Room-temperature phosphorescent materials derived from natural resources

High-Efficiency Organic Mechanophosphorescence from A Phenoselenazine Phosphor for Multiple Applications

Mechanoluminescence (ML) materials with phosphorescent characteristics hold significant potential for applications in pressure sensing and material damage inspection. However, currently reported mechanophosphorescence (MP) materials suffer from low luminescence efficiency and insufficient brightness. Herein, we report a piezoelectric material, p-BPM, with an exceptionally high phosphorescence efficiency of 61.4%, which is the highest value among reported pure organic MP materials. Benefiting from its excellent ML performance, we have developed a display device using crystals that allow for clear observation of the written letter paths (letters M and L), which have promising prospects in pressure-sensitive display. Amazingly, we also observed that the crystals produce bright ultrasound induced luminescence in the medium at a low ultrasonic operating frequency (40 kHz). The composite films of crystal and poly(butylene adipate-co-terephthalate) (PBAT) polymer exhibit significant tensile strength while maintaining effective MP. The composite films show good piezoelectric energy harvesting properties with a maximum open-circuit voltage of 0.47 V and short-circuit current of 0.046 μA, demonstrating promise for precise sonic location. This work will facilitate the development of highly efficient organic MP materials, expanding the potential in stress-monitoring, imaging, and marine robotics.

Recent advances in dopant-matrix afterglow systems: high-performance organic afterglow materials and the critical role of organic matrices in materials fabrication

Organic afterglow materials have garnered significant attention due to their long-lived excited states, demonstrating promising applications across diverse fields. Over the past few decades, these materials have experienced rapid development, particularly dopant-matrix systems. This review focuses on the progress made in dopant-matrix organic afterglow materials over the past three years, emphasizing two key aspects: high-performance organic afterglow materials and the critical role of organic matrices in materials fabrication. In the first section, we summarize strategies for enhancing afterglow performance through molecular design, focusing on representative luminescent systems such as benzophenone derivatives, polycyclic aromatic hydrocarbons, and difluoroboron β-diketonate compounds. The second section explores the pivotal functions of organic matrices, including protecting triplet excited states, facilitating intersystem crossing, sensitizing triplet states, and promoting charge separation, which collectively contribute to novel functionalities of afterglow materials. Beyond the molecular design of luminophores, the selection of organic matrices is equally crucial for achieving high-performance afterglow materials and expanding their functionality. This review provides a comprehensive compilation of chemical structures for various organic matrices, serving as a valuable reference for researchers. Given the intricate photophysical processes in organic afterglow systems, we also present experimental methods that support or refute specific mechanisms, providing critical insights for future studies. Overall, dopant-matrix organic afterglow materials represent a highly promising class of luminescent materials. We anticipate their large-scale adoption and high-value applications in real-world scenarios in the near future.

Triggering anti-Kasha organic room temperature phosphorescence of clusteroluminescent materials

Clusterization-triggered emission (CTE) from organic materials without π-conjugated structures for room temperature phosphorescence (RTP) is fascinating with extraordinary photophysical properties and diversified applications, but rather challenging in material design owing to the limited mechanism understanding. Here, we demonstrate a facile strategy to construct CTE polymers with stimuli-responsive emission, anti-Kasha RTP and organic ultralong RTP (OURTP) by introducing ions into the hydrolyzed nonconjugated maleic anhydride and acrylamide copolymers. Thanks to the synergistic effects of hydrogen and ionic bonding with the ion-triggered electrostatic and coordinate interactions to suppress non-radiative decays and promote intersystem crossing, the amorphous copolymers show efficient photoluminescence with quantum efficiencies up to 13.5%, anti-Kasha RTP blue-shift of 29 nm, and OURTP lifetime up to 420 ms. Moreover, the temperature-dependent and water-sensitive anti-Kasha RTP and OURTP are also observed due to the formation of highly emissive CTE structure regulated by ionization. With the excellent processability and flexibility of the copolymer, lifetime-, temperature- and color-encrypted information anti-counterfeiting is designed and explored. The anti-Kasha RTP in CTE materials realized for the first time demonstrates impressive potential for multi-level encryption/anti-counterfeiting applications and more importantly, providing fundamental mechanism understanding for the rational modulation and design of CTE materials with extraordinary photophysical properties.

Bio-Based Thermoplastic Room Temperature Phosphorescent Materials with Closed-Loop Recyclability

Producing thermoplastic room temperature phosphorescent (RTP) materials with closed-loop recyclability from natural sources is an attractive approach but hard to achieve. Here, the study develops such RTP materials, Poly(TA)/Cell, by thermally polymerizing thioctic acid in the presence of cellulose. Specifically, polymerized thioctic acid poly(TA) forms strong hydrogen bonding interactions with CNF, promoting formation of molecular clusters between the oxygen-containing units. The as-formed clusters generate humidity- and excitation-sensitive green RTP emission. Red afterglow emission is also obtained by integrating Poly(TA)/Cell together with Rhodamine B (RhB) via an energy transfer process. Attributed to the thermoplastic properties, the as-obtained Poly(TA)/Cell can be thermally molded into flexible shapes with uncompromised RTP performance. Moreover, owing to the alkali-cleavable properties of the disulfide bond in Poly(TA)/Cell, thioctic acid and cellulose can be successfully recycled from Poly(TA)/Cell with a yield of 92.3% and 81.5%, respectively. As a demonstrator for potential utility, Poly(TA)/Cell is used to fabricate materials for information encryption.

Polyimides with Excited-State Intramolecular Proton Transfer and Room-Temperature Phosphorescence Properties by End-capping

Organic polymers possessing excited-state intramolecular proton transfer (ESIPT) significantly impact their electronic and optical properties through stimulus response, leading to unique photoluminescence behaviors such as large Stokes shifts, dual emission, and environmental sensitivity. In this work, polyimides (PIs) exhibiting both ESIPT and room-temperature phosphorescence (RTP) properties were designed and synthesized by end-capping with 5-amino-2-(2-hydroxyphenyl) benzothiazole (HBTA) and 5-amino-2-(2-hydroxyphenyl) benzimidazole (HBIA), respectively. HBTA-PI and HBIA-PI exhibit bright yellow-green and sky-blue fluorescence at 510 nm and 470 nm, with a relatively high photoluminescence quantum yields of about 27.2% and 25.1%, respectively. Importantly, HBTA-PI and HBIA-PI show excellent RTP emissions at 520 nm and 485 nm, with decay lifetimes of 76.5 ms and 53.2 ms. The theoretical results indicate that the effective and large spin-orbit coupling (SOC) constants from their keto forms in the excited state can enhance the intersystem crossing (ISC) process to produce triplet excitons. The rigid polyimide networks further inhibit the nonradiative decay of triplet excitons and enhance phosphorescence emission. Additionally, the excellent ESIPT properties of HBTA-PI and HBIA-PI enable the detection of HCl vapor, which induces multiple fluorescent and phosphorescent color changes. This work provides good examples of polyimides for organic polymers with ESIPT properties and multi-stimulus response emissions.

Time-Division Multiplexing Physical Unclonable Functions Based on Multicolor Phosphorescent Carbon Dots

Phosphorescent materials offer a promising approach to information encryption due to their long luminescence lifetimes and high signal-to-noise ratios. However, fixed phosphorescent patterns are vulnerable to imitation over time, limiting their effectiveness in advanced encryption. Here, a time-division multiplexing physical unclonable function (TDM-PUF) label utilizing multicolor phosphorescent carbon dots (CDs) is proposed that leverages variations in wavelength and lifetime to construct time-resolved, multidimensional cryptographic protocols. Efficient multi-color phosphorescence in CDs is achieved by enhancing intersystem crossing, suppressing non-radiative transitions through confinement effects, and regulating emission spectra via energy transfer. The random spatial distribution and unpredictable emissions of phosphorescent CDs significantly enhance the complexity of the PUF system, thereby fortifying its defenses against mimicry attacks. Furthermore, this PUF system exhibits multiple optical responses over time, allowing correct information recognition only at specified time nodes, achieving time-resolved anti-counterfeiting. Finally, by segmenting PUF labels based on emission color and time channels, non-overlapping multicolor and multi-time segments are achieved, enabling highly secure time-division multiplexed encryption. The study provides a competitive anti-counterfeiting label and inspires the development of novel anti-counterfeiting strategies.

Highly Bright Pure Room Temperature Phosphorescence for Circularly Polarized Organic Hyperafterglow

Pure room-temperature phosphorescence (pRTP) promises great advantages in both exciton utilization and lifetime manipulation over existing organic luminophores for a variety of emerging applications, but the low brightness, low efficiency, and low color purity constrain the afterglow luminescence significantly. Here, a promising approach to design highly bright, efficient, and narrowband pRTP with long-lifetime for organic hyperafterglow is proposed by isolating a conjugated energy donor with circularly polarized (CP) luminescence and energy acceptor with multi-resonance effect into a rigid host. It is shown that the aggregation of chiral P-containing binaphthyl promotes the generation of CP-pRTP and afterglow with high brightness up to ≈50 cd m-2, while the simultaneous energy transfer and chirality transfer afford multi-color organic hyperafterglow with photoluminescence efficiency of ≈90%, full-width at half maxima of 31-39 nm, lifetime of 120-770 ms, and luminescent dissymmetry of ≈10-3. Also, excellent stability capable of resisting quenching effects of oxygen, organic solvents, and aqueous solutions of strong acids and bases are observed. With these advantages, applications of chirality information encryption, afterglow grayscale imaging, and 3D high-resolution afterglow models are realized, promoting significantly the fundamental understandings on the modulation of organic afterglow brightness and construction of high-performance pRTP materials with advanced photophysical properties and applications.

Lignin-Assisted Photoreactions: Unveiling New Frontiers in Light-Induced Chemistry

Lignin, the most abundant aromatic biopolymer, is emerging as a mainstay of the upcoming revolution in sustainable materials processing. Despite the inherent challenges associated with the heterogeneous structure of lignin, significant progress has recently been made in developing innovative strategies to valorize this fascinating aromatic biopolymer to deliver industry-demanded products via photoreactions. The purpose of this concept article is to unravel insights into these creative approaches in lignin-assisted photoreactions, focusing on photopolymerization to construct functional polymeric materials and photoreduction to provide valuable chemicals, wherein lignin serves as a macromolecular photoinitiator and a reductive photocatalyst, respectively. The existing strategies for improving the photochemical quantum yield of lignin in photopolymerization and harnessing lignin macromolecules as photoresponsive polymers to facilitate electron transfer in photocatalytic reactions are also summarized. In the future, such photochemical lignin valorization concepts could potentially provide new possibilities for achieving a profitable value chain for integrated biorefinery processes.

Red Room Temperature Phosphorescence in Non-Aromatic Carbonized Polymer Dots

Achieving red organic room temperature phosphorescence (RTP) remains a significant challenge, especially in a non-aromatic system. Herein, red RTP with emission at 605 and 645 nm is achieved through inducing and confining carboxyl dimer association (CDA), a unique hydrogen-bonded coupling red phosphorescence unit, in non-aromatic carbonized polymer dots (CPDs). The CPDs are synthesized via microwave method by using polyacrylic acid (PAA), succinic acid (SA), and traces of phosphoric acid as precursors. Small molecule SA can flexibly enter the polymer cluster of PAA and pair with the isolated carboxyl groups to form CDA. The intrinsic local carbonized structure formed in CPDs can effectively stabilize CDA to achieve red RTP. The red afterglow can last for 1 s to naked eye, and the corresponding lifetimes for emission at 605 and 645 nm were 61 and 45 ms, respectively, after 365 nm excitation off. This work not only reported the non-aromatic red organic RTP materials for the first time, but also explored CPDs as an effective platform for achieving such non-aromatic long-wavelength RTP.

Regulating Room-Temperature Phosphorescence of Organic Luminophores Through Stepwise Stabilization by Coordination and In-Situ Precipitation Reaction

Developing efficiency and long-lived room-temperature phosphorescence (RTP) materials through straightforward methods is highly desired. In this work, a stepwise stabilization strategy was proposed by the coordination and in-situ precipitation reactions among organic precursors, inorganic cation and anions, producing room-temperature phosphorescence materials with high emission efficiency (phosphorescence quantum yield of 45 %). Structural and photophysical characterizations revealed the coordination reaction reduced the energy gaps between singlet and triplet states and stabilized the excited states of the guest molecules. The in-situ precipitation reaction produced a solid matrix, which provided isolated environments for protecting the excitons from quenching. The applications of RTP materials in information encryption were demonstrated. The presented results provided a new clue for producing RTP materials, and extended their applications in wide fields.

Room-temperature phosphorescent transparent wood

Transparent wood with high transmittance and versatility has attracted great attention as an energy-saving building material. Many studies have focused on luminescent transparent wood, while the research on organic afterglow transparent wood is an interesting combination. Here, we use luminescent difluoroboron β-diketonate (BF2bdk) compounds, methyl methacrylate (MMA), delignified wood, and initiators to prepare room-temperature phosphorescent transparent wood by thermal initiation polymerization. The resultant PMMA has been found to interact with BF2bdk via dipole-dipole interactions and consequently enhance the intersystem crossing of BF2bdk excited states. The transparent wood matrix can provide a rigid environment for BF2bdk triplets and serve as oxygen barrier to suppress non-radiative decay and oxygen quenching. The prepared afterglow material has the characteristics of diverse composition, long afterglow emission lifetimes, and high photoluminescence quantum yield. This afterglow transparent wood also demonstrates potential application value in areas such as high mechanical strength, good hydrophobicity, and high cost-effectiveness.

Efficient and Ultralong Room Temperature Phosphorescence from Isolated Molecules under Visible Light Excitation

Visible-light-excited ultralong organic phosphorescence (UOP) materials hold significant potential for various practical applications. Red-shifted excitation wavelength can be achieved by introducing large π-conjugation structures into organic molecules, thereby increasing intermolecular interactions and coupling. However, generating visible-light-excited UOP from isolated molecules poses a great challenge. Herein, we pioneered a strategy to achieve visible-light-excited UOP by doping organic molecules into a rigid polymer. The resulting materials exhibit an ultralong lifetime of up to 2.226 s and a high phosphorescence efficiency of 42.6% under ambient conditions. Impressively, poly(vinyl alcohol) films doped with 1 wt % different guests demonstrate blue and green visible-light-excited UOP. Moreover, they show long-persistent luminescence, lasting over 30 min at room temperature. Through control experiments and theoretical calculations, we discovered that hydrogen bonding between the guests and PVA confines the molecular motion, promoting efficient UOP. The intramolecular charge transfer within the single molecular state contributes to the low energy level, thus leading to the red-shifted absorption. This work will open a new way for developing visible-light-excited UOP based on amorphous polymers, offering highly efficient UOP and long-persistent luminescence under ambient conditions.

High-Temperature Solid-State Post-Synthetic Modification of Highly Luminescent Cu(I) Metallacycles toward New Luminescent Thermic Tracers

A new luminescent Cu(I) tetrametallic metallacycle B is reported that features very rare semi-bridging aqua ligands. When heated markedly above room temperature, this compound undergoes a post-synthetic transformation in the solid-state, affording the new luminescent metallacycle C. Thermogravimetric analysis, IR spectroscopy and single-crystal X-ray diffraction reveal that this alteration preserves the gross tetrametallic macrocycle structure, but is caused by the release of the coordinated water molecules with the concomitant formation of cuprophilic interactions. This transition induces a shift from eye-perceived green (B) to blue (C) room-temperature luminescence for these molecular solids. Photophysical measurements and time-dependent density-functional theory calculations have been conducted to identify the origins of the emission properties lying in these structurally related assemblies, and suggest that thermally activated delayed fluorescence dominates the radiative relaxation pathways. This study highlights the innovative feature of Cu(I) derivatives, offering access to stimuli-sensitive materials that can witness, a posteriori, the exceeding of critical temperatures in their environment.

Stable, Full-Color, Long-Lasting Aqueous Room-Temperature Phosphorescent Materials

Ultralong room-temperature phosphorescent (URTP) materials have garnered significant attention in anti-counterfeiting, optoelectronic displays, and bio-imaging due to their unique optical properties. However, most URTP materials exhibit weak emission or are quenched in aqueous solutions. This study proposes a simple and effective strategy for preparing full-color aqueous URTP materials using a one-step microwave method. Guest molecules are embedded in a rigid cyanuric acid (CA) matrix formed from urea. By enhancing the conjugation of the guest molecules, a series of full-color URTP materials is successfully produced. These materials exhibit excellent phosphorescent properties, with a maximum phosphorescent lifetime of 7.96 s. Protected by the CA matrix, they retain phosphorescence even in aqueous environments, displaying an afterglow visible to the naked eye for over 30 s in water. Additionally, under low water content conditions, the materials exhibit exceptional water-enhanced properties, achieving a phosphorescence quantum yield (PhQY) of 40.4%. Importantly, these aqueous URTP materials can be prepared in just 5 min, showcasing great potential in information encryption and afterglow displays.

Room temperature phosphorescent wood hydrogel

Room temperature phosphorescent (RTP) hydrogels exhibit great potential but show poor mechanical performance (Tensile strengthen <1 MPa) and non-tunable RTP performance, hindering their practical applications. Here, we develop wood hydrogel (W-hydrogel) by the in situ polymerization of acrylamide in the presence of delignified wood. As a result of the molecular interactions between the components of delignified wood and polyacrylamide, the W-hydrogel exhibit a tensile strengthen of 38.4 MPa and green RTP emission with a lifetime of 32.5 ms. Moreover, the tensile strength and RTP lifetime are increased to 153.8 MPa and 69.7 ms, upon treating W-hydrogel with ethanol. Significantly, the mechanical and RTP performance of W-hydrogel is switched by alternating "ethanol and water" treatments. Additionally, W-hydrogel is used as energy donor in order to produce red afterglow emission using RhB via an energy transfer process. Taking advantage of these properties, W-hydrogel is processed into multiple hydrogel-based luminescent materials.

Bio-sourced flexible supramolecular glasses for dynamic and full-color phosphorescence

Glass, a diverse family of amorphous materials, has significantly advanced human society across various fields. The demand for flexible ultrathin glass, driven by modern optical displays and portable optoelectronics, presents challenges in energy consumption, fabrication complexity, and recycling. Here, we demonstrate flexibility and full-color luminescence in large-scale ultrathin glasses derived from readily available natural resources, specifically egg albumen (EA) and gelatin (GEL), via an evaporation-driven self-assembly process. The dynamic crosslinked networks formed through hydrogen bonding between EA and GEL impart both high hardness and flexibility to the glasses, with hardness and flexural strength values comparable to state-of-the-art inorganic and organic glasses. Additionally, the EA-GEL-based glasses exhibit excitation-dependent and time-gated chiral ultralong phosphorescence with color from blue and red, and a lifetime of up to 180.4 ms. With their easy processability and full-color emission, these biogenic glasses can be fabricated into anti-counterfeiting patterns and optical information codes.

Constructing Organic Phosphorescent Scintillators with Enhanced Triplet Exciton Utilization Through Multi-Mode Radioluminescence for Efficient X-Ray Imaging

The development of organic phosphorescent scintillators with high exciton utilization efficiency has attracted significant attention but remains a difficult challenge because of the inherent spin-forbidden feature of X-ray-induced triplet excitons. Herein, a design strategy is proposed to develop organic phosphorescent scintillators through thermally activated exciton release to convert stabilized spin-forbidden triplet excitons to spin-allowed singlet excitons, which enables singlet exciton-dominated multi-mode emission simultaneously from the lowest singlet, triplet, and stabilized triplet states. The resultant scintillators demonstrate a maximum photoluminescence efficiency of 65.8% and a minimum X-ray radiation detection limit of 110 nGy s-1; this allows efficient radiography imaging with a spatial resolution of ≈10.0 lp mm-1. This study advances the fundamental understanding of exciton dynamics under X-ray excitation, significantly broadening the practical use of phosphorescent materials for safety-critical industries and medical diagnostics.

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.

Twisted Structure Induced Solid-State Fluorescence and Room-Temperature Phosphorescence from Furan-Based Carbon Dots

Boron doping can effectively induce solid-state fluorescence (SSF) in carbon dots (CDs); however, research on the intrinsic mechanism underlying this phenomenon is lacking. Herein, a design strategy for boron-doped furan-based CDs is proposed, CDs with aggregation-induced emission (AIE) properties are synthesized, and the mechanism by which boron atom dopants induces SSF and room-temperature phosphorescence (RTP) is elucidated. The morphology and structural characterization of the CDs indicate that boron doping leads to structural twisting of the CDs. The AIE phenomenon of CDs arises from the inhibition of the twisted structure motions and a reduction in the nonradiative relaxation rate during the aggregation process. In addition, CDs with twisted structures exhibit a smaller overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), effectively reducing the singlet-triplet splitting energy (ΔEST). CDs embedded in microcrystalline cellulose (MCC) exhibit green RTP because the nonradiative transitions are suppressed, and the excited triplet species remain stable. For the first time, this study reveals the structure-activity relationship between the twisted structure and optical properties of CDs, providing a new approach for the preparation of solid-state light-emitting CDs.

Edible Ultralong Organic Phosphorescent Excipient for Afterglow Visualizing the Quality of Tablets

Stimuli-responsive ultralong organic phosphorescence (UOP) materials that in response to external factors such as light, heat, and atmosphere have raised a tremendous research interest in fields of optoelectronics, anticounterfeiting labeling, biosensing, and bioimaging. However, for practical applications in life and health fields, some fundamental requirements such as biocompatibility and biodegradability are still challenging for conventional inorganic and aromatic-based stimuli-responsive UOP systems. Herein, an edible excipient, sodium carboxymethyl cellulose (SCC), of which UOP properties exhibit intrinsically multistimuli responses to excited wavelength, pressure, and moisture, is reported. Impressively, as a UOP probe, SCC enables nondestructive detection of hardness with superb contrast (signal-to-background ratio up to 120), while exhibiting a response sensitivity to moisture that is more than 5.0 times higher than that observed in conventional fluorescence. Additionally, its applicability for hardness monitoring and high-moisture warning for tablets containing a moisture-sensitive drug, with the quality of the drug being determinable through the naked-eye visible UOP, is demonstrated. This work not only elucidates the reason for stimulative corresponding properties in SCC but also makes a major step forward in extending the potential applications of stimuli-responsive UOP materials in manufacturing high-quality and safe medicine.

Room Temperature Phosphorescent Nanofiber Membranes by Bio-Fermentation

Stimuli-responsive materials exhibiting exceptional room temperature phosphorescence (RTP) hold promise for emerging technologies. However, constructing such systems in a sustainable, scalable, and processable manner remains challenging. This work reports a bio-inspired strategy to develop RTP nanofiber materials using bacterial cellulose (BC) via bio-fermentation. The green fabrication process, high biocompatibility, non-toxicity, and abundant hydroxyl groups make BC an ideal biopolymer for constructing durable and stimuli-responsive RTP materials. Remarkable RTP performance is observed with long lifetimes of up to 1636.79 ms at room temperature. Moreover, moisture can repeatedly quench and activate phosphorescence in a dynamic and tunable fashion by disrupting cellulose rigidity and permeability. With capabilities for repeatable moisture-sensitive phosphorescence, these materials are highly suitable for applications such as anti-counterfeiting and information encryption. This pioneering bio-derived approach provides a reliable and sustainable blueprint for constructing dynamic, scalable, and processable RTP materials beyond synthetic polymers.

Photoactivated room temperature phosphorescence from lignin

Sustainable photoactivated room temperature phosphorescent materials exhibit great potential but are difficult to obtain. Here, we develop photoactivated room temperature phosphorescent materials by covalently attaching lignin to polylactic acid, where lignin and polylactic acid are the chromophore and matrix, respectively. Initially the phosphorescence of the lignin is quenched by residual O2. However, the phosphorescence is switched on when the residual oxygen is consumed by the triplet excitons of lignin under continuous UV light irradiation. As such, the lifetime increases from 3.0 ms to 221.1 ms after 20 s of UV activation. Interestingly, the phosphorescence is quenched again after being kept under an atmosphere of air for 2 h in the absence of UV irradiation due to the diffusion of oxygen into the materials. Using these properties, as-developed material is successfully used as a smart anti-counterfeiting logo for a medicine bottle and for information recording.

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.

Solar-Driven Biomass Reforming for Hydrogen Generation: Principles, Advances, and Challenges

Hydrogen (H2) has emerged as a clean and versatile energy carrier to power a carbon-neutral economy for the post-fossil era. Hydrogen generation from low-cost and renewable biomass by virtually inexhaustible solar energy presents an innovative strategy to process organic solid waste, combat the energy crisis, and achieve carbon neutrality. Herein, the progress and breakthroughs in solar-powered H2 production from biomass are reviewed. The basic principles of solar-driven H2 generation from biomass are first introduced for a better understanding of the reaction mechanism. Next, the merits and shortcomings of various semiconductors and cocatalysts are summarized, and the strategies for addressing the related issues are also elaborated. Then, various bio-based feedstocks for solar-driven H2 production are reviewed with an emphasis on the effect of photocatalysts and catalytic systems on performance. Of note, the concurrent generation of value-added chemicals from biomass reforming is emphasized as well. Meanwhile, the emerging photo-thermal coupling strategy that shows a grand prospect for maximally utilizing the entire solar energy spectrum is also discussed. Further, the direct utilization of hydrogen from biomass as a green reductant for producing value-added chemicals via organic reactions is also highlighted. Finally, the challenges and perspectives of photoreforming biomass toward hydrogen are envisioned.

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.

Tailored Fabrication of Full-Color Ultrastable Room-Temperature Phosphorescence Carbon Dots Composites with Unexpected Thermally Activated Delayed Fluorescence

The development of single-system materials that exhibit both multicolor room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) with tunable after glow colors and channels is challenging. In this study, four metal-free carbon dots (CDs) are developed through structural tailoring, and panchromatic high-brightness RTP is achieved via strong chemical encapsulation in urea. The maximum lifetime and quantum yield reaches 2141 ms and 56.55%, respectively. Moreover, CDs-IV@urea, prepared via coreshell interaction engineering, exhibits a dual afterglow of red RTP and green TADF. The degree of conjugation and functional groups of precursors affects the binding interactions of the nitrogen cladding on CDs, which in turn stabilizes triplet energy levels and affects the energy gap between S1 and T1 (ΔEST) to induce multicolor RTP. The enhanced wrapping interaction lowers the ΔEST, promoting reverse intersystem crossing, which leads to phosphorescence and TADF. This strong coreshell interaction fully stabilizes the triplet state, thus stabilizing the material in water, even in extreme environments such as strong acids and oxidants. These afterglow materials are tested in multicolor, time, and temperature multiencryption as well as in multicolor in vivo bioimaging. Hence, these materials have promising practical applications in information security as well as biomedical diagnosis and treatment.

Nucleic-acid-base photofunctional cocrystal for information security and antimicrobial applications

Cocrystal engineering is an efficient and simple strategy to construct functional materials, especially for the exploitation of novel and multifunctional materials. Herein, we report two kinds of nucleic-acid-base cocrystal systems that imitate the strong hydrogen bond interactions constructed in the form of complementary base pairing. The two cocrystals studied exhibit different colors of phosphorescence from their monomeric counterparts and show the feature of rare high-temperature phosphorescence. Mechanistic studies reveal that the strong hydrogen bond network stabilizes the triplet state and suppresses non-radiative transitions, resulting in phosphorescence even at 425 K. Moreover, the isolation effects of the hydrogen bond network regulate the interactions between the phosphor groups, realizing the manipulation from aggregation to single-molecule phosphorescence. Benefiting from the long-lived triplet state with a high quantum yield, the generation of reactive oxygen species by energy transfer is also available to utilize for some applications such as in photodynamic therapy and broad-spectrum microbicidal effects. In vitro experiments show that the cocrystals efficiently kill bacteria on a tooth surface and significantly help prevent dental caries. This work not only provides deep insight into the relationship of the structure-properties of cocrystal systems, but also facilitates the design of multifunctional cocrystal materials and enriches their potential applications.

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.

Biobased and biodegradable films exhibiting circularly polarized room temperature phosphorescence

There is interest in developing sustainable materials displaying circularly polarized room-temperature phosphorescence, which have been scarcely reported. Here, we introduce biobased thin films exhibiting circularly polarized luminescence with simultaneous room-temperature phosphorescence. For this purpose, phosphorescence-active lignosulfonate biomolecules are co-assembled with cellulose nanocrystals in a chiral construct. The lignosulfonate is shown to capture the chirality generated by cellulose nanocrystals within the films, emitting circularly polarized phosphorescence with a 0.21 dissymmetry factor and 103 ms phosphorescence lifetime. By contrast with most organic phosphorescence materials, this chiral-phosphorescent system possesses phosphorescence stability, with no significant recession under extreme chemical environments. Meanwhile, the luminescent films resist water and humid environments but are fully biodegradable (16 days) in soil conditions. The introduced bio-based, environmentally-friendly circularly polarized phosphorescence system is expected to open many opportunities, as demonstrated here for information processing and anti-counterfeiting.

Ground-State Orbital Descriptors for Accelerated Development of Organic Room-Temperature Phosphorescent Materials

Organic materials with room-temperature phosphorescence (RTP) are in high demand for optoelectronics and bioelectronics. Developing RTP materials highly relies on expert experience and costly excited-state calculations. It is a challenge to find a tool for effectively screening RTP materials. Herein we first establish ground-state orbital descriptors (πFMOs ) derived from the π-electron component of the frontier molecular orbitals to characterize the RTP lifetime (τp ), achieving a balance in screening efficiency and accuracy. Using the πFMOs , a data-driven machine learning model gains a high accuracy in classifying long τp , filtering out 836 candidates with long-lived RTP from a virtual library of 19,295 molecules. With the aid of the excited-state calculations, 287 compounds are predicted with high RTP efficiency. Impressively, experiments further confirm the reliability of this workflow, opening a novel avenue for designing high-performance RTP materials for potential applications.