本文报道用不同尺寸的金纳米粒子(AuNPs)来修饰单层WS2和MoS2纳米片,通过表面增强拉曼散射(SERS)技术检测微量的罗丹明6G染料,并对比了它们在不同波长的激光激发下的等离子体特性。AuNPs在WS2和MoS2纳米片上的均匀沉积是通过种子介导的...本文报道用不同尺寸的金纳米粒子(AuNPs)来修饰单层WS2和MoS2纳米片,通过表面增强拉曼散射(SERS)技术检测微量的罗丹明6G染料,并对比了它们在不同波长的激光激发下的等离子体特性。AuNPs在WS2和MoS2纳米片上的均匀沉积是通过种子介导的生长方法还原HAuCl4来实现的。我们进一步使用扫描电子显微镜和拉曼光谱对所制备的异质结构进行了表征。几种优化结构的拉曼增强因子接近108,几乎达到检测单分子需要的灵敏度。我们的研究结果表明,通过贵金属纳米粒子对超薄过渡金属双硫属元素化合物进行可控修饰是完全可行的。这个策略也适合于制备高效且灵活的基底,用在新一代基于表面增强拉曼散射的化学传感器和生物传感器上。Jason D Orlando 1,Ethan Kahn 2,Cindy Y Wong 3,Yin-ting Yeh 4,5,Tej B Limbu 1,Basant Chitara 1,Ana L Elias 4,5,Mauricio Terrones 4,5,YAN Fei(1.Department of Chemistry and Biochemistry,North Carolina Central University,Durham,NC.27707,USA;2.Department of Materials Science and Engineering,The Pennsylvania State University,University Park,PA.16802,USA;3.School for Engineering of Matter,Transport and Energy,Arizona State University,Tempe,AZ.85287,USA;4.Department of Physics,The Pennsylvania State University,University Park,PA.16802,USA;5.Center for Nanoscale Science,The Pennsylvania State University,University Park,PA.16802,USA)展开更多
Inspired by recent experimental results,the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag nanoribbons have been studied using fi rst principles calculations in the framework of the lo...Inspired by recent experimental results,the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag nanoribbons have been studied using fi rst principles calculations in the framework of the local spin density approximation.In the case of the ZnO nanoribbons,the sulfur atoms or thiol groups were attached in different ways to the zinc or oxygen atoms located at the edges,whereas in clusters,the sulfur atoms were set on the surface,mainly interacting with atoms with low-coordinate number.After an exhaustive atomic relaxation,we found that a magnetic moment emerges in zigzag nanoribbons both with and without sulfur-passivation on the edges.However,the magnitude of the magnetic moment is very sensitive to sulfur passivation.In particular,we found that when sulfur is attached to the zinc atoms in an alternating fashion along the ribbon edges,the magnetic moment is a maximum(1.4μB/unit cell).In the case of clusters,we found that the Zn_(15)O_(15) cluster exhibits a high spin moment of 5.5μB when capped with sulfur atoms.Our calculations indicate that sulfur-passivating of ZnO nanosystems could be responsible for recently observed ferromagnetic responses.展开更多
Carbon nanotube(CNT)sponge exhibits unique porous and hierarchical structure that are beneficial to the design of ultralight and tough composites.In this study,CNT sponges(undoped and boron doped)reinforced polydimeth...Carbon nanotube(CNT)sponge exhibits unique porous and hierarchical structure that are beneficial to the design of ultralight and tough composites.In this study,CNT sponges(undoped and boron doped)reinforced polydimethylsiloxane(PDMS)composites were fabricated.Mechanical properties of the composite,including compressive modulus,rate-dependent modulus,stress relaxation behaviors,dynamic viscoelastic properties,and their dependency on temperature,were systematically investigated.A micromechanical model,Mori-Tanaka model,was validated to describe the mechanical behaviors of CNT sponge reinforced composites.By coupling with boron-doped CNT sponge,PDMS composites showed remarkable improvement of mechanical properties,including compressive modulus(70%),viscous modulus(243%)and damping capacity(50%).Such reinforcement effects can be controlled by the morphology of CNT sponges,as the boron-doped and undoped nanocomposites showed distinct viscoelastic behaviors.The results proved that CNT sponge reinforcement is a promising strategy to develop engineering composites with both outstanding mechanical stiffness and controllable viscoelastic performances.展开更多
Individual atomic defects in 2D materials impact their macroscopic functionality.Correlating the interplay is challenging,however,intelligent hyperspectral scanning tunneling spectroscopy(STS)mapping provides a feasib...Individual atomic defects in 2D materials impact their macroscopic functionality.Correlating the interplay is challenging,however,intelligent hyperspectral scanning tunneling spectroscopy(STS)mapping provides a feasible solution to this technically difficult and time consuming problem.Here,dense spectroscopic volume is collected autonomously via Gaussian process regression,where convolutional neural networks are used in tandem for spectral identification.Acquired data enable defect segmentation,and a workflow is provided for machine-driven decision making during experimentation with capability for user customization.We provide a means towards autonomous experimentation for the benefit of both enhanced reproducibility and user-accessibility.Hyperspectral investigations on WS_(2)sulfur vacancy sites are explored,which is combined with local density of states confirmation on the Au{111}herringbone reconstruction.Chalcogen vacancies,pristine WS_(2),Au face-centered cubic,and Au hexagonal close-packed regions are examined and detected by machine learning methods to demonstrate the potential of artificial intelligence for hyperspectral STS mapping.展开更多
Two-dimensional transition metal dichalcogenides are of great interest for second harmonic generation due to their large second-order susceptibility χ^((2)),atomically thin structure,and relaxed phase-matching condit...Two-dimensional transition metal dichalcogenides are of great interest for second harmonic generation due to their large second-order susceptibility χ^((2)),atomically thin structure,and relaxed phase-matching conditions.Such materials are also promising candidates for miniaturizing nonlinear optical devices for versatile applications in photon manipulation,quantum emission and sensing,and nanophotonic circuits.However,their strong second harmonic response is limited by nanometer-scale light-matter interaction and material impurities.Although there is considerable work toward engineering these materials for enhancing their nonlinear responses,all-optical methods are still in the exploration stages.We incorporate,to the best of our knowledge,the first experimental demonstration of feedback-based wavefront shaping techniques in atomically thin media to reveal and enhance the weak second harmonic generation of monolayer WS_(2).Phase tuning of the incident wavefront leads to the increase in the intensity of the second harmonic generated in the target regions up to an order of magnitude.We enhance the local nonlinear signal conversion from monolayer WS_(2)up to 41× using phase-only modulation.Furthermore,by introducing a shift in the transverse phase structure,we achieve observable second harmonic generation at the destructively interfering grain boundaries of polycrystalline monolayers.This method allows for all-optical tuning of transition metal dichalcogenides'nonlinear responses,opening up possibilities for dynamic signal routing and on-demand enhancement in nanoscale photonic systems.展开更多
基金supported in part by the U.S.National Science Foundation(Awards#1831133 and#1523617)
文摘本文报道用不同尺寸的金纳米粒子(AuNPs)来修饰单层WS2和MoS2纳米片,通过表面增强拉曼散射(SERS)技术检测微量的罗丹明6G染料,并对比了它们在不同波长的激光激发下的等离子体特性。AuNPs在WS2和MoS2纳米片上的均匀沉积是通过种子介导的生长方法还原HAuCl4来实现的。我们进一步使用扫描电子显微镜和拉曼光谱对所制备的异质结构进行了表征。几种优化结构的拉曼增强因子接近108,几乎达到检测单分子需要的灵敏度。我们的研究结果表明,通过贵金属纳米粒子对超薄过渡金属双硫属元素化合物进行可控修饰是完全可行的。这个策略也适合于制备高效且灵活的基底,用在新一代基于表面增强拉曼散射的化学传感器和生物传感器上。Jason D Orlando 1,Ethan Kahn 2,Cindy Y Wong 3,Yin-ting Yeh 4,5,Tej B Limbu 1,Basant Chitara 1,Ana L Elias 4,5,Mauricio Terrones 4,5,YAN Fei(1.Department of Chemistry and Biochemistry,North Carolina Central University,Durham,NC.27707,USA;2.Department of Materials Science and Engineering,The Pennsylvania State University,University Park,PA.16802,USA;3.School for Engineering of Matter,Transport and Energy,Arizona State University,Tempe,AZ.85287,USA;4.Department of Physics,The Pennsylvania State University,University Park,PA.16802,USA;5.Center for Nanoscale Science,The Pennsylvania State University,University Park,PA.16802,USA)
基金This work was supported in part by CONACYT-México grants:56787(Laboratory for Nanoscience and Nanotechnology Research-LINAN),60218(FLU),45762(HT),45772(MT),58899-Inter American Collaboration(MT),2004-01-013/SALUD-CONACYT(MT)Fondo Mixto de San Luis Potosi63001 S-3908(MT)+1 种基金Fondo Mixto de San Luis Potosí63072 S-3909(HT)a PhD Scholarship(ARBM).
文摘Inspired by recent experimental results,the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag nanoribbons have been studied using fi rst principles calculations in the framework of the local spin density approximation.In the case of the ZnO nanoribbons,the sulfur atoms or thiol groups were attached in different ways to the zinc or oxygen atoms located at the edges,whereas in clusters,the sulfur atoms were set on the surface,mainly interacting with atoms with low-coordinate number.After an exhaustive atomic relaxation,we found that a magnetic moment emerges in zigzag nanoribbons both with and without sulfur-passivation on the edges.However,the magnitude of the magnetic moment is very sensitive to sulfur passivation.In particular,we found that when sulfur is attached to the zinc atoms in an alternating fashion along the ribbon edges,the magnetic moment is a maximum(1.4μB/unit cell).In the case of clusters,we found that the Zn_(15)O_(15) cluster exhibits a high spin moment of 5.5μB when capped with sulfur atoms.Our calculations indicate that sulfur-passivating of ZnO nanosystems could be responsible for recently observed ferromagnetic responses.
基金This work was supported by the U.S.Air Force Office of Scientific Research MURI Grant(FA9550-12-1-0035)NIGMS-IDeA Grant(U54-GM104941)J.Suhr also would like to thank the financial support from the National Research Foundation of Korea funded by the Ministry of Education(2017R1D1A1B03030429).
文摘Carbon nanotube(CNT)sponge exhibits unique porous and hierarchical structure that are beneficial to the design of ultralight and tough composites.In this study,CNT sponges(undoped and boron doped)reinforced polydimethylsiloxane(PDMS)composites were fabricated.Mechanical properties of the composite,including compressive modulus,rate-dependent modulus,stress relaxation behaviors,dynamic viscoelastic properties,and their dependency on temperature,were systematically investigated.A micromechanical model,Mori-Tanaka model,was validated to describe the mechanical behaviors of CNT sponge reinforced composites.By coupling with boron-doped CNT sponge,PDMS composites showed remarkable improvement of mechanical properties,including compressive modulus(70%),viscous modulus(243%)and damping capacity(50%).Such reinforcement effects can be controlled by the morphology of CNT sponges,as the boron-doped and undoped nanocomposites showed distinct viscoelastic behaviors.The results proved that CNT sponge reinforcement is a promising strategy to develop engineering composites with both outstanding mechanical stiffness and controllable viscoelastic performances.
基金Work was performed at the Molecular Foundry supported by the Office of Science,Office of Basic Energy Sciences,of the U.S.Department of Energy under contract no.DE-AC02-05CH11231Work was also funded through the Center for Advanced Mathematics for Energy Research Applications(CAMERA),which is jointly funded by the Advanced Scientific Computing Research(ASCR)and Basic Energy Sciences(BES)within the Department of Energy’s Office of Science,under Contract No.DE-AC02-05CH11231+1 种基金S.K and J.A.R.acknowledge support from the National Science Foundation Division of Materials Research(NSF-DMR)under awards 2002651 and 2011839L.F.acknowledges funding from the Swiss National Science Foundation(SNSF)via Early PostDoc Mobility Grant no.P2ELP2_184398.
文摘Individual atomic defects in 2D materials impact their macroscopic functionality.Correlating the interplay is challenging,however,intelligent hyperspectral scanning tunneling spectroscopy(STS)mapping provides a feasible solution to this technically difficult and time consuming problem.Here,dense spectroscopic volume is collected autonomously via Gaussian process regression,where convolutional neural networks are used in tandem for spectral identification.Acquired data enable defect segmentation,and a workflow is provided for machine-driven decision making during experimentation with capability for user customization.We provide a means towards autonomous experimentation for the benefit of both enhanced reproducibility and user-accessibility.Hyperspectral investigations on WS_(2)sulfur vacancy sites are explored,which is combined with local density of states confirmation on the Au{111}herringbone reconstruction.Chalcogen vacancies,pristine WS_(2),Au face-centered cubic,and Au hexagonal close-packed regions are examined and detected by machine learning methods to demonstrate the potential of artificial intelligence for hyperspectral STS mapping.
基金Gordon and Betty Moore FoundationU.S.Department of Energy(DE-SC0024676)+2 种基金National Geospatial-Intelligence Agency(HM04762010012)U.S.Department of Energy(DE-SC0023148)Air Force Office of Scientific Research(FA9550-23-1-0325).
文摘Two-dimensional transition metal dichalcogenides are of great interest for second harmonic generation due to their large second-order susceptibility χ^((2)),atomically thin structure,and relaxed phase-matching conditions.Such materials are also promising candidates for miniaturizing nonlinear optical devices for versatile applications in photon manipulation,quantum emission and sensing,and nanophotonic circuits.However,their strong second harmonic response is limited by nanometer-scale light-matter interaction and material impurities.Although there is considerable work toward engineering these materials for enhancing their nonlinear responses,all-optical methods are still in the exploration stages.We incorporate,to the best of our knowledge,the first experimental demonstration of feedback-based wavefront shaping techniques in atomically thin media to reveal and enhance the weak second harmonic generation of monolayer WS_(2).Phase tuning of the incident wavefront leads to the increase in the intensity of the second harmonic generated in the target regions up to an order of magnitude.We enhance the local nonlinear signal conversion from monolayer WS_(2)up to 41× using phase-only modulation.Furthermore,by introducing a shift in the transverse phase structure,we achieve observable second harmonic generation at the destructively interfering grain boundaries of polycrystalline monolayers.This method allows for all-optical tuning of transition metal dichalcogenides'nonlinear responses,opening up possibilities for dynamic signal routing and on-demand enhancement in nanoscale photonic systems.
