Two-dimensional(2D)layered oxides have recently attracted wide attention owing to the strong coupling among charges,spins,lattice,and strain,which allows great flexibility and opportunities in structure designs as wel...Two-dimensional(2D)layered oxides have recently attracted wide attention owing to the strong coupling among charges,spins,lattice,and strain,which allows great flexibility and opportunities in structure designs as well as multifunctionality exploration.In parallel,plasmonic hybrid nanostructures exhibit exotic localized surface plasmon resonance(LSPR)providing a broad range of applications in nanophotonic devices and sensors.A hybrid material platform combining the unique multifunctional 2D layered oxides and plasmonic nanostructures brings optical tuning into the new level.In this work,a novel self-assembled Bi2MoO6(BMO)2D layered oxide incorporated with plasmonic Au nanoinclusions has been demonstrated via one-step pulsed laser deposition(PLD)technique.Comprehensive microstructural characterizations,including scanning transmission electron microscopy(STEM),differential phase contrast imaging(DPC),and STEM tomography,have demonstrated the high epitaxial quality and particle-in-matrix morphology of the BMO-Au nanocomposite film.DPC-STEM imaging clarifies the magnetic domain structures of BMO matrix.Three different BMO structures including layered supercell(LSC)and superlattices have been revealed which is attributed to the variable strain states throughout the BMO-Au film.Owing to the combination of plasmonic Au and layered structure of BMO,the nanocomposite film exhibits a typical LSPR in visible wavelength region and strong anisotropy in terms of its optical and ferromagnetic properties.This study opens a new avenue for developing novel 2D layered complex oxides incorporated with plasmonic metal or semiconductor phases showing great potential for applications in multifunctional nanoelectronics devices.展开更多
An individual suspended graphene sheet was connected to a scanning tunneling microscopy probe inside a transmission electron microscope,and Joule heated to high temperatures.At high temperatures and under electron bea...An individual suspended graphene sheet was connected to a scanning tunneling microscopy probe inside a transmission electron microscope,and Joule heated to high temperatures.At high temperatures and under electron beam irradiation,the few-layer graphene sheets were removed layer-by-layer in the viewing area until a monolayer graphene was formed.The layer-by-layer peeling was initiated at vacancies in individual graphene layers.The vacancies expanded to form nanometer-sized holes,which then grew along the perimeter and propagated to both the top and bottom layers of a bilayer graphene joined by a bilayer edge.The layer-by-layer peeling was induced by atom sublimation caused by Joule heating and facilitated by atom displacement caused by high-energy electron irradiation,and may be harnessed to control the layer thickness of graphene for device applications.展开更多
Isolation and purification of single-walled carbon nanotubes （SWCNTs） are prerequisites for their implementation in various applications. In this work, we present a fast （-5 min）, low-cost, and easily scalable ben...Isolation and purification of single-walled carbon nanotubes （SWCNTs） are prerequisites for their implementation in various applications. In this work, we present a fast （-5 min）, low-cost, and easily scalable bench-top approach to the extraction of high-quality isolated SWCNTs from bundles and impurities in an aqueous dispersion. The extraction procedure, based on aqueous two-phase （ATP） separation, is widely applicable to any SWCNT source （tested on samples up to 1.7 nm in diameter） and independent of defect density, purity, diameter, and length. The extracted dispersions demonstrate that the removal of large aggregates, small bundles, and impurities is comparable to that by density gradient ultracentrifugation, but without the need for high-end instrumentation. Raman and fluorescence-excitation spectroscopy, single-nanotube fluorescence imaging, atomic force and transmission electron microscopy, and thermogravimetric analysis all confirm the high purity of the isolated SWCNTs. By predispersing the SWCNTs without sonication （only gentle stirring）, full-length, pristine SWCNTs can be isolated （tested up to 20 μm）. Hence, this simple ATP method will find immediate application in the generation of SWCNT materials for all levels of nanotube research and applications, from fundamental studies to high-performance devices.展开更多
Epitaxial PrBaCo_(2)O_(5+δ)(PBCO,0≤δ≤1)thin films were deposited by pulsed laser deposition.The structural and electrical properties of the films were characterized at high temperatures in reduced environments.X-r...Epitaxial PrBaCo_(2)O_(5+δ)(PBCO,0≤δ≤1)thin films were deposited by pulsed laser deposition.The structural and electrical properties of the films were characterized at high temperatures in reduced environments.X-ray diffraction scans at high temperature in reduced environment show potential structural transitions of PBCO as evidenced by both a large(Dl=0.335 nm)expansion of the out-plane(caxis)lattice,due to thermal and chemical expansion,and a step in the expansion of the c-axis lattice parameter.These transitions indicate the presence of oxygen vacancy ordering as the oxygen content in the films is reduced.Resistivity measurements under the same environments also show evidence of sharp transitions related with the structural transformations.This study helps the understanding of the structure-property relationship of PBCO at high temperature and provides important technological information to utilize these materials for solid oxide fuel cell at intermediate temperatures.展开更多
基金This work was supported by the U.S.Department of Energy,Office of Science,Basic Energy Sciences(BES)under Award DESC0020077.D.Z.,J.S.,Z.S.,and H.W.acknowledge the support from the U.S.Office of Naval Research under contract Nos.N00014-20-1-2043 for the TEM work and N00014-20-1-2600 for the thin film growth effort.The work at Los Alamos National Laboratory was supported by the NNSA’s Laboratory Directed Research and Development Program and was performed,in part,at the Center for Integrated Nanotechnologies,an Office of Science User Facility operated for the U.S.Department of Energy Office of Science.Los Alamos National Laboratory,an affirmative action equal opportunity employer,is managed by Triad National Security,LLC for the U.S.Department of Energy’s NNSA,under contract 89233218CNA000001.
文摘Two-dimensional(2D)layered oxides have recently attracted wide attention owing to the strong coupling among charges,spins,lattice,and strain,which allows great flexibility and opportunities in structure designs as well as multifunctionality exploration.In parallel,plasmonic hybrid nanostructures exhibit exotic localized surface plasmon resonance(LSPR)providing a broad range of applications in nanophotonic devices and sensors.A hybrid material platform combining the unique multifunctional 2D layered oxides and plasmonic nanostructures brings optical tuning into the new level.In this work,a novel self-assembled Bi2MoO6(BMO)2D layered oxide incorporated with plasmonic Au nanoinclusions has been demonstrated via one-step pulsed laser deposition(PLD)technique.Comprehensive microstructural characterizations,including scanning transmission electron microscopy(STEM),differential phase contrast imaging(DPC),and STEM tomography,have demonstrated the high epitaxial quality and particle-in-matrix morphology of the BMO-Au nanocomposite film.DPC-STEM imaging clarifies the magnetic domain structures of BMO matrix.Three different BMO structures including layered supercell(LSC)and superlattices have been revealed which is attributed to the variable strain states throughout the BMO-Au film.Owing to the combination of plasmonic Au and layered structure of BMO,the nanocomposite film exhibits a typical LSPR in visible wavelength region and strong anisotropy in terms of its optical and ferromagnetic properties.This study opens a new avenue for developing novel 2D layered complex oxides incorporated with plasmonic metal or semiconductor phases showing great potential for applications in multifunctional nanoelectronics devices.
基金This work was performed,in part,at the Center for Integrated Nanotechnologies,the U.S.Department of Energy,Office of Basic Energy Sciences user facility.Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation,a Lockheed-Martin Company,for the U.S.Department of Energy under Contract No.DE-AC04-94AL85000JL would like to acknowledge support by Honda Research Institute USA,NSF CMMI-0728069,AFOSR,and ONR N00014-05-1-0504J.Y.H.would like to thank Dr.Ping Lu at Sandia National Laboratories for conducting the HRTEM image simulations.
文摘An individual suspended graphene sheet was connected to a scanning tunneling microscopy probe inside a transmission electron microscope,and Joule heated to high temperatures.At high temperatures and under electron beam irradiation,the few-layer graphene sheets were removed layer-by-layer in the viewing area until a monolayer graphene was formed.The layer-by-layer peeling was initiated at vacancies in individual graphene layers.The vacancies expanded to form nanometer-sized holes,which then grew along the perimeter and propagated to both the top and bottom layers of a bilayer graphene joined by a bilayer edge.The layer-by-layer peeling was induced by atom sublimation caused by Joule heating and facilitated by atom displacement caused by high-energy electron irradiation,and may be harnessed to control the layer thickness of graphene for device applications.
文摘Isolation and purification of single-walled carbon nanotubes （SWCNTs） are prerequisites for their implementation in various applications. In this work, we present a fast （-5 min）, low-cost, and easily scalable bench-top approach to the extraction of high-quality isolated SWCNTs from bundles and impurities in an aqueous dispersion. The extraction procedure, based on aqueous two-phase （ATP） separation, is widely applicable to any SWCNT source （tested on samples up to 1.7 nm in diameter） and independent of defect density, purity, diameter, and length. The extracted dispersions demonstrate that the removal of large aggregates, small bundles, and impurities is comparable to that by density gradient ultracentrifugation, but without the need for high-end instrumentation. Raman and fluorescence-excitation spectroscopy, single-nanotube fluorescence imaging, atomic force and transmission electron microscopy, and thermogravimetric analysis all confirm the high purity of the isolated SWCNTs. By predispersing the SWCNTs without sonication （only gentle stirring）, full-length, pristine SWCNTs can be isolated （tested up to 20 μm）. Hence, this simple ATP method will find immediate application in the generation of SWCNT materials for all levels of nanotube research and applications, from fundamental studies to high-performance devices.
基金This research was partially supported by the National Institute on Minority Health and Health Disparities of the National Institutes of Health under Award Number G12MD007591This work was performed,in part,at the Center for Integrated Nanotechnologies,an Office of Science User Facility operated for the U.S.Department of Energy(DOE)Office of Science.Los Alamos National Laboratory,an affirmative action equal opportunity employer,is operated by Los Alamos National Security,LLC,for the National Nuclear Security Administration of the U.S.Department of Energy under contract DE-AC52-06NA25396.
文摘Epitaxial PrBaCo_(2)O_(5+δ)(PBCO,0≤δ≤1)thin films were deposited by pulsed laser deposition.The structural and electrical properties of the films were characterized at high temperatures in reduced environments.X-ray diffraction scans at high temperature in reduced environment show potential structural transitions of PBCO as evidenced by both a large(Dl=0.335 nm)expansion of the out-plane(caxis)lattice,due to thermal and chemical expansion,and a step in the expansion of the c-axis lattice parameter.These transitions indicate the presence of oxygen vacancy ordering as the oxygen content in the films is reduced.Resistivity measurements under the same environments also show evidence of sharp transitions related with the structural transformations.This study helps the understanding of the structure-property relationship of PBCO at high temperature and provides important technological information to utilize these materials for solid oxide fuel cell at intermediate temperatures.
