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Patterning single-layer materials by electrical breakdown using atomic force microscopy

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Nanotechnology and Precision Engineering 2024年第1期7卷 71-77页

作者： Yajie Yang Jiajia Lu Yanbo Xie Libing duan School of Physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China School of Aeronautics and Institute of Extreme Mechanics Northwestern Polytechnical UniversityXi’an 710072China

The development of nanoelectronics and nanotechnologies has been boosted signiﬁcantly by the emergence of 2d materials because of their atomic thickness and peculiar properties,and developing a universal,precise patterning technology for single-layer 2d materials is critical for assembling nanodevices.demonstrated here is a nanomachining technique using electrical breakdown by an AFM tip to fabricate nanopores,nanostrips,and other nanostructures on demand.This can be achieved by voltage scanning or applying a constant voltage while moving the tip.By measuring the electrical current,the formation process on single-layer materials was shown quantitatively.The present results provide evidence of successful pattern fabrication on single-layer MoS2,boron nitride,and graphene,although further conﬁrmation is still needed.The proposed method holds promise as a general nanomachining technology for the future.

关键词： 2d material Nanopattern AFM Electrical breakdown Lithography

Wetting of MXenes and Beyond

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Nano-Micro Letters 2023年第8期15卷 141-153页

作者： Massoud Malaki Rajender S.Varma department of Mechanical Engineering Isfahan University of TechnologyDaneshgah e Sanati HwyKhomeyni ShahrIsfahan 84156‑83111Iran Regional Centre of Advanced Technologies and materials Palacky University in OlomoucŠlechtitelů2778371 OlomoucCzech Republic

MXenes are a class of 2d nanomaterials with exceptional tailormade properties such as mechano-ceramic nature,rich chemistry,and hydrophilicity,to name a few.However,one of the most challenging issues in any composite/hybrid system is the interfacial wetting.Having a superior integrity of a given composite system is a direct consequence of the proper wettability.While wetting is a fundamental feature,dictating many physical and chemical attributes,most of the common nanomaterials possesses poor affinity due to hydrophobic nature,making them hard to be easily dispersed in a given composite.Thanks to low contact angle,MXenes can offer themselves as an ideal candidate for manufacturing different nano-hybrid structures.Herein this review,it is aimed to particularly study the wettability of MXenes.In terms of the layout of the present study,MXenes are first briefly introduced,and then,the wettability phenomenon is discussed in detail.Upon reviewing the sporadic research efforts conducted to date,a particular attention is paid on the current challenges and research pitfalls to light up the future perspectives.It is strongly believed that taking the advantage of MXene’s rich hydrophilic surface may have a revolutionizing role in the fabrication of advanced materials with exceptional features.

关键词： MXene Wetting Hydrophilicity Composites 2d material

Reducing dielectric confinement effect in ionic covalent organic nanosheets to promote the visible-light-driven hydrogen evolution

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Journal of Energy Chemistry 2023年第7期82卷 40-46,I0002页

作者： Guoqing Li Xiaolong Zhao Qihong Yue Ping Fu Fangpei Ma Jun Wang Yu Zhou State Key Laboratory of materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 211816JiangsuChina

Ultra-thin two-dimensional(2d)organic semiconductors are promising candidates for photocatalysts because of the short charge diffusion pathway and favorable exposure of active sites plus the versatile architecture.Nonetheless,the inherent dielectric confinement of 2d materials will induce a strong exciton effect hampering the charge separation.Herein,we demonstrated an effective way to reduce the dielectric confinement effect of 2d ionic covalent organic nanosheets(iCONs)by tailoring the functional group via molecular engineering.Three ultra-thin CONs with different functional groups and the same ionic moieties were synthesized through Schiff base condensation between ionic amino monomer triaminoguanidinium chloride(TG)and aldehyde linkers.The integration of the hydroxyl group was found to significantly increase the dielectric constant by enhancing the polarizability of ionic moieties,and thus reduced the dielectric confinement and the corresponding exciton binding energy(E_(b)).The champion hydroxyl-functional iCON exhibited promoted exciton dissociation and in turn a high photocatalytic hydrogen production rate under visible-light irradiation.This work provided insights into the rationalization of the dielectric confinement effect of low-dimensional photocatalysts.

关键词： Photocatalysis H_(2)evolution Ionic covalent organic framework Nanosheets 2d material Polarization

Layer-dependent photoexcited carrier dynamics of WS_(2) observed using single pulse pump probe method

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Chinese Optics Letters 2022年第10期20卷 2-7页

作者：张林刘佳敏江浩谷洪刚刘世元 State Key Laboratory of digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China Optics Valley Laboratory Wuhan 430074China

Understanding the ultrafast carrier dynamics and the mechanism of two-dimensional(2d)transition metal dichalcogenides(TMds)is key to their applications in the field of optoelectronic devices.In this work,a single pulse pump probe method is introduced to detect the layer-dependent ultrafast carrier dynamics of monolayer and few-layer WS_(2) excited by a femtosecond pulse.Results show that the ultrafast carrier dynamics of the layered WS_(2) films can be divided into three stages:the fast photoexcitation phase with the characteristic time of 2–4 ps,the fast decay phase with the characteristic time of 4–20 ps,and the slow decay phase lasting several hundred picoseconds.Moreover,the layer dependency of the characteristic time of each stage has been observed,and the corresponding mechanism of free carrier dynamics has been discussed.It has been observed as well that the monolayer WS_(2) exhibits a unique rising time of carriers after photoexcitation.The proposed method can be expected to be an effective approach for studying the dynamics of the photoexcited carriers in 2d TMds.Our results provide a comprehensive understanding of the photoexcited carrier dynamics of layered WS_(2),which is essential for its application in optoelectronics and photovoltaic devices.

关键词： photoexcited carrier pump probe 2d material single pulse measurement

Electric field and charge doping induced superconducting transition in 2d freestanding perovskite barium bismuthate

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中国科学:物理学、力学、天文学英文版 2023年第7期66卷 102-111页

作者： Yaning Cui Tianhao Su Lei Qiao Zongquan Gu Gianni Profeta Alessandra Continenza Wei Ren Physics department Materials Genome InstituteInternational Center for Quantum and Molecular StructuresShanghai UniversityShanghai 200444China Shanghai Key Laboratory of High Temperature Superconductors Shanghai UniversityShanghai 200444China Zhejiang Laboratory Hangzhou 311100China School of Microelectronics Fudan UniversityShanghai 200433China department of Physical and Chemical Sciences Universitàdegli Studi dell'AquilaCoppito(L'Aquila)67100Italy Consiglio Nazionale delle Ricerche CNR-SPIN Coppito(L'Aquila)67100Italy

We present an ab-initio study of monolayer BaBiO_(3) focused on how to harness the insulator-metal transition through suppression of the charge density wave(CdW)phase in this material.After the determination of the most stable structure for the freestanding monolayer,we investigate the effects of an applied electric field and of charge doping on the electronic properties of the system.Our results show that external electric fields of the order of 0.1-0.3 V/A are able to stabilize the metallic phase,destroy the CdW phase and,in addition,lead to a metallic metastable phase.On this same footing,we show that hole doping could also suppress the CdW phase and drive the system toward a metallic phase with large electron-phonon coupling.To this end,we also study the dependence of the electron-phonon coupling on hole-doping concentration and show that this could drive the onset of superconductivity.Indeed,low-dimensional BaBiO3 is an extremely flexible material with electronic properties that could be tuned using different and possibly combined external tools such as electric fields and charge doping,paving the way to achieve effective control on the transition from the CdW,to the metallic and then superconducting phase.

关键词： charge wave density phase transition superconductivity 2d material

Toughening of vinyl ester resins by two-dimensional MXene nanosheets

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Frontiers of Chemical Science and Engineering 2022年第11期16卷 1651-1658页

作者： Yurun dai Heng Fang Zong Lu Zhuohong Yang Yanying Wei School of Chemistry and Chemical Engineering Guangdong Provincial Key Lab of Green Chemical Product TechnologyState Key Laboratory of Pulp and Paper EngineeringSouth China University of TechnologyGuangzhou 510640China Key Laboratory for Bio-based materials and Energy of Ministry of Education College of Materials and EnergySouth China Agricultural UniversityGuangzhou 510642China

Two-dimensional nanosheets are highly effective tougheners for vinyl ester resins.The toughening effect is related to the high specific surface area and unique two-dimensional planar structure of the nanosheets.In this study,a coupling agentγ-(2,3-epoxypropoxy)propytrimethoxysilane(Kh-560)was used to modify MXene nanosheets(M-MXene)for use in toughening vinyl ester resin.The mechanical properties,including the tensile strength,flexural strength,Young’s modulus and elongation,of neat vinyl ester resin and vinyl ester resin modified with MXene and M-MXene were investigated.The results showed that modification significantly improved the mechanical properties of the vinyl ester resin.The tensile and flexural strengths of the MXene-nanosheet-modified vinyl ester resin were 27.20%and 25.32%higher,respectively,than those of the neat vinyl ester resin.The coupling agent improved the interfacial compatibility between the MXene nanosheets and vinyl ester resin,which resulted in the tensile and flexural strengths of the M-MXene-nanosheet-modified vinyl ester resin being 52.57%and 54.60%higher,respectively,than those of the neat vinyl ester resin for a loading quantity of nanosheets of only 0.04 wt%,which is economically viable.The main mechanisms by which the nanosheets toughen the resin are crack deflection and crack pinning.

关键词： MXene nanosheets 2d material vinyl ester resin modification coupling agent

PdMoSb trimetallene as high-performance alcohol oxidation electrocatalyst

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Nano Research 2023年第2期16卷 2041-2048页

作者： Junfeng Liu Qiuxia Wang Tong Li Yong Wang Huaming Li Andreu Cabot Institute for Energy Research School of Chemistry and Chemical EngineeringJiangsu UniversityZhenjiang 212013China Catalonia Institute for Energy Research-IREC Sant Adriàde BesòsBarcelona 08930Spain ICREA Pg.Lluís Companys 23Barcelona 08010Spain

Metallenes are an emerging class of two-dimensional(2d)material with outstanding potential in electrocatalysis.Herein,we present a new PdMoSb trimetallene produced by a facile wet-chemistry procedure and tested for the alcohol oxidation reaction.PdMoSb shows an extremely high Pd utilization and superior performance toward ethanol,methanol,and glycerol electro-oxidation compared with PdMo and commercial Pd/C catalysts.Experimental results and density functional theory calculations reveal that the enhanced activity relies not only on the high surface area that characterizes the ultrathin 2d metallene structure,but also on the particular electronic configuration of Sb.Sb facilitates OH−adsorption in the reactive-intermediate pathway and strongly enhances the CO tolerance in the poisoning-intermediate pathway for alcohol oxidation.The excellent alcohol oxidation performance of PdMoSb trimetallene demonstrates the high potential of multimetallenes in the field of electrocatalysis.

关键词： metallene ternary alloy 2d material alcohol oxidation reaction electrocatalysis

Nanotribology of SiP nanosheets: Effect of thickness and sliding velocity

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Friction 2022年第12期10卷 2033-2044页

作者： Zishuai WU Tongtong YU Wei WU Jianxi LIU Zhinan ZHANG daoai WANG Weimin LIU Center of Advanced Lubrication and Seal materials School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Qingdao Center of Resource Chemistry and New materials Qingdao 266100China State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China

Two-dimensional compounds combining group IV A element and group V A element were determined to integrate the advantages of the two groups.As a typical 2d group IV–V material,SiP has been widely used in photodetection and photocatalysis due to its high carrier mobility,appropriate bandgap,high thermal stability,and low interlayer cleavage energy.However,its adhesion and friction properties have not been extensively grasped.Here,large-size and high-quality SiP crystals were obtained by using the flux method.SiP nanosheets were prepared by using mechanical exfoliation.The layer-dependent and velocity-dependent nanotribological properties of SiP nanosheets were systematically investigated.The results indicate the friction force of SiP nanosheets decreases with the increase in layer number and reaches saturation after five layers.The coefficient of friction of multilayer SiP is 0.018.The mean friction force,frictional vibrations,and the friction strengthening effect can be affected by sliding velocity.Specially,the mean friction force increases with the logarithm of sliding velocity at nm/s scale,which is dominated by atomic stick-slip.The influence of frequency on frictional vibration is greater than speed due to the different influences on the change in contact quality.The friction strengthening saturation distance increases with the increase in speed for thick SiP nanosheets.These results provide an approach for manipulating the nanofriction properties of SiP and serve as a theoretical basis for the application of SiP in solid lubrication and microelectromechanical systems.

关键词： SiP nanosheet 2d material atomic force microscopy(AFM) nanotribology

Monolayer MoSi_(2)_N(4-x) as promising electrocatalyst for hydrogen evolution reaction: A dFT prediction

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Journal of materials Science & Technology 2022年第4期99卷 215-222页

作者： Wangwang Qian Zhe Chen Jinfeng Zhang Lichang Yin Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Center of Artificial Photosynthesis for Solar Fuels School of ScienceWestlake UniversityHangzhou 310024China department of Physics and Electronic Information Huaibei Normal UniversityHuaibei 235000China

The density functional theory(dFT)calculations have been performed to investigate the catalytic properties of monolayer MoSi_(2)N_(4) for hydrogen evolution reaction(HER).The dFT results show that similar to the majority of other two-dimensional(2d)materials,the pristine MoSi_(2)N_(4) is inert for HER due to its weak affinity toward hydrogen,while monolayer MoSi_(2)N_(4-x)(x=0–0.25)exhibits the highly desirable HER catalytic activities by introducing surface nitrogen vacancy(NV).The predicted HER overpotential(0–60 mV)of monolayer MoSi_(2)N_(4-x) is lower than that(90 mV)of noble metal Pt,when the concentration of surface NV is lower than 5.6%.Electronic structure calculations show that the spin-polarized states appear around the Fermi level after introducing surface NV,thus making the surface NV on 2d MoSi_(2)N_(4) a quite suitable site for HER.Moreover,the HER activity of MoSi_(2)N_(4-x) is highly dependent on the surface NV concentration,which can be further related to the center of Si-3p band.Our results demonstrate that the newly discovered 2d MoSi_(2)N_(4) can be served as a promising electrocatalyst for HER via appropriate defect engineering.

关键词： Hydrogen evolution reaction Electrocatalyst 2d material MoSi_(2)N_(4) Surface nitrogen vacancy