Scintillators are widely utilized for radiation detections in many fields, such as nondestructive inspection, medical imaging, and space exploration. Lead halide perovskite scintillators have ...recently received extensive research attention owing to their tunable emission wavelength, low detection limit, and ease of fabrication. However, the low light yields toward X‐ray irradiation and the lead toxicity of these perovskites severely restricts their practical application. A novel lead‐free halide is presented, namely Rb2CuBr3, as a scintillator with exceptionally high light yield. Rb2CuBr3 exhibits a 1D crystal structure and enjoys strong carrier confinement and near‐unity photoluminescence quantum yield (98.6%) in violet emission. The high photoluminescence quantum yield combined with negligible self‐absorption from self‐trapped exciton emission and strong X‐ray absorption capability enables a record high light yield of ≈91056 photons per MeV among perovskite and relative scintillators. Overall, Rb2CuBr3 provides nontoxicity, high radioluminescence intensity, and good stability, thus laying good foundations for potential application in low‐dose radiography.
A new lead‐free halide Rb2CuBr3 scintillator with 1D crystal structure is presented. It exhibits self‐trapped exciton emission with a large Stokes shift (0.91 eV). Thus, it has near‐unity photoluminescence quantum yield (98.6%) and a high radioluminescence light yield of ≈91 056 photons per MeV.
Metal halide perovskites and derivatives exhibit a high sensitivity and low detection limit as direct X‐ray detectors. Inorganic 2D bismuth halide perovskites are promising for X‐ray detections, but ...have not been reported. Moreover, the quantitative relationship between the structural dimensionality of A3B2X9 perovskites and their compositions has never been investigated, and the underlying mechanism is unclear. Here, the key structural descriptors for 2D A3B2X9 perovskite derivatives are reported: i) octahedral factor μ, 0.377 < μ < 0895; ii) tolerance factor t, 0.8 < t < 1.06; iii) (rA‐0.55)/t < 1.48 Å. Accordingly, a new 2D A3B2X9 perovskite derivative, Rb3Bi2I9, with high X‐ray attenuation coefficients is found. The assembled X‐ray detector exhibits a high μτ product of 2.51 × 10−3 cm2 V−1, good sensitivity for 159.7 μC Gyair−1 cm−2, and a record low detection limit of 8.32 nGyair s−1 among all direct and indirect perovskite X‐ray detectors. The device also exhibits good stability toward external bias and continuous gamma ray radiations (480 000 Gy). This work provides crystal structural insights to rationally design 2D perovskites for new types of radiation detectors.
The key structural descriptors are reported for 2D A3B2X9 perovskite derivatives. By following the above designing rules, Rb3Bi2I9 is assembled into an X‐ray detector, exhibiting a low detection limit of 8.32 nGyair s−1 and suppressed ions migration. The inorganic composition also guarantees excellent stability toward continuous radiation from the 60Co source.
Abstract
X-ray detectors are broadly utilized in medical imaging and product inspection. Halide perovskites recently demonstrate excellent performance for direct X-ray detection. However, ionic ...migration causes large noise and baseline drift, limiting the detection and imaging performance. Here we largely eliminate the ionic migration in cesium silver bismuth bromide (Cs
2
AgBiBr
6
) polycrystalline wafers by introducing bismuth oxybromide (BiOBr) as heteroepitaxial passivation layers. Good lattice match between BiOBr and Cs
2
AgBiBr
6
enables complete defect passivation and suppressed ionic migration. The detector hence achieves outstanding balanced performance with a signal drifting one order of magnitude lower than all previous studies, low noise (1/
f
noise free), a high sensitivity of 250 µC Gy
air
−1
cm
–2
, and a spatial resolution of 4.9 lp mm
−1
. The wafer area could be easily scaled up by the isostatic-pressing method, together with the heteroepitaxial passivation, strengthens the competitiveness of Cs
2
AgBiBr
6
-based X-ray detectors as next-generation X-ray imaging flat panels.
OBJECTIVE : To identify the genetic characteristics in a large-scale of patients with Charcot-Marie-Tooth disease (CMT). METHODS: From May 2012 to August 2016, we collected 1005 cases with suspected ...CMT throughout Japan, whereas
duplication/deletion were excluded in advance for demyelinating CMT cases. We performed next-generation sequencing targeting CMT-related gene panels using Illumina MiSeq or Ion Proton, then analysed the gene-specific onset age of the identified cases and geographical differences in terms of their genetic spectrum. RESULTS : From 40 genes, we identified pathogenic or likely pathogenic variants in 301 cases (30.0%). The most common causative genes were
(n=66, 21.9%),
(n=66, 21.9%) and
(n=51, 16.9%). In demyelinating CMT, variants were detected in 45.7% cases, and the most common reasons were
(40.3%),
(27.1%),
point mutations (6.2%) and
(4.7%). Axonal CMT yielded a relatively lower detection rate (22.9%), and the leading causes, occupying 72.4%, were
(37.2%),
(9.0%),
(8.3%),
(7.7%),
(5.1%) and
(5.1%). First decade of life was found as the most common disease onset period, and early-onset CMT cases were most likely to receive a molecular diagnosis. Geographical distribution analysis indicated distinctive genetic spectrums in different regions of Japan. CONCLUSIONS : Our results updated the genetic profile within a large-scale of Japanese CMT cases. Subsequent analyses regarding onset age and geographical distribution advanced our understanding of CMT, which would be beneficial for clinicians.
The growing demand for scalable solar‐blind image sensors with remarkable photosensitive properties has stimulated the research on more advanced solar‐blind photodetector (SBPD) arrays. In this work, ...the authors demonstrate ultrahigh‐performance metal‐semiconductor‐metal (MSM) SBPDs based on amorphous (a‐) Ga2O3 via a post‐annealing process. The post‐annealed MSM a‐Ga2O3 SBPDs exhibit superhigh sensitivity of 733 A/W and high response speed of 18 ms, giving a high gain‐bandwidth product over 104 at 5 V. The SBPDs also show ultrahigh photo‐to‐dark current ratio of 3.9 × 107. Additionally, the PDs demonstrate super‐high specific detectivity of 3.9 × 1016 Jones owing to the extremely low noise down to 3.5 fW Hz−1/2, suggesting high signal‐to‐noise ratio. Underlying mechanism for such superior photoelectric properties is revealed by Kelvin probe force microscopy and first principles calculation. Furthermore, for the first time, a large‐scale, high‐uniformity 32 × 32 image sensor array based on the post‐annealed a‐Ga2O3 SBPDs is fabricated. Clear image of target object with high contrast can be obtained thanks to the high sensitivity and uniformity of the array. These results demonstrate the feasibility and practicality of the Ga2O3 PDs for applications in solar‐blind imaging, environmental monitoring, artificial intelligence and machine vision.
Ultraviolet imaging technology is widely used in meteorology, medical science, and military science. For the first time, a high‐uniformity 32 × 32 solar‐blind image sensor array with outstanding imaging capability is demonstrated based on high‐performance Ga2O3 photodetectors. Schottky barrier lowering effect is experimentally revealed to attribute to the internal gain mechanism.
Surface passivation is proved to be an effective way to adjust material properties or to explore new two-dimensional (2D) materials. Herein, we proposed three hydrocarbons with high stability for the ...first time via hydrogenation on the Kagome graphene, namely, C6H4, C6H6-I, and C6H6-II. Unlike the Kagome graphene, which is metallic, all these 2D monolayers are wide-bandgap semiconductors (4.06–4.81 eV). Among them, C6H4 is an indirect bandgap semiconductor, but both C6H6-I and C6H6-II possess the direct bandgap feature. Considerable carrier mobilities (102 to 103 cm2 V–1 s–1) have been further confirmed in the three hydrocarbons on the basis of modified deformation potential theory. Specifically, for C6H4, the hole mobilities are as high as 104 to 105 cm2 V–1 s–1, comparable to those of graphene and black phosphorus. The intrinsic vertical electric field induced by the asymmetric crystal structures in C6H4 and C6H6-I will be beneficial to the spatial separation of electrons and holes in semiconductors, promising in the field of optoelectronics. In addition, hydrogenation has a great influence on the mechanical properties of Kagome graphene, no matter whether it is Young’s modulus, Poisson’s ratio, or ideal tensile strength. Particularly, in-plane axial negative Poisson’s ratios (−0.011/–0.018 along the a-/b-direction) were found in C6H6-I, mainly originated from the interaction of carbon pentagons and octagons. These interesting findings in our work may pave the way for the application of hydrogenated Kagome graphene in the future.
Two-dimensional (2D) materials are excellent candidates for advanced flexible electronics and gas sensors. Herein, we systematically investigate the layer-dependent electronic structures, mechanical ...properties and gas sensing characteristics of the newly synthesized γ-SnSe based on first-principles calculations. Bulk γ-SnSe is a typical van der Waals layered material with an indirect narrow band gap, while monolayer and multilayer γ-SnSe can be obtained through mechanical exfoliation due to its low cleavage energy. The band gap of γ-SnSe gradually increases with decreasing layers, reaching a value of 2.25 eV for the monolayer due to weakened interlayer coupling. Mechanical analysis reveals strong anisotropy in multilayer γ-SnSe, whereas the monolayer exhibits a negative Poisson's ratio (−0.023/−0.025). Additionally, based on the analysis of electronic structures, adsorption energies and charge transfer of the host materials after adsorption of various gases, it is found that the γ-SnSe monolayer demonstrates enhanced sensitivity and selectivity towards NO, NO
2
, and SO
2
compared to CO, CO
2
, H
2
S and NH
3
. These findings highlight the potential of γ-SnSe as an excellent gas-sensitive material for the detection of nitrogen oxides and sulfur dioxide.
Two-dimensional (2D) materials are excellent candidates for advanced flexible electronics and gas sensors.
Lead halide perovskites have recently emerged as promising X/γ-ray scintillators. However, the small Stokes shift of exciton luminescence in perovskite scintillators creates problems for the light ...extraction efficiency and severely impedes their applications in hard X/γ-ray detection. Dopants have been used to shift the emission wavelength, but the radioluminescence lifetime has also been unwantedly extended. Herein, we demonstrate the intrinsic strain in 2D perovskite crystals as a general phenomenon, which could be utilized as self-wavelength shifting to reduce the self-absorption effect without sacrificing the radiation response speed. Furthermore, we successfully demonstrated the first imaging reconstruction by perovskites for application of positron emission tomography. The coincidence time resolution for the optimized perovskite single crystals (4 × 4 × 0.8 mm
) reached 119 ± 3 ps. This work provides a new paradigm for suppressing the self-absorption effect in scintillators and may facilitate the application of perovskite scintillators in practical hard X/γ-ray detections.
Summary
The inward‐rectifying K+ channel AKT1 constitutes an important pathway for K+ acquisition in plant roots. In glycophytes, excessive accumulation of Na+ is accompanied by K+ deficiency under ...salt stress. However, in the succulent xerophyte Zygophyllum xanthoxylum, which exhibits excellent adaptability to adverse environments, K+ concentration remains at a relatively constant level despite increased levels of Na+ under salinity and drought conditions. In this study, the contribution of ZxAKT1 to maintaining K+ and Na+ homeostasis in Z. xanthoxylum was investigated. Expression of ZxAKT1 rescued the K+‐uptake‐defective phenotype of yeast strain CY162, suppressed the salt‐sensitive phenotype of yeast strain G19, and complemented the low‐K+‐sensitive phenotype of Arabidopsis akt1 mutant, indicating that ZxAKT1 functions as an inward‐rectifying K+ channel. ZxAKT1 was predominantly expressed in roots, and was induced under high concentrations of either KCl or NaCl. By using RNA interference technique, we found that ZxAKT1‐silenced plants exhibited stunted growth compared to wild‐type Z. xanthoxylum. Further experiments showed that ZxAKT1‐silenced plants exhibited a significant decline in net uptake of K+ and Na+, resulting in decreased concentrations of K+ and Na+, as compared to wild‐type Z. xanthoxylum grown under 50 mm NaCl. Compared with wild‐type, the expression levels of genes encoding several transporters/channels related to K+/Na+ homeostasis, including ZxSKOR, ZxNHX, ZxSOS1 and ZxHKT1;1, were reduced in various tissues of a ZxAKT1‐silenced line. These findings suggest that ZxAKT1 not only plays a crucial role in K+ uptake but also functions in modulating Na+ uptake and transport systems in Z. xanthoxylum, thereby affecting its normal growth.
Significance Statement
Succulent plants can better adapt to drought and salinity. Here we show that an inward‐rectifying potassium channel (ZxAKT1) contributes to this adaptation in Z. xanthoxylum, as unlike in glycophytes, where excessive accumulation of Na+ is accompanied by K+ deficiency under salt stress, in succulents K+ was maintained at a relatively constant level, despite increased Na+. Thus ZxAKT1 not only plays a crucial role in K+ uptake but also functions in modulating Na+ uptake and transport systems.
Two-dimensional (2D) materials with both ferroelasticity and negative Poisson's ratios have attracted intensive interest, but it is very rare to have both ferroelasticity and negative Poisson's ...ratios in a single material. Directional positive and negative Poisson's ratios in a switchable ferroelastic dielectric may enable non-destructive readout in ferroelastic data storage. Herein, we propose 14 kinds of stable 2D semiconductors: AB monolayers (A = Sc, Y, La; B = N, P, As, Sb, Bi) based on first-principles calculations. The band gaps of AB monolayers cover a wide range from 0.69 eV to 2.15 eV. Mechanical analysis reveals that these materials are flexible and 12 of 14 are predicted to possess an in-plane negative Poisson's ratio (NPR). Moreover, 10 of these 14 systems possess an out-of-plane NPR. More encouragingly, all AB monolayers are identified as 2D ferroelastic materials with reversible strains of around 5.94% to 20.30%. The ferroelastic switching barriers, mechanical properties and electronic structures of these materials are discussed in detail. Such outstanding properties make the AB monolayers very promising as switchable anisotropic 2D materials for nanoelectronics and micromechanical applications.
Two-dimensional (2D) materials with both ferroelasticity and negative Poisson's ratios have attracted intensive interest, but it is very rare to have both ferroelasticity and negative Poisson's ratios in a single material.
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