Nanowires are fantastic nanostructures for designing new functional devices because of their extraordinary properties.However,nanowires usually suffer pronounced size and surface effects with decreasing diameter size....Nanowires are fantastic nanostructures for designing new functional devices because of their extraordinary properties.However,nanowires usually suffer pronounced size and surface effects with decreasing diameter size.Whether their structure and thermal stability can still fill the requirements of practical applications is a critical issue to be figured out.Herein,Te nanowires with diameters ranging from sub-10 to over 80 nm are used as samples to probe into this issue.In situ heating experiments are performed on these Te nanowires using an aberration-corrected transmission electron microscopy combined with a chip-based heating holder.It is found that Te nanowires suffer sublimation at elevated temperatures rather than melting,showing sizedependent sublimation scenarios.The Te nanowires with diameter smaller than 20 nm sublimate below 205℃,while the larger ones with diameter around 85 nm require a higher temperature of around 225℃.During sublimation-induced shape evolution,the interfacial wetting equilibrium and crystal orientations play critical roles,leading to the formation of spherical surfaces or featured facets at the free surfaces.A mean contact angle of 107.5°is determined at the C-Te interface when the crystalline Te nanowires stay in a quasi-liquid equilibrium state.However,once the crystalline feature is overwhelming,e.g.,at moderate temperatures,the(1011),(1120),and(1010)facets govern the free surface,despite the wetting condition at the interfaces.展开更多
Bio-chemical molecular detection in the nanoscale, based on alloyed nanorods(NRs) with tunable surface plasmon resonance(SPR) properties and high chemical stability, has attracted particular interest. In this work,all...Bio-chemical molecular detection in the nanoscale, based on alloyed nanorods(NRs) with tunable surface plasmon resonance(SPR) properties and high chemical stability, has attracted particular interest. In this work,alloyed Au-Ag NRs with tunable aspect ratios were achieved by annealing Au nanobipyramid-directed Au@Ag core-shell NRs. The core-shell NRs were encapsulated within mesoporous silica outer shells to avoid fusion or aggregation. The structural stability of fully alloyed Au-Ag NRs, including chemical and thermal stability, is remarkably improved compared with that of Au@Ag core-shell NRs. The alloyed NRs would maintain the rod-like structure after being incubated in etchant solution, while Au@Ag core-shell NRs would decay into nanobipyramids.Additionally, fully alloyed NRs present stable morphology under annealing at high temperatures of up to 600℃ in air. Benefiting from excellent structural and chemical stabilities, the surface-enhanced Raman scattering effect based on alloyed NRs is stable in harsh environments. Taking advantage of tunable SPR properties(600–1800 nm) and excellent stability, the obtained nanostructures can serve as drug carriers. The perfect photo-thermal effect induced by the particular SPR of alloyed NRs can improve the release efficiency of drugs.展开更多
As one of the most important narrow bandgap ternary semiconductors, GaAs1−xSbx nanowires (NWs) have attracted extensive attention recently, due to the superior hole mobility and the tunable bandgap, which covers the w...As one of the most important narrow bandgap ternary semiconductors, GaAs1−xSbx nanowires (NWs) have attracted extensive attention recently, due to the superior hole mobility and the tunable bandgap, which covers the whole near-infrared (NIR) region, for technological applications in next-generation high-performance electronics and NIR photodetection. However, it is still a challenge to the synthesis of high-quality GaAs1−xSbx NWs across the entire range of composition, resulting in the lack of correlation investigation among stoichiometry, microstructure, electronics, and NIR photodetection. Here, we demonstrate the success growth of high-quality GaAs1−xSbx NWs with full composition range by adopting a simple and low-cost surfactant-assisted solid source chemical vapor deposition method. All of the as-prepared NWs are uniform, smooth, and straight, without any phase segregation in all stoichiometric compositions. The lattice constants of each NW composition have been well correlated with the chemical stoichiometry and confirmed by high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectrum. Moreover, with the increase of Sb concentration, the hole mobility of the as-fabricated field-effect-transistors and the responsivity and detectivity of the as-fabricated NIR photodetectors increase accordingly. All the results suggest a careful stoichiometric design is required for achieving optimal NW device performances.展开更多
Serving as nanoelectrodes or frame units,small-volume metals may critically affect the performance and reliability of nanodevices,especially with feature sizes down to the nanometer scale.Small-volume metals usually b...Serving as nanoelectrodes or frame units,small-volume metals may critically affect the performance and reliability of nanodevices,especially with feature sizes down to the nanometer scale.Small-volume metals usually behave extraordinarily in comparison with their bulk counterparts,but the knowledge of how their sizes and surfaces give rise to their extraordinary properties is currently insufficient.In this study,we investigate the influence of surface conditions on mechanical behaviors in nanometer-sized Pb crystals by performing in situ mechanical deformation tests inside an aberration-corrected transmission electron microscope(TEM).Pseudoelastic deformation and plastic deformation processes were observed at atomic precision during deformation of pristine and surface-oxidized Pb particles,respectively.It is found that in most of the pristine Pb particles,surface atom diffusion dominates and leads to a pseudoelastic deformation behavior.In stark contrast,in surface-passivated Pb particles where surface atom diffusion is largely inhibited,deformation proceeds via displacive plasticity including dislocations,stacking faults,and twinning,leading to dominant plastic deformation without any pseudoelasticity.This research directly reveals the dramatic impact of surface conditions on the deformation mechanisms and mechanical behaviors of metallic nanocrystals,which provides significant implications for property tuning of the critical components in advanced nanodevices.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52071077 and 11774050)the National Key R&D Program of China(No.2017YFA0305500)the Fundamental Research Funds for the Central Universities.
文摘Nanowires are fantastic nanostructures for designing new functional devices because of their extraordinary properties.However,nanowires usually suffer pronounced size and surface effects with decreasing diameter size.Whether their structure and thermal stability can still fill the requirements of practical applications is a critical issue to be figured out.Herein,Te nanowires with diameters ranging from sub-10 to over 80 nm are used as samples to probe into this issue.In situ heating experiments are performed on these Te nanowires using an aberration-corrected transmission electron microscopy combined with a chip-based heating holder.It is found that Te nanowires suffer sublimation at elevated temperatures rather than melting,showing sizedependent sublimation scenarios.The Te nanowires with diameter smaller than 20 nm sublimate below 205℃,while the larger ones with diameter around 85 nm require a higher temperature of around 225℃.During sublimation-induced shape evolution,the interfacial wetting equilibrium and crystal orientations play critical roles,leading to the formation of spherical surfaces or featured facets at the free surfaces.A mean contact angle of 107.5°is determined at the C-Te interface when the crystalline Te nanowires stay in a quasi-liquid equilibrium state.However,once the crystalline feature is overwhelming,e.g.,at moderate temperatures,the(1011),(1120),and(1010)facets govern the free surface,despite the wetting condition at the interfaces.
基金National Natural Science Foundation of China(NSFC)(11774050,11774171,11874220,51571060)National Key R&D Program of China(2017YFA0305500)Open Fund of Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education(INMD-2016M05)
文摘Bio-chemical molecular detection in the nanoscale, based on alloyed nanorods(NRs) with tunable surface plasmon resonance(SPR) properties and high chemical stability, has attracted particular interest. In this work,alloyed Au-Ag NRs with tunable aspect ratios were achieved by annealing Au nanobipyramid-directed Au@Ag core-shell NRs. The core-shell NRs were encapsulated within mesoporous silica outer shells to avoid fusion or aggregation. The structural stability of fully alloyed Au-Ag NRs, including chemical and thermal stability, is remarkably improved compared with that of Au@Ag core-shell NRs. The alloyed NRs would maintain the rod-like structure after being incubated in etchant solution, while Au@Ag core-shell NRs would decay into nanobipyramids.Additionally, fully alloyed NRs present stable morphology under annealing at high temperatures of up to 600℃ in air. Benefiting from excellent structural and chemical stabilities, the surface-enhanced Raman scattering effect based on alloyed NRs is stable in harsh environments. Taking advantage of tunable SPR properties(600–1800 nm) and excellent stability, the obtained nanostructures can serve as drug carriers. The perfect photo-thermal effect induced by the particular SPR of alloyed NRs can improve the release efficiency of drugs.
基金We acknowledge the National Key R&D Program of China(No.2017YFA0305500)the National Natural Science Foundation of China(Nos.61904096 and 11774050)+3 种基金the Taishan Scholars Program of Shandong Province(No.tsqn201812006)Royal Society-Newton Advanced Fellowship(No.NA170214)Aero-Science Fund ASFC-20170269003,Shandong University multidisciplinary research and the innovation team of young scholars(No.2020QNQT015)“Outstanding youth scholar and Qilu young scholar”programs of Shandong University.
文摘As one of the most important narrow bandgap ternary semiconductors, GaAs1−xSbx nanowires (NWs) have attracted extensive attention recently, due to the superior hole mobility and the tunable bandgap, which covers the whole near-infrared (NIR) region, for technological applications in next-generation high-performance electronics and NIR photodetection. However, it is still a challenge to the synthesis of high-quality GaAs1−xSbx NWs across the entire range of composition, resulting in the lack of correlation investigation among stoichiometry, microstructure, electronics, and NIR photodetection. Here, we demonstrate the success growth of high-quality GaAs1−xSbx NWs with full composition range by adopting a simple and low-cost surfactant-assisted solid source chemical vapor deposition method. All of the as-prepared NWs are uniform, smooth, and straight, without any phase segregation in all stoichiometric compositions. The lattice constants of each NW composition have been well correlated with the chemical stoichiometry and confirmed by high-resolution transmission electron microscopy, X-ray diffraction, and Raman spectrum. Moreover, with the increase of Sb concentration, the hole mobility of the as-fabricated field-effect-transistors and the responsivity and detectivity of the as-fabricated NIR photodetectors increase accordingly. All the results suggest a careful stoichiometric design is required for achieving optimal NW device performances.
基金This research was supported by the National Natural Science Foundation of China(Grant Nos.52071077,11525415,11774050,51801024,and51420105003).
文摘Serving as nanoelectrodes or frame units,small-volume metals may critically affect the performance and reliability of nanodevices,especially with feature sizes down to the nanometer scale.Small-volume metals usually behave extraordinarily in comparison with their bulk counterparts,but the knowledge of how their sizes and surfaces give rise to their extraordinary properties is currently insufficient.In this study,we investigate the influence of surface conditions on mechanical behaviors in nanometer-sized Pb crystals by performing in situ mechanical deformation tests inside an aberration-corrected transmission electron microscope(TEM).Pseudoelastic deformation and plastic deformation processes were observed at atomic precision during deformation of pristine and surface-oxidized Pb particles,respectively.It is found that in most of the pristine Pb particles,surface atom diffusion dominates and leads to a pseudoelastic deformation behavior.In stark contrast,in surface-passivated Pb particles where surface atom diffusion is largely inhibited,deformation proceeds via displacive plasticity including dislocations,stacking faults,and twinning,leading to dominant plastic deformation without any pseudoelasticity.This research directly reveals the dramatic impact of surface conditions on the deformation mechanisms and mechanical behaviors of metallic nanocrystals,which provides significant implications for property tuning of the critical components in advanced nanodevices.
