Tailoring MXene Thickness and Functionalization for Enhanced Room‑Temperature Trace NO_(2) Sensing

In this study,precise control over the thickness and termination of Ti3C2TX MXene flakes is achieved to enhance their electrical properties,environmental stability,and gas-sensing performance.Utilizing a hybrid method involving high-pressure processing,stirring,and immiscible solutions,sub-100 nm MXene flake thickness is achieved within the MXene film on the Si-wafer.Functionalization control is achieved by defunctionalizing MXene at 650℃ under vacuum and H2 gas in a CVD furnace,followed by refunctionalization with iodine and bromine vaporization from a bubbler attached to the CVD.Notably,the introduction of iodine,which has a larger atomic size,lower electronegativity,reduce shielding effect,and lower hydrophilicity(contact angle:99°),profoundly affecting MXene.It improves the surface area(36.2 cm^(2) g^(-1)),oxidation stability in aqueous/ambient environments(21 days/80 days),and film conductivity(749 S m^(-1)).Additionally,it significantly enhances the gas-sensing performance,including the sensitivity(0.1119Ωppm^(-1)),response(0.2% and 23%to 50 ppb and 200 ppm NO_(2)),and response/recovery times(90/100 s).The reduced shielding effect of the–I-terminals and the metallic characteristics of MXene enhance the selectivity of I-MXene toward NO2.This approach paves the way for the development of stable and high-performance gas-sensing two-dimensional materials with promising prospects for future studies.

Equalized Electronegativity Based on the Valence Electrons and Its Application

We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group electronegativity, and atomic charge. The ionization potential of alkanes and mono-substituted alkanes, the chemical shift of 1H NMR, and the gas phase proton affinity of aliphatic amines, alcohols, and ethers were estimated. All the expressions have good correlations. Moreover, the Sanderson method and Bratsch method were modified on the basis of the valence electrons equilibration theory. The modified Sanderson method and modified Bratsch method are more effective than their original methods to estimate these properties.

Dipole polarization modulating of vinylene-linked covalent organic frameworks for efficient photocatalytic hydrogen evolution

Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency,achieved through atomic modulation(O,S,and Se)of the COF monomer.Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment,thereby affecting charge separation efficiency and photostability,which in turn affects the rates of photocatalytic H_(2) evolution.As a result,the newly developed TMT-BO-COF,which contains highly electronegative O atoms,exhibits the lowest exciton binding energy,the highest efficiency in charge separation and transportation,and the longest lifetime of the active charges.This leads to an impressive average H_(2) production rate of 23.7 mmol g^(−1) h^(−1),which is 2.5 and 24.5 times higher than that of TMT-BS-COF(containing S atoms)and TMT-BSe-COF(containing Se atoms),respectively.A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations.Our findings provide new insights into the design of highly photoactive organic framework materials for H_(2) evolution and beyond.

诱导触发型气体间隙开关快速绝缘恢复特性

气体间隙开关动作迅速、结构简单,在电力系统中应用前景良好,但对其绝缘恢复特性研究尚少。为此,文中采用双脉冲法研究开关间隙距离、触发介质气压及其种类对气体开关绝缘恢复特性的影响规律。结果表明:诱导触发型气体间隙开关绝缘恢复经历过渡期、快速恢复期和饱和期3个阶段,饱和期的持续时间远大于前两阶段之和,且在快速恢复期无“平台现象”出现。减小开关间隙距离,气体开关绝缘恢复速率渐进增大,其绝缘基本恢复时间(绝缘恢复系数R_(U)>90%)可降低50%。触发介质气压对气体开关绝缘恢复特性影响显著,对绝缘恢复过程的影响特性存在差异。增大触发介质气压会减缓气体开关的绝缘恢复过程,0.1~0.3 MPa压缩干燥空气中,气体间隙开关绝缘基本恢复时间对应为11~40 ms。强电负性SF_(6)对气体开关绝缘恢复具有明显增强作用,其绝缘恢复速率接近于空气中的4倍。研究结果可为气体间隙开关快速绝缘恢复技术提供理论指导。

桂西二叠系沉积型铝土矿鲕粒成因机制探讨

已有研究表明铝土矿中鲕粒的Al含量普遍高于基质,但鲕粒富集Al过程尚不清楚。本文通过对桂西地区铝土矿进行宏微观观察以及电子探针测试(EPMA)和X粉晶衍射分析,研究了矿石构造和元素地球化学变化规律,试图分析铝土矿中鲕粒生长机制。含矿岩系层序多变特征表明桂西铝土矿为陆相成因;鲕粒内部圈层Al含量大于50%,而Si含量小于1%,Fe含量波动于1%左右,证明矿石中鲕粒Al的含量比基质的高,同时硬水铝石的结晶程度亦较高;与鲕粒生成有密切关系的构造主要为凝胶和裂隙,两者为正反馈关系;胶体在分离过程中出现分凝,主要形成富铝、富硅和富铁凝胶,分凝过程中Fe、Si亲和性强,两者的迁移能力均高于Al。分析认为鲕粒形成于浅埋阶段,是一种凝胶的反复分凝过程,受控于湿润-干热气候,成鲕可大致分为3个阶段,即充水阶段、湿润阶段和干热阶段,成核机制为脱水收缩,圈层增长机制为成胶-凝胶老化交替。铝土矿型风化壳的物质搬运过程使鲕粒的圈层停止生长,形成夭折鲕,若条件有利则形成再生鲕。首次引入磁场的概念解释了鲕粒保持浑圆形习性的原因。

The Electronegativity Analysis of c-C_4F_8 as a Potential Insulation Substitute of SF_6

The density distributions related to gas electronegativity for c-C4Fs gas, including negative ion, electron number and electron energy densities in the discharge process, are derived theoretically in both plane-to-plane and point-to-plane electrode geometries. These calculations have been performed through the Boltzmann equation in the condition of a steady-state Townsend （SST） experiment and a fluid model in the condition of both uniform and non-uniform electric fields. The electronegativity coefficients a = n-/ne of c-C4Fs and SF6 are compared to further describe the electron affinity of c-C4Fs. The result shows that c-C4Fs represents an obvious electron-attachment performance in the discharge process. However, c-C4Fs still has much weaker gas electronegativity than SF6, whose electronegativity coefficient is lower than that of SF6 by at least three orders of magnitude.

Regulation of Excited-State Intramolecular Proton Transfer Process and Photophysical Properties for Benzoxazole Isothiocyanate Fluorescent Dyes by Changing Atomic Electronegativity

Excited-state intramolecular proton transfer(ESIPT)is favored by researchers because of its unique optical properties.However,there are relatively few systematic studies on the effects of changing the electronegativity of atoms on the ESIPT process and photophysical properties.Therefore,we selected a series of benzoxazole isothiocyanate fluorescent dyes(2-HOB,2-HSB,and 2-HSe B)by theoretical methods,and systematically studied the ESIPT process and photophysical properties by changing the electronegativity of chalcogen atoms.The calculated bond angle,bond length,energy gap,and infrared spectrum analysis show that the order of the strength of intramolecular hydrogen bonding of the three molecules is 2-HOB<2-HSB<2-HSe B.Correspondingly,the magnitude of the energy barrier of the potential energy curve is 2-HOB>2-HSB>2-HSe B.In addition,the calculated electronic spectrum shows that as the atomic electronegativity decreases,the emission spectrum has a redshift.Therefore,this work will offer certain theoretical guidance for the synthesis and application of new dyes based on ESIPT properties.

Quasi-delta negative ions density of Ar/O_(2)inductively coupled plasma at very low electronegativity

One of the novel phenomena of Ar/O_(2)inductively coupled plasma,the delta negative ions density profile is discovered by the fluid simulation at very low electronegativity.The anions delta is found to be formed by the collaboration of successive plasma transport phases.The plasma transport itself is affected by the delta,exhibiting many new phenomena.A new type of Helmholtz equation is devised to mathematically explain the delta forming mechanism.For revealing the physics behind,a revised spring oscillator dynamic equation has been constructed according to the Helmholtz equation,in a relevant paper[Zhao S X and Li J Z(2021)Chin.Phys.B 30055202].The investigation about the anions delta distribution is a nice prediction of new phenomenon in low temperature electronegative plasmas,waiting for the validation of related experiments.

Measurement of electronegativity during the E to H mode transition in a radio frequency inductively coupled Ar/O2 plasma

This paper presents the evolution of the electronegativity with the applied power during the E to H mode transition in a radio frequency(rf)inductively coupled plasma(ICP)in a mixture of Ar and O2.The densities of the negative ion and the electron,as well as their ratio,i.e.,the electronegativity,are measured as a function of the applied power by laser photo-detachment combined with a microwave resonance probe,under different pressures and O2 contents.Meanwhile,the optical emission intensities at Ar 750.4 nm and O 844.6 nm are monitored via a spectrograph.It was found that by increasing the applied power,the electron density and the optical emission intensity show a similar trench,i.e.,they increase abruptly at a threshold power,suggesting that the E to H mode transition occurs.With the increase of the pressure,the negative ion density presents opposite trends in the E-mode and the H-mode,which is related to the difference of the electron density and energy for the two modes.The emission intensities of Ar 750.4 nm and O 844.6 nm monotonously decrease with increasing the pressure or the O2 content,indicating that the density of high-energy electrons,which can excite atoms,is monotonically decreased.This leads to an increase of the negative ion density in the H-mode with increasing the pressure.Besides,as the applied power is increased,the electronegativity shows an abrupt drop during the E-to H-mode transition.

Quantitative Structure-retention Relationship Study of Polychlorinated Dibenzothiophenes by Molecular Electronegativity Distance Vector(MEDV)

Polychlorinated dibenzothiophenes（PCDTs） are classified as persistent organic pollutants in the environment,so the analysis of PCDTs by their gas chromatographic behaviors is of great significance.Quantitative structure-retention relationship（QSRR） analysis is a useful technique capable of relating chromatographic retention time to the molecular structure.In this paper,a QSRR study of 37 PCDTs was carried out by using molecular electronegativity distance vector（MEDV） descriptors and multiple linear regression（MLR） and partial least-squares regression（PLS） methods.The correlation coefficient R of established MLR,PLS models,leave-one-out（LOO） cross-validation（CV）,Q2ext were 0.9951,0.9942,0.9839（MLR） and 0.9925,0.9915,0.9833（PLS）,respectively.Results showed that the model exhibited excellent estimate capability for internal sample set and good predictive capability for external sample set.By using MEDV descriptors,the QSRR model can provide a simple and rapid way to predict the gas-chromatographic retention indices of polychlorinated dibenzothiophenes in conditions of lacking standard samples or poor experimental conditions.

ELECTRONEGATIVITY TOPOLOGICAL INDEX AND ITS APPLICATION IN CORRELATION WITH MX,MX_2,MX_3,MX_4 MOLECULAR PROPERTIES

A New electronegativity topological index is defined and used to correlate with properties of MX,MX_2,MX_3,MX_4.

The Electronegativity and the Global Hardness Are Periodic Properties of Atoms

The electronegativity and the hardness are two popular and useful theoretical descriptors of chemistry and physics successfully used by both physicists and chemists in correlating chemico-physical properties of atoms, molecules and condensed matter physics. We have tried to explore the fundamental nature of the hardness and electronegativity of atoms and have observed that their fundamental nature is basically lying in electrostatics and manifest as the electron attracting power emanating from the nucleus of the atom. We have tried to correlate the periodic nature of variation of the electronegativity and the hardness to the electron attracting power of the nucleus from which they are originated and developed. We have developed the formulae for evaluating both electronegativity and hardness and found that they have the direct correlation with the effective nuclear charge of the atoms and hence their periodicity.

QSRR Study on the Components of Styrax Japonicus Sieb Flowers Using Improved Molecular Electronegativity-distance Vector (I-MEDV)

Atoms in most organic molecules are often carbon,oxygen,nitrogen,sulfur,halogens,etc. Based on the three-dimensional structure of a molecule,a molecular structural characterization（MSC） method called improved molecular electronegativity-distance vector（I-MEDV） was developed. It was used to describe the structures of 37 compounds of styrax japonicus sieb flowers. Through multiple linear regression（MLR）,a QSRR model was built up. The correlation coefficient（R1） of the model was 0.980. Then,4 vectors were selected to build another model through the method of stepwise multiple regression（SMR） ,and the correlation coefficient（R2） of the model was 0.975. Moreover,all the two models were evaluated by performing the crossvalidation with the leave-one-out（LOO） procedure and the correlation coefficients（Rcv） were 0.948 and 0.968,respectively. The results show that the I-MEDV could successfully describe the structures of organic compounds. The stability and predictability of the models were good.

城市污水中诺如病毒两种富集浓缩方法的比较研究

目的比较聚乙二醇沉淀法和阴离子膜吸附—超声振荡法富集浓缩污水中诺如病毒(norovirus,NoV)的回收率,选择更适用于城市污水中诺如病毒监测工作的富集浓缩方法。方法将诺如病毒稀释三个梯度分别加入到城市生活污水(100 mL)中,采用聚乙二醇沉淀法和阴离子膜吸附—超声振荡法进行富集浓缩,采用实时荧光反转录聚合酶链式反应(RT-PCR)检测富集浓缩后GI型和GⅡ型病毒浓度,并进一步计算回收率。结果结果表明:①当NoV GI型浓度为10^(1.4) copies/μL时,阴离子膜吸附—超声振荡法回收率高于聚乙二醇沉淀法(P<0.05)。②当NoV GⅡ型浓度为10^(2.6) copies/μL时,阴离子膜吸附—超声振荡法回收率高于聚乙二醇沉淀法(P<0.05)。结论综合考虑富集浓缩效率等相关因素,阴离子膜吸附—超声振荡法更适合小体积污水中诺如病毒的富集浓缩。

含咪唑盐聚离子液体微凝胶的制备及其抗菌性能研究

大多数咪唑盐聚离子液体以线性聚合物的形式存在于抗菌材料中,将其制备成纳米颗粒形式可提高抗菌活性、降低细胞毒性。本研究采用乳液聚合法设计并制备了含咪唑盐聚离子液体的微凝胶,并将所制备的咪唑盐聚离子液体微凝胶与其相对应的线性聚合物进行对比。结果表明,微凝胶可有效提高聚合物的电负性,其对金黄色葡萄球菌的抑制率达到了99.8%,抗菌性能明显提高。本研究制备的含咪唑盐聚离子液体微凝胶具有高抗菌性以及低细胞毒性,可作为一种新型聚合物抗菌剂应用于生物医学材料中。

Study of a collisionless magnetized plasma sheath with nonextensively distributed species

A weakly magnetized sheath for a collisionless, electronegative plasma comprising positive ions,electrons, and negative ions is investigated numerically using the fluid approach. The electrons are considered to be non-Maxwellian in nature and are described by Tsalli's distribution. Such electrons have a substantial effect on the sheath properties. The study also reveals that non-Maxwellian distribution is the most realistic description for negative ions in the presence of an oblique magnetic field. In addition to the negative ion temperature, the sheath potential is also affected by the nonextensive parameters. The present research finds application in the plasma processing and semiconductor industry as well as in space plasmas.

表面氧修饰纳米金刚石制备及抗菌性能

表面修饰可有效提升纳米金刚石的抗菌性能。通过在空气中高温退火的方式实现了纳米金刚石的表面氧修饰,并对其进行了一系列表征以及抗菌测试。表征结果与采用光密度(OD)法进行抗菌测试结果表明,空气中400℃下退火进行的氧修饰可在纳米金刚石表面引入C=O官能团,并显著提高纳米金刚石的抗菌能力,对于金黄色葡萄球菌与大肠杆菌的抗菌率分别可达64.8%与83.4%。C=O官能团的形成将大量电子引入体系,并在氧原子作用下在表面富集,从而形成强负电性表面,该结论与Zeta电位结果一致。强负电性表面可抑制细菌的生长和繁殖,这使氧修饰纳米金刚石具有良好的抗菌性能。

电负性评估稀土离子电荷转移跃迁理论及在量子调控发光中的应用

发光过程中存在微观粒子之间的相互作用,可将其归结为量子行为。而稀土晶态材料作为发光的载体,包含了晶格、电荷、自旋以及轨道在内的多种自由度。稀土离子在晶体中可以看作一种无机晶格活性掺杂剂。由于稀土离子半径较大,其掺杂到晶体中容易引起晶格畸变,形成空位缺陷,并进一步导致晶体的电子结构和晶格环境发生改变,形成缺陷、晶格、电子结构等多尺度结构。由稀土离子掺杂引起的缺陷可以归结为局域对称性破缺,影响晶格自由度。此外,稀土离子f电子的复杂性导致了体系中的电荷、自旋、轨道等自由度的不稳定性。因此,通过多自由度耦合方法可以明确稀土晶态材料中发光来源的本质。通过电负性评估稀土离子电荷转移跃迁理论,可以将稀土晶态材料中离子尺度的晶格自由度,以及电子尺度的电荷、自旋以及轨道自由度整合起来,实现稀土晶态材料发光的量子调控。本文主要论述电负性评估稀土离子电荷转移跃迁理论及其在量子调控发光中的应用。

钙钛矿型(ABO_3)化合物的光催化活性及其影响因素

:ABO3钙钛矿型复合氧化物具有光催化活性 .其光催化活性与 A- O、B- O的电负性差值、B离子的