Designing a deep-UV nonlinear optical monofluorophosphate

As structural variants of famous hexagonal tungsten bronzes,hexagonal tungsten oxides(HTO)represent an important family with fascinating functional properties,such as piezoelectric,ferroelectric,pyroelectric,and nonlinear optical(NLO)properties.However,none of them are transparent in the deep-UV spectral region,which limits their applications.Herein,we report the first HTO-type monofluorophosphate K_(3)Sc_(3)(PO_(4))(PO_(3)F)_(2)F_(5)(I)with deep-UV transparency.Such a monofluorophosphate is NLO-active with a phase-matchable powder second harmonic generation efficiency of 0.9 times that of KH_(2)PO_(4)at 1,064 nm.Importantly,the UV-Vis reflectance spectrum indicates that it is deep-UV transparent down to 200 nm.This work pushes the transparent window of NLO materials with HTO-type structures down to the deep-UV spectral region for the first time and opens up a new door for HTO materials.

New cross-section measurements for the (n, 2n), (n, p), and (n, a) reactions on bromine in the 14 MeV region with detailed uncertainty quantification

Measurement of the cross-sections of the ^(79)Br(n,2n)^(78)Br,^(81)Br(n,p)^(81)mSe,^(81)Br(n,α)^(78)As,and ^(79)Br(n,α)^(76)As reactions was performed at specific neutron energies,precisely,13.5±0.2,14.1±0.2,14.4±0.2,and 14.8±0.2 MeV,relative to the standard ^(93)Nb(n,2n)^(92)mNb and ^(27)Al(n,α)^(24)Na reference reactions using offlineγ-ray spectrometry and neutron activation.Monoenergetic neutrons were generated at the China Academy of Engineering Physics via a ^(3)H(d,n)^(4)He reaction using the K-400 Neutron Generator equipped with a solid ^(3)H-Ti based target.The activity of the reaction produce was obtained using a high-purity germanium detector.The cross-sections of the(n,2n),(n,p),and(n,α)reactions on the bromine isotopes were measured in the 13–15 MeV neutron energy range.The covariance analysis approach was employed for a thorough inspection of any uncertainties within the measured cross-section data.A discussion and comparison of the observed outcome were carried out with previously published data,especially with the results of the JENDL-4.0,JEFF-3.3,TENDL-2019,and ENDF/B-VIII.0 data libraries,along with the theoretical excitation function curve derived by employing the TALYS-1.95 program.Improved cross-section restrictions for the investigated processes in the 13–15 MeV neutron energy range will be obtained using the current findings,which will help to raise the caliber of associated databases.Furthermore,the parameters of relevant nuclear reaction models can be verified using this data.

室温克级构筑Cu@CuO及其在法拉第葡萄糖电氧化过程中的动力学提升机制

在临床应用中,一次性条形血糖传感器可以日常监测和维持糖尿病患者的血糖水平,以预防和避免危及生命的并发症.本文采用室温可控原位氧化商业铜的工艺制备了Cu@CuO材料.将具有电催化性能的Cu@CuO丝网印刷到一次性银碳工作电极上,制备了条形无酶葡萄糖传感器.该传感器对葡萄糖的电催化氧化表现出优异的性能:高灵敏度(0.03μA mmol^(-1)L cm^(-2))、低检测限(1.3μmol L^(-1))、宽线性范围(0.0013-2.5 mmol L^(-1))、良好的选择性、重复性(20个电极的相对标准偏差为4.28%),以及在室温下超过3周的稳定性.计算结果表明,铜组分提高了Cu@CuO的导电性和对葡萄糖的吸附能力,从而改善了其在葡萄糖法拉第催化过程中的动力学性能.更重要的是,Cu@CuO的批量制备及其在临床型电极中的应用为其在无酶血糖传感方面的应用提供了一个参考方案.

Maximizing the linear and nonlinear optical responses of alkaline tricyanomelaminate

High-performance bi-functional materials are in urgent demand for the next-generation integrated optical devices.In this work,we successfully synthesized the first tricyanomelaminate with bi-functional optical responses,namely Cs_(3)C_(6)N_(9)•H_(2)O(I),from its analogue Na_(3)C_(6)N_(9)•3H_(2)O by a facile ion exchange method.In contrast to Na_(3)C_(6)N_(9)•3H_(2)O,I realizes an optimal arrangement of𝜋π-conjugated(C_(6)N_(9))3−anion groups in its crystal structure.As a result,the second-order nonlinear optical(NLO)response is greatly enhanced from nearly zero of Na_(3)C_(6)N_(9)•3H_(2)O to∼9.8×KH_(2)PO_(4)of I.Furthermore,I exhibits a giant linear optical anisotropic response(i.e.birefringence)of 0.52 at the wavelength of 550 nm.Both responses are almost the largest among the inorganic compounds ofπ-conjugated rings,which indicates that I has great potential as a bi-functional optical crystal.Structural and theoretical analyses reveal the microscopic origin of excellent optical properties.This work would attract a lot of interest to the persistently neglected potential of tricyanomelaminates as linear optical and NLO crystals.

Recent advances in non-π-conjugated nonlinear optical sulfates with deep-UV absorption edge

Deep-ultraviolet(deep-UV)nonlinear optical(NLO)crystals are of current interest because they play an indis-pensable role in modern scientific equipment.Searching these crystals was traditionally limited toπ-conjugated systems,such as borates and carbonates.In 2019,our group reported two non-π-conjugated sulfates as new sources of deep-UV NLO crystals for the first time.In this mini review,we provide a comprehensive overview of the recent development of non-π-conjugated NLO sulfates with deep-UV absorption edge in aspect of synthesis methods,crystal structures,thermal stability,and optical performance.Besides,we conclude the crucial structure-property relationships,and further give some prospects for exploring non-π-conjugated NLO sulfates with deep-UV absorption edge with high thermal stability,enhanced second-order NLO effects,birefringence,etc.We believe that this mini review will not only facilitate researchers to design superior non-π-conjugated NLO sulfates with deep-UV absorption edge but also shed useful insights on the explorations of other non-π-conjugated deep-UV NLO crystal systems.

厘米级无铅卤化物双钙钛矿单晶实现铁弹性相变触发介电开关性质

在铅基卤化物钙钛矿突破性发展的推动下,卤化物双钙钛矿因其环境友好、丰富的物理化学性能和结构可调性而成为杰出的多用途材料.尽管卤化物双钙钛矿的研究取得了飞速的进展,但在这个吸引人的钙钛矿家族中对可切换电介质的探索仍然很少.本工作通过溶液冷却法成功地生长了单层卤化物双钙钛矿(3-溴丙胺)_(4)AgBiBr_(8)(1)的大尺寸单晶,其尺寸达20 mm×17 mm×5 mm.它经历了由Aizu符号定义的mmm F2/m的铁弹性相变,通过结构分析可知该铁弹相变是八面体畸变和柔性分子运动协同作用的结果.值得注意的是,它在373 K附近具有理想的铁弹性相变触发的可切换电介质性能,可以在两个稳定的电介质状态之间切换.而且,1展现出间接带隙半导体特性和X射线响应,其中在40 V的偏压下1的灵敏度高达517μC Gy_(air)^(-1)cm^(-2).这项工作为具有智能功能的无铅卤化物双钙钛矿提供了一条有效的应用路径.

Ferroelectric perovskite-type films with robust in-plane polarization toward efficient room-temperature chemiresistive sensing

Ferroelectric materials have become key components for versatile device applications,and their thin films are highly desirable for integrating the miniaturized devices.Despite substantial endeavors,it is still challenging to achieve effective chemiresistive sensing in the ferroelectric films.Here,for the first time,we have exploited ferroelectric thin films of 2D hybrid perovskite BA_(2)EA_(2)Pb_(3)I_(10)(1),to fabricate the high-performance chemiresistor gas sensors.The spin-coated films of 1 exhibit high orientation and good crystallinity,thus preserving robust in-plane spontaneous polarization(P_(s)~2.0μC/cm^(2))and low electric coercivity.Notably,such ferroelectric filmbased sensors after electric poling enable the dramatic room-temperature sensing responses to NO_(2) gas,including high sensitivity(0.05 ppm^(-1)),extremely low detection limit(1 ppm)and fast responding rate(~6 s).Besides,the chemiresistive responses are remarkably enhanced by threefold(up to 320%)through electric poling.It is proposed that this behavior closely involves with strong in-plane ferroelectric polarization of 1 that generates a built-in electric field inhibiting the recombination of charge carriers.As far as we know,this ferroelectric-based film chemiresisor is one of the best room-temperature sensors for NO_(2) gas among all the existing candidate materials.These findings highlight great potential of ferroelectrics toward effective chemiresistive performances,and also establish a bright direction to explore their future device applications.

A new 2D van der Waals material with air stability and in-plane anisotropy

1.Text 2D van der Waals materials possess intriguing features[1],especially optically,such as high nonlinear optical responses[2],broadband spectral response[3],and accessible exciton effects[4].Unlike conventional 2D materials with in-plane isotropy,such as graphene and M0S_(2),2D van der Waals materials with in-plane anisotropic possess in-plane low symmetry structure,inducing the in-plane anisotropic physical properties.Meanwhile,they can be easily moved to various substrates without lattice-matching problems.

基于二维杂化钙钛矿铁电晶体组装低检测限的超灵敏偏振光探测器

二维(2D)杂化钙钛矿铁电体的自发极化(P_(s))与光耦合作用有利于光生载流子分离,在光电器件方面显示出潜在的应用前景.然而,基于2D杂化钙钛矿铁电体组装的低检测限的偏振光检测器未见报道.本文基于2D杂化钙钛矿铁电体BA_(2)CsPb_(2)Br_(7)(BA为正丁胺)的高质量单晶,组装超灵敏的偏振光探测器.材料独特的双层钙钛矿结构产生较强的光学各向异性,沿不同晶轴方向的吸收比率高达α_(c)/α_(a)≈3.2(λ=405 nm).此外,铁电自发极化在极轴(c轴)方向产生较高的内建电场,有利于产生优异光电性能.在光强为40 n W/cm^(2)的辐射光下,晶体探测器表现出显著的二向色性比(电流比Iphc/Ipha≈1.5)、较高的响应度(~39.5 m A/W)和探测率(~1.2×10^(12)Jones),以及较短的响应时间(~300μs)与出色的抗疲劳性能.

Emerging two-dimensional bismuth oxychalcogenides for electronics and optoelectronics

Atomically thin two-dimensional(2D)bismuth oxychalcogenides(Bi_(2)O_(2)X,X=S,Se,Te)have recently attracted extensive attention in the material research community due to their unique structure,outstanding long-term ambient stability,and high carrier mobility,which enable them as promising candidates for high-performance electronic and optoelectronic applications.Herein,we present a comprehensive review on the recent advances of 2D bismuth oxychalcogenides research.We start with an introduction of their fundamental properties including crystal structure and electronic band structure.Next,we summarize the common techniques for synthesizing these 2D structures with high crystallinity and large lateral size.Furthermore,we elaborate on their device applications including transistors,artificial synapses,optical switch and photodetectors.The last but not the least,we summarize the existing challenges and prospects for this emerging 2D bismuth oxychalcogenides field.

通过π共轭限域策略实现了光学各向异性晶体中带隙和双折射的有效平衡

光学各向异性晶体受限于带隙和双折射之间的权衡.本文采用简单的溶液法获得了一例光学各向异性晶体NaPO(NH)(CO).值得注意的是,NaPO(NH)(CO)晶体同时具有大的光学各向异性(Δn=0.280@550 nm)和较宽的带隙(E≥6.5 eV).就我们所知,NaPO(NH)(CO)的双折射远大于目前的商用宽带隙双折射晶体.理论计算表明,这种优异的光学性能归因于[PO(NH)(CO)]~-结构单元中的π共轭限域效应.其中,非π共轭PO(NH)四面体部分解耦了π共轭之间的相互作用.这项工作将通过操纵偏振来促进新型光学各向异性宽带隙晶体的合理设计和合成,并用作高效光隔离器或其他器件.

超薄二维三元Bi_(2)Te_(2)Se纳米片用于响应度栅压可调的快速响应光电探测器

二维(2D)三元材料近年来如雨后春笋般兴起,由于其物理性质能够通过调整化学计量比来实现自由设计而被认为在光电子学中具有重要的应用前景.然而,具有良好化学计量比的高质量二维三元材料的可控制备仍然面临挑战,严重阻碍了它们进一步的发展和在未来器件中的应用.本文中,我们通过一种常压固体源热蒸发法在云母衬底上制备了厚度薄至4 nm,横向尺寸约为60μm的三元Bi_(2)Te_(2)Se(BTS)薄片.通过变温拉曼光谱和导电性测量研究了二维BTS的声子振动和电传输特性.进一步地,基于二维BTS的光电探测器表现出优异的光电响应特性,其光开关比在365 nm光照下约为1300,光谱响应范围宽至365–980 nm,同时其响应速度快至2μs.此外,栅极电压能够有效调控BTS的电输运和光电性能,从而将980 nm下的红外响应度和光开关比提高至2.74 A W^(-1)和2266.我们的工作介绍了一种有效获得二维BTS薄片的方法,并展示了其在光电领域良好的应用前景.

Nonpolar Na_(10)Cd(NO_(3))_(4)(SO_(3)S)_(4) Exhibits a Large Second-Harmonic Generation

Conventional wisdom says that nonpolar structures do not favorably produce strong second-harmonic generation(SHG)responses since the polarization in their microscopic functional groups are counteracted.Herein,we report the first nonlinear optical thiosulfate,Na_(10)Cd(NO_(3))_(4)(SO_(3)S)_(4),which crystallizes in a nonpolar space group of P−4.However,this thiosulfate exhibits a strong SHG response of about 4.2 times that of the benchmark KH2PO4,which is larger than those of polar sulfates.According to first-principles calculations and a flexible dipole model,the SHG enhancement is mainly ascribed to the larger flexibility of the S=S bond in the SO_(3)S tetrahedra in comparison with the S–O bond in the SO4 tetrahedra.These findings indicate that constructing flexible bonds is an effective strategy to design highperformance nonlinear optical materials regardless of polarity.

A Nonlinear Optical Switchable Sulfate of Ultrawide Bandgap

Nonlinear optical(NLO)switchable materials have attracted intense attention because of their promising applications in optoelectronic devices.However,previous studies are mainly limited to molecular-based compounds that usually exhibit narrow bandgaps.Here,we report all-inorganic Li_(9)Na_(3)Rb_(2)(SO_(4))_(7) as an ultrawide-bandgap NLO switchable material.

合理组装混合阳离子增强金属卤素钙钛矿晶体阵列光电探测性能

二维Ruddlesden-Popper型杂化钙钛矿(A′)_(2)(A)_(n-1)M_(n)X_(3n+1)表现出独特的物理特性与结构兼容性,已经发展成为光电材料的强有力候选者,其无机组分与有机组分的准确调控为优化材料性能提供了广阔空间.到目前为止,将大尺寸有机基元作为A位离子占据钙钛矿空腔仍是一项挑战,形成此类结构的二维多层钙钛矿材料非常稀少.鉴于此,我们将仲胺和芳香胺作为混合阳离子,利用复合阳离子自组装方法成功制备了结构新颖的Ruddlesden-Popper型钙钛矿(4-TFBMA)_(2)(DMA)Pb_(2)I_(7),其中4-TFBMA为4-(三氟甲基)苄胺,DMA为二甲胺.该化合物具有典型的双层钙钛矿结构,DMA作为A位阳离子处于骨架空腔内,突破容忍因子制约;无机骨架层与间隔阳离子4-TFBMA层交替排列产生量子阱.以高质量晶体为基础组装的阵列探测器表现出优异的面内光电性能,如探测率高、响应度大、暗电流低和响应速率快等,性能参数可以媲美二维无机材料.综上,该工作为设计合成新颖二维钙钛矿化合物及实现高效光电探测性能提供了重要参考.

Cross-sections for(n,2n),(n,α),(n,p),(n,d),and(n,t)reactions on molybdenum isotopes in the neutron energy range of 13 to 15 MeV

Given the insufficient cross-sectional data regarding the 14-MeV-neutron experiment of molybdenum,the vital fusion reactor structural material,and the significant heterogeneities among the reported values,this study examined the(n,2n),(n,α),(n,p),(n,d),and(n,t)reaction cross sections in molybdenum isotopes based on the neutrons produced via a T(d,n)4He reaction carried out in the Pd-300 Neutron Generator at the China Academy of Engineering Physics(CAEP).A high-resolution gamma-ray spectrometer,which was equipped with a coaxial high-purity germanium detector,was used to measure the product nuclear gamma activities.In addition,27Al(n,α)24Na and 93Nb(n,2n)92mNb reactions were utilized as the neutron fluence standards.The experimental 92Mo(n,2n)91Mo,94Mo(n,2n)93mMo,100Mo(n,2n)99Mo,98Mo(n,α)95Zr,100Mo(n,α)97Zr,92Mo(n,p)92mNb,96Mo(n,p)96Nb,97Mo(n,p)97Nb,98Mo(n,p)98mNb,92Mo(n,d)91mNb,and 92Mo(n,t)90Nb reaction cross sections were acquired within the 13-15 MeV neutron energy range.Thereafter,we compared and analyzed these obtained cross sections based on the existing IAEA-EXFOR database-derived experimental data,together with evaluation results corresponding to ENDF/B-Ⅷ.0,JEFF-3.3,BROND-3.1,and CENDL-3.1 and the theoretical outcomes acquired through TALYS-1.95 and EMPIRE-3.2.3(nuclear-reaction modeling tools).

Noncentrosymmetric K_(2)Mn_(3)(SO_(4))_(3)F_(2)·4H_(2)O and Rb_(2)Mn_(3)(SO_(4))_(3)F_(2)·2H_(2)O with pseudo-KTP structures

Two fluoride sulfates,K_(2)Mn_(3)(SO_(4))_(3)F_(2)·4H_(2)O(Ⅰ) and Rb_(2)Mn_(3)(SO_(4))_(3)F_(2)·2H_(2)O (Ⅱ) are obtained by water solution method.Single-crystal X-ray diffraction analysis indicated that they crystallize in space groups of Cmc2_(1.)Their structures feature a pseudo-KTP structure consisting of interconnecting[Mn_(3)(SO_(4))3F_(2)(H_(2)O)2]_(∞) layers,which are further packing along the a axis with alkali metal cations balancing the charges.The structure relationships between the two compounds are discussed.Secondharmonic generation measurements manifest that Ⅰ and Ⅱ have similar second-harmonic generation responses of about 0.2 and 0.25 times that of KH_(2)PO_(4).

Cross-section measurements of(n,2n)and(n,p)reactions on ^(124,126,128,130,131,132)Xe in the 14 MeV region and theoretical calculations of their excitation functions

The reaction cross-sections of ^(124)Xe(n,2n)^(123)Xe,^(126)Xe(n,2n)^(125)Xe,^(128)Xe(n,2n)^(127)Xe,^(130)Xe(n,2n)^(129)mXe,^(132)Xe(n,2n)^(131)mXe,^(130)Xe(n,p)^(130)I,^(131)Xe(n,p)^(131)I,and ^(132)Xe(n,p)^(132)I were measured at the 13.5,13.8,14.1,14.4,and 14.8 MeV neutron energies.The monoenergetic neutrons were generated via the ^(3)H(d,n)^(4)He reaction at the China Academy of Engineering Physics using the K-400 Neutron Generator with a solid ^(3)H-Ti target.A high-purity germanium detector was employed to measure the activities of the product.The reactions ^(93)Nb(n,2n)^(92m)Nb and ^(27)Al(n,α)^(24)Na were adopted for neutron flux calibration.The cross sections of the(n,2n)and(n,p)reactions of the xenon isotopes were obtained within the 13-15 MeV neutron energy range.These cross-sections were then compared with the IAEA-exchange format(EXFOR)database-derived experimental data,together with the evaluation results of the CENDL-3,ENDF/B-Ⅷ.0,JENDL-4.0,RUSFOND,and JEFF-3.3 data libraries,as well as the theoretical excitation function obtained using the TALYS-1.95 code.The cross-sections of the reactions(except for the ^(124)Xe(n,2n)^(123)Xe and ^(132)Xe(n,p)^(132)I)at 13.5,13.8,and 14.1 MeV are reported for the first time in this study.The obtained results are beneficial in providing better cross-section constraints for the reactions in the 13-15 MeV region,thus improving the quality of the corresponding database.Meanwhile,these data can also be used for the verification of relevant nuclear reaction model parameters.

Highly Efficient White-Light Emission Induced by Carboxylic Acid Dimers in a Layered Hybrid Perovskite

Broadband white-light emission in metal halides has been intensely explored because of their facile solution processability,structural adjustability,and high color rendering index.However,the most reported quantum yields for white-light emission remain low despite great efforts.Herein,we report a metal-halide layered perovskite,(HOOC_(4)H_(9)NH_(3))_(2)PbBr_(4),showing the typical white-light emission with a highly enhan ced quantumyield up to 21.2% compared to previously reported noncarboxyl layered hybrid perovskites(0.5-9%).Notably,mechanistic studies reveal that the distinctive carboxylic acid dimers largely increase the structure rigidity and in consequence reduce the nonradiative recombination induced by stretching vibration.To the best of our knowledge,this strategy is important in hybrid perovskites,which is effective and propagable to acquire prominent photoluminescence.This work will shed light on the design of highly emissive white-light materials involving intense intermolecular interaction and promote their potential in displaying application.

Triethylammonium picrate： An above-room-temperature phase transition material to switch quadratic nonlinear optical properties

To switch quadratic nonlinear optical（NLO） effects has become an exciting branch of the NLO material science. However, solid-state molecular crystals showing tunable and switchable NLO behaviors remain scarce. Here, we report an organic picrate-based binary molecular crystal, triethylammonium picrate（TEAP）, which undergoes an above-room-temperature phase transition at T_c=319 K, being solidly confirmed by the thermal and dielectric measurements. A large thermal hysteresis of ~7 K discloses the first-order feature for its phase transition. More strikingly, the quadratic NLO effects of TEAP can be switched in the vicinity of Tc. That is, TEAP exhibits NLO-active response of ~1.5 times as large as that of KDP below T_c（i.e., NLO-on state）, while its NLO effects totally disappear above T_c（NLO-off state）. Structure analyses disclose that the order-disorder transformations of triethylammonium cations and picrate anions collectively contribute to its phase transition, as well as switchable NLO behaviors. This work opens up a new pathway to the designing and assembling of stimuli-responsive materials.