不同横向尺寸单层Ti3C2Tx纳米片的制备及其电化学性能研究

近年来, 一种新型二维过渡金属碳化物及氮化物(MXene)凭借大的比表面积、良好的亲水性、金属导电性等物理化学性质而广受关注。通过LiF和HCl刻蚀Ti₃AlC₂的Al层, 改变机械剥离强度和方式, 以及离心速率和时间, 可控制备出平均横向尺寸为625 和2562 nm的单层Ti₃C₂T_x型MXene。借助扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射仪(XRD)对二维Ti₃C₂T_x进行形貌、结构和成分的表征。使用电化学工作站表征Ti₃C₂T_x的电化学性能。结果表明: 小片层Ti₃C₂T_x(625 nm)的质量比电容高达561.9 F/g, 远高于文献报道的石墨烯、碳纳米管和二氧化锰等电极材料; Ti₃C₂T_x电极在循环测试10 ⁴次后, 其比电容仍保持初始96%的容量。     

表面活性剂辅助插层制备二维Ti3C2Tx及其电化学性能研究

采用一种改进的方法制备了类石墨烯的Ti_3C_2T_x二维材料。首先采用氢氟酸刻蚀Ti_3AlC_2,然后向插层溶剂二甲亚砜中添加表面活性剂十六烷基三甲基溴化铵协助二甲亚砜共同插层,最后经超声处理制备Ti_3C_2T_x。XRD测试表明,由于表面活性剂的协助插层作用,插层剂分子更容易进入Ti_3C_2T_x层间,显著增加其层间距,减小层间的相互作用力,便于其剥离。氮气吸脱实验证实该方法制备的Ti_3C_2T_x具有更高的比表面积和孔容。电化学测试表明,由制备的Ti_3C_2T_x组装成的对称性电容器具有更高的比电容,在0.5 A/g电流密度下的比电容达75.0 F/g,当充电电流增加至4 A/g时,其电容维持在57.0 F/g。在1 A/g的电流密度下,经过2 500次的充放电循环后,制备的Ti_3C_2T_x材料的比电容为61.5 F/g,循化稳定率达87.0%。     

Cr3C2及(W,Ti)C对Al2O3/Cr3 C2/(W,Ti)C复合陶瓷材料Vickers硬度的影响

热压烧结制备了Al2O3/Cr3C2/(W,Ti)C复合陶瓷材料(以下简称ACW复合材料),对其Vickers硬度及组织形貌进行了研究,分析了Cr3C2及(W,Ti)C对Vickers硬度的影响.结果表明,(W,Ti)C和Cr3C2的添加利于阻止晶界迁移,抑制晶粒长大,Cr、W、Ti离子在Al2O3基体晶粒中的固溶起强化作用.每一相的添加量在10%～20%(体积分数,下同)为宜,添加总量在30%左右ACW复合材料硬度最佳.     

Ti3C2Tx MXene 基复合材料驱动器的制备及研究进展

驱动器具备质轻、柔软、微小、智能化等特点,能够通过感受外界刺激如光、电、温度、湿度等产生相应的力、位移或形变,在软机器人、智能穿戴设备、仿生工程等领域具备巨大的应用潜力。然而,驱动器也存在着响应灵敏性和稳定性方面的缺陷。MXene具有高导电性、表面官能团可调性和优越的力学性能,有望成为解决上述问题的关键。目前,MXene材料主要面临易氧化和相对较高的生产成本等挑战,相关研究处于早期阶段,需要进一步验证其实际应用潜力。因此,本文介绍了MXene及MXene基驱动器的制备方法,并梳理光热响应型驱动器、离子响应型驱动器、湿度响应型驱动器及其他响应型驱动器的研究进展,同时对MXene基驱动器未来的研究方向进行了展望。     

MoS2/Ti3SiC2层状复合材料的制备

采用热压烧结方法制备MoS2/Ti3SiC2(MoS2质量分数为2%)的层状复合材料.研究了不同烧结温度对烧结试样性能的影响.研究表明,在1 400℃,30 MPa压力和保温2 h条件下,可以得到致密度达99%以上的MoS2/Ti3SiC2复合材料;在Ti3SiC2中添加MoS2后,烧结温度越高维氏硬度越大;在1 400℃,烧结试样维氏硬度达6 220 MPa,高于纯Ti3SiC2材料的4 000 MPa;MoS2有良好的导电性能,使得烧结试样的电导率比较高,在1 400℃,烧结试样电导率达9.68×106 S·m-1,是纯Ti3SiC2材料的2倍.     

电池负极材料Ti3C2M2MXene表面修饰及Li存储能力的第一性原理计算研究

Ti3 C2是一种具有较好Li存储能力的电池负极材料,表现为金属导电性,具有较好的循环使用率和低的迁移势垒等优点.本研究采用密度泛函理论(DFT),运用第一性原理计算了多种表面基团作表面修饰结构的电子性能.本研究选取九种表面基团,分别是卤族F、Cl,氧族O、S、Se、Te,等相对分子质量OH、NH2、CH3.表面基团吸附设计了三种方法:Ti(2)上方吸附、C上方吸附、Ti(1)上方吸附,计算结果表明,同一种表面基团中的Ti(2)上方吸附具有更低的体系总能量E0,结构表现更加稳定.而在同一组中质量分数小的基团及原子数少的基团,电子性能越好,有更好的电子传输性能.最终对比表面基团F、O、OH的结合能,分别是-5.37 eV、-4.96 eV、-5.00 eV,F基团的结合能最低,表现为最好的结构稳定性,而Ti3 C2 O2具有最大的开路电压0.44 eV和最高的Li存储容量268.61 mA·h·g-1.     

Ti3C2Tx MXene基电磁屏蔽材料的研究进展

随着电子设备和无线通讯的迅猛发展,电磁干扰问题也随之日益严重,迫切需要发展高性能的电磁屏蔽防护材料来减轻电磁波干扰危害.MXene(Ti3C2Tx)是一种新型二维材料,具有超高的电导率和活跃的化学活性表面,因而展现出极其优异的电磁屏蔽性能.本文重点介绍了Ti3C2Tx的制备方法、结构特性以及电磁屏蔽机理,客观地综述和评价了近年来国内外关于Ti3C2Tx基薄膜和三维多孔材料在电磁屏蔽应用方面的重要研究进展,并分析了目前存在的主要问题.此外,从Ti3C2Tx的制备、结构调控、设计组装等方面展望了Ti3C2Tx基电磁屏蔽材料的发展方向及趋势,包括发展低成本绿色环保且高效的Ti3C2Tx制备工艺、解决Ti3C2Tx不耐氧化的问题、设计新型Ti3C2Tx电磁屏蔽材料结构及探究其他种类的MXenes电磁屏蔽材料,为开发下一代高电磁屏蔽性能材料提供新的思路和指导.     

Al2O3/Ti3SiC2层状复合材料的制备与性能

采用两种方法制备Al2O3／Ti3SiC2层状复合材料，一是原位-热压法，即Ti3SiC2是在层状材料的制备过程中同时被合成的；一是分步法，即制备过程分两步进行，首先制备出Ti3SiC2高纯粉，再采用热压法进行烧结制备层状材料。两种方法制备的Al2O3／Ti3SiC2层状复合材料强度保持在450MPa以上，断裂功达到1200-1560J／m^2，相对Al2O3块体材料提高十余倍。另外，不同的制备方法得到不同的组成和显微结构，决定了这两种Al2O3／Ti3SiC2层状复合材料性能的差异：前者强度较高韧性较低，后者强度较低而韧性较高。     

分步法制备MoS2/Ti3SiC2层状复合材料

研究了采用分步法制备MoS2/Ti3SiC2层状复合材料的工艺,其制备过程分2步进行.首先制备Ti3SiC2高纯粉,再在1 400℃,30 MPa条件下热压烧结制备MoS2/Ti3SiC2层状复合材料.其MoS2含量分别为2%,4%,6%,8%(w/%).用XRD分析比较4种不同MoS2含量的烧结试样的相组成,并测试维氏硬度和电导率.实验结果表明,当MoS2含量为4%时,MoS2/Ti3SiC2烧结试样的硬度达到7.83 GPa,且电导率达到10.05×106 S·m-1.MoS2含量再增加时,烧结试样的硬度有所增大,但电导率有所下降.     

Filling Ti3C2Tx nanosheets into melamine foam towards a highly compressible all-in-one supercapacitor

The development of compressible supercapacitors strongly relies on the design of electrode materials combining superior compressibility,high conductivity with t...     

Fabrication of metal half-shells using colloidal particle monolayer and their application in surface-enhanced Raman scattering

Three types of Au shells, an isolated half-shell, one-dimensional strings of shells, and two-dimensional films, were fabricated by using a monolayer of polystyrene (PS) particles with diameters of 213, 560, and 1360 nm. The three types of Au shells that were removed from the PS particle monolayer and the as-deposited Au shells that adhered to PS particles were modified with 4-mercaptopyridine for use as platforms for surface-enhanced Raman scattering (SERS). We examined the effects of the shapes and sizes of Au shells on their SERS efficiency and found that the Au shells exhibited strong SERS signals and that Au shells prepared by using 560-nm PS particles were the most suitable platform for SERS at both 632.8- and 785-nm excitations. Further, we found that SERS enhancements depended on the shape of Au shells and on whether Au shells adhered to PS particles or not.     

Highly-ordered, 3D petal-like array for surface-enhanced Raman scattering

Despite the great potential of the application of surface-enhanced Raman scattering (SERS), the difficulty in fabricating suitable SERS substrates is still a problem. Based on the self-assembly of silica nanoparticles, a simple method is here proposed to fabricate a highly-ordered, 3D, petal-like arrayed structure (3D PLAS) that serves as a promising SERS substrate for both its high reproducibility and enormous SERS enhancement. Such a novel structure is easily achieved by anisotropically etching a self-assembly bilayer of silica nanoparticles, followed by metal deposition. The SERS performance of the 3D PLAS and its relationship with the main parameters, including the etching time, the diameter of silica nanoparticles, and the deposited metal film, are characterized using 632.8 nm incident light. With Rhodamine 6G as a probe molecule, the spatially averaged SERS enhancement factor is on the order of 5 × 10(7) and the local enhancement factor is much higher, both of which can be improved further by optimizing the parameters.     

Novel Ag-Cu substrates for surface-enhanced Raman scattering

Ag dendrites were deposited on rough Cu plate by a simple galvanic displacement process between Ag ion and Cu under room temperature. Surface-enhanced Raman scattering (SERS) performances have been studied using Rhodamine 6G (R6G) probe molecules on this kind of Ag-Cu substrates. The high SERS enhancements are attributed to the highly branched Ag dendritic nanostructures and Ag nanoparticles formed on the trunks, branches, and even leaves.     

In situ surface-enhanced Raman scattering analysis of biofilm

Biofilms represent the predominant form of microbial life on Earth. They are aggregates of microorganisms embedded in a matrix formed by extracellular polymeric substances (EPS). Detailed information about chemical composition and structure of the EPS matrix is relevant e.g. for the optimization of biocides, of antifouling strategies and for biological wastewater treatment. Raman microscopy (RM) is a capable tool that can provide detailed chemical information about biofilm constituents with spatial resolution of optical microscope. However, the sensitivity of RM is limited. Surface-enhanced Raman scattering (SERS), which enables investigations of biomolecules at very low concentration levels, allows overcoming this drawback. To our knowledge, this paper is the first report on reproducible SERS spectra from different constituents of a multispecies biofilm. We believe that the reproducibility is partly owed to the in situ measurement of the biofilm, while up to now SERS measurements of microbiological samples by RM were carried out after sample drying. We employed colloidal silver nanoparticles for in situ SERS measurements by RM. The achieved enhancement factor of up to 2 orders of magnitude illustrates a high potential of SERS for ultrasensitive chemical analysis of biofilms, including the detection of different components and the determination of their relative abundance in the complex biofilm matrix.     

Aligned silver nanorod arrays for surface-enhanced Raman scattering

Silver nanorods were prepared by a seed-mediated growth approach, and self-assembled into two-dimensional ordered arrays on glass substrates. The polarization-dependent optical responses of the rods were measured, which indicated ordered alignment. These arrays were evaluated as potential surface-enhanced Raman spectroscopy (SERS) substrates using trans-bis(4-pyridyl)ethylene molecules. The SERS signals were observed to be enhanced with the increase of the aspect ratio of the Ag nanorod, and this was mainly attributed to the local field enhancement. The lateral arrangement of the Ag nanorod arrays was also partially responsible for the SERS enhancement.     

Simple multiplex genotyping by surface-enhanced resonance Raman scattering

The accurate detection of DNA sequences is essential for a variety of post human genome projects including detection of specific gene variants for medical diagnostics and pharmacogenomics. A specific DNA sequence detection assay based on surface-enhanced resonance Raman scattering (SERRS) and an amplification refractory mutation system (ARMS) is reported. Initially, generation of PCR products was achieved by using specifically designed allele-specific SERRS active primers. Detection by SERRS of the PCR products confirmed the presence of the sequence tested for by the allele-specific oligonucleotides. This lead directly to the multiplex genotyping of human DNA samples for the deltaF508 mutational status of the cystic fibrosis transmembrane conductance regulator gene using SERRS active primers in an ARMS assay. Removal of the unincorporated primers allowed fast and accurate analysis of the three genotypes possible in this system in a multiplex format without any separation of amplicons. The results indicate that SERRS can be used in modern genetic analysis and offers an opportunity for the development of novel assays. This is the first demonstration of the use of SERRS in multiplex genotyping and shows potential advantages over fluorescence as a detection technique with considerable promise for future development.