Long-lived Room-temperature Phosphorescence Research Articles

The El-Sayed’s rule analogy enables long-lived room temperature phosphorescence in twisted biphenyls

The El-Sayed’s rule analogy enables long-lived room temperature phosphorescence in twisted biphenyls

One-Pot Three Carbon Dots with Various Lifetimes Rooted in Different Decarboxylation Degrees for Matrix-Free, Anti-Oxygen, and Time-Resolved Information Encryption and Cellular Imaging.

Activating long-lived room temperature phosphorescence (RTP) in the aqueous environment and thus realizing matrix-free, anti-oxygen, and time-resolved information encryption and cellular imaging remain a great challenge. Here, we fabricated three types of carbon dots (C-dots), i.e., fluorescent C-dots (F-C-dots) and two types of phosphorescent C-dots denoted as Pw-C-dots and Py-C-dots by a one-pot strategy. Their formation was attributed to the difference in the decarboxylation degree at high temperatures using trimesic acid (TMA) as a sole precursor. Unexpectedly, the yield reached as high as ∼92%, and the proportions were ∼27% for F-C-dots, ∼17% for Pw-C-dots, and ∼56% for Py-C-dots. These nanomaterials could help implement carbon peaking and carbon neutrality. Both green RTP of the two C-dots resulted from the small energy gap (ΔEST). These two RTP C-dots had a long lifetime of over 270 ms with a relatively high quantum yield (4.5 and 6.2%). They exhibited excellent photostability and anti-photobleaching performances. The dry and wet powders of the RTP C-dots were applied to high-level information encryption. The lifelike patterns were greatly different from those of the original ones and could last for several seconds to the naked eye, demonstrating that the RTP C-dots could be potentially employed as anti-oxygen and time-resolved contrast reagents. Most significantly, the cellular imaging experiments showed that the biofriendly PVP-coated Py-C-dots could localize at lysosomes and sustain hundreds of milliseconds. This approach not only pioneers a time-resolved lysosome localization model but also opens up a promising door for anti-oxygen and time-resolved RTP cytoimaging.

Ultralong Room-Temperature Phosphorescence of Boron Carbon Oxynitride Nanodots Encapsulated in Pyrophosphate in Dry and Wet States for Fingerprint Detection and Information Protection

Room-temperature phosphorescence (RTP) materials have attracted wide interest due to their long lifetime and free from background autofluorescence. Nevertheless, simultaneous activation of stable long-lived RTP emission in both solid and aqueous phases remains a tremendous challenge. Herein, a molten salt method to synthesize boron carbon oxynitride nanodot-based RTP composites (BCNO nanodots@pyrophosphate) was carried out by employing pyrophosphate as the inert shell for BCNO nanodots. The BCNO nanodots@pyrophosphate1 with the average size of 3.69 nm show bright-green RTP because the introduction of phosphorus is beneficial to the intersystem crossing process and increases the RTP emission. What is more, whether in solid or aqueous dispersion, BCNO nanodots@pyrophosphate1 retains good phosphorescent properties with a high phosphorescence quantum yield (29.5% and 18.6%) and a long lifetime (1.39 and 1.29 s), which lasts over 15 s to the naked eye. This is the first report on BCNO nanodots with RTP in aqueous solution. The unique RTP characteristics allow BCNO nanodots@pyrophosphate as a hopeful indicator for detection of latent fingerprints with high contrast and multilevel information protection.

Host-guest doping induced excited state energy transfer for efficient room temperature phosphorescence emission

The 1,8-naphthalimide derivatives as the guest and the benzophenone (BP) analogues bis(4-chlorophenyl)methanone (BP2C) and bis(4-fluorophenyl)methanone (BP2F) benzophenone derivatives as the host, we constructed a series of novel doping systems with fluorescence and room temperature phosphorescence (RTP) dual emission. The steady-state spectroscopy, ultrafast spectroscopy techniques, and theoretical calculations indicate that Förster resonance energy transfer (FRET) between singlet states between host and guest components enables energy redistribution in doped systems. At the same time, the Dexter energy transfer (DET) between the triplet states realizes the obvious absorption of the excited triplet state of the guest, resulting in the long-lived room temperature phosphorescence of the doped system. Doping materials have unlimited potential for information storage and anti-counterfeiting by exploiting the properties of photo activation.

Full-color Persistent Room-temperature Phosphorescence from Carbon Dot Composites Based on a Single Nonaromatic Carbon Source.

Herein, a series of carbon dot composites (CDC) with full-color and long-lived room-temperature phosphorescence (RTP) are prepared by a simple solid-phase one-step method from a single non-conjugated and non-aromatic carbon source. The RTP emission wavelength can be adjusted from 462 to 623 nm by changing the feeding ratio and reaction temperature. The luminescent lifetime and quantum yield of a green emissive CDC (AB-CDC-3) reach 1.1 s and 39%, respectively, because of the close interaction between carbon dots and inorganic matrix. Due to the existence of multiple luminescent centers, these CDC exhibit excitation wavelength-dependent RTP and a white emission when excited at a specific wavelength. A single-component afterglow luminescent diode based on AB-CDC-4 shows a high-quality white emission with CIE of (0.30, 0.33) and color-rendering index of 88. Based on the unique photophysical properties of the composites, they exhibit huge application potential in the field of multilevel anti-counterfeiting, fingerprint identification, and optoelectronic devices.

Achieving long-lived room-temperature phosphorescence via charge transfer technology and dopant-matrix design strategy

Unlike heavy atom effect and n-π* transition that would increase both kISC and kP, here we report that charge transfer technology and dipole effect can significantly enhance kISC and simultaneously allow long-lived room-temperature phosphorescence (τP, 1.2 s) in dopant-matrix systems. The luminescent difluoroboron β-diketonate (BF2bdk) dopants show intramolecular charge transfer characters in S1 state and possess multiple phenyl groups to enrich their excited state natures. Some Tn states mediate the intersystem crossing of BF2bdk dopants to give T1 state with significant portion of localized excitation characters. The crystalline matrices selected are found to suppress nonradiative decay and oxygen quenching of the T1 state, leading to long-lived and bright room-temperature phosphorescence materials. This strategy based on charge transfer technology and dopant-matrix design would pave the way for constructing high-performance afterglow materials.

Ultraviolet activate room temperature ultralong organic phosphorescence from non-crystal benzoylcarbazole-doped polymer system

The host-guest doping strategy is widely used in the construction of room temperature phosphorescence (RTP) materials. The current methods for developing carbazole (Cz)-based RTP materials are mainly based on crystallization engineering. Herein, we report a general strategy for carbazole-based RTP materials by doping non-crystal benzoylcarbazole (BzCz) phosphor into polymer matrices. BzCz exhibited fluorescence in solution and RTP in powder state. Notably, the doped BzCz powder@PVA film displays yellow RTP emissions with an afterglow duration of around 7 s. Based on the theoretical calculations, it demonstrated that the co-assembly effect between the BzCz and PVA chains could enhance the long-lived RTP systems. This research provides great convenience for developing carbazole (Cz) molecule-doped polymer RTP materials under ambient conditions.

Poly(arylene piperidine) Quaternary Ammonium Salts Promoting Stable Long-Lived Room-Temperature Phosphorescence in Aqueous Environment.

Room-temperature phosphorescence (RTP) materials have garnered considerable research attention owing to their excellent luminescence properties and potential application prospects in anti-counterfeiting, information storage, and optoelectronics. However, several RTP systems are extremely sensitive to humidity, and consequently, the realization of long-lived RTP in water remains a formidable challenge. Herein, a feasible and effective strategy is presented to achieve long-lived polymeric RTP systems, even in an aqueous environment, through doping of synthesized polymeric phosphor PBHDB into a poly(methyl methacrylate) (PMMA) matrix. Compared to the precursor polymer PBN and organic molecule HDBP, a more rigid polymer microenvironment and electrostatic interaction are formed between the PMMA matrix and polymer PBHDB, which effectively reducethe nonradiative decay rate of triplet excitons and dramatically increasethe phosphorescence intensity. Specifically, the phosphorescence lifetime of the PBHDB@PMMA film (1258.62ms) is much longer than those of PBN@PMMA (674.20ms) and HDBP@PMMA (1.06ms). Most importantly, a bright-green afterglow can be observed after soaking the PBHDB@PMMA film in water for more than a month. The excellent water resistance and reversible response properties endow these systems with promising potential for dynamic information encryption even in water.

Hydrogen bonding-induced oxygen clusters and long-lived room temperature phosphorescence from amorphous polyols

Developing non-conjugated luminescent polymers (NCLPs) with fluorescence and long-lived room-temperature phosphorescence is of great significance for revealing the essence of NCLPs luminescence, which has gradually attracted the attention of researchers in recent years. Herein, polymethylol (PMO) and poly(3-butene-1,2-diol) (PBD) with polyhydroxy structures were prepared and their luminescence behaviors were investigated to reveal the clusteroluminescence (CL) mechanism. Compared with polyvinyl alcohol with non-luminescent behavior, PMO and PBD exhibit cyan-blue fluorescence with quantum yields of ca. 12% and green room-temperature phosphorescence with lifetimes of ca. 89 ms in the solid state. Both fluorescence and phosphorescence exhibit typical excitation-dependent CL behavior. Experimental and theoretical analyses show that the strong hydrogen-bonding interaction of PMO and PBD greatly promotes the formation of oxygen clusters and the through-space n-n interaction of oxygen atoms, enabling fluorescence and phosphorescence emission. Our results have enormous implications for understanding the CL mechanism of NCLPs and provide a new polymer design strategy for the rational design of novel NCLPs materials.

Long-Lived Organic Room-Temperature Phosphorescence from Amorphous Polymer Systems.

Long-lived organic room-temperature phosphorescence (RTP) materials have recently drawn extensive attention because of their promising applications in information security, biological imaging, optoelectronic devices, and intelligent sensors. In contrast to conventional fluorescence, the RTP phenomenon originates from the slow radiative transition of triplet excitons. Thus, enhancing the intersystem crossing (ISC) rate from the lowest excited singlet state (S1) to the excited triplet state and suppressing the nonradiative relaxation channels of the lowest excited triplet state (T1) are reasonable methods for realizing highly efficient RTP in purely organic materials. Over the past few decades, many strategies have been designed on the basis of the above two crucial factors. The introduction of heavy atoms, aromatic carbonyl groups, and other heteroatoms with abundant lone-pair electrons has been demonstrated to strengthen the spin-orbit coupling, thereby successfully facilitating the ISC process. Furthermore, the rigid environment is commonly constructed through crystal engineering to restrict intramolecular motions and intermolecular collisions to decrease excited-state energy dissipation. However, most crystal-based organic RTP materials suffer from poor processability, flexibility, and reproducibility, becoming a thorny obstacle to their practical application.Amorphous organic polymers with long-lived RTP characteristics are more competitive in materials science. The intertwined structures and long chains of polymers not only ensure the rigid environment with multiple interactions but also protect triplet excitons from the surroundings, which are conducive to realizing ultralong and bright RTP emission. Exploring the fabrication strategies, intrinsic mechanisms, and practical applications of organic long-lived RTP polymers is highly desirable but remains a formidable challenge. In particular, intelligent organic RTP polymer systems that are capable of dynamically responding to external stimuli (e.g., light, temperature, oxygen, and humidity) have been rarely reported. To develop multifunctional RTP materials and expand their potential applications, a great amount of effort has been expended.This Account gives a summary of the significant advances in amorphous organic RTP polymer systems, especially smart stimulus-responsive ones, focusing on the construction of a rigid environment to suppress nonradiative deactivation by abundant inter/intramolecular interactions. The typical interactions in RTP polymer systems mainly include hydrogen bonding, ionic bonding, and covalent bonding, which can change the molecular electronic structures and affect the energy dissipation channels of the excited states. An in-depth understanding of intrinsic mechanisms and an extensive exploration of potential applications for excitation-dependent color-tunable, ultraviolet (UV) irradiation-activated, temperature-dependent, water-responsive, and circularly polarized RTP polymer systems are distinctly illustrated in this Account. Furthermore, we propose some detailed perspectives in terms of materials design, mechanism exploration, and promising application potential with the hope to provide helpful guidance for the future development of amorphous organic RTP polymers.

Full-Color Long-Lived Room Temperature Phosphorescence in Aqueous Environment.

Long-lived room temperature phosphorescence (RTP) materials are widely utilized in the field of biological and chemical sensing, due to their unique characteristics of long-lived luminescence and no background autofluorescence. However, the realization of full-color RTP in aqueous solution still remains a great challenge. Herein, a feasible strategy for achieving high stability and full-color RTP of carbon dots (CDs)-based composite materials in aqueous environment is reported by constructing a rigid hydrogen bonds' network. The obtained m,p-CDs@CA composite materials exhibit deep-blue RTP with phosphorescence quantum yield of 23.2% and lifetime of 1.74 s, and the afterglow can last for over 12 s. More importantly, the m,p-CDs@CA composite materials are desirable in the detection of biomarkers, because of excellent stability, dispersion, and long-lived RTP properties. The m,p-CDs@CA suspension also displays excellent sensitivity, and a limitation of detection as low as 5.61 and 550nm for biomarkers 5-hydroxyindole-3-acetic acid (HIAA) and serotonin (5-hydroxytryptamine, HT), respectively. Meanwhile, the sensing performance exhibits excellent selectivity even in the presence of other competitive species in blood plasma and urine. With superior selectivity, the long-lived phosphorescence probe based on m,p-CDs@CA suspension can be as an effective biomarker for carcinoid identification, which has potential application in clinical analysis.

Long-Lived Room Temperature Phosphorescence Crystals with Green Light Excitation.

Long-lived room temperature phosphorescence (RTP) materials are promising for applications in various fields including security information, medical diagnostics, and molecular imaging because of their unique optical properties. Previous RTP materials are mainly excited by ultraviolet light, while synthesizing long-lived RTP materials with visible-light-excitation remains a challenge. In particular, long-lived RTP materials that can be excited by green light are rare. Herein, a feasible and concise chemical strategy for constructing hydrogen-bonded frameworks in an aqueous environment is developed to fabricate large-size, green-light-excited, and excitation-dependent long-lived RTP carbon dot crystals (m,p/CDs-ME). The RTP performance of the crystals exhibits strong excitation wavelength dependence, leading to a full range of visible-light tuning from blue to red. Importantly, the maximum excitation wavelength of the RTP crystals is around 500 nm, thus successfully realizing green light excitation. m,p/CDs-ME presents long-lived phosphorescence (130 ms) under 500 nm excitation in aqueous solution, making it highly suitable for dopamine detection. This work not only provides a general guideline for the development of large size long-lived RTP crystals but also extends the operation scope of long-lived RTP materials in the detection of biomarkers by visible light excitation.

Long-Lived Color-Tunable Room-Temperature Phosphorescence of Boron-Doped Carbon Dots.

Carbon dots (CDs) with long-lived room-temperature phosphorescence (RTP) or long afterglow properties draw much attention. However, most room-temperature phosphorescent materials are metal containing, and the exploitation of long-lived color-tunable RTP materials faces great challenges. Here, we report metal-free boron-doped CDs (B-CDs) for room-temperature phosphorescence with tunable color and an ultralong lifetime. B-CDs were obtained by simply calcining a mixture of boric acid and 1,3,5-benzenetricarboxylic acid in the atmosphere. The as-prepared B-CDs were characterized through UV-vis spectroscopy, photoluminescence spectroscopy, and so forth. Under the excitation of 310 nm UV light, B-CDs show RTP that appears as blue with a phosphorescence lifetime of 1042 ms, and after switching the excited wavelength to 365 nm, the RTP appears as green with a phosphorescence lifetime of 590 ms. Due to the unique RTP properties, B-CDs display promising applications in anticounterfeiting and information encryption.

Single-component color-tunable circularly polarized organic afterglow through chiral clusterization

Circularly polarized organic afterglow (CPOA) with both long-lived room-temperature phosphorescence (RTP) and circularly polarized luminescence (CPL) is currently attracting great interest, but the development of multicolor-tunable CPOA in a single-component material remains a formidable challenge. Here, we report an efficient strategy to achieve multicolor CPOA molecules through chiral clusterization by implanting chirality center into non-conjugated organic cluster. Owing to excitation-dependent emission of clusters, highly efficient and significantly tuned CPOA emissions from blue to yellowish-green with dissymmetry factor over 2.3 × 10−3 and lifetime up to 587 ms are observed under different excitation wavelengths. With the distinguished color-tunable CPOA, the multicolor CPL displays and visual RTP detection of ultraviolent light wavelength are successfully constructed. These results not only provide a new paradigm for realization of multicolor-tunable CPOA materials in single-component molecular systems, but also offer new opportunities for expanding the applicability of CPL and RTP materials for diversified applications.

Long-lived room temperature phosphorescence from amorphous non-traditional intrinsic clusteroluminescence polymers

The H-bond and ionic bond of the well-defined PSMA hydrolysates induce the TSI-n–π of carbonyl clusters to emit fluorescence and RTP.

Natural hybrid-mediated long-lived room temperature phosphorescence of milk powder

Natural room temperature phosphorescence is charming. Milk powder can emit striking afterglow with the duration and lifetime exceeding 10 s and 2 s under ambient conditions, respectively, not inferior to most advanced artificial organic phosphors.

Mononuclear aggregation-induced emission (AIE)-active gold(I)-isocyanide phosphors: Contrasting phosphorescent mechanochromisms and effect of halogen substitutions on room-temperature phosphorescence nature

Developing phosphors with long-lifetime (millisecond scale or even longer) solid state room temperature phosphorescence (RTP) feature has attracted considerable attention. However, to date, stimuli-responsive phosphors with RTP nature are still rare due to the absence of effective guidelines for the exploitation of luminophors synchronously possessing stimuli-responsive and RTP characteristics. In this work, a series of mononuclear gold(I) complexes are reported. All these complexes exhibit various solid-state RTP properties, and phosphor 1-Cl exhibits long-lived RTP behavior. The effect of halogen atoms on the RTP nature of these complexes is investigated in detail. Furthermore, the introduction of different types of halogen atoms can effectively regulate the phosphorescent mechanochromism phenomena of these gold(I)-containing complexes. In addition, these phosphors display typical aggregation-induced emission (AIE) effect except for phosphor 5-CCl, which lacks hydrogen-bonding interactions compared with the other four phosphors. This work will be very helpful to the development of mechanical-force-responsive AIE phosphors with lasting RTP.

Reversible Photoswitching between Fluorescence and Room Temperature Phosphorescence by Manipulating Excited State Dynamics in Molecular Aggregates.

Regulation of fluorescence-phosphorescence pathways in organic molecular aggregate remains a challenge due to the complicated singlet-triplet excited state dynamics process. Herein, we demonstrated a successful example (o-BFT) to realize photoreversible fluorescence and room temperature phosphorescence (RTP) switching based on an effective strategy of integrating a phosphor (dibenzofuran) with a photoswitch (dithienylbenzothiophene). o-BFT exhibited dual emission of fluorescence and RTP in both powder and doping polymer film. Notably, the long-lived RTP of o-BFT could be repeatedly erased and restored through reversible photocyclization and decyclization under alternate ultraviolet and visible photoirradiation. In-depth theoretical and spectroscopic investigations revealed that the triplet inactivation was dominated by a photo-controlled triplet-to-singlet Förster resonance energy transfer from light-activated o-BFT to photoisomer c-BFT. Yet, the initial fluorescence could be preserved in this process to afford a photoreversible fluorescence-RTP switching.

Dynamic Manipulating Space-Resolved Persistent Luminescence in Core-Shell MOFs Heterostructures via Reversible Photochromism.

Photo-controllable persistent luminescence at the single crystal level can be achieved by the integration of long-lived room temperature phosphorescence (RTP) and photochromism within metal-organic frameworks (MOFs) for the first time. Moreover, the multiblock core-shell heterojunctions have been prepared utilizing the isostructural MOFs through an epitaxial growth process, in which the shell exhibits bright yellow afterglow emission that gradually disappears upon further irradiation, but the core does not show such property. Benefitting from combined persistent luminescence and photochromic behavior, a multiple encryption demo can be facilely designed based on the dynamic manipulating RTP via reversible photochromism. This work not only develops new types of dynamically photo-controllable afterglow switch, but also provides a method to obtain MOFs-based optical heterojunctions towards potential space/time-resolved information encryption and anti-counterfeiting applications.

Polyacrylamide-Based Binary Luminescent Copolymer Materials Exhibit Color-Tunable and Efficient Long-Lived Room Temperature Phosphorescence.

Polymer-based pure organic room temperature phosphorescence (RTP) materials have garnered considerable interest, among which RTP systems with prolonged lifetimes and tunable emission colors are promising for applications in sensing, flexible electronics, bioassay, anti-counterfeiting, and data encryption. Herein, facile doping method is reported based on two types of copolymers with benzene/biphenyl-based light-emitting cores as their side chains, whereby the two copolymers are robustly crosslinked via noncovalent interactions including hydrogen bonding and halogen bonding that occur between the light-emitting cores and polyacrylamide backbones. Persistent RTP emission with prolonged lifetime up to 1.9 s and phosphorescence quantum yield as high as 40.1% are obtained in single copolymers, attributed to the conformation restriction of phosphorescent dyes originating from the rigid microenvironment. Furthermore, multicolor phosphorescence signals are observed in the doped binary luminescent copolymer systems that can be effectively regulated by the feed ratio of luminescent cores and irradiation wavelengths. Possible mechanisms for this efficient and long-lived color-tunable RTP system are discussed on the basis of the experimental data and theoretical calculations. In addition, it is also demonstrated that the color-tunable RTP emission of the doped copolymer systems under ambient conditions allows for further exploitation in the application of dynamic information encryption.