Microwave-Responsive Flexible Room-Temperature Phosphorescence Materials Based on Poly(vinylidene fluoride) Polymer

Bright and Ultralong Organic Phosphorescence via Sulfonic Acid Functionalization for High-Contrast Real-Time Light-Writing Display

It is challenging to achieve room-temperature phosphorescence (RTP) in pure organics with both high efficiency and long lifetime. While much effort has been placed on discovering efficient phosphor skeletons, the importance of phosphor functionalization in enhancing the RTP performance has not received adequate attention. Herein, we demonstrate that functionalization of phosphors with sulfonic acid can ensure both bright and ultralong RTP, outperforming other substituents. The unique trigonal pyramidal structure of sulfonic acid group allows for more effective (n, π*) transitions to enhance intersystem crossing efficiency. Its highly polarized S-O bonds render strengthened hydrogen bonding interactions and a narrower confinement within the poly(vinyl alcohol) (PVA) matrix, to minimize the nonradiative dissipation. Furthermore, its excellent water solubility contributes to the outstanding transparency of PVA film (over 97%), yielding high-quality optical imaging with a high contrast ratio of 48.0 and a low blurriness of 0.24. Moreover, full-color phosphorescence with exceptional performance (ΦP, max = 37.2%, τP, max = 2.09 s) is achieved from different sulfonic acids, validating the effectiveness and universality of this strategy. By leveraging these advantages, real-time light-writing displays with sharp imaging, high sensitivity, and exceptional rewritability are demonstrated. This work not only contributes to the substituent engineering in the molecular design of phosphors but also opens new opportunities for RTP materials in the next-generation intelligent optoelectronic materials.

Progress in Polymer-Based Pure Organic Room Temperature Phosphorescent Materials

To date, organic room-temperature phosphorescent (RTP) materials have received much attention due to their long lifetime and large Stokes shift, and have been widely used in anti-counterfeiting encryption, bio-imaging, and sensing and monitoring. Researchers have used a variety of approaches to construct ultra-long, efficient RTP materials, with the confinement of chromophores in polymers being widely favored to improve RTP performance. The polymer entanglement structure restricts the vibration and rotation of the chromophore, which successfully suppresses the non-radiative excitation of the triplet exciton and protects the triplet exciton from the external environment (oxygen, water), which is conducive to the realization of the ultra-long and bright RTP emission, and makes the RTP material easy to process, which broadens the application range of the RTP material. This review summarizes recent advances in the study of polymeric RTP materials, the underlying mechanisms and design strategies, discusses the RTP properties of chromophores in amorphous and crystalline polymers respectively, as well as the latest applications of RTP polymers, and finally discusses the challenges for the development of RTP polymers and the outlook for the future.

Multivariate Distribution Structured Anisotropic Inorganic Polymer Composite Electrolyte for Long-Cycle and High-Energy All-Solid-State Lithium Metal Batteries

Solid polymer electrolytes are promising candidates for solid-state Li metal batteries owing to their favorable rheological properties and interfacial compatibility with cathodes and Li anodes. However, their limited ionic conductivity and low modulus lead to inferior electrochemical performance and dendrite growth. Herein, we developed a composite solid-state electrolyte comprising vermiculite sheets and a poly(vinylidene fluoride) (PVDF) matrix with multivariate distribution and an anisotropic structure. Within this assembly, some vermiculite sheets were suspended in the PVDF matrix to facilitate Li salt dissociation and Li+ transport, while others were tiled on the electrolyte surface, generating a dense, high-modulus Li2SiO3-rich solid electrolyte interphase via in situ electrochemical reduction, which further improved interfacial kinetics and suppressed dendrite growth. As a result, a high conductivity of 1.38 mS cm-1 was achieved at room temperature, and the Li||Li cells displayed robust stability over 3000 h. The LiNi0.6Co0.2Mn0.2O2||Li full cells delivered a specific capacity of 172 mAh g-1 at 0.2 C and 86% capacity retention after 500 cycles at 0.5 C. Additionally, practical cycle performance at a high loading (4.4 mAh cm-2) was achieved in pouch cells. Overall, multivariate distribution and anisotropic structuring offers a novel perspective for the preparation of high-performance solid-state electrolytes.

Achieving High-Temperature Resistant Afterglow by Modulating Dual-Mode Emission of Organic Emitters through Defects Engineering

Dual-mode afterglow, integrating ultralong phosphorescence and delayed fluorescence, offers promising opportunities for developing high-temperature resistant luminescent materials. However, there is an obvious gap between the emission lifetime of delayed fluorescence and phosphorescence. In this work, a dehydration-induced doping strategy is proposed to achieve high-temperature resistant afterglow by balancing phosphorescence and delayed fluorescence lifetime. The critical role of structural defects is demonstrated in the afterglow mechanism, where energy transferred between the defect states and guest molecules determines the lifetime of afterglow. In addition, efficient reverse intersystem crossing processes are achieved between the defect states and singlet states, facilitating the long-lived fluorescence. These synergistic effects result in the prolonged lifetime of delayed fluorescence to approach that of phosphorescence, which produced high-temperature resistant afterglow materials, even up to 125 °C. These results provide a clue for modulating the emission dynamics of afterglow materials for applications in information security, biomedical diagnosis, and chemical sensing.

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.

Hour-Long Afterglow in Flexible Polymeric Materials through the Introduction of Electron Donor/Acceptor Exciplexes

The development of organic afterglow materials has garnered significant attention due to their diverse applications in smart devices, optoelectronics, and bioimaging. However, polymeric afterglow materials often suffer from short emission lifetimes, typically ranging from milliseconds to seconds, posing a significant challenge for achieving hour-long afterglow (HLA) polymers. This study presents the successful fabrication of transparent HLA polymers by introducing electron donor/acceptor exciplexes. Employing aromatic polyesters as the polymer electron acceptor and charge reservoirs, the resulting HLA polymers exhibited a remarkable green afterglow that persisted for 12 hours under ambient conditions, representing the longest duration achieved for polymeric afterglow materials to date. Intriguingly, these HLA polymers could be activated solely by sunlight, maintaining a green afterglow for over 6 hours at room temperature in air, which outperformed all previously reported afterglow polymers. The doped polymers exhibited superior flexibility and transparency, making them ideal candidates for flexible display applications. Furthermore, successfully spinning these doped polymers into fibers while retaining their HLA properties opens up exciting possibilities for their use in wearable smart devices.

Tenon-and-Mortise Structure-Inspired MOF/PVDF Composites with Enhanced Piezocatalytic Performance via Dipole-Engineering Strategy

Fabricating poly(vinylidene fluoride) (PVDF) and its composite ferroelectrics are essential for the development of next-generation lightweight, portable, wearable, and implantable intelligent devices. However, integrating and maximizing spontaneous polarization and interfacial electromechanical conversion efficiency remain major challenges in the contemporary PVDF-based composites field. Herein, inspired by the tenon-and-mortise structure associated with ancient Chinese architecture, an amino-anchored metal-organic framework (MOF)/PVDF piezoelectric composite using a dipole-engineering strategy to deliver enhanced piezocatalytic performance is constructed. Homogeneous and long-range ordered hydrogen-bond networks have been formed with the PVDF matrix after introducing periodically arranged amino anchors into the NH2-HU MOF. The NH2-HU10wt%/PVDF composite exhibits a 40% greater β-phase content and a remnant polarization value more than 550% higher than that of the bare PVDF fibers. These amino anchors synergistically enhance both the local electric field and collaborative dipole alignment resulting in a piezocatalytic bactericidal performance of 97.4% when irradiated under clinical ultrasound conditions. Moreover, the enhanced polarizability within the MOF/PVDF composite simultaneously improves its responsiveness to X-rays via its periodic amino anchoring networks, thereby doubling CT imaging efficacy for implants at lower voltages. Integrating piezoelectric MOFs and polymer matrices through molecular design presents a viable approach for optimizing ferroelectric properties and expanding piezoelectric-composite applications.

Precise Control of Efficient Phosphorescence in Host-Guest Doping Systems via Dynamic Metal-Ligand Coordination

Organic room-temperature phosphorescent (RTP) materials have wide-ranging applications in anticounterfeiting, biodiagnostics, and optoelectronic devices due to their unique properties. However, it remains a challenge to give organic RTP materials dynamic tunability to satisfy the demands of various advanced applications. Herein, we propose an effective strategy to precisely modulate phosphorescent performance by incorporating dynamic metal-ligand coordination within a host-guest doped system. The organic phosphors of bipyridine derivatives with excellent coordination properties were doped into a small-molecule host matrix. Halide salts were doped in the host-guest system effectively tuning the phosphorescent performance, including efficiency and lifetime, through dynamic metal-ligand coordination. Notably, leveraging the reversible feature of the metal-ligand coordination, multilevel information encryption, including thermal development and time-resolved applications with high reversibility, is successfully demonstrated. The work demonstrates that dynamic metal-ligand coordination could serve as an effective method for developing efficient RTP materials with precisely tunable properties.

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

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

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.

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.

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.