Secondary through-space interactions facilitated single-molecule white-light emission from clusteroluminogens

Specific Quenching of Natural Clusterization-Triggered Emission Probes for Rapid Fluorescent Detection of Antipsychotics

The development of rapid, cost-effective fluorescent probes for antipsychotic drug detection remains challenging due to the synthetic complexity of conventional probes and limited exploration of natural alternatives. Herein, we pioneered bovine serum albumin (BSA) as a natural clusterization-triggered emission (CTE) probe for one-step detection of chlorpromazine hydrochloride (CPZ) and perphenazine (PPZ). The unique CTE property of BSA displayed concentration-dependent quenching with CPZ and PPZ. Moreover, the quenching effect achieved balance within 5 minutes and maintained stability for more than 30 minutes. Based on these advantages, the proposed detection platform showed rapid response, operational simplicity, visual signal readout, wide detection range, ultra-low detection limits, compared with other methods. Moreover, the assay method exhibited excellent selectivity, facilitating satisfactory reliability for the real sample assay. Thermodynamic analyses revealed distinct interaction mechanisms between BSA and antipsychotics, both inducing static quenching by suppressing clusterization-induced electron transitions. Overall, this research not only develops a novel assay method for CPZ and PPZ, but also broadens the application potential of the CTE effect in natural biomacromolecules. As the first demonstration of natural CTE probes for antipsychotic detection, this work opens new frontiers for sustainable analytical technologies by circumventing synthetic probe complexities and leveraging inherent biorecognition.

Triggering anti-Kasha organic room temperature phosphorescence of clusteroluminescent materials

Clusterization-triggered emission (CTE) from organic materials without π-conjugated structures for room temperature phosphorescence (RTP) is fascinating with extraordinary photophysical properties and diversified applications, but rather challenging in material design owing to the limited mechanism understanding. Here, we demonstrate a facile strategy to construct CTE polymers with stimuli-responsive emission, anti-Kasha RTP and organic ultralong RTP (OURTP) by introducing ions into the hydrolyzed nonconjugated maleic anhydride and acrylamide copolymers. Thanks to the synergistic effects of hydrogen and ionic bonding with the ion-triggered electrostatic and coordinate interactions to suppress non-radiative decays and promote intersystem crossing, the amorphous copolymers show efficient photoluminescence with quantum efficiencies up to 13.5%, anti-Kasha RTP blue-shift of 29 nm, and OURTP lifetime up to 420 ms. Moreover, the temperature-dependent and water-sensitive anti-Kasha RTP and OURTP are also observed due to the formation of highly emissive CTE structure regulated by ionization. With the excellent processability and flexibility of the copolymer, lifetime-, temperature- and color-encrypted information anti-counterfeiting is designed and explored. The anti-Kasha RTP in CTE materials realized for the first time demonstrates impressive potential for multi-level encryption/anti-counterfeiting applications and more importantly, providing fundamental mechanism understanding for the rational modulation and design of CTE materials with extraordinary photophysical properties.

NIR-II Photosensitizer-Based Nanoparticles Defunctionalizing Mitochondria to Overcome Tumor Self-Defense by Promoting Heat Shock Protein 40

Inherent self-defense pathways within malignant tumors include the action of heat shock proteins (HSPs) and often impede photothermal therapy efficacy. Interestingly, HSP40 inhibits glycolysis and disrupts mitochondrial function to overcome tumor self-defense mechanisms and exhibits a tumor-suppressive effect. Reactive oxygen species (ROS), especially hydroxyl radicals, generated by type-I photodynamic therapy inhibit adenosine triphosphate (ATP) production and lead to ATP-independent HSP40 overexpression during heat stress. However, the regulatory mechanisms linking heat and hydroxyl radicals to induce HSP40 expression remain unclear. Therefore, it is imperative to elucidate the underlying mechanism governing the induction of HSP40 expression during heat stress and explore its potential as a promising therapeutic strategy against tumor development. By strategically modifying the aza-BODIPY structure to precisely distribute the excited-state energy, we have demonstrated that HSP40 specific expression is correlated with the proportion of heat to hydroxyl radicals rather than their individual levels. This orchestrated NIR-II photosensitizer-based nanoparticles reduced tumor glycolysis and disrupted ATP production, driving cell apoptosis and amplifying the efficacy of photothermal therapy. Silencing and compensation of HSPs under heat and ROS stress represent a promising and effective strategy for overcoming tumor self-defense mechanisms in cancer therapy.

Emergent clusteroluminescence from nonemissive molecules

Once considered the exclusive property of conjugated molecules, efficient and visible-light luminescence from non-conjugated and nonemissive molecules in the clustered state, known as clusteroluminescence (CL), has attracted much attention recently due to its special photophysical behaviors and behind electronic interactions. This perspective discusses the development of the CL phenomenon, followed by the typical photophysical features, examples, mechanisms, and potential applications of CL materials, to provide a comprehensive picture of this emerging field. Starting with organic clusters, inorganic, metallic, and hybrid clusters with CL properties are also introduced, and the perspective shift from covalent interactions at the molecular level to non-covalent interactions at the aggregate level is invoked.

Integration of Through-Space Conjugation of an Adjacent Arene with a Nitrogen/Carbonyl Framework for Narrowband Emission

Organic luminescent materials featuring noncovalent through-space conjugation (TSC) have attracted considerable attention. However, the presence of multiple vibrational energy levels and weak spatial electron delocalization typically results in broad emission peaks for TSC-based emitters, significantly impeding their extensive application in optoelectronic technologies. Herein, two TSC emitters, TSFQ-TRZ and TSFQ-Ph, were synthesized by integrating a fused nitrogen/carbonyl skeleton with various adjacent arene 2,4,6-triphenyl-1,3,5-triazine (TPTRZ) and phenyl group segments through a rigid spiro spacer. These emitters exhibited narrow emissions, with full widths at half-maximum of 19 nm and 25 nm, respectively. Experimental and theoretical investigations unveiled that the TPTRZ segment introduces steric hindrance, while simultaneously suppressing molecular vibrations through intramolecular interactions-a key factor in achieving narrow emissions. Leveraging this narrow blue emission, electroluminescent devices employing TSFQ-TRZ as the emitter achieved an impressive maximum external quantum efficiency of 26.7 %, which further increased to 28.3 % when sensitized by phosphorescent emitter. This work demonstrates highly efficient, narrowband emissions from TSC-based emitters, thereby expanding their potential applications in the electroluminescence field.

Lone Pairs-Mediated Multiple Through-Space Interactions for Efficient Room-Temperature Phosphorescence

The simultaneous generation and stabilization of triplet excitons are the key to realizing efficient organic room temperature phosphorescence (RTP), which is challenging owing to the obscure mechanism and structure-property relationships. Herein, a strategy of lone-pair-mediated multiple through-space interactions (TSIs) is proposed to availably induce RTP. By incorporating heteroatoms to facilitate through-space n-n and n-π interactions, the lone pairs are delocalized throughout the structure, resulting in the dense splitting of the excited-state energy levels. Thus, more matched energy levels with a small energy gap between singlet and triplet states (ΔEST) emerge, resulting in multiple intersystem crossing (ISC) transition channels that assist triplet excitons generation. The strong TSIs also effectively rigidify the molecular structures and thus stabilize triplet excitons for radiation. Furthermore, the manipulation of TSI intensity allows efficiency enhancement, persistent time prolongation, and tolerance to high temperatures of RTP. This work not only explores the fundamental principle of the RTP mechanism from a new view but also provides a universal strategy for ISC promotion and triple excitons stabilization.

Tunable Cluster Luminescence and High Quantum Yield in Amine-Modified Maleic Anhydride Polymers

Cluster luminescent materials (CLgens) with nonconjugated structures have attracted considerable attention. However, their low quantum yield and limited emission wavelengths, which are confined to the blue-green spectrum, continue to restrict their applicability. In this study, maleic anhydride polymer chains were modified with N-tristyrylene-1,2-diamine (TPM-NH2), creating a secondary donor-acceptor structure through freely rotatable phenyl groups and amino-anhydride interactions. This modification facilitated the formation of charge transfer (CT) states and strengthened the through-space interaction (TSI), resulting in a remarkable red shift in emission wavelength from 400 to 640 nm. The flexible ethyl chain acted as a bridging unit within this framework, enhancing through-space charge transfer (TSCT) and elevating the quantum yield (QY) to 28.28%. This research offers a strategy for improving the QY of anhydride copolymers and demonstrates the potential for controllable emission wavelengths, thereby broadening their application domains, including in light-conversion agricultural films.

Revealing the excited-state mechanisms of the polymorphs of a hot exciton material

As the investigation of high efficiency thermally activated delayed fluorescence (TADF) materials become more mature, regulating the emission properties for single organic luminescence molecules has gained increasing interest recently. Herein, the donor-acceptor compounds F-AQ comprised of fluorene and anthraquinone is reported, and it exhibits a polymorphism with muti-color emission and TADF from high-level intersystem crossing (hRISC). The photodynamics and excited-state transient species were studied by femtosecond transient absorption (fs-TA) spectroscopy. As a result, an unambiguous signal of through space charge transfer (TSCT) was observed in the fs-TA spectra of the crystal with the π-π interaction between the fluorene and anthraquinone groups, whereas the other amorphous solids and crystal only show a conventional deactivation pathway of hRISC-TADF. In this study, we successfully realize the direct observation of the morphism-dependent TSCT in a crystal, which provides the observations in solid-state ultrafast excited-state dynamics and deepens the insight into the design of potential mechanochromic materials and thermochromic utilization of the polymorphism of organic luminescence molecules.

Two-Photon Clusteroluminescence Enabled by Through-Space Conjugation for In Vivo Bioimaging

Clusteroluminescence (CL) materials without largely conjugated structures have gained significant attention due to their unique photophysical properties and potential in bioimaging. However, low luminescence efficiency and short emission wavelength limit their development. This work designs three luminogens with CL properties (CLgens) by introducing n-electron-involved through-space conjugation (TSC) into diarylmethane. Apart from single-photon excited long-wavelength (686 nm) and high-efficiency (29 %) CL, two-photon clusteroluminescence (TPCL) is successfully achieved in such small luminogens with only two isolated heteroatomic units. TSC stabilized in the aggregate state has been proven to realize efficient spatial electron delocalization similar to conventionally conjugated compounds. Encouraged by the excellent TPCL properties, two-photon imaging of blood vessels in vivo and biocompatibility verification utilizing CLgens are also achieved. This work illustrates the essential role of TSC in promoting nonlinear optical properties of CLgens and may facilitate further design and development of the next generation of bioprobes with excellent biocompatibility.

Monitoring Glutathione Content of the Endoplasmic Reticulum under Scrap Leather-Induced Endoplasmic Reticulum Stress via an Endoplasmic Reticulum-Targeted Two-Photon Fluorescent Probe

Maintaining tissue homeostasis necessitates the coordinated efforts of various cell types to regulate inflammation. Endoplasmic reticulum (ER) stress, a hallmark of inflammation, exacerbates tissue pathology in various human diseases. Glutathione (GSH), a pivotal regulator of cellular redox balance, controls disulfide bond formation in the ER, thereby shielding cells from oxidative stress. In this study, we developed a two-photon fluorescent probe, ER-GSH, with specific ER targeting and demonstrated its high sensitivity and rapid response to GSH. Experiments conducted on BV2 cells and a mice model of neuroinflammation induced by scrap leather revealed that inflammatory reactions led to ER stress and a substantial reduction in GSH levels. Notably, the anti-inflammatory drug NS-398 effectively inhibited cell inflammation and ER stress by maintaining GSH levels. These findings underscore the potential therapeutic significance of modulating GSH levels to alleviate the impact of neuroinflammation.

A Facile One-Step Self-Assembly Strategy for Novel Carbon Dots Supramolecular Crystals with Ultralong Phosphorescence Controlled by NH4. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024;20:e2402236. [PMID: 38970543 DOI: 10.1002/smll.202402236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

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) (733.56 ms) 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 +.

Thiol-containing hyperbranched polysiloxane for scavenging reactive oxygen species

Unconventional luminescent polymers have attracted considerable attention in the biological field due to their intrinsic fluorescence properties and excellent biocompatibility. However, exploring the luminescent properties of thiol-containing polymers and the mechanism of their scavenging of ROS remains unclear. In this work, we synthesised three kinds of hyperbranched polysiloxanes (HE, HP, and HB) with terminal thiol groups containing different chain lengths by the polycondensation reaction. Surprisingly, HP exhibits longer-wavelength emission at 480 nm with a quantum yield of 12.23% compared to HE and HB. Experiments and density functional theory (DFT) calculations have revealed that the rigidity of the conformation is enhanced by substantial hydrogen bonds and through-space O⋯O interactions in the polymer structure. These interactions, combined with the rigid carbon chains, balance the flexibility of the Si-O-C chain segments, which emerges as a critical factor contributing to the superior fluorescence performance of HP. In addition, HP exhibits excellent biocompatibility and ROS scavenging ability with a scavenging capacity of up to 35.095%. This work provides a new fluorescent polymer for scavenging ROS for the treatment of ROS-related diseases.

Unexpected full-color luminescence produced from the aggregation of unconventional chromophores in novel polyborosilazane dendrimers

Non-conjugated fluorescent polymers (NCPLs) are of interest due to their remarkable biocompatibility, processability and biodegradability. However, the realization of multicolor emitting NCPLs through structure modulation remains a great challenge. In this work, a series of novel yttrium-branched polyborosilazane (PBSZ) structures (PY1-PY3) were prepared. PBSZ exhibits a blue emission peaked at 450 nm, and the introduction of an yttrium-branched-chain generates a new long-wavelength emission center. As the degree of yttrium branching increases, the emerged emission peak shifts from 532 to 646 nm, and its intensity gradually increases to 1.4 times that of the blue emission. CIE chromaticity coordinates indicate that yttrium-branching modulates the emission color from blue (0.19, 0.21) to near white (0.34, 0.40) and red (0.43, 0.36). Particularly, the PY3 sample exhibits an ultra-broad emission spectrum; covering the range of 400-750 nm. Theoretical calculation indicates that the yttrium-branched-chains promote heteroatom delocalization to form "cluster chromophores", generating new orbitals with lower gaps. In addition, experimental results prove that the yttrium-branched-chains balance the flexibility of the molecular backbone and generate stable fluorescent clusters, which intensifies the non-conjugated linking and through-space-conjugation (TSC) effects, thus generating long-wavelength emission. This work proves that yttrium "end-grafting" is a feasible strategy for equilibrium flexibility and to realize full-color emission in non-conjugated polymers.

White Light Emission from Zn(II) and DMSO-Induced Copper Nanocluster Assembly

An assembly of metal nanoclusters driven by appropriate surface ligands and solvent environment may engender entirely new photoluminescence (PL). Herein, we first synthesize histidine (His) stabilized copper nanoparticles (CuNPs) and, subsequently, copper nanoclusters (CuNCs) from it using 3-mercaptopropionic acid (MPA) as an etchant. The CuNCs originally emit bluish-green (λem=470 nm) PL with a low quantum yield (QY∼1.8 %). However, it transformed into a dual-emissive nanocluster assembly (Zn-CuNCs) in the presence of Zn(II) salt, having a distinct blue emission band (λem=420 nm) and a red emission band (λem=615 nm) with eight times QY (∼9.1 %) enhancement. The temperature-dependent emission spectra of Zn-CuNCs depicted that the blue emission band persists for all the temperature ranges (0-80 °C) while the red emission band vanishes at high temperatures (70-80 °C). Thus, the blue emission may originate from the locally excited state (LES) emission of the nanoclusters, while the red emission originates from through-space interaction (TSI) and Cu(I)…Cu(I) interaction within the assembly. Adding dimethyl sulfoxide (DMSO) further modifies the emission intensities; the red band was amplified four times, while the blue band was diminished by 2.5 times. The transmission electron microscopy (TEM) images unveiled that the Zn-CuNCs are a large assembly of tiny nanoclusters, which become more compact in DMSO. The blue emission possesses steady-state fluorescence anisotropy, while the red emission shows no anisotropy. Further, near-perfect white light emission(WLE) was rendered with CIE coordinates of (0.33, 0.32) by combining the dual emission of the Zn-CuNCs with the original green emission of the CuNCs.

Exciton Dissociation and Recombination Afford Narrowband Organic Afterglow Through Efficient FRET

Organic afterglow with long-persistent luminescence (LPL) after photoexcitation is highly attractive, but the realization of narrowband afterglow with small full-width at half-maximum (FWHM) is a huge challenge since it is intrinsically contradictory to the triplet- and solid-state emission nature of organic afterglow. Here, narrow-band, long-lived, and full-color organic LPL is realized by isolating multi-resonant thermally activated delayed fluorescent (MR-TADF) fluorophores in a glassy steroid-type host through a facile melt-cooling treatment. Such prepared host becomes capable of exciton dissociation and recombination (EDR) upon photoirradiation for both long-lived fluorescence and phosphorescence; and, the efficient Förster resonance energy transfer (FRET) from the host to various MR-TADF emitters leads to high-performance LPL, exhibiting small FWHM of 33 nm, long persistent time over 10 s, and facile color-tuning in a wide range from deep-blue to orange (414-600 nm). Moreover, with the extraordinary narrowband LPL and easy processability of the material, centimeter-scale flexible optical waveguide fibers and integrated FWHM/color/lifetime-resolved multilevel encryption/decryption devices have been designed and fabricated. This novel EDR and singlet/triplet-to-singlet FRET strategy to achieve excellent LPL performances illustrates a promising way for constructing flexible organic afterglow with easy preparation methods, shedding valuable scientific insights into the design of narrow-band emission in organic afterglow.

Unveiling the potential of triphenylphosphine salts in tuning organic room temperature phosphorescence

Triphenylphosphine (TPP) salt derivatives, with their rich chemistry of core-substitution, have emerged as promising candidates for ultralong room temperature phosphorescence (RTP) materials owing to their distinct molecular structures, high quantum efficiency and exceptional phosphorescence properties. This feature article highlights the vast potential of TPP salt derivatives in tunable RTP properties by exploring some factors such as the alkyl chains, halogen anions, through-space charge transfer states, etc., and recent advancements in multi-level information encryption, high-level anticounterfeiting tags and X-ray imaging applications. We anticipate that this article will assist in directing future analyses based on the mechanisms underlying the RTP behavior of TPP derivatives and offer guidance for the rational design of high-performance RTP materials.

Switchable Dual Circularly Polarized Luminescence in Through-Space Conjugated Chiral Foldamers

Organic materials with switchable dual circularly polarized luminescence (CPL) are highly desired because they can not only directly radiate tunable circularly polarized light themselves but also induce CPL for guests by providing a chiral environment in self-assembled structures or serving as the hosts for energy transfer systems. However, most organic molecules only exhibit single CPL and it remains challenging to develop organic molecules with dual CPL. Herein, novel through-space conjugated chiral foldamers are constructed by attaching two biphenyl arms to the 9,10-positions of phenanthrene, and switchable dual CPL with opposite signs at different emission wavelengths are successfully realized in the foldamers containing high-polarizability substitutes (cyano, methylthiol and methylsulfonyl). The combined experimental and computational results demonstrate that the intramolecular through-space conjugation has significant contributions to stabilizing the folded conformations. Upon photoexcitation in high-polar solvents, strong interactions between the biphenyl arms substituted with cyano, methylthio or methylsulfonyl and the polar environment induce conformation transformation for the foldamers, resulting in two transformable secondary structures of opposite chirality, accounting for the dual CPL with opposite signs. These findings highlight the important influence of the secondary structures on the chiroptical property of the foldamers and pave a new avenue towards efficient and tunable dual CPL materials.

Narrowband clusteroluminescence with 100% quantum yield enabled by through-space conjugation of asymmetric conformation

Different from traditional organic luminescent materials based on covalent delocalization, clusteroluminescence from nonconjugated luminogens relies on noncovalent through-space conjugation of electrons. However, such spatial electron delocalization is usually weak, resulting in low luminescent efficiency and board emission peak due to multiple vibrational energy levels. Herein, several nonconjugated luminogens are constructed by employing biphenyl as the building unit to reveal the structure-property relationship and solve current challenges. The intramolecular through-space conjugation can be gradually strengthened by introducing building units and stabilized by rigid molecular skeleton and multiple intermolecular interactions. Surprisingly, narrowband clusteroluminescence with full width at half-maximum of 40 nm and 100% efficiency is successfully achieved via an asymmetric conformation, exhibiting comparable performance to the traditional conjugated luminogens. This work realizes highly efficient and narrowband clusteroluminescence from nonconjugated luminogens and highlights the essential role of structural conformation in manipulating the photophysical properties of unconventional luminescent materials.

Achieving Efficient Dark Blue Room-Temperature Phosphorescence with Ultra-Wide Range Tunable-Lifetime

Tunable-lifetime room-temperature phosphorescence (RTP) materials have been widely studied due to their broad applications. However, only few reports have achieved wide-range lifetime modulation. In this work, ultra-wide range tunable-lifetime efficient dark blue RTP materials were realized by doping methyl benzoate derivatives into polyvinyl alcohol (PVA) matrix. The phosphorescence lifetimes of the doped films can be increased from 32.8 ms to 1925.8 ms. Such wide range of phosphorescence lifetime modulation is extremely rare in current reports. Moreover, the phosphorescence emission of the methyl 4-hydroxybenzoate-doped film is located in the dark blue region and the phosphorescence quantum yield reaches as high as 15.4 %, which broadens their applications in organic optoelectronic information. Further studies demonstrated that the reason for the tunable lifetime was that the magnitude of the electron-donating ability of the substituent group modulates the HOMO-LUMO and singlet-triplet energy gap of methyl benzoate derivatives, as well as the ability to non-covalent interactions with PVA. Moreover, the potential applications of luminescent displays and optical anti-counterfeiting of these high-performance dark blue RTP materials have been conducted.

Tuning vibration-induced emission through macrocyclization and catenation

In order to investigate the effect of macrocyclization and catenation on the regulation of vibration-induced emission (VIE), the typical VIE luminogen 9,14-diphenyl-9,14-dihydrodibenzo[a, c]phenazine (DPAC) was introduced into the skeleton of a macrocycle and corresponding [2]catenane to evaluate their dynamic relaxation processes. As investigated in detail by femtosecond transient absorption (TA) spectra, the resultant VIE systems revealed precisely tunable emissions upon changing the solvent viscosity, highlighting the key effect of the formation of [2]catenane. Notably, the introduction of an additional pillar[5]arene macrocycle featuring unique planar chirality endows the resultant chiral VIE-active [2]catenane with attractive circularly polarized luminescence in different states. This work not only develops a new strategy for the design of new luminescent systems with tunable vibration induced emission, but also provides a promising platform for the construction of smart chiral luminescent materials for practical applications.

Multiple hydrogen-bonding induced nonconventional red fluorescence emission in hydrogels

The development of unconventional long-wavelength fluorescent polymer hydrogels without using polycyclic aromatic hydrocarbons or extended π-conjugation is a fundamental challenge in luminescent materials owing to a lack of understanding regarding the spatial interactions induced inherent clustering-triggered emission under water-rich conditions. Inspired by the color change of protein astaxanthin as a result of heat-induced denaturation, we propose a thermodynamically driven strategy to develop red fluorescence (~610 nm) by boiling multiple hydrogen-bonded poly(N-acryloylsemicarbazide) hydrogels in a water bath. We reveal that thermodynamically driven conformational changes of polymer chains from isolated hydrogen bonding donor-acceptor structures to through-space interaction structures induce intrinsic fluorescence shifts from blue to red during clustering-triggered emission. The proposed multiple hydrogen-bonding supramolecular hydrogel shows good fluorescence stability, mechanical robustness, and 3D printability for customizable shaping. We provide a viable method to prepare nonconventional long-wavelength fluorescent hydrogels towards soft fluorescent devices without initially introducing any fluorescent components.

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.

Chirality-Regulated Clusteroluminescence in Polypeptides

The low emission efficiency of clusteroluminogens restricts their practical applications in the fields of sensors and biological imaging. In this work, the clusteroluminescence of ordered/disordered polypeptides was observed, and the photoluminescence (PL) intensity of polypeptides can be modulated by the chirality of amino acid residues. Polyglutamates with different chiral compositions were synthesized, and the racemic polypeptides exhibited a significantly higher PL intensity than the enantiopure ones. This emission originates from the n-π* transition between C═O groups of polypeptides and is enhanced by clusterization of polypeptides. CD and Fourier transform infrared spectra demonstrated that the enantiopure and racemic polypeptides form α-helix and random coil structures, respectively. The disordered polypeptides can form more chain entanglements and interchain interactions because of their high flexibility, leading to more clusterizations and stronger PL intensity. The rigidity of ordered helical structures restrains the chain entanglements, and the formation of intrachain hydrogen bonds between amide groups of the backbone impairs the interchain interaction between polypeptides, resulting in lower PL intensity. The PL intensity of the polypeptides can also be manipulated by the addition of urea or trifluoroacetic acid. Our study not only elucidates the chirality/order-based structure-property relationship of clusteroluminescence in peptide-based polymers but also offers implications for the rational design of fluorescent peptides/proteins.

How the Length of Through-Space Conjugation Influences the Clusteroluminescence of Oligo(Phenylene Methylene)s

The length and mode of conjugation directly affect the molecular electronic structure, which has been extensively studied in through-bond conjugation (TBC) systems. Corresponding research greatly promotes the development of TBC-based luminophores. However, how the length and mode of through-space conjugation (TSC), one kind of weak interaction, influence the photophysical properties of non-conjugated luminophores remains a relatively unexplored field. Here, we unveil a non-linear relationship between TSC length and emission characteristics in non-conjugated systems, in contrast to the reported proportional correlation in TBC systems. More specifically, oligo(phenylene methylene)s (OPM[4]-OPM[7]) exhibit stronger TSC and prominent blue clusteroluminescence (CL) (≈440 nm) compared to shorter counterparts (OPM[2] and OPM[3]). OPM[6] demonstrates the highest solid-state quantum yield (40 %), emphasizing the importance of balancing flexibility and rigidity. Further theoretical calculations confirmed that CL of these oligo(phenylene methylene)s was determined by stable TSC derived from the inner rigid Diphenylmethane (DPM) segments within the oligomers instead of the outer ones. This discovery challenges previous assumptions and adds a new dimension to the understanding of TSC-based luminophores in non-conjugated systems.

Capturing Doublet Intermediate Emitters by Chemically Crosslinking Confinement towards Spatiotemporal Encryption

Photoluminescence is one of the most meticulous ways to manipulate light energy. Typical photoluminescent emitters are mostly stable substances with a pure photophysical process of spontaneous photon-emission from their excited states. Intermediate emitters are elusive attributing to their synchronous energy transfer process including photophysical and incomplete photochemical pathways. An intermediate emitter containing radicals is more difficult to be observed due to its inherent chemical reactivity. Here, these challenges are overcome by spontaneously formed space limitations in polymer crosslinking networks meanwhile chemically active intermediates are captured. These doublet intermediates exhibit unique long-wavelength emissions under chemically crosslinking confinement conditions, and their luminous mechanism provides a novel perspective for designing intermediate emitters with liquid-crystal character and photoresponsive features towards spatiotemporal encryption, promising for the detection of photochemical reactions and the development of fascinating luminescent systems.

Hyperbranched Polyborosiloxanes: Non-traditional Luminescent Polymers with Red Delayed Fluorescence

Non-traditional fluorescent polymers have attracted significant attention for their excellent biocompatibility and diverse applications. However, designing and preparing non-traditional fluorescent polymers that simultaneously possess long emission wavelengths and long fluorescence lifetime remains challenging. In this study, a series of novel hyperbranched polyborosiloxanes (P1-P4) were synthesized. As the electron density increases on the monomer diol, the optimal emission wavelengths of the P1-P4 polymers gradually red-shift to 510, 570, 575, and 640 nm, respectively. In particular, P4 not only exhibits red emission but also demonstrates delayed fluorescence with a lifetime of 9.73 μs and the lowest critical cluster concentration (1.76 mg/mL). The experimental results and theoretical calculations revealed that the synergistic effect of dual heteroatom-induced electron delocalization and through-space O⋅⋅⋅O and O⋅⋅⋅N interaction was the key factor contributing to the red-light emission with delayed fluorescence. Additionally, these polymers showed excellent potential in dual-information encryption. This study provides a universal design strategy for the development of unconventional fluorescent polymers with both delayed fluorescence and long-wavelength emission.

Recent advances in the design of afterglow materials: mechanisms, structural regulation strategies and applications

Afterglow materials are attracting widespread attention owing to their distinctive and long-lived optical emission properties which create exciting opportunities in various fields. Recent research has led to the discovery of many new afterglow materials featuring high photoluminescence quantum yields (PLQY) and lifetimes of up to several hours under ambient conditions. Afterglow materials are typically categorized according to their luminescence mechanism, such as long-persistent luminescence (LPL), room temperature phosphorescence (RTP), or thermally activated delayed fluorescence (TADF). Through rational design and novel synthetic strategies to modulate spin-orbit coupling (SOC) and populate triplet exciton states (T1), luminophores with long lifetimes and bright afterglow characteristics can be realized. Initial research towards afterglow materials focused mainly on pure inorganic materials, many of which possessed inherent disadvantages such as metal toxicity or low energy emissions. In recent years, organic-inorganic hybrid afterglow materials (OIHAMs) have been developed with high PLQY and long lifetimes. These hybrid materials exploit the tunable structure and easy processing of organic molecules, as well as enhanced SOC and intersystem crossing (ISC) processes involving heavy atom dopants, to achieve excellent afterglow performance. In this review, we begin by briefly discussing the structure and composition of inorganic and organic-inorganic hybrid afterglow materials, including strategies for regulating their lifetime, PLQY and luminescence wavelength. The specific advantages of organic-inorganic hybrid afterglow materials, including low manufacturing costs, diverse molecular/electronic structures, tunable structures and optical properties, and compatibility with a variety of substrates, are emphasized. Subsequently, we discuss in detail the fundamental mechanisms used by afterglow materials, their classification, design principles, and end applications (including sensing, anticounterfeiting, and photoelectric devices, among others). Finally, existing challenges and promising future directions are discussed, laying a platform for the design of afterglow materials for specific applications.

Multicolor Luminescence of a Polyurethane Derivative Driven by Heat/Light-Induced Aggregation

The study of aggregate formation and its controllable effect on luminescence behavior has a far-reaching influence in establishing a universal aggregation photophysical mechanism. In this paper, we obtained clusters with different extents of aggregation by heat-induced or light-triggered aggregation of a new polyurethane derivative (PUE). The controllable regulation of multicolor fluorescence of a single (nondoped) polymeric material is realized. The luminescence behavior of PUE varies with microscopic control of the aggregation structure. Compared with the powder state, the enhanced atom-atom and group-group interactions of PUE-gel effectively limit the nonradiative transitions in the excited state and result in a red-shift in emission. This work avoids complex organic synthesis and demonstrates a simple strategy to induce aggregation and regulate the emitting color of macromolecules, providing a template for developing new materials for multicolor fluorescence. In addition, a pattern was constructed with encryption, anticounterfeiting, and information transmission functions which provide a proof-of-concept demonstration of the practical potential of PUE as a smart material.

Hydrogen-Bonding-Driven Nontraditional Photoluminescence of a β-Enamino Ester

Nontraditional luminogens (NTLs) do not contain any conventional chromophores (large π-conjugated structures), but they do show intrinsic photoluminescence. To achieve photoluminescence from NTLs, it is necessary to increase the extent of through-space conjugation (TSC) and suppress nonradiative decay. Incorporating strong physical interactions such as hydrogen bonding is an effective strategy to achieve this. In this work, we carried out comparative studies on the photoluminescence behaviors of two β-enamino esters with similar chemical structures, namely methyl 3-aminocrotonate (MAC) and methyl (E)-3-(1-pyrrolidinyl)-2-butenoate (MPB). MAC crystal emits blue fluorescence under UV irradiation. The critical cluster concentration of MAC in ethanol solutions was determined by studying the relationship between the photoluminescence intensity (UV-visible absorbance) and concentration. Furthermore, MAC exhibits solvatochromism, and its emission wavelength redshifts as the solvent polarity increases. On the contrary, MPB is non-emissive in both solid state and solutions. Crystal structures and theoretical calculation prove that strong inter- and intramolecular hydrogen bonds lead to the formation of large amounts of TSC of MAC molecules in aggregated states. No hydrogen bonds and thus no effective TSC can be formed between or within MPB molecules, and this is the reason for its non-emissive nature. This work provides a deeper understanding of how hydrogen bonding contributes to the luminescence of NTLs.

Multilevel Simultaneous Lighting-Imaging System

In a III-nitride multiple quantum well (MQW) diode biased with a forward voltage, electrons recombine with holes inside the MQW region to emit light; meanwhile, the MQW diode utilizes the photoelectric effect to sense light when higher-energy photons hit the device to displace electrons in the diode. Both the injected electrons and the liberated electrons are gathered inside the diode, thereby giving rise to a simultaneous emission-detection phenomenon. The 4 × 4 MQW diodes could translate optical signals into electrical ones for image construction in the wavelength range from 320 to 440 nm. This technology will change the role of MQW diode-based displays since it can simultaneously transmit and receive optical signals, which is of crucial importance to the accelerating trend of multifunctional, intelligent displays using MQW diode technology.

Achieving White-Light Emission Using Organic Persistent Room Temperature Phosphorescence

Artificial lighting currently consumes approximately one-fifth of global electricity production. Organic emitters with white persistent RTP have potential for applications in energy-efficient lighting technologies, due to their ability to harvest both singlet and triplet excitons. Compared to heavy metal phosphorescent materials, they have significant advantages in cost, processability, and reduced toxicity. Phosphorescence efficiency can be improved by introducing heteroatoms, heavy atoms, or by incorporating luminophores within a rigid matrix. White-light emission can be achieved by tuning the ratio of fluorescence to phosphorescence intensity or by pure phosphorescence with a broad emission spectrum. This review summarizes recent advances in the design of purely organic RTP materials with white-light emission, describing single-component and host-guest systems. White phosphorescent carbon dots and representative applications of white-light RTP materials are also introduced.

As Fiber Meets with AIE: Opening a Wonderland for Smart Flexible Materials

Aggregation-induced emission luminogens (AIEgens) have recently been developed at a tremendous pace in the area of organic luminescent materials by virtue of their superior properties. However, the practical applications of AIEgens still face the challenge of transforming AIEgens from molecules into materials. Till now, many AIEgens have been integrated into fiber, endowing the fiber with prominent fluorescence and/or photosensitizing capacities. AIEgens and fiber complement each other for making progress in flexible smart materials, in which the utilization of AIEgens creates new application possibilities for fiber, and the fiber provides an excellent carrier for AIEgens towards realizing the conversion from molecule to materials and an ideal platform to research the aggregate state of AIEgens in mesoscale and macroscale. This review begins with a brief summary of the recent advances related to some typical AIEgens with various functions and the technology for the fabrication of AIEgen-functionalized fiber. The most representative applications are then highlighted by focusing on energy conversion, personal protective equipment, biomedical, sensor, and fluorescence-related fields. Finally, the challenges, opportunities, and tendencies in future development are discussed in detail. This review hopes to inspire innovation in AIEgens and fiber from the view of mesoscale and macroscale.

Ascorbic Acid-Caused Quenching Effect of Protein Clusteroluminescence Probe: The Fast Fluorescent Detection of Ascorbic Acid in Vegetables

It is interesting and meaningful to explore fluorescent probes for novel rapid detection methods. In this study, we discovered a natural fluorescence probe, bovine serum albumin (BSA), for the assay of ascorbic acid (AA). Due to clusterization-triggered emission (CTE), BSA has the character of clusteroluminescence. AA shows an obvious fluorescence quenching effect on BSA, and the quenching effect increases with increasing concentrations of AA. After optimization, a method for the rapid detection of AA is established by the AA-caused fluorescence quenching effect. The fluorescence quenching effect reaches saturation after 5 min of incubation time and the fluorescence is stable within more than one hour, suggesting a rapid and stable fluorescence response. Moreover, the proposed assay method shows good selectivity and a wide linear range. To further study the mechanisms of AA-caused fluorescence quenching effect, some thermodynamic parameters are calculated. The main intermolecular force between BSA and AA is electrostatic, presumably leading to the inhibiting CTE process of BSA. This method also shows acceptable reliability for the real vegetable sample assay. In summary, this work will not only provide an assay strategy for AA, but also open an avenue for the application expansion of CTE effect of natural biomacromolecules.

Molecular-level enhanced clusterization-triggered emission of nonconventional luminophores in dilute aqueous solution

Nonconjugated and nonaromatic luminophores based on clustering-triggered emission derived from through-space conjugation have drawn emerging attention in recent years. The reported nonconventional luminophores are emissive in concentrated solution and/or in the solid state, but they tend to be nonluminescent in dilute solution, which greatly limits their sensing and imaging applications. Herein, we design unique clusteroluminogens through modification of cyclodextrin (CD) with amino acids to enable the intermolecular and intramolecular clusterization of chromophores in CD-based confined space. The resulted through-space interactions along with conformation rigidification originated from hydrogen bond interaction and complexation interaction generate blue to cyan fluorescence even in the dilute solution (0.035 wt.%, quantum yield of 40.70%). Moreover, the prepared histidine-modified CD (CDHis) is demonstrated for fluorescent detection of chlortetracycline with high sensitivity and selectivity. This work provides a new and universal strategy to synthesize nonconventional luminophores with bright fluorescence in dilute aqueous solution through molecular-level enhanced clusterization-triggered emission.

Long-Lived Dynamic Room Temperature Phosphorescence from Carbon Dots Based Materials

As a type of room temperature phosphorescence (RTP) material, carbon dots (CDs) always show short lifetime and low phosphorescence efficiency. To counter these disadvantages, several strategies, such as embedding in rigid matrix, introducing of heteroatom, crosslink-enhanced emission, etc., are well developed. Consequently, lots of CDs-based RTP materials are obtained. Doping of CDs into various matrix is the dominant method for preparation of long-lived CDs-based RTP materials so far. The desired CDs@matrix composites always display outstanding RTP performances. Meanwhile, matrix-free CDs and carbonized polymer dots-based RTP materials are also widely developed. Amounts of CDs possessing ultra-long lived, multiple colored, and dynamic RTP emission are successfully obtained. Herein, the recent progress achieved in CDs-based RTP materials as well as the corresponding efficient strategies and emission mechanisms are summarized and reviewed in detail. Due to CDs-based RTP materials possess excellent chemical stability, photostability and low biological toxicity, they exhibit great application potential in the fields of anti-counterfeiting, data encryption, and biological monitoring. The application of the CDs-based RTP materials is also introduced in this review. As a promising functional material, development of long wavelength RTP emitting CDs with long lifetime is still challengeable, especially for the red and near-infrared emitting RTP materials.

A processable, scalable, and stable full-color ultralong afterglow system based on heteroatom-free hydrocarbon doped polymers

Although room-temperature phosphorescence (RTP) organic materials are a widely-studied topic especially popular in recent decades, long-lived RTP able to fulfil broad time-resolved application requirements reliably, are still rare. Polymeric materials doped with phosphorescent chromophores generally feature high productivity and diverse applications, compared with their crystalline counterparts. This study proves that pure polycyclic aromatic hydrocarbons (PAHs) may even outperform chromophores containing hetero- or heavy-atoms. Full-color (blue, green, orange and red) polymer-PAHs with lifetimes >5000 ms under ambient conditions are constructed, which provide impressive values compared to the widely reported polymer-based RTP materials in the respective color regions. The polymer-PAHs could be fabricated on a large-scale using various methods (solution, melt and in situ polymerization), be processed into diverse forms (writing ink, fibers, films, and complex 3D architectures), and be used in a range of applications (anti-counterfeiting, information storage, and oxygen sensors). Plus their environmental (aqueous) stability makes the polymer-PAHs a promising option to expand the portfolio of organic RTPs.

Photoinduced Clusteroluminescence Redshift of Poly(methyl acrylate) via Radicals

One-step photopolymerization and photochromism of clusteroluminescence (CL) polymers mean that the polymer materials can be prepared on a large scale and applied widely. Herein, we reported unique photochromic CL polymers prepared by one-step radical photopolymerization. Seven copolymerized films (PMA_xBA) with methyl acrylate and butyl acrylate as monomers, a cross-linked PMA (PMA-CL) film, a double-network PMAPBA film based on the first network PMA-CL, and four PMA films with increasing content of photoinitiator ethoxy benzoin (BEE) were prepared to study CL formation and transition. Experimental results prove that increasing the ratio of the PMA chains in PMA_xBA enhances the photochromic effect, which verifies the main role of PMA chains with the shorter branched alkanes. Surprisingly, cross-linking in PMA-CL strengthens interchain packing and interchain through-space interactions (TSIs), leading to the formation of larger clusters and further CL redshift from 410 to 491 nm, whereas the PBA chains filled in the cross-linked network weakens interchain TSIs among PMA chains and makes CL red shift from 410 to 472 nm. In addition, as the BEE content increases in the PMA films, a higher radical concentration also promotes the formation of TSIs and clusters, which benefits the photochromism. For applications, colorless, dissolvable, and thermoplastic PMA featuring photochromism in this case can be widely used in information loading, rewriting, and multifunctional coating. This work provides a new strategy to enrich the properties of CL polymers toward diverse applications.