Ultralong Phosphorescence Research Articles

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.

In situ Cyclization of Aromatic Thioethers in Emissive Materials to Generate Phosphorescent Dibenzothiophenes

AbstractIn this contribution, we explored the photocyclization of thioethers to highly substituted dibenzothiophenes (DBT) using solely UV‐light without any need for additives. This cost‐effective, robust and environmentally friendly approach yielded phosphorescent compounds, which were characterized by X‐ray crystallography and state‐of‐the‐art photophysical methods. The resulting DBTs feature ultralong photoluminescence lifetimes and quantum yields close to unity in frozen glassy matrices. The reaction mechanism was elucidated in detail through a combination of quantum chemical calculations and experimental results, providing evidence that triplet states are involved in the cyclization process. Additionally, the photoreaction can also be induced within materials. For this purpose, the precursors were integrated into polymer films or polymer resins suitable for 3D printing. Irradiation of these polymeric objects allows motifs with ultralong phosphorescence to be irreversibly inscribed through the proceeding photocyclization. The in situ photogeneration of DBTs from aromatic thioethers overcomes the observed incompatibilities regarding solubility in polymer resins for 3D printing.

In Situ Reversible and Robust Mechano-Responsive Ultralong Phosphorescence of Polyurethane Elastomer.

Though mechano-responsive luminescent materials obtained much attention, most of their responses are non-reversible, let alone in situ reversible. Here, the study presents a new strategy to push through this limitation for their applications, which relies on the reversible mechano-responsive (MR) hydrogen bonding interactions and polymer chain orientation among a doped polyurethane (PU) elastomer. The radiative and nonradiative transitions inside these phosphorescent triphenylene-based aromatic secondary amines (TpNP and TpNPO) doped in the PU matrix can be accordingly modulated by these MR variations, including the PU chains orientation and the interactions between emitters and PU, respectively. Surprisingly, the intensities, quantum yields, and even lifetimes of their ultralong phosphorescence correlate well with the stress of PU, showing triple mechano-enhancement with a small threshold value of 7.9MPa. Importantly, these in situ and rapidly reversible MR phosphorescences possess excellent repeatability, which is still displayed even after >500 cycles of loading/unloading. Based on such a robust and highly sensitive MR afterglow, these PU materials have been demonstrated applications with no interruption of background in several fields, including micro-crack detection, material damage prediction, limb movement monitoring, and information encryption. This work provides new insights for developing innovative ultralong phosphorescence materials with improved luminescence and reversible mechano-responsive behavior.

Site Effect of Electron Acceptors on Ultralong Organic Room-Temperature Phosphorescence.

Herein, we successfully observe the site effect of electron acceptors on ultralong organic room-temperature phosphorescence (UORTP) in the case of 7H-benzo[c]carbazole (BCz) derivatives: cyanophenyl on the nitrogen site can promote intersystem crossing (ISC) efficiency and enhance phosphorescence intensity by facilitating n-π* transitions but make a slight change to the phosphorescence wavelength; cyanophenyl on the naphthalene site can cause a remarkable red shift of phosphorescence wavelength by reducing the T1 energy level of BCz derivatives and also enhance phosphorescence intensity by promoting ISC but weaken phosphorescence intensity by lowering the molecular symmetry. Three BCz derivatives (1-BCzPhCN, 2-BCzPhCN, and 3-BCzPhCN) with the electron acceptor cyanophenyl at different sites (nitrogen site and naphthalene site) were synthesized through a combination of the nucleophilic substitution reaction and the Suzuki coupling reaction. The phosphorescence properties of 1-BCzPhCN, 2-BCzPhCN, and 3-BCzPhCN in toluene solution, in a copolymerized MMA film, and in a PVA film were measured and analyzed. 1-BCzPhCN emits intrinsic green ultralong phosphorescence at ∼500, ∼536, and ∼580 nm, while 2-BCzPhCN and 3-BCzPhCN give out intrinsic yellow ultralong phosphorescence with a red shift of 27 and 40 nm, showing that cyanophenyl on the naphthalene site leads to a remarkable red shift of the intrinsic phosphorescence wavelength, but cyanophenyl on the nitrogen site makes a slight difference to the intrinsic phosphorescence wavelength. Under the same condition, the phosphorescence intensity is usually ranked as 1-BCzPhCN/3-BCzPhCN > 2-BCzPhCN, demonstrating that cyanophenyl on the nitrogen site promotes ISC and enhances phosphorescence intensity, but cyanophenyl on the naphthalene site reduces molecular symmetry and accelerates nonradiative dissipation. Time-dependent density functional theory calculations verify that cyanophenyl on the naphthalene site shifts the phosphorescence wavelength by reducing the T1 energy level, and cyanophenyl on the nitrogen site facilitates n-π* transitions to strengthen the phosphorescence intensity. Moreover, three BCz derivatives were doped into DMAP and BBP, separately. The BCz derivatives exhibited different phosphorescence colors and shifts due to interactions with the host materials. We believe this work will give an insight into the structure-property relationship of organic phosphorescence molecules and pave a way for design of colorful UORTP materials.

Effect of ionic bonding on luminescence properties of histidine maleic anhydride derivatives

Polymeric materials exhibiting room-temperature phosphorescent (RTP) have attracted wide attention for their easy synthesis, low toxicity, and applications in various fields such as data encryption, cell imaging, information security and other fields. Nevertheless, the conventional ways of preparing such materials are mainly focused on doping, which may suffer from phase separation, poor compatibility, and lack of effective methods to promote intersystem crossing and suppress the nonradiative deactivation rates. Herein, a series of polymers with fluorescence and phosphorescence dual emission were prepared by simple radical solution copolymerization. Through rigid ion-bonded cross-linked networks and cross-linked hydrogen-bonded networks between the polymer chains, the non-radiative jumps and achieve ultra-long phosphorescence lifetimes were able to suppress. By suppressing non-radiative transitions through rigid ion-bonded cross-linked networks and intermolecular hydrogen-bonding networks between polymer chains, ultra-long phosphorescence is achieved. Impressively, a LRTP lifetime of up to 815.38 ms in polymers under ambientconditions is set up. Moreover, in this study, phosphorescence emission can be easily tuned by balancing ion radius and charge states. These results outline the construction of polymeric materials, endowing traditional polymers with new characteristics and promising potential applications.

In situ Cyclization of Aromatic Thioethers in Emissive Materials to Generate Phosphorescent Dibenzothiophenes.

In this contribution, we explored the photocyclization of thioethers to highly substituted dibenzothiophenes (DBT) using solely UV-light without any need for additives. This cost-effective, robust and environmentally friendly approach yielded phosphorescent compounds, which were characterized through X-ray crystallography and state-of-the-art photophysical methods. The resulting DBTs feature ultralong photoluminescence lifetimes and quantum yields close to unity in frozen glassy matrices. The reaction mechanism was investigated in detail through a combination of quantum chemical calculations and experimental results, providing evidence that triplet states are involved in the cyclization process. Additionally, the photoreaction can also be induced within materials. For this purpose, the precursors can be integrated into polymer films or polymer resins suitable for 3D printing. Irradiation of these polymeric objects allows motifs with ultralong phosphorescence to be irreversibly inscribed through the proceeding photocyclization. The in situ photogeneration of DBTs from aromatic thioethers overcomes the observed incompatibilities regarding solubility in polymer resins for 3D printing.

Supramolecular Assembly of Hydrogen-Bonded Organic Frameworks with Carbon Dots: Realizing Ultralong Aqueous Room-Temperature Phosphorescence for Anticounterfeiting.

Room-temperature phosphorescent carbon dots (RTP-CDs) have received increasing attention due to their excellent optical properties and potential applications. Nevertheless, the realization of RTP-CDs in aqueous solutions remains a considerable challenge due to the water-molecule- and oxygen-induced deactivation of the triplet excitons, which leads to phosphorescence quenching. In this study, ultralong phosphorescence in water was achieved by in situ self-assembly of CDs encapsulated in a rigid hydrogen-bonded organic framework (HOF). The phosphorescence lifetime reaches an impressive 956.96 ms and exhibits long-lasting optical and structural stability in water for more than 90 days. The composite material not only has ultralong luminescence life and excellent luminescence stability but also has two-color phosphorescence emission, as well as excellent antiphotobleaching and phosphorescence stability in aqueous solution, which can solve the current problem that RTP is easily burst out by water and moisture. In addition, this study introduced a fluorescent dye based on the triplet-singlet Förster resonance energy transfer system (TS-FRET) to fine-tune the afterglow properties. This work will inspire the design of RTP systems with dual phosphor light sources and provide new strategies for the development of smart RTP materials in water.

Enabling efficient and ultralong room-temperature phosphorescence from organic luminogens by locking the molecular conformation in polymer matrix

Tackling the challenge of developing ultralong organic phosphorescence (UOP) materials with a high phosphorescence quantum yield (Φphos.) and an ultralong phosphorescence lifetime (τphos.) under ambient conditions is urgently needed. Herein, typical organic luminogens with simple chemical structures, namely, triphenylamine (TPA), 9-phenylcarbazole (PCz), and indolo[3,2,1-jk]carbazole (ICz), are doped into a melamine–formaldehyde (MF) polymer matrix with a compact three-dimensional covalent network to prepare UOP materials, respectively. Both experiments and theoretical calculations suggest that restricting intramolecular motions to suppress the nonradiative decay of triplet excitons plays a critical role in achieving ultralong room-temperature phosphorescence from organic molecules in polymer matrices. The luminophore ICz with a planar and rigid chemical structure, constructed by locking the molecular conformation of TPA via carbon–carbon single bonds, exhibits a bright organic afterglow with a Φphos. up to 38.31 % and a τphos. up to 2.73 s in the MF polymer under ambient conditions, representing one of the most excellent polymer-based organic afterglow materials in comprehensive UOP performance. The gradual enhancement in UOP of the resulting luminescent materials has led to their successful use in multi-level anti-counterfeiting. This work provides an effective strategy for developing organic afterglow materials with both high Φphos. and τphos. values.

Polymer-Based Room-Temperature Phosphorescence Materials Exhibiting Emission Lifetimes up to 4.6 s under Ambient Conditions.

The long-emission-lifetime nature of room-temperature phosphorescence (RTP) materials lays the foundation of their applications in diverse areas. Despite the advantage of mechanical property, processability and solvent dispersity, the emission lifetimes of polymer-based room-temperature phosphorescence materials remain not particularly long because of the labile nature of organic triplet excited states under ambient conditions. Specifically, ambient phosphorescence lifetime (τP) longer than 2 s and even 4 s have rarely been reported in polymer systems. Here, luminescent compounds with small phosphorescence rate on the order of approximately 10-1 s-1 are designed, ethylene-vinyl alcohol copolymer (EVOH) as polymer matrix and antioxidant 1010 to protect organic triplets are employed, and ultralong phosphorescence lifetime up to 4.6 s under ambient conditions by short-term and low-power excitation are achieved. The resultant materials exhibit high afterglow brightness, long afterglow duration, excellent processability into large area thin films, high transparency and thermal stability, which display promising anticounterfeiting and data encryption functions.

Ultralong room temperature phosphorescence and broad color-tunability persistent luminescence via new strategy

Pure organic materials with ultralong room-temperature phosphorescence (RTP) and persistent luminescence in broad color gamut exhibit tremendous potential and broad application prospects due to their unique optical properties. This article proposes a simple strategy, polyatomic synergistic effect, to endow persistent luminescent materials with ultralong lifetime and broad color-tunability through polyatomic synergistic effect and non-traditional phosphorescence resonance energy transfer (PRET). By leveraging the polyatomic synergistic effect to enhance the intersystem crossing (ISC) in bibenzimidazole (BBI) derivatives and suppress the non-radiative transition process, ultralong persistent room-temperature phosphorescence has been successfully achieved after incorporating BBI-Cl-M into poly(methyl methacrylate) (PMMA) to form a rigid matrix(BBI-Cl-M@PMMA). Specifically, the ester functionalized bibenzimidazole with modified chlorine on molecular skeleton (BBI-Cl-M) demonstrates a remarkable phosphorescent lifetime (τp) of up to 256.4 ms. In addition, the behaviors and mechanism of RTP via polyatomic synergistic effect have been further understood by theoretical calculation and single crystal analysis. Subsequently, utilizing BBI-Cl-M as the energy donor and Rhodamine B (RB) as the energy acceptor, persistent and multicolor organic afterglow covering from green to red has been realized successfully by simply regulating the doping composition and concentration of PRET systems. These RTP materials have also been applied in underwater afterglow emission and multilevel anti-counterfeiting technology successfully.

Entropy-Dominated Triplet Exciton Emission in Carbon Dots.

Phosphorescence in carbon dots (CDs) from triplet exciton radiative recombination at room temperature has achieved significant advancement. Confinement and nanoconfinement, serving as valuable techniques, are commonly utilized to brighten triplet exciton in CDs, thereby enhancing their phosphorescence. However, a comprehensive and universally applicable physical description of confinement-enhanced phosphorescence is still lacking, despite efforts to understand its underlying nature. In this study, the dominance of entropy is revealed in triplet exciton emission from CDs through the establishment of a microscopic vibration state model. CDs with varying entropy levels are studied, indicatingthat in a low entropy system, the multi-energy triplet exciton emission in CDs exhibits enhanced brightness, accompanied by a corresponding increase in their lifetimes. The product of lifetime and intensity in CDs serves as a descriptor for their phosphorescence properties. Moreover, an entropy-dependent information variation system based on the CDs is demonstrated. Specifically, in a low-entropy system, information is retained, whereas the corresponding information is erased in a high-entropy system. This work elucidates the underlying physical nature of confinement-enhanced triplet exciton emission, offering a deeper understanding of achieving ultralong phosphorescence in the future.

A Facile One-Step Self-Assembly Strategy for Novel Carbon Dots Supramolecular Crystals with Ultralong Phosphorescence Controlled by NH4.

A new methodological design is proposed for carbon dots (CDs)-based crystallization-induced phosphorescence (CIP) materials via one-step self-assembled packaging controlled by NH4 +. O-phenylenediamine (o-PD) as a nitrogen/carbon source and the ammonium salts as oxidants are used to obtain CDs supramolecular crystals with a well-defined staircase-like morphology, pink fluorescence and ultralong green room-temperature phosphorescence (RTP) (733.56ms) that is the first highest value for CDs-based CIP materials using pure nitrogen/carbon source by one-step packaging. Wherein, NH4 + and o-PD-derived oxidative polymers are prerequisites for self-assembled crystallization so as to receive the ultralong RTP. Density functional theory calculation indicates that NH4 + tends to anchor to the dimer on the surface state of CDs and guides CDs to cross-arrange in an X-type stacking mode, leading to the spatially separated frontier orbitals and the through-space charge transfer (TSCT) excited state in turn. Such a self-assembled mode contributes to both the small singlet-triplet energy gap (ΔEST) and the fast inter-system crossing (ISC) process that is directly related to ultralong RTP. This work not only proposes a new strategy to prepare CDs-based CIP materials in one step but also reveals the potential for the self-assembled behavior controlled by NH4 +.

Construction of Binary Matrix for Efficient Room Temperature Phosphorescence Emission

AbstractDespite the extensive research on room temperature phosphorescent (RTP) materials, it remains a great challenge to further improve the photophysical properties of RTP materials. In this study, the RTP emission of guest molecule is significantly enhanced by constructing binary matrices containing cyanuric acid (CA) and amino‐containing compounds. Systematic studies show that the strong interaction between the two components of binary matrix induced variations in the guest molecular configuration and excited state electron distribution, thus facilitating the production of more triplet excitons. Furthermore, the binary matrix also exhibits stronger domain‐limiting effect compared to the CA mono‐matrix, effectively inhibits the energy loss of triplet excitons due to quenching and non‐radiative transitions. The prepared binary matrix RTP materials present ultralong phosphorescence lifetime and high phosphorescence quantum yield (up to 3.21 s and 7.31%, respectively), and even achieve bright RTP emission in a variety of organic solvents and aqueous media. Moreover, the RTP emission intensity of the best binary matrix composite can reach more than 28 times that of the CA mono‐matrix composite, and the RTP lifetime can be extended by 1.51 s.

Zero-dimensional halide hybrid bulk glass exhibiting reversible photochromic ultralong phosphorescence

Dynamically responsive materials, capable of reversible changes in color appearance and/or photoemission upon external stimuli, have attracted substantial attention across various fields. This study presents an effective approach wherein switchable modulation of photochromism and ultralong phosphorescence can be achieved simultaneously in a zero-dimensional organic-inorganic halide hybrid glass doped with 4,4´-bipyridine. The facile fabrication of large-scale glasses is accomplished through a combined grinding-melting-quenching process. The persistent luminescence can be regulated through the photochromic switch induced by photo-generated radicals. Furthermore, the incorporation of the aggregation-induced chirality effect generates intriguing circularly polarized luminescence, with an optical dissymmetry factor (glum) reaching the order of 10–2. Exploiting the dynamic ultralong phosphorescence, this work further achieves promising applications, such as three-dimensional optical storage, rewritable photo-patterning, and multi-mode anti-counterfeiting with ease. Therefore, this study introduces a smart hybrid glass platform as a new photo-responsive switchable system, offering versatility for a wide array of photonic applications.

Nylons with Highly-Bright and Ultralong Organic Room-Temperature Phosphorescence

Endowing the widely-used synthetic polymer nylon with high-performance organic room-temperature phosphorescence would produce advanced materials with a great potential for applications in daily life and industry. One key to achieving this goal is to find a suitable organic luminophore that can access the triplet excited state with the aid of the nylon matrix by controlling the matrix-luminophore interaction. Herein we report highly-efficient room-temperature phosphorescence nylons by doping cyano-substituted benzimidazole derivatives into the nylon 6 matrix. These homogeneously doped materials show ultralong phosphorescence lifetimes of up to 1.5 s and high phosphorescence quantum efficiency of up to 48.3% at the same time. The synergistic effect of the homogeneous dopant distribution via hydrogen bonding interaction, the rigid environment of the matrix polymer, and the potential energy transfer between doped luminophores and nylon is important for achieving the high-performance room-temperature phosphorescence, as supported by combined experimental and theoretical results with control compounds and various polymeric matrices. One-dimensional optical fibers are prepared from these doped room-temperature phosphorescence nylons that can transport both blue fluorescent and green afterglow photonic signals across the millimeter distance without significant optical attenuation. The potential applications of these phosphorescent materials in dual information encryption and rewritable recording are illustrated.

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.

Visualizing Motion Trail via Phosphorescence Carbon Nanodots-Based Delay Display Array.

A scene that contains both old and instant events with a clear motion trail is visually intriguing and dynamic, which can convey a sense of change, transition, or evolution. Developing an eco-friendly delay display system offers a powerful tool for fusing old and instant events, which can be used for visualizing motion trails. Herein, we brighten triplet excitons of carbon nanodots (CNDs) and increase their emission yield by a multidimensional confinement strategy, and the CND-based delay display array is demonstrated. The intense confinement effects via multidimensional confinement strategy suppress nonradiative transitions, and 240% enhancement in the phosphorescence efficiency and 260% enhancement in the lifetime of the CNDs are thus realized. Considering their distinctive phosphorescence performances, a delay display array containing a 4 × 4 CND-based delay lighting device is demonstrated, which can provide ultralong phosphorescence over 7 s, and the motion that occurred in different timelines is recorded clearly. This finding will motivate the investigation of phosphorescent CNDs in motion trail recognition.

A co-doping strategy to fabricate ultralong organic room temperature phosphorescence (ORTP) materials: Designing, preparation and advanced applications

Isophthalic acid (IPA) is a star phosphorescence molecule, which is a commercially available raw material with simple chemical structure, but is of good phosphorescence performance. However, the great research vacancy is still maintained because of its limited applications. Absolutely, polymer-matrix strategy is a common method to produce phosphorescence amorphous material by dispersing IPA into matrix such as polyvinyl alcohol (PVA). But how to further optimize the phosphorescence property of the resulted doping material (PVA-IPA)? Up to now, this question is new and very little attention has been paid. In this work, a co-doping strategy was explored, that is, charging the second dopant of ClCH2COOH into PVA-IPA was verified as a promising method to further enhance the phosphorescence property of PVA-IPA, leading to the co-doping material PVA-IPA-ClCH2COOH with ultralong phosphorescence lifetime as 500 ms and high phosphorescence quantum yield (ΦP) as 23.7%. Depending on these promising phosphorescence behaviors, PVA-IPA-ClCH2COOH was successfully applied in the fields of information anti-counterfeiting and artificial light harvest.

Dual-channel mechano-phosphorescence: a combined locking effect with twisted molecular structures and robust interactions

Organic mechanoluminescence materials, featuring dual emission and ultralong phosphorescence characteristics, exhibit significant potential for applications in real-time stress sensing, pressure-sensitive lighting, advanced security marking techniques, and material breakage monitoring. However, due to immature molecular design strategies and unclear luminescence mechanisms, these materials remain rarely reported. In this study, we propose a valuable molecular design strategy to achieve dual-channel mechano-phosphorescence. By introducing the arylphosphine oxide group into a highly twisted molecular framework, enhanced intra- and intermolecular interactions could be achieved within rigid structures, leading to dual-channel mechanoluminescence with greatly promoted ultralong phosphorescence. Further investigations reveal the substantial boosting effect of intra- and intermolecular interactions on mechanoluminescence and ultralong phosphorescence properties by locking the highly twisted molecular skeleton. This work provides a concise and guiding route to develop novel smart responsive luminescence materials for widespread applications in material science.

Host-guest doped room/high-temperature phosphorescence of diarylfuro[3,2-b]pyridine derivatives

Due to the high temperature that can easily lead to non-radiative transitions of triplet excitons, obtaining high-temperature phosphorescence (HTP) materials is challenging. Herein, using diarylfuro[3,2-b]pyridines as the guest molecules and polyacrylic acid (PAA) as the host molecule, the two-component doped materials exhibit green room-temperature phosphorescence (RTP) with afterglow times of 2–8 s, delayed lifetimes of 256–939 ms, and phosphorescence quantum efficiencies of 140.3–21.2 %, and green HTP emissions with 2 s afterglow and 208 ms delayed lifetime at 373 K. The HTP activity of the doped system originates from the rigid environment provided by PAA, planar and rigid molecular structures of diarylfuro[3,2-b]pyridines, and strong interactions between PAA and diarylfuro[3,2-b]pyridines. Furthermore, using organic small molecules as the reference host molecules, compared to benzophenone, 5-methylphthalic anhydride, and butane-1,2,3,4-tetracarboxylic acid with chemical structures similar to PAA result in better RTP/HTP properties, revealing that strong interactions between host and guest molecules play a very important role in ultralong phosphorescence emissions of these host–guest doped materials. Moreover, these doped materials based on diarylfuro[3,2-b]pyridines can be developed as advanced anti-counterfeiting and encryption materials. This result provides valuable reference for developing excellent RTP/HTP materials based on N,O-containing fused-ring compounds.