Color-Tunable and Stable Copper Iodide Cluster Scintillators for Efficient X-Ray Imaging

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.

Emerging 0D Hybrid Metal Halide Luminescent Glasses

0D hybrid metal halide (HMH) luminescent glasses have garnered significant attentions for its chemical diversity in optoelectronic applications and it also retains the skeleton connectivity and coordination mode of the crystalline counterparts while exhibiting various physics/chemistry characteristics distinct from the crystalline states. However, understanding of the glass-forming ability and the specific structural origins underpinning the luminescent properties of 0D HMH glasses remains elusive. In this review, it is started from the solid-liquid phase transition and thermodynamic analysis of 0D HMHs formed through melt-quenching, and summarize the current compounds capable of stably forming glassy phases via chemical structural design. The structural characterization methods are further discussed and highlight the exceptional transparency, specific luminescent properties, and glass crystallization behaviors. Moreover, the application prospects demonstrated by these 0D HMH glasses have been presented accordingly in X-ray detection and imaging, anti-counterfeiting, and information encryption. Finally, perspective is offered into the future development of this emerging family of 0D HMH glasses and their applications.

Reversible Interconversion between Ag2 and Ag6 Clusters and Their Responsive Optical Properties

The exploration of structural interconversion in clusters triggered by external stimuli has attracted significant interest due to its potential to elucidate structure-property relationships of metal clusters. In this study, two types of silver clusters, Ag2 and Ag6, are synthesized. Interestingly, the clusters exhibit reversible transformations in response to changes in the solvent conditions. The structures and optical properties of these clusters are thoroughly characterized using techniques such as mass spectrometry, single-crystal X-ray diffraction, photoluminescence, and radioluminescence spectroscopy. While both Ag2 and Ag6 display excellent photoluminescence properties, Ag2 demonstrates superior performance in X-ray radioluminescence compared to Ag6. Flexible scintillator films fabricated from Ag2 clusters exhibit outstanding X-ray imaging capabilities, achieving a spatial resolution of 15.0 lp/mm and an impressive detection limit for an X-ray dose of 0.58 μGy s-1. This detection limit is nearly 10 times lower than the typical dose rate used in X-ray diagnostics (5.5 μGy s-1). This work introduces a novel approach for designing thiol-free silver clusters capable of solvent-dependent reversible interconversion, offering new insights into the development of silver clusters for advanced X-ray imaging applications.

Highly Efficient Manganese Bromides with Reversible Luminescence Switching through Amorphous-Crystalline Transition

While luminescent stimuli-responsive materials (LSRMs) have become one of the most sought-after materials owing to their potential in optoelectronic applications, the use of earth-scarce lanthanides remains a crucial problem to be solved for further development. In this work, two manganese-based LSRMs, (R)-(+)-1-phenylethylammonium manganese bromide, (R-PEA)2MnBr4, and (S)-(-)-1-phenylethylammonium manganese bromide, (S-PEA)2MnBr4, are successfully demonstrated. Both (R-PEA)2MnBr4 and (S-PEA)2MnBr4 show a kinetically stable red-emissive amorphous state and a thermodynamically stable green-emissive crystalline state at room temperature, where the fully reversible transition can be done through melt-quenching and annealing processes. Based on this property, a reusable manganese-halide-based time-temperature indicator is demonstrated for the first time. Furthermore, an X-ray scintillator with a low limit of detection (18.1 nGy/s) and a high spatial resolution limit (30.0 lp/mm) are achieved by exploiting the high transparency of amorphous states. These results uncover the multifunctionality of manganese halides and pave the way for upcoming research.

One-Dimensional Red Light-Emissive Organic Manganese(II) Halides as X-Ray Scintillators

Although metal halide-based X-ray scintillators have obtained significant development with adjustable radioluminescent spectral range, the red light-emitting scintillator has been sparsely reported and remains a great challenge until now. To remedy this research blank, we investigated the scintillating property of red light-emissive one-dimensional (1D) organic manganese halide of (MBIZ)(MnCl3H2O)·H2O (MBIZ = 2-methyl-1H-benzoimidazolium) with a high PLQY of 71% under UV light excitation. Remarkably, this manganese halide single crystal exhibits a compelling X-ray scintillating property in the red light spectral range with a light yield of 19 600 photons MeV-1 and detection limit of 0.204 μGy/s, which is significantly better than the standard dosage for X-ray diagnostics. Furthermore, this manganese halide also exhibits excellent radiation resistance ability toward long-term continuous irradiation of high-dose X-ray with stable radiophotoluminescence intensity. Benefiting from the abovementioned combined merits, (MBIZ)(MnCl3H2O)·H2O demonstrates high-performance X-ray imaging with an outstanding spatial resolution of 11.1 lpmm-1. As far as we know, this is an infrequent red-emissive X-ray scintillator in metal halide materials, which highlights a successful structural design concept to explore new manganese halides as more desirable scintillators and expand the application field in medical diagnosis.

Biodegradable copper-iodide clusters modulate mitochondrial function and suppress tumor growth under ultralow-dose X-ray irradiation

Both copper (Cu2+/+) and iodine (I-) are essential elements in all living organisms. Increasing the intracellular concentrations of Cu or I ions may efficiently inhibit tumor growth. However, efficient delivery of Cu and I ions into tumor cells is still a challenge, as Cu chelation and iodide salts are highly water-soluble and can release in untargeted tissue. Here we report mitochondria-targeted Cu-I cluster nanoparticles using the reaction of Cu+ and I- to form stable bovine serum albumin (BSA) radiation-induced phosphors (Cu-I@BSA). These solve the stability issues of Cu+ and I- ions. Cu-I@BSA exhibit bright radioluminescence, and easily conjugate with the emission-matched photosensitizer and targeting molecule using functional groups on the surface of BSA. Investigations in vitro and in vivo demonstrate that radioluminescence under low-dose X-ray irradiation excites the conjugated photosensitizer to generate singlet oxygen, and combines with the radiosensitization mechanism of the heavy atom of iodine, resulting in efficient tumor inhibition in female mice. Furthermore, our study reveals that BSA protection causes the biodegradable Cu-I clusters to release free Cu and I ions and induce cell death by modulating mitochondrial function, damaging DNA, disrupting the tricarboxylic acid cycle, decreasing ATP generation, amplifying oxidative stress, and boosting the Bcl-2 pathway.

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.

Organosilicon-Based Ligand Design for High-Performance Perovskite Nanocrystal Films for Color Conversion and X-ray Imaging

Perovskite nanocrystals (PNCs) bear a huge potential for widespread applications, such as color conversion, X-ray scintillators, and active laser media. However, the poor intrinsic stability and high susceptibility to environmental stimuli including moisture and oxygen have become bottlenecks of PNC materials for commercialization. Appropriate barrier material design can efficiently improve the stability of the PNCs. Particularly, the strategy for packaging PNCs in organosilicon matrixes can integrate the advantages of inorganic-oxide-based and polymer-based encapsulation routes. However, the inert long-carbon-chain ligands (e.g., oleic acid, oleylamine) used in the current ligand systems for silicon-based encapsulation are detrimental to the cross-linking of the organosilicon matrix, resulting in performance deficiencies in the nanocrystal films, such as low transparency and large surface roughness. Herein, we propose a dual-organosilicon ligand system consisting of (3-aminopropyl)triethoxysilane (APTES) and (3-aminopropyl)triethoxysilane with pentanedioic anhydride (APTES-PA), to replace the inert long-carbon-chain ligands for improving the performance of organosilicon-coated PNC films. As a result, strongly fluorescent PNC films prepared by a facile solution-casting method demonstrate high transparency and reduced surface roughness while maintaining high stability in various harsh environments. The optimized PNC films were eventually applied in an X-ray imaging system as scintillators, showing a high spatial resolution above 20 lp/mm. By designing this promising dual organosilicon ligand system for PNC films, our work highlights the crucial influence of the molecular structure of the capping ligands on the optical performance of the PNC film.

Mechanochemical Synthesis of Cuprous Complexes for X-ray Scintillation and Imaging

Cuprous complex scintillators show promise for X-ray detection with abundant raw materials, diverse luminescent mechanisms, and adjustable structures. However, their synthesis typically requires a significant amount of organic solvents, which conflict with green chemistry principles. Herein, we present the synthesis of two high-performance cuprous complex scintillators using a simple mechanochemical method for the first time, namely [CuI(PPh3)2R] (R = 4-phenylpyridine hydroiodide (PH, Cu-1) and 4-(4-bromophenyl)pyridine hydroiodide (PH-Br, Cu-2). Both materials demonstrated remarkable scintillation performances, exhibiting radioluminescence (RL) intensities 1.52 times (Cu-1) and 2.52 times (Cu-2) greater than those of Bi4Ge3O12 (BGO), respectively. Compared to Cu-1, the enhanced RL performance of Cu-2 can be ascribed to its elevated quantum yield of 51.54%, significantly surpassing that of Cu-1 at 37.75%. This excellent luminescent performance is derived from the introduction of PH-Br, providing a more diverse array of intermolecular interactions that effectively constrain molecular vibration and rotation, further suppressing the nonradiative transition process. Furthermore, Cu-2 powder can be prepared into scintillator film with excellent X-ray imaging capabilities. This work establishes a pathway for the rapid, eco-friendly, and cost-effective synthesis of high-performance cuprous complex scintillators.

Time-resolved radioluminescence of the Cu(I) cluster Cu4I62-. Different responses to photo, X-ray, β-ray and α-particle excitation

Time-resolved radioluminescence (TRRL) properties of the Cu(I) cluster Cu4I62- upon pulsed X-ray, β-ray or α-particle excitation are described. The longer (>2 μs) TRRL component displays exponential decay comparable to pulsed UV excitation; however, temporal behaviour at shorter times indicates that high local excited state density provides an alternative decay channel.

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 .

Visualized X-ray Dosimetry for Multienvironment Applications

X-ray dose detection plays a critical role in various scientific fields, including chemistry, materials, and medicine. However, the current materials used for this purpose face challenges in both immediate and delayed radiation detections. Here, we present a visual X-ray dosimetry method for multienvironment applications, utilizing NaLuF4 nanocrystals (NCs) that undergo a color change from green to red upon X-ray irradiation. By adjustment of the concentrations of Ho3+, the emission color of the NCs can be tuned thanks to the cross-relaxation effects. Furthermore, X-ray irradiation induces generation of trapping centers in NaLuF4:Ho3+ NCs, endowing the generation of mechanoluminescence (ML) behavior upon mechanical stimulation after X-ray irradiation ceases. The ML intensity shows a linear correlation with the X-ray dose, facilitating the detection of delayed radiation. This breakthrough facilitates X-ray dose inspection in flaw detection, nuclear medicine, customs, and civil protection, thereby enhancing opportunities for radiation monitoring and control.

A copper-iodide cluster microcube-based X-ray scintillator

Newly developed copper-iodide cluster microcubes offer a solution to the issues commonly faced by powder scintillation screens. These problems include inadequate scintillation performance and significant light scattering, resulting in poor image quality. With the advent of monodisperse copper-iodide cluster microparticle scintillators, efficient and long-term stable scintillation is achieved, while ensuring biocompatibility. Moreover, they enable high-resolution static and dynamic X-ray imaging, providing high image quality.

High-Performance X-Ray Imaging using Lanthanide Metal-Organic Frameworks

Scintillating materials that convert ionizing radiation into low-energy photons hold great potential for radiation detection, nondestructive inspection, medical radiography, and space exploration. However, organic scintillators are characterized by low radioluminescence, while bulky inorganic scintillators are not suitable for the development of flexible detectors. Here, high-resolution X-ray imaging using solution-processable lanthanide-based metal-organic frameworks as microscale scintillators is demonstrated. Mechanistic studies suggest that lanthanide ions absorb X-rays to generate high-density molecular triplet excitons, and excited linkers subsequently sensitize lanthanide ions via nonradiative resonance energy transfer. Furthermore, the crystalline nature offers a delocalized electronic feature rather than isolated subunits, which enables direct trapping of charge carriers by lanthanide emitters. By controlling the concentration ratio between Tb³⁺ and Eu³⁺ ions, efficient and color-tunable radioluminescence of lanthanide ions can be achieved. When coupled with elastic, transparent polymer matrices, these metal-organic framework-based microscintillators allow the fabrication of flexible X-ray detectors. Such detectors feature a detection limit of 23 nGy s^-1 , which is 240 times lower than the typical radiation dose for medical diagnosis. X-ray imaging with resolution higher than 16.6 line pairs per millimeter is further demonstrated. These findings provide insight into the future design of hybrid scintillators for optoelectronics and X-ray sensing and imaging.

Copper Organometallic Iodide Arrays for Efficient X-ray Imaging Scintillators

Lead-free organic metal halide scintillators with low-dimensional electronic structures have demonstrated great potential in X-ray detection and imaging due to their excellent optoelectronic properties. Herein, the zero-dimensional organic copper halide (18-crown-6)2Na2(H2O)3Cu4I6 (CNCI) which exhibits negligible self-absorption and near-unity green-light emission was successfully deployed into X-ray imaging scintillators with outstanding X-ray sensitivity and imaging resolution. In particular, we fabricated a CNCI/polymer composite scintillator with an ultrahigh light yield of ∼109,000 photons/MeV, representing one of the highest values reported so far for scintillation materials. In addition, an ultralow detection limit of 59.4 nGy/s was achieved, which is approximately 92 times lower than the dosage for a standard medical examination. Moreover, the spatial imaging resolution of the CNCI scintillator was further improved by using a silicon template due to the wave-guiding of light through CNCI-filled pores. The pixelated CNCI-silicon array scintillation screen displays an impressive spatial resolution of 24.8 line pairs per millimeter (lp/mm) compared to the resolution of 16.3 lp/mm for CNCI-polymer film screens, representing the highest resolutions reported so far for organometallic-based X-ray imaging screens. This design represents a new approach to fabricating high-performance X-ray imaging scintillators based on organic metal halides for applications in medical radiography and security screening.