Ultrasensitive and stable X-ray detection using zero-dimensional lead-free perovskites

Sensitive and reliable X-ray detectors are essential for medical radiography,industrial inspection and security screening.Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence.Three-dimensional(3 D)organic-inorganic hybrid lead halide perovskites are promising for direct X-ray detection-they show improved sensitivity compared to conventional X-ray detectors.However,their high and unstable dark current,caused by ion migration and high dark carrier concentration in the 3 D hybrid perovskites,limits their performance and long-term operation stability.Here we report ultrasensitive,stable X-ray detectors made using zero-dimensional(0 D)methylammonium bismuth iodide perovskite(MA3Bi2I9)single crystals.The 0 D crystal structure leads to a high activation energy(Ea)for ion migration(0.46 e V)and is also accompanied by a low dark carrier concentration(~10^6 cm^-3).The X-ray detectors exhibit sensitivity of 10,620μC Gy-1 air cm-2,a limit of detection(Lo D)of 0.62 nG yairs-1,and stable operation even under high applied biases;no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of^23,800 m Gyair,equivalent to>200,000 times the dose required for a single commercial X-ray chest radiograph.Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.

Square-Free Pure Triangular Decomposition of Zero-Dimensional Polynomial Systems

Triangular decomposition with different properties has been used for various types of problem solving.In this paper,the concepts of pure chains and square-free pure triangular decomposition(SFPTD)of zero-dimensional polynomial systems are defined.Because of its good properties,SFPTD may be a key way to many problems related to zero-dimensional polynomial systems.Inspired by the work of Wang(2016)and of Dong and Mou(2019),the authors propose an algorithm for computing SFPTD based on Gr¨obner bases computation.The novelty of the algorithm is that the authors make use of saturated ideals and separant to ensure that the zero sets of any two pure chains are disjoint and every pure chain is square-free,respectively.On one hand,the authors prove the arithmetic complexity of the new algorithm can be single exponential in the square of the number of variables,which seems to be among the rare complexity analysis results for triangular-decomposition methods.On the other hand,the authors show experimentally that,on a large number of examples in the literature,the new algorithm is far more efficient than a popular triangular-decomposition method based on pseudodivision,and the methods based on SFPTD for real solution isolation and for computing radicals of zero-dimensional ideals are very efficient.

Synthesis and transformation of zero-dimensional Cs3BiX6(X=Cl,Br)perovskite-analogue nanocrystals

The unique structure of zero-dimensional(0D)perovskite-analogues has attracted a great amount of research interest in recent years.To date,the current compositional library of 0D perovskites is largely limited to the lead-based Cs4PbX6(X=Cl,Br,and I)systems.In this work,we report a new synthesis of lead-free 0D Cs3BiX6(X=Cl,Br)perovskite-analogue nanocrystals(NCs)with a uniform cubic shape.We observe a broad photoluminescence peak centered at 390 nm for the 0D Cs3BiCl6 NCs at low temperatures.This feature originates from a self-trapped exciton mechanism.In situ thermal stability studies show that Cs3BiX6 NCs remain stable upon heating up to 200°C without crystal structural degradation.Moreover,we demonstrate that the Cs3BiX6 NCs can transform into other bismuth-based perovskite-analogues via facile anion exchange or metal ion insertion reactions.Our study presented here offers the opportunity for further understanding of the structure-property relationship of 0D perovskite-analogue materials,leading toward their future optoelectronic applications.

Dietary zero-dimensional fullerene supplementation improves the meat quality,lipid metabolism,muscle fiber characteristics,and antioxidative status in finishing pigs

With the increasing demand for high-quality pork,more nutritional substances have been studied for the regulation of meat quality.Zero-dimensional fullerenes(C60)can modulate the biological behavior of a variety of cell lines and animals.In this study,we report the biological effects of C60 on finishing pigs at different concentrations.A total of 24 barrows(Duroc×Large White×Landrace),with an average body weight of 21.01±0.98 kg,were divided into 3 groups and each treated daily with C60(100 or 200 mg per kg feed)or a control diet until the end of the experiment.Our results showed that dietary C60 supplementation improved flesh color,marbling scores,and flavor amino acid contents of longissimus dorsi(LD)of growing-finishing pigs(P<0.05).C60 improved meat quality by regulating lipid metabolism and muscle fiber morphology by mediating the expression of genes,L-lactic dehydrogenase(LDH),myosin heavy chain(MyHC)IIa,MyHCIIb,peroxisome proliferator-activated receptor γ(PPARγ),and fatty acid transport protein 1(FATP1)(P<0.05).Moreover,C60 substantially promoted the mRNA expression of antioxidant enzyme genes(P<0.05),which also contributed to improving meat quality.These findings have important implications for the application of C60 in the livestock industry,especially for improving the meat quality of fattening pigs.

Strongly Zero-Dimensional Locales

New kinds of strongly zero-dimensional locales are introduced and characterized, which are different from Johnstone's, and almost all the topological properties for strongly zero-dimensional spaces have the pointloss localic forms. Particularly. the Stone-Cech compactification of a strongly zero-diluensional locale is stongly zero-dimensional.

Highly luminescent zero-dimensional lead-free manganese halides forβ-ray scintillation

Because of their moderate penetration power,β-rays(high-energy electrons)are a useful signal for evaluating the surface contamination of nuclear radiation.However,the development ofβ-ray scintillators,which convert the absorbed high-energy electrons into visible photons,is hindered by the limitations of materials selection.Herein,we report two highly luminescent zerodimensional(0D)organic-inorganic lead-free metal halide hybrids,(C_(13)H_(30)N)_(2)MnBr_(4)and(C_(19)H_(34)N)_(2)MnBr_(4),as scintillators exhibiting efficientβ-ray scintillation.These hybrid scintillators combine the superior properties of organic and inorganic components.For example,organic components that contain light elements C,H,and N enhance the capturing efficiency ofβparticles;isolated inorganic[MnBr_(4)]2−tetrahedrons serve as highly localized emitting centers to emit intense radioluminescence(RL)underβ-ray excitation.Both hybrids show a narrow-band green emission peaked at 518 nm with photoluminescence quantum efficiencies(PLQEs)of 81.3%for(C_(13)H_(30)N)_(2)MnBr_(4)and 86.4%for(C_(19)H_(34)N)_(2)MnBr_(4),respectively.To enable the solution processing of this promising metal halide hybrid,we successfully synthesized(C_(13)H_(30)N)_(2)MnBr_(4)colloidal nanocrystals for the first time.Being excited byβ-rays,(C_(13)H_(30)N)_(2)MnBr_(4)scintillators show a linear response toβ-ray dose rate over a broad range from 400 to 2,800 Gy·s^(−1),and also display robust radiation resistance that 80%of the initial RL intensity can be maintained after an ultrahigh accumulated radiation dose of 240 kGy.This work will open up a new route for the development ofβ-ray scintillators.

Combination-based nanomaterial designs in single and double dimensions for improved electrodes in lithium ion-batteries and faradaic supercapacitors

In the past decade, researchers in the fields of energy production have concentrated on the improvement of new energy storage devices. Lithium-ion batteries(LIBs) and faradaic supercapacitors(FSs) have attracted special attention as a result of the rapid development of new electrode nanomaterials, especially hybrid nanomaterials, which can meet the increasingly higher requirements for future energy, such as the capability to deliver high-power performance and an extremely long life cycle. In these hybrid nanostructures, a series of synergistic effects and unique properties arising from the combination of individual components are a major factor leading to improved charge/discharge capability, energy density, and system lifetime. This paper describes the most recent progress in the growth of hybrid electrode materials for LIBs and FSs systems, focusing on the combination of zero-dimensional(0 D), one-dimensional(1 D), two-dimensional(2 D), and three-dimensional(3 D) nanomaterials, respectively.

An equivalent model of discharge instability in the discharge chamber of Kaufman ion thruster

The industrial application of the Kaufman ion thruster in its arc stage is limited owing to the instability of the discharge pulse.Presently,a complete prediction model that can predict the discharge pulse in the high-current stage does not exist.In this study,a complete prediction model for the pulse in the ion thruster is established using the zero-dimensional plasma discharge model and equivalent circuit model.The zero-dimensional plasma discharge model is used to obtain the corresponding plasma parameters by calculating the beam current,discharge current,voltage,and gas flow under actual working conditions.The input parameters of the equivalent circuit model are calculated using empirical formulae to acquire the estimated discharge waveforms.The pulse waveforms obtained using the model are found to be consistent with the experimental results.The model is used to evaluate the process of rapid changes in plasma density.Additionally,this model is employed to predict changes in the pulse waveforms when the volume of the discharge chamber and grid plate transmittance are changed.

Effects of size and location of distal tear on hemodynamics and wave propagation in type B aortic dissection

The type B aortic dissection(TBAD)is a perilous disease with high morbidity and mortality rates.The hemodynamics of TBAD in different scenarios has been widely studied by computational fluid dynamics(CFD)research.However,the flow pattern and wave propagation characteristics in the cardiovascular system with TBAD are not yet clear,and the effect of the distal tear is still unknown.In this work,a onedimensional(1D)cardiovascular system model coupling with a zero-dimensional(0D)lumped-parameter model is introduced to study the hemodynamics and wave propagation in the cardiovascular system.The results show that the proposed 0D-1D method well captures the oscillation and retrograde characteristics for the flow in the false lumen(FL),and the smaller distal tear damps the retrograde flow.Besides,the distal tear should also be paid attention to,and the wave intensity(WI)can be used as an access mark of the degree of the aortic dissection(AD).

具有高效发光性能的亚铜卤化物纳米团簇应用于X-射线闪烁体

闪烁体可以将高能辐射转化为可见光,作为一种光电功能材料已经广泛应用于各种放射探测领域.虽然三维Pb基钙钛矿纳米晶可以开发为X射线闪烁体材料,但是其较低的光产额和铅毒性问题在一定程度上限制了其应用.为解决这一问题,本文重点关注零维金属卤化物发光材料,合成了一系列基于孤立[Cu_(4)X_(6)]^(2−)纳米团簇的零维卤化物,并将其开发应用为闪烁体发光材料.在紫外线或蓝光激发下,该卤化物纳米团簇均显示出宽带光发射,发光颜色可覆盖绿色、橙色到红色,并且具有近乎100%的光量子产率和较大的Stokes位移(>1.3 eV).特别突出的是,该类卤化物纳米团簇由于较高的发光量子产率、较小的光学自吸收和较强的X射线衰减效率,表现出优异的X-射线闪烁发光性能,光产额最高可达到24,240 photons MeV−1.材料的闪烁发光强度与X射线剂量呈现线性关系,检测范围较宽,且检测极限(0.7563μGy_(air)s^(−1))远低于常规医学诊断所要求的计量(5.5μGy_(air)s^(−1)).X-射线成像结果表明该纳米团簇余晖衰减时间较短(1.3 ms),空间分辨率较高(14.83 lp mm^(−1)),在医学成像等领域具有潜在的应用价值.该项工作表明,亚铜卤化物纳米团簇具有高效、稳定、无毒、发光效率高等优点,有望成为一种优异的新型闪烁体发光材料.

功能型有机阳离子诱导实现CsPbI_(3)全无机钙钛矿三维至零维晶相转化与表面重构

铅卤钙钛矿太阳能电池兼具高效率和低成本的突出优势,近年来研究进展迅速、应用前景广阔,对于进一步推进光伏产业发展、实现碳中和目标具有重要意义.相比于有机无机杂化钙钛矿,CsPbI_(3)全无机钙钛矿具有更高的化学稳定性,但同时也面临着缺陷密度较高的挑战,制约了该组分电池器件效率的进一步提升.钙钛矿表面重构是一种降低缺陷密度的有效方法,但受限于全无机结构中铅碘八面体与铯离子之间较强的离子键作用,诱发无机钙钛矿表面二次生长的困难远高于杂化钙钛矿体系.本文通过选取辛基十二烷基二甲基铵这一特殊的季铵阳离子,成功实现了CsPbI_(3)钙钛矿薄膜的表面重构与三维至零维的原位晶相转化.在这种功能型季铵溴盐的诱导作用下,零维Cs_(4)bI_(6)在CsPbI_(3)薄膜的表面晶界处原位生成,有效钝化了缺陷,提高了结构稳定性.基于表面重构与缺陷钝化的无机钙钛矿太阳能电池获得了20.63%的高光电转换效率,实现了长期的高效稳定运行.

DFT-assisted rational design of CoM_(x)P/CC(M=Fe,Mn,and Ni) as efficient electrocatalyst for wide pH range hydrogen evolution and oxygen evolution

Rational design of highly active transition-metal phosphides for electrocatalyzing overall water splitting in a wide pH range assisted by first-principle calculations can efficiently save the developing cost and hence is quite attractive.Under the guidance of density-functional theory(DFT)calculations that the introduction of dopants(Fe,Mn,and Ni)into CoP could promote the hydrogen evolution reaction(HER)performances,a series of binder-free CoM_(x)P/carbon cloth(CC;M=Fe,Mn,and Ni;x=0,0.05,0.2,0.5,and 1)were fabricated.Both experimental measurements and DFT calculations confirm the electronic modulation of dopants.DFT calculations further reveal that the modulated electronic structure promotes the electronic conductivity,favors the adsorption of key species,and consequently promotes the electrochemical performances.As predicted,the bimetallic phosphides demonstrate excellent HER performances in alkaline,acidic,and alkaline simulated seawater solutions and also deliver excellent oxygen evolution reaction(OER)performances,overwhelming the commercial RuO_(2).Benefiting from the modulated electronic structure and the hierarchical structure with massive CoFe0.05P zero-dimensional(0D)quantum dots anchored on two-dimensional(2D)N-doped porous carbon,CoFe0.05P delivered the best HER in four kinds of electrolytes(ƞ10 of 73 mV in an alkaline simulated seawater solution)and OER in two kinds of electrolytes(ƞ10 of 264 mV in an alkaline solution)with excellent stability of 45 h in the alkaline solution.The assembled CoFe0.05P/CC//CoFe0.05P/CC with the electrodes folded by 180°can still maintain a low cell potential of 1.62 V at 10 mA·cm^(−2).This work proves the feasibility of the reported rational design strategy of developing efficient electrocatalysts for overall water splitting in a wide pH range.

The Invertibility of Rational Univariate Representations

In this paper,the so-called invertibility is introduced for rational univariate representations,and a characterization of the invertibility is given.It is shown that the rational univariate representations,obtained by both Rouillier’s approach and Wu’s method,are invertible.Moreover,the ideal created by a given rational univariate representation is defined.Some results on invertible rational univariate representations and created ideals are established.Based on these results,a new approach is presented for decomposing the radical of a zero-dimensional polynomial ideal into an intersection of maximal ideals.

Lead-Free Hybrid Indium Perovskites with Highly Efficient and Stable Green Light Emissions

Lead halide perovskite nanocrystals(PNCs)have emerged as new-generation light-emitting materials with important potentials in optoelectronic applications.However,the toxicity of lead metal and the instabilities of PNCs overwhelmingly hinder their device engineering;thus,it is still urgent to construct new single crystalline lead-free perovskites with high-performance luminescent properties.

Whether or Not Emission of Cs4PbBr6 Nanocrystals:High-Pressure Experimental Evidence

The origin of green emission in the zero-dimensional(0D)perovskite Cs4PbBr6 nanocrystals(NCs)remains a considerable debate.Herein,an approach involving a combination of high-pressure experiments and theoretical simulation was employed to elucidate the controversial origin of photoluminescence from emissive Cs4PbBr6 NCs(E416).Results obtained from first-principles density functional theory(DFT)calculations,as implemented in the Vienna ab initio simulation package codes,implied that the photoluminescence energies from bromine vacancy decreased persistently with pressure.Experimentally,the photoluminescence energies tended to decrease in the low-pressure region,followed by an increase beyond∼1.4 GPa.While the emergent disagreement between the first-principles calculation and highpressure experiment excludes the possibility of vacancy-tuning,the consistent change observed in the pressure-dependent emission between E416 and CsPbBr_(3) NCs offered a reliable interpretation for the occurrence of green emission from a CsPbBr_(3) impurity embedded in the Cs4PbBr6 matrix.Further comprehensive analysis demonstrated that the strong green emission of E416 NCs originated from the impurity CsPbBr_(3) NCs embedded in Cs4PbBr6 matrix.Our study represents a significant step forward to a deeper understanding of the emissive origins of Cs4PbBr6 NCs and promotes the application of this novel strategy in light-emitting devices.

Reduced groups of abelian group rings

It is well known that K0R（?）Z（?）（?）0R, where R is a commutative ring. So the Grothendieck group of R can be given by the reduced group （?）0R. On the other hand, linear representations of groups can be seen as the finitely generated projective modules over group rings. Thus, it is very useful to study the properties of reduced groups of group rings.

On Direct Limits of Finite Products of Fields as Subrings of a Commutative Ring

Let R be a commutative ring. In this paper, we develop the existence of direct limits of finite products of fields as subrings of R.

Synthesis and Characterization of a New Quaternary Selenide Ba_(4)Sn_(3)GeSe_(9)Containing[SnGeSe_(5)]^(4-)and[Sn_(2)Se_(4)]^(4-)Units

A new quaternary selenide Ba4Sn3GeSe9 was synthesized by high temperature solid state reaction method and fully characterized by elemental analysis,UV-vis spectrum,and single-crystal X-ray diffraction.The title compound crystallizes in the orthorhombic space group Pnma with a=12.463(3),b=9.308(2)and c=17.892(5)Å.Ba_(4)Sn_(3)GeSe_(9)can be characterized by a zero-dimensional compound composed by special[GeSnSe_(5)]4-units,[Sn_(2)Se_(4)]^(4-)units and the adjacent cations Ba^(2+)ions.The[GeSnSe_(5)]^(4-)unit is composed of a SnSe3 trigonal pyramid formed by divalent Sn2+and edge-sharing with a GeSe4 tetrahedron,and the[Sn_(2)Se_(4)]^(4-) unit is composed of two SnSe3 trigonal pyramids.Ba_(4)Sn_(3)GeSe_(9)is an indirect semiconductor with a band gap of 1.21 eV.