Quantum Capacitance of Mo2N MXene for Supercapacitor Applications

MXenes for supercapacitor (SC) electrodes is a very promising area of research. Supercapacitors are still behind batteries when to be used as primary energy source due to their low energy densities. Hence, additional research is vital to explore materials like MXenes for SC electrodes. The electronic properties of molybdenum nitride Mo₂N are studied and its quantum capacitance (QC) is calculated to explore its potential for SC electrodes. The MXene is found to be metallic in nature. The QC values for Mo₂N MXene are extremely high around Fermi level. Maximum value of 746.69 µF cm⁻² is achieved which is way higher than that of graphene. The value remains high for the negative bias voltage as well.     

Chemistry of two-dimensional MXene nanosheets in theranostic nanomedicine

Transition metal carbide,carbonitride and nitride MXenes,as the emerging two-dimensional(2D)nanomaterials,have aroused burgeoning research interest in a broad range of applications ranging from energy conversion to biomedicines attributing to their distinctive planar nanostructure,physiochemical properties and biological effects.They are featured with fascinating electronic,optical,magnetic,mechanical and thermal properties,which exert significant roles in biomedical applications of 2D MXenes.In this review,we briefly summarize the recent research progress of 2D MXenes and highlight their intrinsic chemistry in theranostic nanomedicines,focusing on the synthetic chemistry for MXenes construction,surface chemistry for surface engineering,physiochemical property for theranostic application and biological chemistry for biosafety evaluation.Furthermore,based on the current achieve ments on MXenes,their potential research directio n,critical challenges and future development in biomedicine are also discussed.It is highly expected that 2D MXene-based nanosystems would have a broad application prospect in theranostic biomedicine provided the current facing critical issues and challenges are adequately solved.     

Fluorescence and Nonlinear Optical Response of Graphene Quantum Dots Produced by Pulsed Laser Irradiation in Toluene

Graphene quantum dots (GQDs), the zero dimensional (0D) single nanostructures, have many exciting technological applications in diversified fields such as sensors, light emitting devices, bio imaging probes, solar cells, etc. They are emerging as a functional tool to modulate light by means of molecular engineering due to its merits, including relatively low extend of loss, large outstretch of spatial confinement and control via doping, size and shape. In this article, we present a one pot, facile and ecofriendly synthesis approach for fabricating GQDs via pulsed laser irradiation of an organic solvent (toluene) without any catalyst. It is a promising synthesis choice to prepare GQDs due to its fast production, lack of byproducts and further purification, as well as the control over the product by accurate tuning of laser parameters. In this work, the second (532 nm) and third harmonic (355 nm) wavelengths of a pulsed nanosecond Nd:YAG laser have been employed for the synthesis. It has been found that the obtained GQDs display fluorescence and is expected to have potential applications in optoelectronics and light-harvesting devices. In addition, nonlinear optical absorption of the prepared GQDs was measured using the open aperture z-scan technique (in the nanosecond regime). These GQDs exhibit excellent optical limiting properties, especially those synthesized at 532 nm wavelength.     

Synergistic Catalytic Acceleration of MXene/MWCNTs as Decorating Materials for Ultrasensitive Detection of Morphine

Ti₃C₂T_X MXene was synthesized by exfoliating pristine Ti₃AlC₂ phase with hydrofluoric acid. The simple methods of mechanical mixing and drop-casting of Ti₃C₂T_X and MWCNTs were carried out to prepare sensing electrode of Ti₃C₂T_X/MWCNTs/GCE. The composite and topography, especially the surface functional groups of Ti₃C₂T_X/MWCNTs were analyzed by XRD, SEM, FTIR, XPS, and Raman spectrum. The results turned out that Ti₃C₂T_X was characteristic by accordion-like 2D nanostructure with the surfaces terminated with −OH, −F, and =O. When combining with acid pretreated, the interaction between the functional groups of Ti₃C₂T_X and MWCNTs facilitated the convenience and reproducibility of the robust modified electrodes and could make Ti₃C₂T_X/MWCNTs/GCE possess good synergistic catalytic acceleration by increasing the electron transfer efficiency as well as adsorption and aggregation of MOP analyte onto the electrode surface. Versatile electrochemical measurements of CV, DPV and EIS were used to investigate the electrochemical performance of Ti₃C₂T_X/MWCNTs/GCE sensing platform. The linear detection range is 0.01–100 μM with the limit of detection of 0.0092 μM (S/N=3). The sensor has good stability, repeatability, reproducibility and anti-interference. In the detection of serum and urine samples, it has a good recovery rate.     

Constructing 2D Sandwich-like MOF/MXene Heterostructures for Durable and Fast Aqueous Zinc-Ion Batteries

Two-dimensional metal–organic frameworks (2D MOFs) can be used as the cathodes for high-performance zinc-ion battery due to their large one-dimensional channels. However, the conventionally poor electrical conductivity and low structural stability hinder their advances. Herein, we report an alternately stacked MOF/MX heterostructure, exhibiting the 2D sandwich-like structure with abundant active sites, improved electrical conductivity and exceptional structural stability. Ex situ characterizations and theoretical calculations reveal a reversible intercalation mechanism of zinc ions and high electrical conductivity in the 2D heterostructure. Electrochemical tests confirm excellent Zn²⁺ migration kinetics and ideal pseudocapacitive behaviors. As a consequence, Cu-HHTP/MX shows a superior rate performance (260.1 mAh g⁻¹ at 0.1 A g⁻¹ and 173.1 mAh g⁻¹ at 4 A g⁻¹) and long-term cycling stability of 92.5 % capacity retention over 1000 cycles at 4 A g⁻¹.     

金属有机配合物的非线性光学特性

从过渡金属有机配合物的中心金属、配体和几何结构的多样性、多变的金属氧化态和金属与配体的电子供－受作用评述了金属有机配合物的二阶、三阶非线性光学效应的分子结构特征和最新进展。参考文献２６篇。     

Pulsed Laser Deposition as a Tool for the Development of All Solid-State Microbatteries

All-solid-state lithium ion batteries (LIB) are currently the most promising technology for next generation electrochemical energy storage. Many efforts have been devoted in the past years to improve performance and safety of these devices. Nevertheless, issues regarding chemical and mechanical stability of the different components still hinder substantial improvements. Pulsed laser deposition (PLD) has proved to be an outstanding technique for the deposition of thin films of materials of interest for the fabrication of LIB. Thanks to its versatility and possible fine tuning of the thin film properties, PLD promises to be a very powerful tool for the fabrication of model systems which would allow to study in detail material properties and mechanisms contributing to LIB degradation. Nevertheless, PLD presents difficulties in the deposition of LIB components, mainly due to the presence of elements with large difference of atomic mass in their chemical composition. In this review, we report the main challenges and solution strategies used for the deposition through PLD of complex oxides thin films for LIB.     

MoS2‐on‐MXene Heterostructures as Highly Reversible Anode Materials for Lithium‐Ion Batteries

Two‐dimensional (2D) heterostructured materials, combining the collective advantages of individual building blocks and synergistic properties, have spurred great interest as a new paradigm in materials science. The family of 2D transition‐metal carbides and nitrides, MXenes, has emerged as an attractive platform to construct functional materials with enhanced performance for diverse applications. Here, we synthesized 2D MoS₂‐on‐MXene heterostructures through in situ sulfidation of Mo₂TiC₂T_x MXene. The computational results show that MoS₂‐on‐MXene heterostructures have metallic properties. Moreover, the presence of MXene leads to enhanced Li and Li₂S adsorption during the intercalation and conversion reactions. These characteristics render the as‐prepared MoS₂‐on‐MXene heterostructures stable Li‐ion storage performance. This work paves the way to use MXene to construct 2D heterostructures for energy storage applications.     

Preparative Solid-State Chemistry with High-Power CO2 Lasers

The establishment of solid state chemistry as an independent field, which also has had a stimulating effect on material sciences, is a consequence of the experimental skill of chemists. The development of new methods led to an abundance of new compounds, the characteristic properties of which are linked with the solid state. The reaction temperature plays an important role in the synthesis of solid compounds; therefore, it is not surprising that a large number of the newly developed experimental techniques involve methods which can produce high temperatures on the openended temperature scale. Since the development of the CO₂ laser, the solidstate chemist has an excellent heat source available, and with the power available today the range of high temperatures possible has been extended considerably. A way is now open for producing metastable, “entropy-supported” high-temperature compounds and substances with anomalous oxidation states and with macroscopic defects.     

非线性光学材料的分子设计研究

非线性光学研究应用电磁场和各种材料的相互作用, 产生新的电磁场, 改变频率, 相或其它物理性质. 本文介绍了非线性光学材料分子设计的原理, 并以共轭长链分子和碳笼及其衍生物为例报道了我们在这方面的研究工作.     

Selective Etching of Silicon from Ti3SiC2 (MAX) To Obtain 2D Titanium Carbide (MXene)

Until now, MXenes could only be produced from MAX phases containing aluminum, such as Ti₃AlC₂. Here, we report on the synthesis of Ti₃C₂ (MXene) through selective etching of silicon from titanium silicon carbide—the most common MAX phase. Liters of colloidal solutions of delaminated Ti₃SiC₂‐derived MXene (0.5–1.3 mg mL^?1) were produced and processed into flexible and electrically conductive films, which show higher oxidation resistance than MXene synthesized from Ti₃AlC₂. This new synthesis method greatly widens the range of precursors for MXene synthesis.     

MXenes材料的光学特性及相关研究进展

过渡金属碳化物、 氮化物或碳氮化物(MXenes)具有丰富的元素组成和结构可调性, 显示出丰富的物理化学性质和巨大的应用潜力. 本文以此类材料的基本光学特性为基础, 从光子发射、 透明导电及储能、 非线性光学、 表面等离激元及拉曼增强、 光热转化、 光催化及光响应等光学相关领域展开分析和综述. 并对此二维材料相关应用的未来发展及机遇作了简单评述, 以期为进一步的研究提供参考.     

飞秒时间分辨光学多道谱仪研究

超快时间分辨光谱学为研究非线性光学，固体物理，化学反应动力学，能量传递和驰豫、生物过程动力学和相干光谱技术提供了一种有效的工具。本文报导了一种飞秒时间分辨光学多道光谱设备，该设备是由一台用氩离子激光器原浦且产生１００ｆｓ光脉冲并调谐在７２０－９８０ｎｍ的飞秒掺钛兰宝石激光器，改进了光学多道器（ＯＭＡ－ＩＩ），３８６计算机及光学系统组成的。激光脉冲用ＬＢＯ晶体倍频，谱仪装置的时间分辨率约１２０ｆｓ，     

An Unprecedented Antimony(III) Borate with Strong Linear and Nonlinear Optical Responses

Antimony(III) borates with a stereochemical active lone pair remained unknown, although the first antimony borate was reported more than twenty years ago. Now, the first antimony(III) borate in a closed system is successfully synthesized, namely SbB₃O₆. Remarkably, SbB₃O₆ not only exhibits an exceptional linear optical response, that is, birefringence of Δn=0.290 at the wavelength of 546 nm, which is the largest among borates, but also has a strong nonlinear optical response of 3.5 times larger than the benchmark KH₂PO₄, exceeding those of most borates. Theoretical calculations reveal that the coexistence of strong linear and nonlinear optical responses in SbB₃O₆ should be attributable to the synergistic effect of π‐conjugated B?O anionic groups and Sb³⁺ with stereochemically active lone pair. This work provides a new class of optical bi‐functional materials with potential prospects in integrated optical devices.     

Theoretical Investigation of Second-Order Nonlinear Optical Properties of Substituted Benzothiazole Derivatives

On the basis of the ZINDO program, we have designed a program to calculate the nonlinear second-order polarizabilities _ijk, ₀, and according to the SOS expression. The second-order nonlinear optical properties of a series of benzothiazole derivatives including 2-(p-donor--styryl)-6-nitrobenzothiazole, 2-(p-donor-phenyl)-azo-6-nitrobenzothiazole, and 2-(p-nitro--styryl)-6-donor-benzothiazole derivatives were studied. The calculated results show that when the benzothiazole rings are connected to the nitro group (acceptor), the values are relatively larger. This does not agree with the theory of auxiliary donor–acceptor effects. The 2-(p-donor--styryl)-6-nitrobenzothiazole derivatives exhibit more nonlinearity than 2-(p-donor-phenyl)-azo-6-nitrobenzothiazole derivatives. The 2-(p-donor--styryl)-6-nitrobenzothiazole derivatives are good candidates as chromophores due to their high nonlinearities and good thermal stability.     

All-Fiber Tunable Pulsed 1.7 μm Fiber Lasers Based on Stimulated Raman Scattering of Hydrogen Molecules in Hollow-Core Fibers

Fiber lasers that operate at 1.7 μm have important applications in many fields, such as biological imaging, medical treatment, etc. Fiber gas Raman lasers (FGRLs) based on gas stimulated Raman scattering (SRS) in hollow-core photonic crystal fibers (HC-PCFs) provide an elegant way to realize efficient 1.7 μm fiber laser output. Here, we report the first all-fiber structure tunable pulsed 1.7 μm FGRLs by fusion splicing a hydrogen-filled HC-PCF with solid-core fibers. Pumping with a homemade tunable pulsed 1.5 μm fiber amplifier, efficient 1693~1705 nm Stokes waves are obtained by hydrogen molecules via SRS. The maximum average output Stokes power is 1.63 W with an inside optical–optical conversion efficiency of 58%. This work improves the compactness and stability of 1.7 μm FGRLs, which is of great significance to their applications.     

一种有机二阶非线性光学开关材料的合成与理论研究

以苄氧基取代的苯胺为电子给体、二氰基乙烯为电子受体经Wittig和Knoevenagel缩合反应合成了一种基于二噻吩乙烯的具有开关效应的非线性光学材料,其结构经¹H NMR、¹³C NMR和HR-MS表征,并通过紫外吸收光谱和理论计算分别对目标分子的开/关环行为和微观非线性光学性能进行了研究。结果表明：目标分子在紫外光（365nm）和可见光照射下可发生关环和开环反应,开/关环状态下化合物的最大吸收波长分别为381nm和812nm。      

Investigation of two-dimensional hf-based MXenes as the anode materials for li/na-ion batteries: A DFT study

Density functional theory calculations are performed to investigate electronic properties and Li/Na storage capability of Hf₃C₂ and its derivatives (uniform passivated: Hf₃C₂T₂ [T = F, O, OH] and hybrid passivated: Hf₃C₂F_xO_2-x and Hf₃C₂O_x(OH)_2-x [x = 1.0, 1.5]). For Hf₃C₂ monolayer, it has excellent performance, such as good conductivity, low diffusion energy barrier, low open circuit voltage, and high storage capacities (Li(1034.70 mAh g⁻¹), Na(444.90 mAh g⁻¹)), providing the most prospective as anode material. However, due to the unsaturated dangling bonds of surface Hf, so it is easily passivated. For the uniform passivated ones, Hf₃C₂T₂, show higher diffusion barriers and lower storage capacities than bare monolayer Hf₃C₂. Nevertheless, compared with uniform passivated ones, the hybrid passivated derivative, Hf₃C₂F_1.5O_0.5 and Hf₃C₂OOH possess a lower energy barrier and a better storage capacity. Therefore, Hf₃C₂F_1.5O_0.5 and Hf₃C₂OOH are deemed to be a suitable candidate as anode electrode material for Li-ion batteries. © 2019 Wiley Periodicals, Inc.     

V2CO2 MXene负载过渡金属单原子催化剂氧还原和氢氧化活性的DFT研究

开发廉价且高性能的电催化剂对推动燃料电池的商业应用具有重要意义.二维(2D) MXenes和单原子(SAs)催化剂是催化研究中的两个前沿领域.2D MXenes材料具有独特的几何和电子结构,能够有效调节负载SAs的催化性能.而负载的SAs又会反过来影响2D MXenes材料的本征活性,使2D MXenes形成更加丰富的活性位,进而提升其催化性能.为了拓展2D负载SAs催化剂在燃料电池中的应用,本文采用密度泛函理论(DFT)计算,系统地研究了V2CO2 MXenes负载过渡金属(TM,包括一系列3d、部分4d和5d金属)SAs催化剂的稳定结构、电子结构及其催化氧还原(ORR)和氢氧化(HOR)的催化活性,并筛选出潜在的可替代贵金属铂的ORR/HOR的双功能催化剂.稳定结构计算结果表明,3d TM SAs倾向于以锚定的形式负载于V2CO2表面与O原子作用,而4d,5d TM原子倾向于以掺杂的形式负载于含氧空穴的V2CO2表面与V原子作用;同时,Sc,Ti,V,Rh,Pd,Pt,Ag和Au SAs在V2CO2表面因具有较高扩散能垒,不易团聚,具有较高的热力学稳定性.电子结构计算结果表明,锚定型的TM SAs与O形成共价键,伴随发生明显的电荷转移,带较多正电荷;掺杂型的TM SAs与V形成金属键,因TM-V和V-O键间电荷转移的协同影响,导致TM SAs仅带有少量的电荷.TM-V2CO2电子结构与ORR/HOR中间物种的吸附关系为,TM位点为ORR中间物种(O,OH和OOH)的吸附位点,且d电子数为1、5、10的TM比其他TM对ORR物种的吸附更弱;而TM-V2CO2表面的O原子为HOR中间物种(H)的有效吸附位点,且H的吸附强弱与O位点的电荷有关,即O位点负电荷越多,对H的吸附越弱.TM-V2CO2催化剂各活性位对ORR和HOR反应物种的选择性吸附结果表明,催化剂有利于形成丰富多样的活性位,并具备作为双功能催化剂的内在优势.TM-V2CO2催化剂ORR和HOR理论活性筛选发现:与Pt(111)相比,Sc-、Mn-、Rh-和Pt-V2CO2具有较高的ORR活性,而Sc-、Ti-、V-、Cr-和Mn-V2CO2表现出较高的HOR活性.其中,Sc-V2CO2和Mn-V2CO2因同时具有较高的ORR和HOR活性和稳定性,有望成为高效和低成本的燃料电池双功能催化剂.本文从研究TM-V2CO2性质和活性出发,深入研究了SAs与2D MXenes间相互作用及其对ORR与HOR催化活性的影响机制,筛选出了高效、低成本的ORR/HOR双功能催化剂,为合理设计燃料电池双功能催化剂提供了理论指导.     

新型同分异构芘基查尔酮的理论研究和超快三阶非线性光学响应

合成了3个新型同分异构芘基查尔酮:1-(芘-1-基)-3-(吡啶-2-基)-2-丙烯-1-酮(3a)、1-(芘-1-基)-3-(吡啶-3-基)-2-丙烯-1-酮(3b)和1-(芘-1-基)-3-(吡啶-4-基)-2-丙烯-1-酮(3c)。 通过核磁共振波谱仪(NMR)、傅里叶变换红外光谱仪(FTIR)和液-质联用仪(LC-MS)等技术手段表征3个化合物的结构、热稳定性和线性光学性质和三阶非线性光学吸收性能。 结果表明,在532 nm和180 fs条件下,化合物3a-3c均表现出超快三阶非线性光学响应,化合物3c的非线性吸收系数分别是化合物3b和3a的1.14和2.67倍。 运用密度泛函理论方法计算了化合物3a-3c的非线性光学性质及其电子性质,结果表明,化合物3c分子具有最大的静态第一超极化率(β₀)(2830.9 a.u.),并具有最小的最高占据分子轨道(HOMO)-最低空分子轨道(LUMO)之间的能隙(3.11 eV)和最小的跃迁能(ΔE)(2.67 eV),这与N原子在吡啶环上的位置有关;分子内部均存在电荷转移现象。 3个化合物的紫外-可见光谱在450 nm以上无吸收,有良好的热稳定性,在激光防护方面有应用前景。