Multifunctional fluorescent probes targeting chemical warfare agents have been highly valued due to high-detection efficiency and cost-effectiveness, but sluggish development and inadequate performance remain imminent. Exploiting innovative design strategies is the most effective program to achieve performance breakthroughs. Here, we propose heteroatom engineering, substituting the sulfur (S) atom with the strongly electron-donating nitrogen (N) atom, and develop the multifunctional fluorescent probes MeBIMPCz and MeBIM3PCz targeting phosgene and diethyl chlorophosphate (DCP, the mimic of Sarin). Computational calculations reveal that the heteroatom substitution markedly decreases the electrostatic potential (ESP) and average localized ionization energy (ALIE), enabling substantial boosting of the reactivity. Hereby, the probes enable highly sensitive detection of phosgene and DCP up to nanomolar-liquid/ppm-vapor (LODs: 1.95 nM-liquid/0.24 ppm-vapor for phosgene; 28.71 nM-liquid/25.54 ppb-vapor for DCP). And the limit of detection for DCP is improved by up to two orders of magnitude, and the response time for phosgene is shortened fourfold (from 20 min to 5 min), with superior specificity and anti-interference performance. Furthermore, the test strips integrated with a smartphone not only fulfill qualitative and semi-quantitative detection but also perform well in multiple realistic scenario simulations (accidental leakage during industrial accidents, hazardous residue from terrorist attacks and chemical screening in security inspections) and long-term monitoring assays (up to 15 days). This work provides a promising molecule design strategy to realize multifunctional probes through heteroatom engineering.

Photochemical upconversion by annihilation of two triplet excitons to a higher-energy singlet state enables energy control of photons in optoelectronics and photonics. Upconversion initiated by a closed-shell sensitiser is limited by energy losses from singlet–triplet intersystem crossing. Here we explore open-shell organic radicals as sensitisers and their closed-shell hydrogenated analogues as annihilators in photon upconversion. The sensitiser combines optical transitions from a triphenylmethyl (TTM-1Cz) radical with energy-degenerate triplet states of an anthracene-based component (DPA) in one molecule (TTM-1Cz-DPA). The difference of one hydrogen atom in its closed-shell counterpart (HTTM-1Cz-DPA) switches the spin-optical properties to an annihilator that can mediate efficient upconversion. Red-to-blue photon upconversion by intermolecular energy transfer, from open-shell sensitiser to closed-shell annihilator, is demonstrated in solution with an apparent anti-Stokes shift higher than 0.9 eV and 7% quantum efficiency. We evaluate this mechanism against true ‘single component’ mixtures for upconversion and find that the presence of hydrogenated precursor with radicals is essential for high performance. Understanding the emergent spin-optical properties from paired open-shell and closed-shell systems enables new opportunities for energy management from the same molecular frame.

Alzheimer-associated neuronal thread protein (AD7c-NTP) is a promising urinary biomarker for Alzheimer's disease (AD), but its extremely low concentration poses a significant challenge for rapid and quantitative detection. In this work, a fluorescence lateral flow immunoassay (LFIA) based on PolyT-templated copper quantum dots (CuQDs) was developed for sensitive determination of AD7c-NTP in urine samples. Long-chain poly-thymidine DNA was employed as a biomacromolecular template to stabilize CuQDs, significantly extending fluorescence lifetime and improving signal reproducibility.The proposed assay enables quantitative detection within 15 min and demonstrates excellent analytical performance. A clinical study involving 150 urine samples (60 CE and 90 non-AD) showed an area under the ROC curve (AUC) of 0.949, with a sensitivity of 93.9% and specificity of 97.4% at a cutoff of 1.24 pg/mL. Good agreement with a reference chemiluminescent immunoassay was observed (r > 0.99).The developed method provides a simple, cost-effective, and reliable platform for quantitative analysis of urinary AD7c-NTP and shows potential for point-of-care applications.

Donor-acceptor type near-infrared luminescent radicals were synthesized in high yields via an iodinated building block. The rigid, quasi-planar configuration promotes the formation of an intramolecular charge-transfer excited state with non-bonding characteristics. This ultimately leads to efficient deep-NIR emission beyond 800 nm, realizing a photoluminescence quantum efficiency as high as 21%.

Photochemical upconversion by annihilation of two triplet excitons to a higher-energy singlet state enables energy control of photons in optoelectronics and photonics. Upconversion initiated by a closed-shell sensitizer is limited by energy losses from singlet-triplet intersystem crossing. Here we explore open-shell organic radicals as sensitizers and their closed-shell hydrogenated analogues as annihilators in photon upconversion. The sensitizer combines optical transitions from a triphenylmethyl (TTM-1Cz) radical with energy-degenerate triplet states of an anthracene-based component (DPA) in one molecule (TTM-1Cz-DPA). The difference of one hydrogen atom in its closed-shell counterpart (HTTM-1Cz-DPA) switches the spin-optical properties to an annihilator that can mediate efficient upconversion. Red-to-blue photon upconversion by intermolecular energy transfer, from open-shell sensitizer to closed-shell annihilator, is demonstrated in solution with an apparent anti-Stokes shift higher than 0.9 eV and 7% quantum efficiency. We evaluate this mechanism against true 'single component' mixtures for upconversion and find that the presence of hydrogenated precursor with radicals is essential for high performance. Understanding the emergent spin-optical properties from paired open-shell and closed-shell systems enables new opportunities for energy management from the same molecular frame.

Chemical warfare agents, particularly nerve agent Sarin and blister agent Sulfur Mustard, are used in warfare and terrorist attacks, severely threatening global security. However, there are few reports on simultaneous gas-phase detection of both using single fluorescent probes, which have high application potential. This study presents a novel dual-functional fluorescent probe BHDTAZ, with dimethyl acridine (DMA) as donor and triazole (TAZ) as acceptor. It shows distinct responses to Sarin simulant diethyl chlorophosphate (DCP) and Sulfur Mustard simulant 2-chloroethyl ethyl sulfide (2-CEES) vapors: DCP induces a photoluminescence (PL) emission intensity ratio (I507/I428) of 9.3, 79 nm red-shift, and LOD of 1.25 ppb; 2-CEES causes 40 % PL enhancement, 12 nm red-shift, and LOD of 1.23 ppm. Notably, naked-eye visible PL color changes occur blue-to-green for DCP, unchanged blue for 2-CEES. Mechanistic studies reveal that modulated intermolecular charge transfer (ICT) effect enables differentiation, with DCP enhancing it more potently. This work provides dual-functional probe for gas-phase identification of the simulants and advances PL-based multiplex chemical threat detection strategies.

Diradical compounds provide an intriguing platform for investigating multicenter bonding and the effects of electronic coupling. However, synthesizing diradicals is challenging because these species are generally highly reactive and transient. In this study, we present a straightforward synthetic method for the preparation of boron-containing diradicals, achieved through the direct addition of diradical precursors to a borane with a redox non-innocent bipyridine substituent under mild conditions, thus eliminating the need for strong reducing agents. These newly synthesized diradicals serve as models to explore how molecular geometry and connectivity influence electronic coupling. Our findings highlight the interplay between dispersion-dominated through-space interactions with multicenter covalent character and diradical character, offering valuable insights for developing advanced materials with tailored properties.

Organic luminescent radicals with efficient doublet emission can directly transfer electrons and energy to oxygen, enabling fluorescence-guided photodynamic therapy. However, their water insolubility and unclear oxygen interaction mechanisms limit their application. To address these challenges, we synthesized an amphiphilic organic radical (TTM-2PyPh) that forms self-assembled water-soluble nanoparticles (TTM-2PyPh_SA@NPs) with deep-red emission, serving as Type-I/II photosensitizers. Quantum chemistry calculations confirm an efficient electron transfer process between the radicals and oxygen. These nanoparticles self-assemble in vivo, target tumors, and produce reactive oxygen species more effectively than core-shell nanoparticles (TTM-2Py_CS@NPs), chlorin e6, and methylene blue. Additionally, TTM-2PyPh_SA@NPs demonstrate superior tumor eradication in vivo. This work advances the development of novel water-soluble radical-based photosensitizers for enhanced photodynamic therapy.

2,5-Dihydro-1H-1,2,4-triazol-2-yl radicals (1,2,4-triazolyl radicals) represent a unique class of organic heterocyclic radicals that exhibit exceptional stability while remaining underexplored. Here, we report the synthesis and systematic investigation of three 1,2,4-triazolyl radical derivatives (TR-NO2, TR-Cz and TR-Au) through introducing electron-donating/withdrawing groups and Au(I) coordination. Combined theoretical, electrochemical and spectroscopic studies reveal precise control over their frontier orbital energetics, redox potentials, and photophysical properties through these modifications. Notably, substituent variations induced substantial changes in molecular packing arrangement, leading to distinct intermolecular magnetic interactions in crystalline state. This study not only establishes 1,2,4-triazolyl radicals as a versatile platform for molecular design but also revitalizes their potential for advanced materials applications, renewing interest in this underutilized class of radicals.

Skeletal isomerism and halogen regulation represent an effective and versatile strategy for tailoring purely organic room-temperature phosphorescence (RTP) toward practical applications. Herein, a series of carbazole- and benzoindole-based luminophores are designed to enable high-performance RTP in hydrogen-bonded polymer matrices, allowing the direct fabrication of phosphorescent 3D-printed patterns. By systematically integrating halogen substitution with skeletal isomerism, the excited-state dynamics are finely regulated, affording RTP lifetimes of up to 1.47 s. Mechanistic investigations reveal that halogen atoms enhance spin-orbit coupling to facilitate intersystem crossing, while skeletal isomerism modulates triplet exciton stabilization through differences in molecular geometry and packing behavior. This synergistic regulation strategy provides a general framework for the rational design of efficient organic RTP materials and offers practical guidance for advanced photonic devices, information encryption, and 3D-printed luminescent architectures.

Organic radicals offer unique optoelectronic properties beyond those of conventional closed-shell materials, making them attractive candidates for advanced biomedical applications. However, their practical use is severely hindered by the intrinsic instability, and effective generation of ultrasound-responsive reactive oxygen species (ROS) with hypoxia tolerance remains largely unexplored. Here, we report a highly stable open-shell radical-based immunogenic sono/photodynamic theranostic system that enables second near-infrared (NIR-II) bioimaging and efficient tumor eradication under both light and ultrasound excitation. By employing a symmetric dual-acceptor molecular design, we develop a donor-acceptor radical (NTM-2) that exhibits a 13-fold enhancement in photodegradation resistance relative to that of the pristine radical. Upon 808 nm irradiation, NTM-2 nanoparticles simultaneously display bright NIR-II emission, pronounced photothermal conversion, and efficient type-I ROS generation. In vivo studies demonstrate high-resolution NIR-II vascular imaging and near-complete tumor ablation under photoactivation. Notably, under ultrasound stimulation, NTM-2 nanoparticles generate type-I ROS efficiently, leading to potent sonodynamic tumor suppression and significantly prolonged survival in tumor-bearing mice. This work establishes a molecular strategy for stabilizing organic radicals and highlights their potential as robust open-shell emitters for hypoxia-tolerant immunogenic sono/photodynamic cancer theranostics.

Abstract Excitons in organic materials are emerging as an attractive platform for tunable quantum technologies. Structures with near-degenerate doublet and triplet excitations in linked trityl radical, acene and carbazole units can host quartet states. These high spin states can be coherently manipulated, and later decay radiatively via the radical doublet transition. However, this requires controlling the deexcitation pathways of all metastable states. Here we establish design rules for efficient quartet generation and recycling to luminescence, using different connection arrangements of the molecular units. We discover that electronic coupling strength between these units dictates quartet formation and delayed emission yields, particularly through a Coulombically tuned acene-radical charge transfer state. This state acts as a source of non-radiative decay when acene-radical separation is small, but facilitates reversible doublet-quartet interconversion when acene-radical separation is large. Using these rules we report a material with 55% luminescence yield, where 94% of emitting excitons are recycled from the quartet with a 1.0 μ s lifetime. This reveals the central role of molecular topology in luminescent quantum materials.

Polyborosiloxane (PBDMS) exhibits promising potential in the modification of ethylene‑vinyl acetate copolymer (EVA) owing to its unique dynamic B‑O bonds. However, the significant polarity difference between the two components leads to poor compatibility, distinct macroscopic phase separation, and weak interfacial adhesion in PBDMS/EVA blends, resulting in inefficient stress transfer and an inability to fully exploit the energy dissipation and recovery properties of the dynamic bonds. In this work, maleic anhydride‑grafted EVA (EVA‑g‑MAH) was used as a reactive compatibilizer, and PBDMS/EVA blends with EVA‑g‑MAH mass fractions ranging from 0 to 12 wt

Triphenylmethyl (trityl) radicals have shown potential for use in organic optoelectronic and spintronic applications. However, due to the poor luminescence of alternant symmetry hydrocarbons, the design of practical trityl structures has been limited to donor-radical intramolecular charge-transfer systems to break the alternant symmetry, which results in poor emission and photostability in polar solvents. Here, we synthesized a series of donor-acceptor (D-A•) neutral radicals based on the tris(2,4,6-trichlorophenyl)methyl (TTM) radical moiety by introducing the 9H-tribenzo[b,d,f]azepine (TBA) ring with 20 π electrons as a donor group. In contrast to other TTM-based D-A• radicals, these TBA radicals exhibit unique and superior properties for luminescent efficiency (56% in acetonitrile) and photostability (t1/2= 4.3 × 105 s, with estimated half-lives reaching up to several days) in polar solvents. Transient absorption (TA) spectra reveal the occurrence of an efficient transformation from the Franck-Condon (FC) state to the zwitterionic resonance intramolecular charge-transfer (ICT) state with a time constant of a few picoseconds. Due to the zwitterionic resonance ICT character, nonradiative decay channels, which are dominated by high-frequency modes (over 1000 cm-1) in TBA radicals, can be efficiently suppressed. The present study highlights the promotion of antiaromaticity relief in luminescent radicals and offers a valuable viewpoint for understanding the ICT excited-state dynamics of D-A-type dyads in polar solvents.

The photoluminescence properties of fluorescent probes directly influence sensing performance, especially regarding distinct signal changes and high-contrast responses. Although the relationship between photoluminescence properties and molecular structure has been extensively explored, the connection among molecular structure, photoluminescence properties, and sensing performance remains insufficiently understood. Herein, a design strategy is proposed to synergistically modulate structural isomerism and intramolecular charge transfer (ICT), enabling a comprehensive investigation into the structure-property-performance relationship in fluorescent probes. The modulation of donor-acceptor binding sites through structural isomerism significantly impacts the sensing performance toward diethyl chlorophosphate (DCP, a mimic of the nerve agent Sarin). Subsequently, ICT tuning through donor substitution of the probe further amplifies the fluorescence response. The resulting optimal probe exhibits an exceptionally high ratiometric fluorescence response ratio (36.8), high sensitivity (LOD as low as 1.32 ppb), rapid response (<5s), excellent reusability (up to 20 cycles), and long-term monitoring performance (up to 42 days of continuous monitoring) for DCP vapors. This work deepens the understanding of the relationship among molecular structure, photoluminescence properties, and sensing performance, and provides a broadly applicable strategy for developing ratiometric probes, particularly for the long-term monitoring of trace-level hazardous substances.

Developing purely organic emitters capable of delivering efficient electroluminescence beyond 800 nm remains a central challenge due to severe non-radiative losses governed by the energy-gap law and strong exciton-vibration coupling. Herein, we report a molecularly engineered luminescent radical, TTM-DPS, synthesized by incorporating N,N-diphenylthiophen-2-amine (DPS) into the tris(2,4,6-trichlorophenyl)methyl (TTM) radical. This donor-acceptor arrangement enhances long-range charge-transfer coupling while preserving a non-bonding hole-electron distribution in the D1 doublet state, effectively suppressing high-frequency vibrational modes that typically trigger non-radiative decay. As a result, TTM-DPS exhibits deep-NIR photoluminescence with a peak at 895 nm and a fourfold enhanced quantum yield (4%) relative to the fused donor analogue TTM-2PTI (2PTI, 4-phenyl-4H-thieno[3,2-b]indole). When incorporated into OLEDs, TTM-DPS enables deep-NIR emission at 883-908 nm, achieving an external quantum efficiency of 1.26% and a radiance of 25800 mW sr-1 m-2, ranking among the best metal-free emitters operating in this spectral region. This work establishes a generalizable donor-engineering strategy to mitigate exciton-vibration coupling in radical systems, offering a promising pathway toward next-generation high-efficiency deep-NIR optoelectronics.

Methamphetamine (MA), a highly potent synthetic illicit drug, poses grave threats to the global public health and societal stability. However, on-site fluorescence detection to MA (particularly those operating in the visible range─remain scarce). In this work, a boron-based ratiometric fluorescent probe, BA-FO-BA, synthesized by covalently conjugating a triarylborane derivative with fluorene is presented. Upon exposure to methylphenethylamine (MPEA, an MA simulant), the probe exhibits a 70 nm blue shift, significant fluorescence enhancement, and rapid and reversible response, accompanied by a distinct visible emission color change from blue to deep purple. This response is also validated using confiscated MA samples. Moreover, a sensing mechanism driven by B-N coordination-induced enhancement of the intramolecular locally excited (LE) state is proposed and substantiated. Therefore, this study not only introduces a novel molecular design strategy for amine detection characterized by a rare blue-shift response but also provides a new pathway for developing the ratiometric fluorescent probe featured LE properties.

The development of polymer-based room-temperature phosphorescent (RTP) materials with ultra-long lifetimes is of great significance for expanding the practical applications of purely organic phosphors. Carbazole (Cz), as a classical electron-rich aromatic heterocycle, exhibits excellent photophysical properties and has been widely used in RTP material design. Interestingly, its structural isomer, benzoindole (Bd), which features a similar conjugated backbone and nitrogen-containing heterocycle, has also emerged as a promising RTP-active scaffold but remains underexplored. This study presents a facile physical doping strategy for constructing a series of polymer-based RTP materials through the incorporation of Cz and Bd derivatives into polyvinyl alcohol (PVA) and poly (methyl methacrylate) (PMMA) matrices, respectively. Benefiting from rigid polymer environments and effective suppression of nonradiative decay, the resulting doped films exhibit distinct RTP performance. Notably, the Cz-OCH3@PVA film achieves an ultralong phosphorescence lifetime of up to 2.24 s. Moreover, Bd derivatives also display efficient RTP behavior when doped into suitable polymer hosts, further validating Bd as a versatile building block for organic phosphorescent materials. In addition, the PMMA-based films demonstrate photoactivated RTP characteristics, while the excellent processability and flexibility of the PVA-based systems enable their potential application in information encryption and anti-counterfeiting. This work highlights the synergistic potential of Cz/Bd-based molecular design and polymer doping strategies in the development of highperformance organic RTP materials.

Abstract Achieving predictable color-tunable organic room-temperature phosphorescence (RTP) remains challenging due to limited understanding of triplet-state regulation in heteroaromatic systems. Carbazole and benzindole isomers provide an ideal platform to clarify how nitrogen positional isomerism governs triplet exciton behavior and emission energetics. Here, we establish a unified comparative framework to systematically investigate carbazole together with Bd[f], Bd[e], and Bd[g]. Nitrogen-site modulation within the fused tricyclic skeleton generates distinct red, yellow, green, and blue phosphorescence, while mechanochemical solvent-free synthesis enables scalable preparation of previously inaccessible benzindole isomers. Photophysical measurements combined with DFT/TD-DFT calculations, single-crystal analysis, and interaction region indicator theory reveal that positional isomerism controls exciton localization, triplet stabilization, and nonradiative decay independent of the host matrix. Here, we show that isomer-regulated triplet dynamics enable full-spectrum RTP, ultralong lifetimes up to 4.23 s, TSFRET behavior, and matrix-universal multifunctionality, establishing a general molecular design principle for rainbow-like organic phosphorescent materials.

Organic ultralong room temperature phosphorescence (URTP) materials have attracted growing interest due to their persistent afterglow and potential applications in information security, anti-counterfeiting, and advanced photonic systems. Herein, a series of benzoindole (Bd)-based emitters with progressively extended π-conjugation (Bd-NH2, Bd-NAP, Bd-PHE, and Bd-PYR) were rationally designed and synthesized to elucidate the effect of π-extension on triplet-state regulation and phosphorescence behavior. Photophysical investigations reveal that all Bd derivatives exhibit characteristic π-π* transitions and efficient triplet emission at low temperature, with emission maxima gradually redshifting as the conjugation length increases. When incorporated into a poly(lactic acid) (PLA) matrix, the resulting Bd@PLA composite films display photo-activated room-temperature phosphorescence with lifetimes extending from hundreds of milliseconds to the second regime. The rigid and oxygen-barrier microenvironment provided by PLA effectively stabilizes triplet excitons and suppresses nonradiative decay. Time-dependent density functional theory (TD-DFT) calculations indicate that π-conjugation extension induces systematic evolution of frontier molecular orbital energy levels and spatial distributions, rationalizing the observed emission redshift and supporting the feasibility of triplet-state formation and stabilization. Benefiting from the excellent processability of PLA, the composites were successfully applied to two-dimensional patterns and three-dimensional printed structures, enabling spatially and temporally programmable luminescent outputs. This work provides a general strategy for constructing wavelength-tunable organic URTP materials through synergistic molecular design and polymer confinement.