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

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.

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.

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.

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.