Polymerization-Induced Crystallization of Dopant Molecules: An Efficient Strategy for Room-Temperature Phosphorescence of Hydrogels

Poly(methyl methacrylate) Nanosphere-Based Photocrosslinked Hydrogels with Ultralong Phosphorescence Lifetimes for High-Precision 3D Printing

Hydrogel-based afterglow materials offer significant potential for broadening the application field of organic room-temperature phosphorescence (RTP) materials owing to their tissue-mimetic flexibility and superior biocompatibility. However, achieving a colorful and efficient RTP in a water-rich hydrogel environment remains challenging. Here, we present a general strategy to fabricate colorful and efficient RTP hydrogels by incorporating compact and hydrophobic nanospheres loaded with chromophores, synthesized via emulsion polymerization, into photocrosslinked hydrogels with oxygen barrier properties. The resultant hydrogel demonstrates a remarkably high water content of 94.6% and a maximum phosphorescence lifetime of up to 1697.0 ms, both significantly surpassing the relevant values of organic RTP hydrogels reported in prior studies. Furthermore, 3D RTP hydrogels with complex geometries and high precision are fabricated using digital light processing (DLP) 3D printing technology. This approach connects the RTP hydrogel and 3D printing fields for the first time, opening up substantial potential for advancing the applications of RTP materials.

Supramolecular Entanglement Driven Emissive Aggregate Densification Enabling Room-Temperature Phosphorescence Hydrogels with Ultrastretchability and Crack-Tolerance

Polymeric room temperature phosphorescence (RTP) hydrogels are emerging candidates for many advanced photonic applications. Unfortunately, phosphorescence of the introduced RTP chromophores can easily be quenched in water-swollen hydrogel networks, limiting their luminescence performance and application adaptability. Herein, we propose a supramolecular confinement-entanglement synergy strategy to produce ultrastretchable RTP hydrogels by in-situ polymerizing high-concentration 2-(acryloyloxy)ethyl trimethylammonium chloride (AETC) in the presence of preassembled 4-biphenylboronic acid@β-cyclodextrin (4-BB@β-CD) emissive aggregates. The hyper-entangled poly(AETC) (PAETC) chains, formed under water-limiting conditions, synergistically densify the 4-BB@β-CD aggregates through supramolecular confinement, effectively suppressing molecular vibrations and stabilizing triplet states. Impressively, the hydrogels exhibit intense afterglow and ultralong phosphorescence lifetime up to 1.1 s under room conditions. Crucially, the entanglement-dominated physical network free of static chemical crosslinking enables continuing chain disentanglement during stretching for efficient energy dissipation. Segment length between physical entanglement points can thus be significantly enlarged to reduce network fracture and avoid crack propagation, achieving record-breaking uniaxial/biaxial (21 000%/10 000%) stretchability. Even the notched hydrogels are capable of being unprecedentedly stretched to 20 500% and exhibit a fracture energy as high as 157 kJ m⁻2, demonstrating intrinsic crack-tolerance. This study opens new avenues of polymeric RTP hydrogels by bringing superior mechanical performance and should merit their application exploration.

p-π Conjugate Triggered Red Room-Temperature Phosphorescence from Single Benzene Derivatives

Benzene is the simplest and the most basic building block for the construction of π conjugated systems, which are widely used in various fields from fluorescent (FL) dyes to optoelectronic displays. However, achieving the red room-temperature phosphorescence (RTP) from single benzene is still challenging. Utilizing the p-π conjugation, herein, we report a single benzene-based push-pull system with red RTP under ambient condition. One of the phosphors shows maximum RTP peak at 585 nm, along with shoulder peaks at 545 nm, 635 nm, and 700 nm. This architecture is uniquely separate from conventional extended π-conjugated systems and minimizes the requirement for red/near-infrared (NIR) phosphors to a single benzene ring.

Multifunctional Hydrogel Electronics for Synergistic Therapy and Visual Monitoring in Wound Healing

To overcome the limitations of precise monitoring and inefficient wound exudate management in wound healing, an advanced multifunctional hydrogel electronics (MHE) platform based on MXene@MOF/Fe3O4@C photonic crystal hydrogel is developed. This platform combines optical/electrical sensing, synergistic therapy, and real-time visual monitoring into a single, efficient system, offering a comprehensive solution for wound healing. Under photothermal stimulation, the hydrogel releases metal ions that generate hydroxyl radicals, effectively eliminating antibiotic-resistant bacteria. Beyond its antibacterial efficacy, this system offers unprecedented real-time monitoring through temperature-responsive visualization, while structural color changes upon wound exudate absorption provide a clear indication for dressing replacement. By integrating these functionalities, MHE platform allows for precise control of the therapeutic process, significantly improving wound healing and treatment monitoring. The platform's optical/electrical sensing capabilities further broaden its potential applications across other biomedical fields. This breakthrough technology provides clinicians with a powerful tool to optimize therapeutic outcomes, marking a major advancement in wound care and biomedical applications.

Disturbance-Triggered Instant Crystallization Activating Bioinspired Emissive Gels

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

Multi-mode geometrically gated encryption with 4D morphing hydrogel

Leveraging the rich stimuli-response of polymers represents a promising direction towards optical communication/encryption. Sign language, which relies on specific geometric change for secured communication, has been widely used for the same purpose since ancient time. We report a strategy that combines both in a validated manner with a hydrogel that not only carries encrypted optical information but also has the hidden behavior to morph geometrically. In particular, the shape morphing behavior is programmable by controlling the oriented state of the polymer chain in the thermo-responsive network. Whether the shape morphing direction is positive (bending) or negative (flattening) cannot be predicted when the polymerization methods are not informed, revealing a hidden manner. Through deciphering the coupling of chain elastic stresses and thermo-induced deswelling stress, the hydrogel can perform designed and diversified 4D morphing which represents evolution of 3D geometries with time as the fourth dimension. Consequently, the corresponding optical information can be gated based on these geometric features, thereby decrypting the correct permutation of information. Our approach that utilizes the geometric 4D morphing for gated verification of optical information offers a strategy for enhancing the security of communication in ways that are quite different from existing strategies.

3D printable organic room-temperature phosphorescent materials and printed real-time sensing and display devices

Polymer-based host-guest organic room-temperature phosphorescent (RTP) materials are promising candidates for new flexible electronic devices. Nowadays, the insufficient fabrication processes of polymeric RTP materials have hindered the development of these materials. Herein, we propose a strategy to realize 3D printable organic RTP materials and have successfully demonstrated real-time sensing and display devices through a Digital Light Processing (DLP) 3D printing process. We have designed and synthesized the molecules EtCzBP, PhCzBP and PhCzPM with A-D-A structures. The crucial role of strong intramolecular charge transfer (ICT) at the lowest triplet states in achieving bright photo-activated phosphorescence in polymer matrices has also been demonstrated. 3D printable RTP resins were manufactured by doping emissive guest molecules into methyl methacrylate (MMA). Based on these resins, a series of complex 3D structures and smart temperature responsive RTP performances were obtained by DLP 3D printing. Additionally, these RTP 3D structures have been applied in real-time temperature sensing and display panels for the first time. This work not only provides a guiding strategy for the design of emissive guest molecules to realize photo-activated RTP in poly(methyl methacrylate) (PMMA), but also paves the way for the development of 3D-printable real-time sensing structures and new-concept display devices.

Mechanics-Photophysics Correlation in Tough, Stretchable and Long-Lived Room Temperature Phosphorescence Ionogels Deciphered by Dynamic Mechanical Analysis

The development of tough, stretchable and long-lived room temperature phosphorescence (RTP) materials holds great significance for manufacturing and processing photoluminescent materials, but limited techniques are available to profile their mechanics-photophysics correlation. Here we report glassy ionogels, and their mechanical properties and photophysical properties are fused by dynamic mechanical analysis (DMA), functioning like a human brain that perceives a material instantaneously by linking sensory perception and cognition. Depending on two special temperatures presented in DMA curves, Tloss (the peak of loss modulus (E")) and Tg (glass transition temperature), the ionogels can vary from being either tough with persistent phosphorescence, extensible with effective phosphorescence or resilience with inefficient phosphorescence. Leveraging this method, we achieve stretchable and long-lived RTP ionogels with tensile yield strength of 53 MPa, tensile strain of 497 %, Young's modulus of 782 MPa, toughness of 111.2 MJ/m3, and lifetime of 113.05 ms. Our work provides a simple yet powerful method to reveal the mechanics-photophysics correlation of RTP ionogels, to predict their performance without laborious synthesis and characterization, opening new avenues for applications of RTP materials, including applications in harsh conditions (257 K or 347 K), shape memory and shape reconstruction.

High-Security Plastic with Integrated Holographic and Phosphorescent Images

Organic room temperature phosphorescence (ORTP) polymer materials have sparked considerable research interests in recent years, but their optical function is still limited for multi-mode optical imaging. Herein, a feasible and universal approach is proposed to endow ORTP polymer materials with periodic refractive index modulation functions by holographic patterning. The key to this approach is to design a two-stage stepwise crosslinking. Stage-1, with low crosslinking density (≤0.75 mol L-1), is phosphorescence-silent but can provide greater free volume for monomer diffusion and thus facilitate the patterning of refractive index modulated holograms via photopolymerization-induced phase separation. The dense crosslinking at stage-2 can turn on phosphorescence with the intensity rising by 144% when the crosslinking density increases from 3.77 to 4.12 mol L-1. The enhanced phosphorescence is primarily ascribed to the increase of conformational distortion and spin-orbit coupling of organic phosphors based on theoretical calculations. Eventually, the first example is demonstrated of holographic plastic with the unique capability of independently displaying holographic andphosphorescent images. This work not only provides a novel paradigm to impart added optical functions to ORTP polymer materials but also paves the way for the development of high-security optical materials to combat counterfeiting.

High-Performance Organic Ultralong Room Temperature Phosphorescence Based on Biomass Macrocycle

The pursuit of sustainable, high-performance organic ultralong room temperature phosphorescence (OURTP) materials with stimulus-responsive properties presents a significant and enticing yet formidable challenge. Herein, an efficient strategy to confining boric acid-based compounds into biomass macrocycle γ-cyclodextrin through multiple interactions is developed, enabling the construction of high-performance and multicolor OURTP doped systems. The synergistic effects of strong hydrogen bonding, C─O─B covalent cross-linking, and host-guest encapsulation significantly suppress non-radiative transition, culminating in an extraordinary lifetime and excellent phosphorescence quantum yield of 4.65 s and 32.8%, respectively, which are far superior to reported biomass RTP materials. Additionally, merging biomass macrocycle with phosphors contributes to multiple stimulus responses, overcoming the inherent limitations of degradation and recycling of organic RTP compounds, and dynamically modulating RTP signals through multiple-stimulus responses, achieving the integration of multifunctional dynamic data processing techniques. This work will provide a direction for new environmentally friendly and potentially commercially available stimulus-responsive OURTP materials.

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.

Cocrystallization-Induced Red Ultralong Organic Phosphorescence

Organic cocrystals formed through multicomponent self-assembly have attracted significant interest owing to their clear structure and tunable optical properties. However, most cocrystal systems suffer from inefficient long-wavelength emission and low phosphorescence efficiency due to strong non-radiative processes governed by the energy gap law. Herein, an efficient long-lived red afterglow is achieved using a pyrene (Py) cocrystal system incorporating a second component (NPYC4) with thermally activated delayed fluorescence (TADF) and ultralong organic phosphorescence (UOP) properties. The cocrystal (NPYC4-Py) not only inherits the excellent luminescence of its monomeric counterparts, but also exhibits unique dual-mode characteristics, including persistent TADF and UOP emission with a high quantum yield of 58 % and a lifetime of 362 ms. The precise cocrystal stacking distinctly reveals that intermolecular interactions lock the cocrystal formation and weaken the intermolecular π-π interactions between NPYC4 and Py, thereby stabilizing the excited triplet excitons. Furthermore, the favorable energy level of NPYC4 acts as a bridge, reducing the energy gap between the S1 and T1 states for Py, therefore activating its red phosphorescence from Py. This research provides direct insights into achieving efficient red UOP through co-crystallization.

Stretchable Full-Color Phosphorescent PVA-Based Ionogels for Multimodal Sensing-Visual Integration Applications

Exploring ionogels with superior conductivity, mechanical properties, and long-lasting room temperature phosphorescence (RTP) offers considerable potential for new-generation optoelectronics. However, reports on ionogels remain limited owing to the contradiction between the flexibility required for stretching and the rigidity necessary for RTP and load-bearing within the same ionogels. Here, a facile strategy is reported to enhance the toughness and extend the RTP of ionogels by salting-out-induced microphase separation, which results in the formation of an IL-rich phase (soft) for stretching and ionic conduction and a polymer-rich phase (stiff) for energy dissipation and clustering-triggered phosphorescence. The obtained ionogels exhibit high stretchability (≈400% strain), toughness (≈∼20 MJ m-3), ionic conductivity (8.4 mS cm-1), and ultralong afterglow lifetime (112.4 ms). This strategy is applicable to chromophores with color-tunable phosphorescence. By leveraging observable full-color RTP and real-time electrical signals in response to diverse stimuli (i.e., stretching and pressing), an intelligent grasping strategy is developed for robust hand pose reconstruction. In addition, a tactile-visual fusion recognition keyboard is created with dual functionality of information encryption and signal transmission. The ease of fabrication, wide tunability, and multifunctionality will help expand the scope of ionogels for smart devices.

Intrinsic Multicolor Emissive Aliphatic Linear Polyphosphate Esters From the Charge-Transfer-Induced Enhanced Spatial Electronic Communication

Unconventional fluorescent polymers are attracting increasing attention because of their excellent biocompatibility and wide applications. However, these polymers typically exhibit weak long-wavelength emission. Herein, three novel aliphatic linear polyphosphate esters are prepared via a one-pot polycondensation reaction. Such polymers can generate strong blue, green, yellow, and red fluorescence under different excitations. Experimental and theoretical results showed that the cluster of C═C and phosphate ester groups attracted the negative charge of isolated functional groups, and the alkane chains and hydrogen atoms also provided a negative charge for spatial electronic communication. Then, intrinsic fluorescence arises from the charge-transfer-induced enhanced spatial electronic communication. Additionally, these polymers show potential applications in fluorescence film, ion detection, bacteria imaging, and visualization of the NaCl crystallization process. This work provides a universal design strategy for developing strong long-wavelength emissive polymers and gains new insight into intrinsic emission mechanisms.

Dynamic Modulation of Afterglow Emission in Polymeric Phosphors via Inverse Opal Photonic Structures

Tuning the afterglow of polymeric phosphors is critical for advancing their use in optical data storage and display technologies. Despite advancements in polymer matrix design and dopant engineering, achieving dynamic control over afterglow intensity remains a significant challenge. In this study, a novel approach is introduced for dynamically tuning the afterglow of polymeric phosphors by integrating them into an inverse opal photonic structure. By precisely aligning the photonic stopband of the inverse opal structure with the afterglow band of the polymer film, a remarkable 15-fold enhancement in afterglow intensity is achieved. This enhancement is tunable, decreasing from 15 to 1.2 by infiltrating the photonic structure with media of varying refractive indices ranging from 1.00 (air) to 1.37 (ethyl acetate). The tunability arises from reducing the mismatch between the stopband and the afterglow band, as the weighted refractive index shifts between 1.15 and 1.40. Additionally, the inverse opal photonic structure induces angle-dependent structural colors in the Janus polymeric phosphors, modulated by the refractive index of the infiltrating media. This integration of dynamically tunable afterglow with angle-dependent structural coloration unlocks new potential for advanced optoelectronic applications.

Promoting WLED-Excited High Temperature Long Afterglow by Orthogonally Anchoring Chromophores into 0D Metal-Organic Cages

Afterglow materials have garnered significant interest due to distinct photophysical characteristics. However, it is still difficult to achieve long afterglow phosphorescence from organic molecules due to aggregation-caused quenching (ACQ) and energy dissipation. In addition, most materials reported so far have long afterglow emission only at room or even low temperatures, and mainly use UV light as an excitation source. In this work, we report a strategy to achieve high temperature long afterglow emission through the assembly of isolated 0D metal-organic cages (MOCs). In which, both ACQ and phosphorescence quenching effects are effectively mitigated by altering the stacking mode of organic chromophores through orthogonally anchoring into the edges of cubic MOCs. Furthermore, improvement in molecular rigidity, promotion of spin-orbit coupling and broadening of the absorption range are achieved through the MOC-engineering strategy. As a result, we successfully synthesized MOCs that can produce afterglow emission even after excitation by WLEDs at high temperatures (380 K). Moreover, the MOCs are capable of generating afterglow emissions when excited by mobile phone flashlight at room temperature. Given these features, the potential applications of MOCs in the visual identification of explosives, information encryption and multicolor display are explored.

Dynamic Organic Phosphorescence Glass by Rigid-Soft Coupling

Organic phosphorescence glass has garnered considerable attention owing to the excellent shaping ability and photophysical behavior, but facile construction from single-component phosphors is still challenging. Herein, a rigid-soft coupling design is adopted in organic phosphors of ICO, CCO and PCO, thus preparing phosphorescence glasses through melting-quenching method to give excellent shaping ability and dynamic phosphorescence. RTP performance is significantly enhanced in the dense-structure glass, and intriguing high-temperature phosphorescence (HTP) is still observable even at 400 K. Direct patterning under UV irradiation is also achieved using photolithography technique, allowing for the creation of high-quality afterglow patterns that can be reversibly erased and rewritten. This rigid-soft conformation in organic phosphors elucidates a promising concept for achieving efficient RTP glass with wide application prospects.

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.

Predicting Fatigue Damage in Hydrogels Through Force-Induced Luminescence Enhancement

Fatigue damage of polymers occurs under long-term load cycling, resulting in irreversible fracture failure, which is difficult to predict. The real-time monitoring of material fatigue damage is of great significance. Here, tough hydrogels are prepared with force-induced confined luminescence enhancement of carbonated polymer quantum dot (CPD) clusters to realize the visualization of fracture process and the monitoring of fatigue damage. The enhanced interactions induced by force between the clusters and the polymer in the confined space inhibit the non-radiative leaps and promote the radiative leaps to quantify the fatigue damage into optical signals. Rigid CPDs with abundant active sites on the surface can form dynamic reversible bonds with polymer and dissipate stress concentration, which significantly enhances the crack propagation strain (8000%) and fracture energy (26.4 kJ m-2) of hydrogels. CPD hydrogels have a wide range of applications in novel information encryption and luminescent robotics.

Stable Persistent Room-Temperature Phosphorescent Hydrogels Based on Ionically Crosslinked Nonaromatic Carboxylate Polymers

Developing pure organic room-temperature phosphorescent (RTP) hydrogels is important for expanding the practical applications of phosphorescent materials. However, most of the reported RTP hydrogels containing aromatic phosphors suffer from short phosphorescent lifetimes, unstable underwater RTP emissions, and complex preparation processes. Herein, novel nonaromatic RTP hydrogels are prepared by using two types of non-traditional luminescent polymers, sodium alginate and a polymeric carboxylate, which are not RTP emissive or very weakly emissive in aqueous environments. The prepared hydrogels exhibit the following features: I) color-tunable RTP emissions with ultra-long lifetimes up to 451.1 ms, II) excellent anti-swelling properties and stable persistent RTP emission even after being immersed in deionized water for months, III) efficient and large-scale preparation of hydrogel fibers by wet spinning technique. Experiment results and theoretical calculations show that the stable and long-lifetime RTP emissions of the hydrogels originate from the introduction of more nonconventional chromophores which are strongly crosslinked with ionic bonding between carboxylate groups and calcium ions and enhanced through-space interactions between them. This work provides a reliable strategy for designing nonaromatic hydrogels with stable and persistent RTP.

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.

Achieving Near-Infrared Phosphorescence Supramolecular Hydrogel Based on Amphiphilic Bromonaphthalimide Pyridinium Hierarchical Assembly

Phosphorescent supramolecular hydrogels are currently a prevalent topic for their great promise in various photonic applications. Herein, an efficient near-infrared (NIR) phosphorescence supramolecular hydrogel is reported via the hierarchical assembly strategy in aqueous solution, which is fabricated from amphiphilic bromonaphthalimide pyridinium derivative (G), exfoliated Laponite (LP) nanosheets, and polymeric polyacrylamide (PAAm). Initially, G spontaneously self-aggregates into spherical nanoparticles covered with positively charged pyridinium units and emits single fluorescence at 410 nm. Driven by electrostatic interactions with negatively charged nanosheets, the nanoparticles subsequently function as the cross-linked binders and coassemble with LP into supramolecular hydrogels with an engendered red room-temperature phosphorescence (RTP) up to 620 nm. Benefiting from hydrogen-bonding interactions-mediated physical cross-linkage, the further introduction of PAAm not only significantly elevates the mechanical strength of the hydrogels showing fast self-healing capability, but also increases phosphorescence lifetime from 2.49 to 4.20 ms, especially generating phosphorescence at even higher temperature (τ 363 K = 2.46 ms). Additionally, efficient RTP energy transfer occurs after doping a small amount of organic dye heptamethine cyanine (IR780) as an acceptor into hydrogels, resulting in a long-lived NIR emission at 823 nm with a high donor/acceptor ratio, which is successfully applied for cell labeling in the NIR window.

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.

Jellyfish-Inspired Artificial Spider Silk for Luminous Surgical Sutures

The development of functional surgical sutures with excellent mechanical properties, good fluorescence, and high cytocompatibility is highly required in the field of medical surgeries. Achieving fibers that simultaneously exhibit high mechanical robustness, good spinnability, and durable fluorescence emission has remained challenging up to now. Taking inspiration from the spinning process of spider silk and the luminescence mechanism of jellyfish, this work reports a luminous artificial spider silk prepared with the aim of balancing the fiber spinnability and mechanical robustness. This is realized by employing highly hydrated segments with aggregation-induced luminescence for enhancing the fiber spinnability and polyhydroxyl segments for increasing the fiber mechanical robustness. Twist insertion during fiber spinning improves the fiber strength, toughness, and fluorescence emission. Furthermore, coating the fiber with an additional polymer layer results in a "sheath-core" architecture with improved mechanical properties and capacity to withstand water. This work provides a new design strategy for performing luminescent and robust surgical sutures.

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.

3D Printed Room Temperature Phosphorescence Materials Enabled by Edible Natural Konjac Glucomannan

Shaping room temperature phosphorescence (RTP) materials into 3D bodies is important for stereoscopic optoelectronic displays but remains challenging due to their poor processability and mechanical properties. Here, konjac glucomannan (KGM) is employed to anchor arylboronic acids with various π conjugations via a facile B─O covalent reaction to afford printable inks, using which full-color high-fidelity 3D RTP objects with high mechanical strength can be obtained via direct ink writing-based 3D printing and freeze-drying. The doubly rigid structure supplied by the synergy of hydrogen bonding and B─O covalent bonding can protect the triplet excitons; thus, the prepared 3D RTP object shows a striking lifetime of 2.14 s. The printed counterparts are successfully used for 3D anti-counterfeiting and can be recycled and reprinted nondestructively by dissolving in water. This success expands the scope of printable 3D luminescent materials, providing an eco-friendly platform for the additive manufacturing of sophisticated 3D RTP architectures.

Multi-role conductive hydrogels for flexible transducers regulated by MOFs for monitoring human activities and electronic skin functions

Metal organic frameworks (MOFs) have garnered significant attention in the development of stretchable and wearable conductive hydrogels for flexible transducers. However, MOFs used in hydrogel networks have been hampered by low mechanical performance and poor dispersibility in aqueous solutions, which affect the performance of hydrogels, including low toughness, limited self-recovery, short working ranges, low conductivity, and prolonged response-recovery times. To address these shortcomings, a novel approach was adopted in which micelle co-polymerization was used for the ex situ synthesis of Zn-MOF-based hydrogels with exceptional stretchability, robust toughness, anti-fatigue properties, and commendable conductivity. This breakthrough involved the ex situ integration of Zn-MOFs into hydrophobically cross-linked polymer chains. Here the micelles of EHDDAB had two functions, first they uniformly dispersed the Zn-MOFs and secondly they dynamically cross-linked the polymer chains, profoundly influencing the mechanical characteristics of the hydrogels. The non-covalent synergistic interactions introduced by Zn-MOFs endowed the hydrogels with the capacity for high stretchability, high stress, rapid self-recovery, anti-fatigue properties, and conductivity, all achieved without external stimuli. Furthermore, hydrogels based on Zn-MOFs can serve as durable and highly sensitive flexible transducers, adept at detecting diverse mechanical deformations with swift response-recovery times and high gauge factor values. Consequently, these hydrogels can be tailored to function as wearable strain sensors capable of sensing significant human joint movements, such as wrist bending, and motions involving the wrist, fingers, and elbows. Similarly, they excel at monitoring subtle human motions, such as speech pronunciation, distinguishing between different words, as well as detecting swallowing and larynx vibrations during various activities. Beyond these applications, the hydrogels exhibit proficiency in distinguishing and reproducing various written words with reliability. The Zn-MOF-based hydrogels hold promising potential for development in electronic skin, medical monitoring, soft robotics, and flexible touch panels.

Visual Quantitation of Dopamine-Inspired Fluorescent Adhesion with Orthogonal Phenanthrenequinone Photochemistry

Quantifying adhesion is crucial for understanding adhesion mechanisms and developing advanced dopamine-inspired materials and devices. However, achieving nondestructive and real-time quantitation of adhesion using optical spectra remains challenging. Here, we present a dopamine-inspired orthogonal phenanthrenequinone photochemistry strategy for the one-step adhesion and real-time visual quantitation of fluorescent spectra. This strategy utilizes phenanthrenequinone-mediated photochemistry to facilitate conjoined network formation in the adhesive through simultaneous photoclick cycloaddition and free-radical polymerization. The resulting hydrogel-like adhesive exhibits good mechanical performance, with a Young's modulus of 300 kPa, a toughness of 750 kJ m-3, and a fracture energy of 4500 J m-2. This adhesive, along with polycyclic aromatic phenanthrenequinones, shows strong adhesion (>100 kPa) and interfacial toughness thresholds (250 J m-2) on diverse surfaces─twice to triple as much as typical dopamine-contained adhesives. Importantly, such an adhesive demonstrates excellent fluorescent performance under UV irradiation, closely correlating with its adhesion strengths. Their fluorescence intensities remain constant after continuous stretching/releasing treatment and even in the dried state. Therefore, this dopamine-inspired orthogonal phenanthrenequinone photochemistry is readily available for real-time and nondestructive visual quantitation of adhesion performance under various conditions. Moreover, the adhesive precursor is chemically ultrastable for more than seven months and achieves adhesion on substrates within seconds upon blue light irradiation. As a proof-of-concept, we leverage the rapid and visual quantitation of adhesion and printability to create fluorescent patterns and structures, showcasing applications in information storage, adhesion prediction, and self-reporting properties. This general and straightforward strategy holds promise for rapidly preparing functional adhesive materials and designing high-performance wearable devices.

Cephalopod-Inspired Chemical-Gated Hydrogel Actuation Systems for Information 3D-Encoding Display

Cephalopods evolve the acetylcholine-gated actuation control function of their skin muscles, which enables their dynamic/static multimode display capacities for achieving perfectly spatial control over the colors/patterns on every inch of skin. Reproduction of artificial analogs that exhibit similar multimodal display is essential to reach advanced information three-dimensional (3D) encoding with higher security than the classic 2D-encoding strategy, but remains underdeveloped. The core difficulty is how to replicate such chemical-gated actuation control function into artificial soft actuating systems. Herein, this work proposes to develop azobenzene-functionalized poly(acrylamide) (PAAm) hydrogel systems, whose upper critical solution temperature (UCST) type actuation responsiveness can be intelligently programmed or even gated by the addition of hydrophilic α-cyclodextrin (α-CD) molecules for reversible association with pendant azobenzene moieties via supramolecular host-guest interactions. By employing such α-CD-gated hydrogel actuator as an analogue of cephalopods' skin muscle, biomimetic mechanically modulated multicolor fluorescent display systems are designed, which demonstrate a conceptually new α-CD-gated "thermal stimulation-hydrogel actuation-fluorescence output" display mechanism. Consequently, high-security 3D-encoding information carriers with an unprecedented combination of single-input multiple-output, dynamic/static dual-mode and spatially controlled display capacities are achieved. This bioinspired strategy brings functional-integrated features for artificial display systems and opens previously unidentified avenues for information security.

Stretchable phosphorescent polymers by multiphase engineering

Stretchable phosphorescence materials potentially enable applications in diverse advanced fields in wearable electronics. However, achieving room-temperature phosphorescence materials simultaneously featuring long-lived emission and good stretchability is challenging because it is hard to balance the rigidity and flexibility in the same polymer. Here we present a multiphase engineering for obtaining stretchable phosphorescent materials by combining stiffness and softness simultaneously in well-designed block copolymers. Due to the microphase separation, copolymers demonstrate an intrinsic stretchability of 712%, maintaining an ultralong phosphorescence lifetime of up to 981.11 ms. This multiphase engineering is generally applicable to a series of binary and ternary initiator systems with color-tunable phosphorescence in the visible range. Moreover, these copolymers enable multi-level volumetric data encryption and stretchable afterglow display. This work provides a fundamental understanding of the nanostructures and material properties for designing stretchable materials and extends the potential of phosphorescence polymers.

Multiple hydrogen-bonding induced nonconventional red fluorescence emission in hydrogels

The development of unconventional long-wavelength fluorescent polymer hydrogels without using polycyclic aromatic hydrocarbons or extended π-conjugation is a fundamental challenge in luminescent materials owing to a lack of understanding regarding the spatial interactions induced inherent clustering-triggered emission under water-rich conditions. Inspired by the color change of protein astaxanthin as a result of heat-induced denaturation, we propose a thermodynamically driven strategy to develop red fluorescence (~610 nm) by boiling multiple hydrogen-bonded poly(N-acryloylsemicarbazide) hydrogels in a water bath. We reveal that thermodynamically driven conformational changes of polymer chains from isolated hydrogen bonding donor-acceptor structures to through-space interaction structures induce intrinsic fluorescence shifts from blue to red during clustering-triggered emission. The proposed multiple hydrogen-bonding supramolecular hydrogel shows good fluorescence stability, mechanical robustness, and 3D printability for customizable shaping. We provide a viable method to prepare nonconventional long-wavelength fluorescent hydrogels towards soft fluorescent devices without initially introducing any fluorescent components.

Multi-Functional Integration of Phosphor, Initiator, and Crosslinker for the Photo-Polymerization of Flexible Phosphorescent Polymer Gels

A general approach to constructing room temperature phosphorescence (RTP) materials involves the incorporation of a phosphorescent emitter into a rigid host or polymers with high glass transition temperature. However, these materials often suffer from poor processability and suboptimal mechanical properties, limiting their practical applications. In this work, we developed benzothiadiazole-based dialkene (BTD-HEA), a multifunctional phosphorescent emitter with a remarkable yield of intersystem crossing (ΦISC, 99.83 %). Its high triplet exciton generation ability and dialkene structure enable BTD-HEA to act as a photoinitiator and crosslinker, efficiently initiating the polymerization of various monomers within 120 seconds. A range of flexible phosphorescence gels, including hydrogels, organogels, ionogels, and aerogels were fabricated, which exhibit outstanding stretchability and recoverability. Furthermore, the unique fluorescent-phosphorescent colorimetric properties of the gels provide a more sensitive method for the visual determination of the polymerization process. Notably, the phosphorescent emission intensity of the hydrogel can be increased by the formation of ice, allowing for the precise detection of hydrogel freezing. The versatility of this emitter paves the way for fabricating various flexible phosphorescence gels with diverse morphologies using microfluidics, film-shearing, roll coating process, and two/three-dimensional printing, showcasing its potential applications in the fields of bioimaging and bioengineering.

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

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

Mechanical Stretch α-Cyclodextrin Pseudopolyrotaxane Elastomer with Reversible Phosphorescence Behavior

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

Photo-Controllable Ultralong Room-Temperature Phosphorescence: State of the Art

In this concept, we showcase the upsurge in the studies of dynamic ultralong room-temperature phosphorescence (RTP) materials containing inorganic and/or organic components as versatile photo-responsive platforms. The goal is to provide a comprehensive analysis of photo-controllable RTP, and meanwhile delve into the underlying RTP properties of various classes of photochromic materials including metal-organic complexes, organic-inorganic co-crystals, purely organic small molecules and organic polymers. In particular, the design principles governing the integration of the photochromic and RTP moieties within a single material system, and the tuning of dynamic RTP in response to light are emphasized. As such, this concept sheds light on the challenges and opportunities of using these tunable RTP materials for potential applications in optoelectronics, particularly highlighting their use of reversible information encryption, erasable light printing and rewritable smart paper.

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

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

Confinement-Modulated Clusterization-Triggered Time-Dependent Phosphorescence Color from Xylan-Carbonized Polymer Dots

Achieving time-dependent phosphorescence color (TDPC) in organic materials is attractive but extremely challenging due to the nonradiative decay and modulation puzzle of triplet state. Herein, xylan, a hemicellulose waste from the paper mill, was used to construct carbonized polymer dots (CPDs) with clusterization-triggered room-temperature phosphorescence (RTP). CPDs were endowed with tuneable triplet energy levels by through-space conjugation of heteroatom groups, which could be confined in silica to simultaneously activate surface oxide-related low-energy and cross-linked core N-related high-energy emissive centers. Thus, the blue emissive center with a lifetime of 425.6 ms and green emissive center with a longer lifetime of 1506 ms coexisted in the confined CPDs; the former was the dominant contribution to RTP at first, and the latter became dominant over time, leading to a typical TDPC evolution with large color contrast from blue to blue-green and then to green. Meanwhile, the TDPC could remain unobstructed after the confined CPDs were soaked in water for more than a month. The CPDs were successfully applied in location and deformation imaging of hydrogel and advanced dynamic information encryption and anticounterfeiting. The work may shed new light on the design of TDPC materials and broaden the high-value use of paper-mill waste xylan.

Molecularly Engineered Room-Temperature Phosphorescence for Biomedical Application: From the Visible toward Second Near-Infrared Window

Phosphorescence, characterized by luminescent lifetimes significantly longer than that of biological autofluorescence under ambient environment, is of great value for biomedical applications. Academic evidence of fluorescence imaging indicates that virtually all imaging metrics (sensitivity, resolution, and penetration depths) are improved when progressing into longer wavelength regions, especially the recently reported second near-infrared (NIR-II, 1000-1700 nm) window. Although the emission wavelength of probes does matter, it is not clear whether the guideline of "the longer the wavelength, the better the imaging effect" is still suitable for developing phosphorescent probes. For tissue-specific bioimaging, long-lived probes, even if they emit visible phosphorescence, enable accurate visualization of large deep tissues. For studies dealing with bioimaging of tiny biological architectures or dynamic physiopathological activities, the prerequisite is rigorous planning of long-wavelength phosphorescence, being aware of the cooperative contribution of long wavelengths and long lifetimes for improving the spatiotemporal resolution, penetration depth, and sensitivity of bioimaging. In this Review, emerging molecular engineering methods of room-temperature phosphorescence are discussed through the lens of photophysical mechanisms. We highlight the roles of phosphorescence with emission from visible to NIR-II windows toward bioapplications. To appreciate such advances, challenges and prospects in rapidly growing studies of room-temperature phosphorescence are described.

Efficient Visible-Light-Activated Ultra-Long Room-Temperature Phosphorescence Triggered by Multi-Esterification

The development of ultra-long room-temperature phosphorescence (UL-RTP) in processable amorphous organic materials is highly desirable for applications in flexible displays, anti-counterfeiting, and bio-imaging. However, achieving efficient UL-RTP from amorphous materials remains a challenging task, especially with activation by visible light and a bright afterglow. Here we report a general and rational molecular-design strategy to enable efficient visible-light-excited UL-RTP by multi-esterification of a rigid large-plane phosphorescence core. Notably, multi-esterification minimizes the aggregation-induced quenching and accomplishes a 'four birds with one stone' possibility in the generation and radiation process of UL-RTP: i) shifting the excitation from ultraviolet light to blue-light through enhancing the transition dipole moment of low-lying singlet-states, ii) facilitating the intersystem crossing process through the incorporation of lone-pair electrons, iii) boosting the decay process of long-lived triplet excitons resulting from a significantly increased transition dipole moment, and iv) reducing the intrinsic triplet nonradiative decay by substitution of high-frequency vibrating hydrogen atoms. All these factors synergistically contribute to the most efficient and stable visible-light-stimulated UL-RTP (lifetime up to 2.01 s and efficiency up to 35.4 % upon excitation at 450 nm) in flexible films using multi-esterified coronene, which allows high-tech applications in single-component time-delayed white light-emitting diodes and information technology based on flashlight-activated afterglow encryption.

Macromolecular Engineered Multifunctional Room-Temperature Phosphorescent Polymers through Reversible Deactivation Radical Polymerization

Despite the intensive research in room-temperature phosphorescent (RTP) polymers, the synthesis of RTP polymers with well-defined macromolecular structures and multiple functions remains a challenge. Herein, reversible deactivation radical polymerization was demonstrated to offer a gradient copolymer (GCP) architecture with controlled heterogeneities, which combines hard segment and flexible segment. The GCPs would self-assemble into a multiphase nanostructure, featuring tunable stretchability, excellent RTP performance, and intrinsic healability without compromising light emission under stretching. The mechanical performance is tunable on demand with elongation at break ranging from 5.0% to 221.7% and Young's modulus ranging from 0.5 to 225.0 MPa.

Biomimetic 3D Color-Changing Hydrogel Actuators Constructed Based on Soft Permeable Photonic Crystals

The integration of photonic crystals and self-shaping actuators is a promising method for constructing powerful biomimetic color-changing actuators. The major barrier is that common photonic crystals generally block the transfer/orientation of monomers/fillers and hence hinder the formation of heterogeneous structures for programmed 3D deformations as well as degrade the deformation capacity and mechanical properties of actuators. Herein, we present the construction of complex and strong 3D color-changing hydrogel actuators by asymmetric photolithography based on soft, permeable photonic crystals. The soft permeable photonic crystals are assembled by hydrogel microspheres with an ultralow volume fraction. During the asymmetric photolithography, the monomers in precursor solutions can thus transfer freely to generate heterogeneous microstructures, spatially patterned internal stresses, and interpenetrating networks for programming the deformation trajectories and initial 3D configurations and enhancing mechanical properties of actuators. Various 3D color-changing hydrogel actuators (e.g., flower and scroll painting) are constructed for applications such as information encryption and display.