Room-temperature Phosphorescence Materials Research Articles

Efficient intersystem crossing and tunable ultralong organic room-temperature phosphorescence via doping polyvinylpyrrolidone with polyaromatic hydrocarbons

Polymer-based pure organic room-temperature phosphorescent materials have tremendous advantages in applications owing to their low cost, vast resources, and easy processability. However, designing polymer-based room-temperature phosphorescent materials with large Stokes shifts as key requirements in biocompatibility and environmental-friendly performance is still challenging. By generating charge transfer states as the gangplank from singlet excited states to triplet states in doped organic molecules, we find a host molecule (pyrrolidone) that affords charge transfer with doped guest molecules, and excellent polymer-based organic room-temperature phosphorescent materials can be easily fabricated when polymerizing the host molecule. By adding polyaromatic hydrocarbon molecules as electron-donor in polyvinylpyrrolidone, efficient intersystem crossing and tunable phosphorescent from green to near-infrared can be achieved, with maximum phosphorescence wavelength and lifetime up to 757 nm and 3850 ms, respectively. These doped polyvinylpyrrolidone materials have good photoactivation properties, recyclability, advanced data encryption, and anti-counterfeiting. This reported design strategy paves the way for the design of polyvinylpyrrolidone-based room-temperature phosphorescent materials.

Narrowband room temperature phosphorescence of closed-loop molecules through the multiple resonance effect

Luminescent materials with narrowband emission show great potential for diverse applications in optoelectronics. Purely organic phosphors with room-temperature phosphorescence (RTP) have made significant success in rationally manipulating quantum efficiency, lifetimes, and colour gamut in the past years, but there is limited attention on the purity of the RTP colours. Herein we report a series of closed-loop molecules with narrowband phosphorescence by multiple resonance effect, which significantly improves the colour purity of RTP. Phosphors show narrowband phosphorescence with full width at half maxima (FWHM) of 30 nm after doping into a rigid benzophenone matrix under ambient conditions, of which the RTP efficiency reaches 51.8%. At 77 K, the FWHM of phosphorescence is only 11 nm. Meanwhile, the colour of narrowband RTP can be tuned from sky blue to green with the modification of methyl groups. Additionally, the potential applications in X-ray imaging and display are demonstrated. This work not only outlines a design principle for developing narrowband RTP materials but also makes a major step forward extending the potential applications of narrowband luminescent materials in optoelectronics.

Urea-formaldehyde resin room temperature phosphorescent material with ultra-long afterglow and adjustable phosphorescence performance

Organic room-temperature phosphorescence materials have attracted extensive attention, but their development is limited by the stability and processibility. Herein, based on the on-line derivatization strategy, we report the urea-formaldehyde room-temperature phosphorescence materials which are constructed by polycondensation of aromatic diamines with urea and formaldehyde. Excitingly, urea-formaldehyde room-temperature phosphorescence materials achieve phosphor lifetime up to 3326 ms. There may be two ways to enhance phosphorescence performance, one is that the polycondensation of aromatic diamine with urea and formaldehyde promotes spin-orbit coupling, and another is that the imidazole derivatives derived from the condensation of aromatic o-diamine with formaldehyde maintains low levels of energy level difference and spin-orbit coupling, thus achieving ultra-long afterglow. Surprisingly, urea-formaldehyde room-temperature phosphorescence materials exhibit tunable phosphorescence emission in electrostatic field. Accordingly, 1,4-phenylenediamine, urea, and formaldehyde are copolymerized and self-assembled into phosphorescence microspheres with different electrostatic potential strengths. By mixing 1 wt% 1,4-phenylenediamine polycondensation microspheres with 1,4-phenylenediamine free microspheres, phosphor lifetime of the composite could be regulated from 27 ms to 123 ms. Moreover, vulcanization process enables precise shaping of urea-formaldehyde room-temperature phosphorescence materials. This work not only demonstrates that urea-formaldehyde room-temperature phosphorescence materials are promising candidates for organic phosphors, but also exhibits the phenomenon of electrostatically regulated phosphorescence.

Room-temperature phosphorescence of defect-engineered silica nanoparticles for high-contrast afterglow bioimaging

Room-temperature phosphorescence (RTP) has tremendous potential in optics and photonics. Unlike fluorescence, RTP has substantial afterglow signals even after the excitation light is removed, which allows for extended acquisition times and higher signal-to-noise ratio under time-gated bioimaging. However, conventional RTP materials, both metal-containing and metal-free organic compounds, typically have limited photostability and inherent toxicity, making them unsuitable for long-term biological applications. Here, we report metal- and organic fluorophore-free silica nanoparticles (SNPs) that facilitate long-lived phosphorescence and exhibit RTP for high-contrast bioimaging. Polycondensation of silicon precursors and silyl biphenyls forms biphenyl-doped SNPs (bSNPs), and thermal decomposition of biphenyl moieties generates optically active defects in the biphenyl-bonded silicate network. The calcined bSNPs (C-bSNPs) have RTP-related biphenyl defects composed of carbon impurities, corresponding to spectroscopic measurements and ab initio calculations. Facile surface functionalization of defect-engineered C-bSNPs with tumor-targeting peptides while maintaining long-lived RTP allows for tissue autofluorescence-free in vivo bioimaging for cancer diagnosis, surpassing the limitations of continuous-wave imaging.

Naphthyl substituted guest induce efficient room temperature phosphorescence by a triplet-triplet energy transfer mechanism

Room-temperature phosphorescent (RTP) materials have attracted more and more attention due to their long luminescence life and large Stokes displacement. Host-guest doping systems are highly regarded for their simplicity of preparation and the absence of complex synthesis processes. Strong RTP emission can be activated by the doping of a guest molecules, in particular by substituting the phenyl group in the host structure with a naphthalene group. In this study, derivatives of benzophenone were constructed as the host molecule, and used 2-Benzoylnaphthalene, a commercially available naphthyl-substituted analogue of benzophenone, as the guest molecule. The phosphorescent lifetime of the doped system can reach 335 ms and the phosphorescent quantum yield can reach 58 %, which is expected to be used in anti-counterfeiting encryption, biological imaging and other fields. This work provides a general and effective host-guest doping strategy for constructing various organic room temperature phosphorescent materials.

Water-Soluble Luminescent Polymers with Room-Temperature Phosphorescence Based on the α-Amino Acids.

Nonconventional luminophores have received increasing attention, owing to their fundamental importance, advantages in outstanding biocompatibility, easy preparation, environmental friendliness, and potential applications in sensing, imaging, and encryption. Purely organic molecules with outstanding fluorescence and room-temperature phosphorescence (RTP) have emerged as a new library of benign afterglow agents. However, the cost, toxicity, high reactivity, and poor stability of materials also limit their practical applications. Therefore, some natural products, synthetic compounds, and biomolecules have entered horizons of people. The as-designed exhibits sky blue and green fluorescence emission and green RTP emission (a lifetime of 343ms and phosphorescence quantum of 15.3%) under air condition. This study presents an organic fluorescence for biological imaging and RTP for anti-counterfeiting and encryption based on amino acids, maleic anhydride and 4-vinylbenzenesulfonic acid sodium salt hydrate. This study provides a strategy for nonconventional luminophores in designing and synthesizing pure organic RTP materials.

Scalable fabrication of red Room-Temperature phosphorescent materials through molecular doping strategy for versatile applications

Room-temperature phosphorescence (RTP) materials renowned for their long emission lifetime have garnered tremendous research interest not only for elucidating their underlying mechanisms but also for exploring their potential applications in anti-counterfeiting, encryption, and bioimaging. Nevertheless, the RTP color of most organic materials has been limited to blue, green, and yellow. In this study, a series of red RTP materials have been successfully fabricated at a large scale through a straightforward molecular doping strategy. Remarkably, the doped materials exhibited red RTP at 622 nm and 678 nm with an ultralong lifetime of 373 ms and an efficiency of 5.21 %, which was among the best performances reported for organic RTP materials. The systematic investigation unveiled that the efficient RTP emanated from the robust interactions between the emitter and matrix molecules as well as the formation of D/A exciplexes. Furthermore, the red RTP materials could be easily manufactured into diverse forms, including fine powders, aqueous inks, and nanoparticles. Their multifunctional applications in fingerprint recognition, encryption, and live bioimaging were demonstrated. With distinctive advantages such as red RTP, ultralong lifetime, scalable production, and cost-effectiveness, these RTP materials pave the way for the extensive utilization of organic RTP materials in various engineering sectors.

Excellent Persistent Near-Infrared Room Temperature Phosphorescence from Highly Efficient Host-Guest Systems.

Organic near-infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal-to-background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy-gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten-folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host-guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs.

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.

Stimulus-responsive room temperature phosphorescent materials based on poly(vinylalcohol) with tunable multicolor afterglow

Stimulus-responsive room temperature phosphorescent materials based on poly(vinylalcohol) with tunable multicolor afterglow

Ultra-long room temperature phosphorescent materials based on tetraphenylethylene derivatives for anti-counterfeiting and encryption applications

Stimuli-responsive room temperature phosphorescent materials have been the subject of considerable research activity in recent years. In this study, the tetraphenylethylene group was selected in combination with arylboronic acid (TIPE-BOH) and used to dope a rigid polyvinyl alcohol (PVA) matrix to generate a film material (TIPE-BOH-PVA) that exhibited an aggregation-induced emission (AIE) effect. The prepared film exhibits excellent room temperature phosphorescence (RTP) performance, with an enhanced emission wavelength and an afterglow time of up to 12 s. The triplet-to-singlet Förster resonance energy transfer (TS-FRET) has been utilized to modify the afterglow color by adding butyl rhodamine B (BRhB) and rhodamine 6G (R6G), employing a water phase without the use of organic solvents. The resultant material exhibits stimulus responsiveness; the RTP properties disappear when the material is exposed to water vapor, but are restored following thermal treatment. The material has potential applications in information encryption and erasure, double anti-counterfeiting ink, and fingerprint acquisition systems. This work offers a new strategy for the design of stimuli-responsive ultra-long RTP materials with far-ranging end applications.

Fully Exploiting Clusterization‐Triggered Room Temperature Phosphorescence of Cellulose by Stepwise Rigidification for Long‐Lived and Excitation Wavelength‐Dependent Afterglows

AbstractAchieving long‐lived room temperature phosphorescence (RTP) in nonconventional luminophores devoid of any conjugated units is fascinating but remains formidably challenging due to their low intersystem crossing efficiency and strong nonradiative decay. Herein, a stepwise rigidification strategy is developed to suppress the nonradiative decay and fully exploit the clusterization‐triggered RTP performance of cellulose. Specifically, the crystallinity is enhanced, and hydrogen bonding is reconstructed by a directed oxidation‐reduction reaction to afford a more rigid environment of cellulose; then, the reconstructed cellulose is further cross‐linked by boric acid to activate double confinement architecture. In return, the phosphorescence lifetime of the target cellulose increases almost one order of magnitude, and the phosphorescence quantum yield increases more than 27 folds. Moreover, the afterglow of the RTP cellulose can be regulated from blue to green by changing excitation wavelength, which is useful for advanced information encryption and anti‐counterfeiting. The stepwise rigidification strategy is also applicable for preparing other nature polysaccharides‐based long‐lived RTP materials, such as chitosan and sodium alginate. Nature polysaccharides are completely biodegradable; thus, this work paves the way for the development of eco‐friendly and practical color‐variable RTP materials.

Finely manipulating room temperature phosphorescence by dynamic lanthanide coordination toward multi-level information security

Room temperature phosphorescence materials have garnered significant attention due to their unique optical properties and promising applications. However, it remains a great challenge to finely manipulate phosphorescent properties to achieve desirable phosphorescent performance on demand. Here, we show a feasible strategy to finely manipulate organic phosphorescent performance by introducing dynamic lanthanide coordination. The organic phosphors of terpyridine phenylboronic acids possessing excellent coordination ability are covalently embedded into a polyvinyl alcohol matrix, leading to ultralong organic room temperature phosphorescence with a lifetime of up to 0.629 s. Notably, such phosphorescent performance, including intensity and lifetime, can be well controlled by varying the lanthanide dopant. Relying on the excellent modulable performance of these lanthanide-manipulated phosphorescence films, multi-level information encryption including attacker-misleading and spatial-time-resolved applications is successfully demonstrated with greatly improved security level. This work opens an avenue for finely manipulating phosphorescent properties to meet versatile uses in optical applications.

Thermally Enhanced Phosphorescent Carbon Nanodots for Monitoring Cold-Chain Logistics.

Room-temperature phosphorescent materials, renowned for their long luminescence lifetimes, have garnered significant attention in the field of optical materials. However, the challenges posed by thermally induced quenching have significantly hindered the advancement of luminescence efficiency and stability. In this study, thermally enhanced phosphorescent carbon nanodots (CND) are developed by incorporating them into fiber matrices. Remarkably, the phosphorescence lifetime of the thermally enhanced CND exhibits a twofold enhancement, increasing from 326 to 753ms, while the phosphorescence intensity experienced a tenfold enhancement, increasing from 25 to 245 as the temperature increased to 373K. Rigid fiber matrices can effectively suppress the non-radiative transition rate of triplet excitons, while high temperatures can desorb oxygen adsorbed on the surface of the CND, disrupting the interaction between the CND and oxygen. Consequently, a thermally enhanced phosphorescence is obtained. In addition, benefiting from the thermally enhanced phosphorescence property of CND, a warning indicator with an anti-counterfeiting function for monitoring cold-chain logistics is demonstrated based on CND.

Achieving Colorful Ultralong-Lifetime Room-Temperature Phosphorescence Based on Benzocarbazole Derivatives through Resonance Energy Transfer.

It is of practical significance to develop polymer-based room-temperature phosphorescence (RTP) materials with ultralong lifetime and multicolor afterglow. Herein, the benzocarbazole derivatives were selected and combined with a poly(vinyl alcohol) (PVA) matrix by a coassembly strategy. Owing to the hydrogen-bonding interactions between benzocarbazole derivatives and the PVA matrix, the nonradiative transition and the quenching of triplet excitons are effectively inhibited. Therefore, the maximum phosphorescence emission lifetime of 2202.17 ms from ABfCz-PVA and the maximum phosphorescence quantum efficiency of 34.97% from ABtCz-PVA were obtained, respectively. In addition, commercially available dye molecules were selected to construct phosphorescent resonance energy transfer (PRET) systems for energy acceptors, enabling full-color afterglow emission in blue, green, yellow, red, and even white. Based on the characteristics of prepared RTP materials, multifunctional applications to flexibility, information encryption, and erasable drawing were deeply explored.

A carbon dot-based time-dependent color-changing room temperature phosphorescent material with facile synthesis.

Carbon dots have attracted widespread attention due to their excellent optical properties and so on and are therefore used in various fields such as anti-counterfeiting. There are many reports on carbon dot-based room-temperature phosphorescent materials, but there are still fewer reports on carbon dot-based room-temperature phosphorescent materials with time-dependent color-changing properties. In this work, a time-dependent color-changing carbon dot-based room-temperature phosphorescent material with the ability to change from green to blue was successfully prepared by a simple one-pot heating method using hydroxyurea as the only raw material. In this process, hydroxyurea is used as both a carbon and nitrogen source, and in the process of material formation, hydroxyurea also partially forms cyanuric acid as a matrix to make the carbon dots uniformly dispersed in it. By blending the ratio of the dual emission centers of the carbon dots themselves, the final effect of time-dependent color-changing is achieved by taking advantage of the intensity changes and color differences of each emission center. The present work provides new ideas for the preparation of time-dependent color-changing carbon dot-based room-temperature phosphorescent materials.

Responsive organic room-temperature phosphorescence materials for spatial-time-resolved anti-counterfeiting

Stimulus-responsive room-temperature phosphorescence (RTP) materials have gained significant attention for their important optoelectronic application prospects. However, the fabrication strategy and underlying mechanism of stimulus-responsive RTP materials remain less explored. Herein, we present a reliable strategy for achieving pH-responsive RTP materials by integrating poly(vinyl alcohol) (PVA) with carboxylic acid or amino group functionalized terpyridine (Tpy) derivatives. The resulting Tpy derivatives-based RTP materials displayed reversible changes in emission color, intensity, and lifetime of both prompt and delayed emission. Notably, the RTP emission undergoes a significant diminish upon exposure to acid due to the protonation of Tpy units. Taking advantage of the decent RTP emission and pH-responsiveness of these RTP films, a spatial-time-resolved anti-counterfeiting application is demonstrated as a proof-of-concept for largely enhancing the security level. This study not only provides new prospects for developing smart RTP materials but also promotes the advancement of optical anti-counterfeiting applications.

High pH Stability and Ultralong‐Lived Room Temperature Phosphorescence Carbon Dots in Aqueous Environment

AbstractLong‐lived room temperature phosphorescence (RTP) materials have many potential applications in areas such as luminescent lighting, biological imaging, and information security owing to their unique optical properties. However, traditional RTP materials are challenged by the fact that their phosphorescence can be easily quenched by dissolved oxygen and solvent‐assisted relaxation, making it difficult for them to emit phosphorescence in aqueous solutions, particularly in extreme pH environments. In this study, a multicolor RTP carbon dot‐based composite material (u‐CDs) is developed with urea and 3‐aminophenylboronic acid as raw materials. This material exhibits ultra‐long phosphorescence emission lifetime and high pH stability by constructing a rigid hydrogen bond network structure in an aqueous environment. The u‐CDs have an optimal emission of 448 nm, a quantum yield of 21.6%, a phosphorescence lifetime of 2.35 s, and an afterglow time of more than 50 s. With such unique properties, u‐CDs have great potential for applications in anti‐counterfeiting, information encryption, and 3D printing.

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.

3-Ethynyltriimidazo[1,2-a:1',2'-c:1″,2″-e][1,3,5]triazine Dual Short- and Long-Lived Emissions with Crystallization-Enhanced Feature: Role of Hydrogen Bonds and π-π Interactions.

Organic room temperature phosphorescent (ORTP) materials with stimuli-responsive, multicomponent emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with an ethynyl group, TT-CCH, is isolated and investigated. The compound possesses crystallization-enhanced emission (CEE) comprising dual fluorescence and dual phosphorescence of both molecular and supramolecular origin with aggregation-induced components highly sensitive to grinding. The mechanisms involved in the emissions have been disclosed thanks to combined structural, spectroscopic and computational investigations. In particular, strong CH⋯N hydrogen bonds are deemed responsible, for the first time in the TT family, together with frequently observed π⋯π stacking interactions, for the aggregated fluorescence and phosphorescence.