Highly Effective Hybrid Copper(I) Iodide Cluster Emitter with Negative Thermal Quenched Phosphorescence for X-Ray Imaging

Bright and Fast-Response Hybrid X-Ray Scintillators by Molecular and Dielectric Confinement

Scintillators featuring bright and fast-response properties are essential for high-speed and dynamic X-ray imaging. Nevertheless, simultaneously possessing high light yields and fast-response remains a significant challenge for most scintillators. Herein, we propose a strategy to achieve the bright and fast-response characteristics of scintillators by leveraging the combined effects of dielectric and molecular confinement in organic-inorganic hybrid scintillators (TPA)2MnBr4. Thereinto, large tetrapropylammonium cations (TPA+) surround [MnBr4]2- units, forming a zero-dimensional (0D) molecular confinement structure that promotes electron localization and achieves a notable light yield of 56800 photons MeV-1. Meanwhile, the low dielectric constant of TPA+ can enhance dielectric confinement of [MnBr4]2- units, mitigating exciton capture by deep defects. These synergistic effects in the scintillators lead to a large exciton binding energy of 1028.8 meV and an ultrafast response time of 500 fs. Notably, under the irradiation of X-rays, (TPA)2MnBr4 exhibits an extremely low detection limit of 18.7 nGyair s-1 and an exceptional spatial resolution of 21.0 lp mm-1. Given the bright and fast-response features of scintillators, we demonstrate the potential applications in 3D dynamic and real-time X-ray imaging. These findings lay the groundwork for designing high-performance scintillators and open avenues for innovative applications in high-resolution and dynamic imaging.

Monitoring α/β Particles Using a Copper Cluster Scintillator Detector

High-energy radiation is widely used in medicine, industry, and scientific research. Meanwhile, the detection of environmental ionizing radiation is essential to ensure the safe use of high-energy radiation. Among radiation detectors, scintillator detectors offer multiple advantages, including simple structure, high sensitivity, excellent environmental adaptability, and a favorable performance-to-price ratio. However, the development of high-performance scintillators that can provide highly sensitive responses to environmental radiation, especially α/β particles, remains a challenge. In this work, a copper cluster (Cu4I4(DPPPy)2) with excellent water-oxygen stability is prepared using a simple one-pot method at room temperature. Cu4I4(DPPPy)2 not only exhibits excellent X-ray excited luminescence (XEL) under X-ray irradiation but also demonstrates a highly sensitive scintillation response to α/β particles. By integrating Cu4I4(DPPPy)2 with a photomultiplier tube (PMT) and nuclear electronics, an α/β surface contamination monitor is successfully developed. This monitor enables the sensitive detection of excessive α/β particles in real-world environments. The detection frequency and signal intensity of Cu4I4(DPPPy)2 significantly surpass those of commercial scintillator of YAP:Ce, BGO, PbWO4, and anthracene under identical conditions, highlighting the promising application of metal clusters in low-dose environmental radiation detection.

Spatial & Temporal Dual-Resolved Anti-Counterfeiting Applications in a Long Afterglow System Based on Bismuth Halides

While anticounterfeiting systems based on long persistent luminescence (LPL) materials demonstrate a mature trend, the integration of tunable luminescent lifetimes and emission colors in LPL-based anticounterfeiting systems remains a challenge. Herein, we propose a temporal and spatial anticounterfeiting strategy utilizing novel zero dimensional (0D) metal halides, specifically (PBA)3BiCl6:xSb3+ (PBA = 4-Phenylbenzylamine, x = 0, 0.05, 0.1, 0.15), which exhibit long persistent luminescence characteristics. A controllable emission color transition can be observed from green to white to orange by varying the excitation wavelength, accompanied by different afterglow durations of the LPL emission. Additionally, various emission colors are observed at different delay times. Furthermore, the controlled LPL duration is achieved through Sb3+ doping in (PBA)3BiCl6, attributed to the triplet energy transfer (TET) process. A noticeable afterglow luminescence is observed when using a mobile phone's flashlight as the excitation source, enhancing the portability of the light source. The multifaceted tuning of emission colors and the modulation of the duration of tunable LPL establish a foundation for multicolor and time-resolved anticounterfeiting, significantly elevating the security level of advanced portable anticounterfeiting systems.

Synthesis and Characterization of Copper(I) Halide Heteroleptic Complexes with Thermally Activated Delayed Fluorescence

In the global context of green chemistry and sustainable development, luminescent copper(I) halide complexes hold broad applications, attributed to their abundant resources and excellent photophysical properties. Herein, two novel copper(I) halide complexes were synthesized and systematically investigated using single-crystal X-ray diffraction, photophysical characterization, and theoretical calculations among other methods. Both solid-state complexes exhibit bright green luminescent emissions with low self-absorption rates. The photoluminescence quantum yields (PLQYs) are as high as 95% and 87%, respectively. Because their singlet-triplet energy gaps (ΔEST) are very small, both being 0.10 eV, these complexes can achieve thermally activated delayed fluorescence emission through efficient reverse intersystem crossing. Theoretical calculations revealed that their high-efficiency luminescence arises from the synergistic effects of metal-to-ligand charge transfer, halogen-to-ligand charge transfer, and ligand-to-ligand charge transfer.

Copper(I) Halide Complex Featuring Blue Thermally Activated Delayed Fluorescence and Aggregate Induced Emission for Efficient X-ray Scintillation and Imaging

Developing solution-processable and stable scintillators with high light yields, low detection limits and high imaging resolutions holds great significance for flexible X-ray imaging. However, attaining an optimal equilibrium among X-ray absorption capacity, exciton utilization efficiency, and decay lifetime of scintillators remains a substantial challenge. Here, a new Cu(I) halide complex was synthesized in a mild condition. It exhibits intense blue thermally activated delayed fluorescence (TADF), remarkable aggregation-induced emission (AIE) characteristic, as well as good water-oxygen stability and photochemical stability. Notably, the complex shows excellent radiation resistance and efficient radioluminescence (RL) with an ultra-low detection limit of 42.5 nGyairs-1. This superior scintillation performance can be attributed to the synergistic effect of effective X-ray absorption by the heavy Cu2I2 core, the high radiation-induced exciton utilization rate in TADF process, and the remarkable suppression of non-radiative transitions by the restriction of intramolecular motions in solid state. Furthermore, the favourable solution processability of the complex facilitates the successful fabrication of a flexible film, achieving high-quality X-ray imaging with a resolution of 17.3 lp mm-1. This work highlights the potential of hybrid Cu(I) halides with AIE-TADF effects for high-energy radiation detection and imaging, opening up new avenues for the exploration of cost-effective and high-performance scintillators.

High-Resolution Flexible X-ray Imaging in a Two-Dimensional Mn2+-Doped Perovskite Scintillator

Flexible scintillator screens characterized by high spatial resolution, low cost, and a simple fabrication process are in significant demand for applications in medical diagnosis and industrial detection. Here, we have demonstrated a new Mn2+-doped two-dimensional (2D) Ruddlesden-Popper type perovskite, (4-tert-butylbenzylamine)2PbBr4:Mn, serving as a highly efficient scintillator candidate. Doping with Mn2+ induces a spin-forbidden internal transition (4T1g → 6A1g) that enhances the energy-transfer efficiency from the strongly bound excitons of the host material to the d electrons of the Mn2+ ions, ultimately leading to intense orange-red emission. This process enhances the photoluminescence quantum yield of (4-tert-butylbenzylamine)2PbBr4 (1) and decreases its self-absorption. Therefore, at the optimal Mn2+-doping concentration, 1:8.4%Mn2+ demonstrates a high light yield of 21,532 Ph/MeV and a low detection limit of 198.19 nGyair s-1, exceeding the performance of a commercial bismuth germanium oxide (BGO) scintillator. Furthermore, we combined ultrafine powders of 1:8.4%Mn2+ with poly(dimethylsiloxane) to fabricate flexible scintillator films. With the optimal film thickness and mass percentage of 1:8.4%Mn2+, the scintillator films achieve their maximum spatial resolution of 17.3 lp mm-1. The above results indicate that the exceptional flexible scintillation imaging performance of 1:8.4%Mn2+ effectively addresses the shortcomings of current commercial scintillators, thereby providing a new option for the scintillator family.

Short Lifetime Radical Metal Cluster Scintillator

Metal clusters, an emerging class of scintillator materials, have attracted much attention owing to their inherently high X-ray absorption, mild synthesis conditions, low toxicity, strong luminescence, and large Stokes shift. However, the decay lifetime of metal clusters is usually on the order of microseconds, which is unfavorable for safety inspection, nondestructive testing, and medical imaging. Here, the open-shell luminescent radical ligand was used to construct the first radical cluster scintillator Cu2I2(L)4. The spin-allowed doublet emission of Cu2I2(L)4 theoretically enabled 100% exciton utilization and exhibited a short radiation decay lifetime on the nanosecond scale. Cu2I2(L)4 can be fabricated into a flexible scintillator screen for X-ray imaging, achieving a high resolution of 30.7 LP mm-1. More importantly, the Cu2I2(L)4 scintillator screen has no residual images during X-ray imaging. This work reports the first luminescent metal cluster with a radical ligand and presents a new strategy for constructing short lifetime X-ray scintillators.

Afterglow Copper(I) Iodine Cluster Scintillator

Copper(I) iodine clusters have drawn intense attention due to their advantageous photophysical properties, such as a high luminescence efficiency, large Stokes shift, and tunable luminescence lifetimes. In this work, a copper(I) iodine cluster (Cu2I2-CH3CN) was synthesized, which exhibits unique afterglow emission, ultrahigh quantum yield (90.1 % in solid state) and aggregation-induced emission (AIE) behavior. It was found that thermally activated delayed fluorescence (TADF) and long-lifetime phosphorescence occur simultaneously in Cu2I2-CH3CN. The unique photoluminescence properties of Cu2I2-CH3CN were attributed to the large spin-orbit coupling (SOC) and long-term rigidity of the crystal. The high quantum efficiency, TADF characteristics, and heavy-atom composition of Cu2I2-CH3CN endow it with excellent X-ray excited luminescence (XEL) properties, making it a promising X-ray scintillator. A flexible scintillator screen made of Cu2I2-CH3CN was successfully fabricated and used for X-ray imaging with a spatial resolution of 23.6 LP mm-1.

Controlling Triplet-Harvesting Pathways and Nonlinear Optical Properties in Cu(I) Iodide-Based Polymers through Ligand Engineering

Organic-inorganic hybrid metal halides have become enormously important in optoelectronics, sensing, photosensitization, etc. In this study, we report a structural transition from a staircase configuration to a cubane configuration in Cu(I) iodide-based polymers influenced by the coordination behavior of two different π*-acceptor ligands. The staircase polymer structure, coordinated with 3-cyanopyridine, demonstrates efficient thermally activated delayed fluorescence from (metal+halide)-to-ligand charge transfer [1/3(M+X)LCT] states, with a singlet-triplet energy splitting of ∼9 meV. Conversely, upon replacement of the cyano with an amino group at the same position, a one-dimensional polymeric structure of Cu4I4 cubane-type clusters is formed, which shows strong cluster-centered (3CC) orange emission at room temperature. Temperature-dependent photoluminescence studies indicate that the 3CC state behaves as a self-trapped excitonic state with significant exciton-phonon coupling having a Huang-Rhys factor of 58.6. Additionally, we report this cubane-type cluster polymer acts as an efficient nonlinear optical material showing third harmonic generation with a χ(3) value of 1.32 × 10-18 m2 V-2 and a laser-induced damage threshold of 25.87 GW/cm2.

Strongly photoluminescent and radioluminescent copper(i) iodide hybrid materials made of coordinated ionic chains

Scintillation-based X-ray detection has been widely used in various fields from medical diagnostics to security. In this study, we report four new CuI-based hybrid materials consisting of anionic inorganic chains coordinated to cationic ligands. Due to their unique bonding nature, these compounds demonstrate high stability, solution processability, and efficient photoluminescence with photoluminescence quantum yields (PLQYs) reaching ∼85%. Their X-ray scintillation properties are characterized by high light yield comparable to that of commercially available scintillators, an excellent linear response to the X-ray dose rate, a low detection limit, and radio-robustness. In addition, the emission mechanisms and structure-property relationships are also analyzed using both experimental and theoretical methods. These findings suggest possibilities for developing new and high-performance CuI-based hybrid materials for efficient radiation detection and imaging.

Luminescence Thermochromism of a Noncluster Copper Iodide Complex

Hybrid copper(I) halide materials are currently attracting significant attention due to their exceptional luminescence properties, offering great potential for the development of multifunctional emissive materials with, in addition, eco-friendly features. A binuclear copper iodide complex, based on the [Cu2I2L4] motif with phosphite derivatives as ligands, has been synthesized and structurally characterized. Photophysical investigations indicate that this complex displays luminescence thermochromic properties, which are characterized by a temperature-dependent change in the relative intensity of two emission bands. The high-contrast luminescence thermochromism, with an important color variation from purple to cyan, is ascribed to the thermal equilibrium of two different excited states. While thermochromism is relatively known for multimetallic complexes, the perfectly controlled thermochromism of the studied compound is unprecedented for a binuclear complex. From theoretical investigations, this original feature is due to the coordination of phosphite ligands, which induces a specific energy layout of the complex, presenting vacant orbitals of varying nature. This single-component, dual-emissive binuclear complex, displaying relevant sensitivity temperature response, presents great potential for luminescence ratiometric thermometry applications. This study underlines the relevance of the ligand engineering strategy in developing original, emissive, and sustainable copper-based materials.

Cations Induced Fluorescence Enhancement in Keggin-Al13 for Quantitative Detection

The Keggin-Al13 hydroxide clusters serve as pivotal models for elucidating molecular pathways in geochemical reactions. In this study, we presented a strategy aiming at the quantitative detection of ε-Al13 Keggin clusters using photoluminescent spectra. Specifically, we manipulate the electronic structure of ε-Al13 by introducing Na ions onto the ε-Al13 surface, encapsulated within a Na-O3 motif. The Na-ion-modified ε-Al13 (Na-ε-Al13) cluster demonstrates incredible photoluminescent qualities, with fluorescence excitation and emission peaks centered at 365 and 436 nm, respectively. In addition, the fluorescence intensities display a linear dependence on the concentrations of Na-ε-Al13, with a detection limit of 15.4 μM. This correlation facilitates the quantitative and precise determination of Na-ε-Al13 concentrations via fluorescence. Both experimental characterizations and theoretical calculations underscore the importance of decorated Na ions in regulating the electronic structure of the ε-Al13 cluster. Lastly, the influence of external anions/cations on the photoluminescent properties of ε-Al13 primarily mirrors modifications to the nonradiative decay process, which is regulated via electrostatic interactions. This work demonstrates an effective strategy for quantitative detection of the ε-Al13 Keggin clusters through photoluminescent spectra.

Lead Bromide Complex in Tri-n-Octylphosphine Oxide Matrix with Bright Photoluminance and Exceptional Thermoplasticity

Metal halide materials have recently drawn increasing research interest for their excellent opto-electronic properties and structural diversity, but their resulting rigid structures render them brittle and poor formability during manufacturing. Here we demonstrate a thermoplastic luminant hybrid lead halide solid by integrating lead bromide complex into tri-n-octylphosphine oxide (TOPO) matrix. The construction of the hybrid materials can be achieved by a simple dissolution process, in which TOPO molecules act as the solvents and ligands to yield the monodispersed clusters. The combination of these functional units enables the near-room-temperature melt-processing of the materials into targeted geometry by simple molding or printing techniques, which offer possibilities for fluorescent writing inks with outstanding self-healing capacity to physical damage. The intermarriage between metal halide clusters with functional molecules expands the range of practical applications for hybrid metal halide materials.

The nature of metallophilic interactions in closed-shell d8-d8 metal complexes

We have quantum chemically analyzed the closed-shell d8-d8 metallophilic interaction in dimers of square planar [M(CO)2X2] complexes (M = Ni, Pd, Pt; X = Cl, Br, I) using dispersion-corrected density functional theory at ZORA-BLYP-D3(BJ)/TZ2P level of theory. Our purpose is to reveal the nature of the [X2(CO)2M]⋯[M(CO)2X2] bonding mechanism by analyzing trends upon variations in M and X. Our analyses reveal that the formation of the [M(CO)2X2]2 dimers is favored by an increasingly stabilizing electrostatic interaction when the M increases in size and by more stabilizing dispersion interactions promoted by the larger X. In addition, there is an overlooked covalent component stemming from metal-metal and ligand-ligand donor-acceptor interactions. Thus, at variance with the currently accepted picture, the d8-d8 metallophilicity is attractive, and the formation of [M(CO)2X2]2 dimers is not a purely dispersion-driven phenomenon.

Zero-Dimensional Copper(I) Halide Microcrystals as Highly Efficient Scintillators for Flexible X-ray Imaging

Commercially available rare-earth-doped inorganic oxide materials have been widely applied as X-ray scintillators, but the fragile characteristics, high detection limit, and harsh preparation condition seriously restrict their wide applications. Furthermore, it remains a huge challenge to realize X-ray flexible imaging technology for real-time monitoring of the curving interface of complex devices. To address these issues, we herein report two isostructural cuprous halides of zero-dimensional (0D) [AEPipz]CuX3·X·H2O (AEPipz = N-aminoethylpiperazine, X = Br and I) with controllable size to nanosize crystal as highly efficient scintillators toward flexible X-ray imaging. These cuprous halides exhibit highly efficient cyan photoluminescence and radioluminescence emissions with the highest quantum yield of 92.1% and light yield of 62,400 photons MeV-1, respectively, surpassing most of the commercially available inorganic scintillators. Meanwhile, the ultralow detection limit of 95.7 nGyair s-1 was far below the X-ray dose required for diagnosis (5.5 μGyair s-1). More significantly, the flexible film is facilely assembled with excellent foldability and high crack resistance, which further acts as a scintillation screen achieving a high spatial resolution of 17.4 lp mm-1 in X-ray imaging, demonstrating the potential application in wearable radiation radiography. The combined advantages of high light yield, low detection limit, and excellent flexibility promote these 0D cuprous halides as the most promising X-ray scintillators.

Bias-Switchable Dual-Mode Organic Photodetector with High Operational Stability Using Self-Trapped Cs3Cu2I5 Interfacial Layer

Conventional photovoltaic (PV)-photodetectors are hard to detect fainted signals, while photomultiplication (PM)-capable devices indispensable for detecting weak light and are prone to degrade under strong light illumination and large bias, and it is urgent to realize highly efficient integrated detecting system with both PM and PV operation modes. In this work, one lead-free Cs3Cu2I5 nanocrystals with self-trapping exciton nature was introduced as interfacial layer adjacent to bulk and layer-by-layer heterojunction structure, and corresponding organic photodetectors with bias-switchable dual modes are demonstrated. The fabricated device exhibits low operating bias (0 V for PV mode and 0.8 V for PM mode), high specific detectivity (~1013 Jones), fast response speed as low as 1.59 μs, large bandwidth over 0.2 MHz and long-term operational stability last for 4 months in ambient condition. This synergy strategy also validated in different materials and device architectures, providing a convenient and scalable production process to develop highly efficient bias-switchable multi-functional organic optoelectrical applications.

Ultrastable Copper Iodide Hybrid with Intrinsic Greenish White-Light Emission by Incorporating an Anionic Inorganic Functional Unit into an Extended Structure

Incorporating a functional unit into the multidimensional coordination polymer skeleton is an efficient way to improve the stability of materials and expand their application. In this paper, anionic copper iodide inorganic functional modules are incorporated into one-dimensional extended chains by using a unique bidentate cationic organic ligand. Benefiting from the ionic extended structure, the resulting hybrid possesses a remarkable stability with a decomposition temperature as high as 300 °C. Meanwhile, the hybrid material exhibits intrinsic greenish white-light emission with a high photoluminescent quantum yield of 70%. The emission was investigated by temperature-dependent emission spectra, which proved to be the result of the synergistic effect of two energy states. The novel synthetic strategy provides an efficient route for the development of functional organic metal halides.

Suppressing the Thermal Quenching Effect via a Cluster Conformer in Copper(I)-Iodide Coordination Polymeric Phosphors for High-Power White LED Lighting

High-power LED lighting is a crucial challenge due to the notorious thermal quenching (TQ) effect of traditional phosphors at high operating currents, which would result in poor device performance and hamper practical optoelectronic application. Herein, we demonstrate ligand engineering of a cubane- versus staircase-like [Cu4I4] conformer as a node in coordination polymers, which remarkably suppresses the TQ effect of cluster-based photoluminescence. For complex 1 (the formula [Cu4I4(bbimb)2]n) with the cubane-like [Cu4I4] conformer as a node, the metallophilicity interaction enables ultrabright triplet emission with a photoluminescence quantum yield over 82%, and the phonon-assisted detrapping process of excitons effectively suppresses the TQ effect in the wide temperature range. In contrast, the staircase-like [Cu4I4] conformer as a node in complex 2 (the formula [Cu4I4(bbtmb)2]n) exhibits a serious TQ effect over the investigated temperature. Phosphor-converted white LEDs (pc-wLEDs) were fabricated by integrating the cluster-based coordination polymers as a color converter, and their electroluminescence performances were investigated under high bias currents. The prototype pc-wLED device by incorporating the phosphor with the suppressed TQ effect exhibits a continuous rise in brightness under a high bias current of 300 mA. The results demonstrate that ligand engineering of the cluster conformer via suppressing the TQ effect proves efficient in designing an ideal color converter for high-power pc-wLED lighting.

Thermally Activated Delayed Fluorescence (TADF)-active Coinage-metal Sulfide Clusters for High-resolution X-ray Imaging

The study of facile-synthesis and low-cost X-ray scintillators with high light yield, low detection limit and high X-ray imaging resolution plays a vital role in medical and industrial imaging fields. However, the optimal balance between X-ray absorption, decay lifetime and excitonic utilization efficiency of scintillators to achieve high-resolution imaging is extremely difficult due to the inherent contradiction. Here two thermally activated delayed fluorescence (TADF)-actived coinage-metal clusters M6 S6 L6 (M=Ag or Cu) were synthesized by simple solvothermal reaction, where the cooperation of heavy atom-rich character and TADF mechanism supports strong X-ray absorption and rapid luminescent collection of excitons. Excitingly, Ag6 S6 L6 (SC-Ag) displays a high photoluminescence quantum yield of 91.6 % and scintillating light yield of 17420 photons MeV-1 , as well as a low detection limit of 208.65 nGy s-1 that is 26 times lower than the medical standard (5.5 μGy s-1 ). More importantly, a high X-ray imaging resolution of 16 lp/mm based on SC-Ag screen is demonstrated. Besides, rigid core skeleton reinforced by metallophilicity endows clusters M6 S6 L6 strong resistance to humidity and radiation. This work provides a new view for the design of efficient scintillators and opens the research door for silver clusters in scintillation application.

Near-Unity Green Luminescent Hybrid Manganese Halides as X-ray Scintillators

The increasing demands in optoelectronic applications have driven the advancement of organic-inorganic hybrid metal halides (OIMHs), owing to their exceptional optical and scintillation properties. Among them, zero-dimensional (0D) low-toxic manganese-based scintillators have garnered significant interest due to their exceptional optical transparency and elevated photoluminescence quantum yields (PLQYs), making them promising for colorful light-emitting diodes and X-ray imaging applications. In this study, two OIMH single crystals of (Br-PrTPP)2MnBr4 (Br-PrTPP = (3-bromopropyl) triphenylphosphonium) and (Br-BuTPP)2MnBr4 (Br-BuTPP = (4-bromobutyl) triphenylphosphonium) were prepared via a facile saturated crystallization method. Benefiting from the tetrahedrally coordinated [MnBr4]2- polyhedron, both of them exhibited strong green emissions peaked at 517 nm owing to the d-d electron transition of Mn2+ with near-unity PLQYs of 99.33 and 86.85%, respectively. Moreover, benefiting from the high optical transparencies and remarkable luminescence properties, these manganese halides also exhibit excellent radioluminescent performance with the highest light yield of up to 68,000 photons MeV-1, negligible afterglow (0.4 ms), and linear response to X-ray dose rate with the lowest detection limit of 45 nGyair s-1. In X-ray imaging, the flexible film made by the composite of (Br-PrTPP)2MnBr4 and PDMS shows an ultrahigh spatial resolution of 12.78 lp mm-1, which provides a potential visualization tool for X-ray radiography.

X-ray-triggered through-space charge transfer and photochromism in silver nanoclusters

Materials exhibiting X-ray-induced photochromism have consistently piqued the interest of researchers. Exploring the photochromic properties of such materials is valuable for understanding the structural changes and electron transfer processes that occur under high energy radiation, such as X-ray irradiation. Here, a crystalline silver(I) nanocluster synthesized from tert-butylacetylene silver was found to have the ability to exhibit color and photoluminescence changes upon exposure to X-ray radiation. The responsive behavior was observed across a wide temperature range of 100-300 K, with the ability to respond particularly well to soft X-rays (λ > 1 Å) and exhibit light responsiveness to hard X-rays (λ < 1 Å). By combining experimental findings including X-ray diffraction, X-ray photoelectron spectroscopy, electron spin resonance, etc. with theoretical calculations, we have proposed that X-ray irradiation induces electron transfer from chloride (Cl-) located in the center of the silver(I) nanocluster to the surrounding Ag14 in the skeleton. This represents the first documented example in which electron transfer induced by X-ray excitation has been observed, accompanied by a photochromism process, in silver nanoclusters. This study contributes to our understanding of X-ray-induced photochromism and the electron transfer process in silver cluster compounds. It also provides valuable insights and potential design strategies for applications such as photochromism, photoluminescence color change, and photoenergy conversion.

A Comprehensive Analysis of Luminescent Crystallized Cu Nanoclusters

Photoluminescence (PL) emission is an intriguing characteristic displayed by atomically precise d10 metal nanoclusters (NCs), renowned for their meticulous atomic arrangements, which have captivated the scientific community. Cu(I) NCs are a focal point in extensive research due to their abundance, cost-effectiveness, and unique luminescent attributes. Despite similar core sizes, their luminescent characteristics vary, influenced by multiple factors. Progress hinges on synthesizing new NCs and modifying existing ones, with postsynthetic alterations impacting emission properties. The rapid advancements in this field pose challenges in discerning essential points for excelling amidst competition with other d10 NCs. This Perspective explores the intricate origins of PL emission in Cu(I) NCs, providing a comprehensive review of their correlated structural architectures. Understanding the mechanistic origin of PL emission in each cluster is crucial for correlating diverse characteristics, contributing to a deeper comprehension from both fundamental and applied scientific perspectives.

Allochroic cluster light-emitting diodes based on unique μ3-tetraphosphine Cu3X3 crowns with tunable excited states

Multicomponent excited states endow copper iodide clusters with allochroic properties under diverse stimuli. However, crystal states are required, and cluster stimulus sensitivity hampers electroluminochromism. We developed PhQPCu3X3 (X = Cl, Br, and I) with the first μ3-bridging tetraphosphine ligand, whose Cu3X3 crowns were exposed to external stimulus. The increased proportion of Cu3X3 results in equal contributions of cluster- and ligand-centered components to excited states, the former of which is highly sensitive to grind, vapor, and, especially, electric stimuli, due to semi-exposed Cu3X3. Through vacuum evaporation and vapor fumigation of cluster-based emissive layers, the diodes' electroluminescence colors changed from yellow to white. Joule heat during device operation induced further color variation to orange, corresponding to Commission Internationale de l'Eclairage coordinates of PhQPCu3I3 changed from (0.44 ± 0.1, 0.34 ± 0.1) to (0.57 ± 0.1, 0.42 ± 0.1). These results demonstrate the superiority of luminescent clusters in accurate excited-state modulation, holding promise for wide applications.

Achieving a Record Scintillation Performance by Micro-Doping a Heterovalent Magnetic Ion in Cs3 Cu2 I5 Single-Crystal

An ultrabright, ultrafast, and low-cost ideal scintillator has been critically absent and is sorely desired in scintillation detection, but has hitherto not been found. Here, a high-quality bulk Cs3 Cu2 I5 :Mn single-crystal scintillator with ultrahigh light yield (≈95 772 photons per MeV, 137 Cs γ-rays), excellent energy resolution (3.79%, 662 keV), and ultrafast scintillation decay time (3 ns, 81.5%) is reported. In mechanism, it is found that micro-doping of a heterovalent magnetic ion (at the ppm level) can effectively modulate the luminescence kinetics of self-trapped excitons in the scintillator. Compared with previous reports, the introduction of trace amounts of magnetic Mn2+ (≈18.6 ppm) in Cs3 Cu2 I5 single-crystal shortens the scintillation decay time by several hundred times, transforming the slow decay into an ultrafast decay. Simultaneously, the light yield is also increased about three times to the highest value so far. From the comprehensive performance of the micro-doped Cs3 Cu2 I5 :Mn single-crystal, these excellent scintillation properties, physical characteristics suitable for practical applications, and low-cost advantages render this single-crystal an ideal scintillator with great potential for commercialization.

High Performance Dynamic X-ray Flexible Imaging Realized Using a Copper Iodide Cluster-Based MOF Microcrystal Scintillator

X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal-organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm-1 .

Thermally Activated Delayed Fluorescence Coinage Metal Cluster Scintillator

X-ray scintillators are widely used in medical imaging, industrial flaw detection, security inspection, and space exploration. However, traditional commercial scintillators are usually associated with a high use cost because of their substantial toxicity and easy deliquescence. In this work, an atomically precise Au-Cu cluster scintillator (1) with a thermally activated delayed fluorescence (TADF) property was facilely synthesized, which is environmentally friendly and highly stable to water and oxygen. The TADF property of 1 endows it with an ultrahigh exciton utilization rate. Combined with the effective absorption of X-ray caused by the heavy-atom effect and a limited nonradiative transition caused by close packing in the crystal state, 1 exhibits an excellent radioluminescence property. Moreover, 1 has good processability for fabricating a large, flexible thin-film device (10 cm × 10 cm) for high-resolution X-ray imaging, which can reach 40 μm (12.5 LP mm^-1). The properties mentioned earlier make the coinage metal cluster promising for use as a substitute for traditional commercial scintillators.

One-Dimensional Chiral Copper Iodide Chain-Like Structure Cu4 I4 (R/S-3-quinuclidinol)3 with Near-Unity Photoluminescence Quantum Yield and Efficient Circularly Polarized Luminescence

Chiral organic-inorganic hybrid metal halide materials have shown great potential for circularly polarized luminescence (CPL) related applications for their tunable structures and efficient emissions. Here, this work combines the highly emissive Cu₄ I₄ cubane cluster with chiral organic ligand R/S-3-quinuclidinol, to construct a new type of 1D Cu-I chains, namely Cu₄ I₄ (R/S-3-quinuclidinol)₃ , crystallizing in noncentrosymmetric monoclinic P2₁ space group. These enantiomorphic hybrids exhibit long-term stability and show bright yellow emission with a photoluminescence quantum yield (PLQY) close to 100%. Due to the successful chirality transfer from the chiral ligands to the inorganic backbone, the enantiomers show intriguing chiroptical properties, such as circular dichroism (CD) and CPL. The CPL dissymmetry factor (g_lum ) is measured to be ≈4 × 10^-3 . Time-resolved photoluminescence (PL) measurements show long averaged decay lifetime up to 10 µs. The structural details within the Cu₄ I₄ reveal the chiral nature of these basic building units, which are significantly different than in the achiral case. This discovery provides new structural insights for the design of high performance CPL materials and their applications in light emitting devices.