow emission. When the Ex is below 300 nm, protons migrate to S1-2 DTT, where strong interactions induce phosphorescent emission of Hs, resulting in afterglow behavior. Conversely, when the Ex is above 300 nm, protons interact with the S0 DTT weakly and the afterglow disappears. In view of amine-based compounds with higher proton accepting capabilities, it can snatch proton from S1-2 DTT and redirect the proton flow toward amine, effectively suppressing the afterglow but obtaining a new redshifted fluorescence emission with Δλ over 200 nm due to the high polarity of amine. Moreover, it is successfully demonstrated that the applications of dual-stimuli-responsive organic afterglow materials in information encryption based on the systematic excitation-wavelength-dependent (Ex-De) behavior and amine selectivity detection.

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.

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.