Piezotronics is a new field integrating piezoelectric effect into nanoelectronics, which has attracted much attention for the fundamental research and potential applications. In this paper, the piezotronic effect of zinc oxide (ZnO) nanowires, including the response of the electrical transport and photoconducting behaviors on the nanowire bending, has been investigated by in situ transmission electron microscopy (TEM), where the crystal structure of ZnO nanowires were simultaneously imaged. Serials of consecutively recorded current‐voltage (I–V) curves along with an increase of nanowire bending show the striking effect of bending on their electrical behavior. With increasing the nanowire bending, the photocurrent of ZnO nanowire under ultraviolet illumination (UV) drops dramatically and the photo response time becomes much shorter. In addition, the dynamic nanomechanics of ZnO nanowires were studied inside TEM. These phenomena could be attributed to the piezoelectric effect of ZnO nanowires, and they suggest the potential applications of ZnO nanowires on piezotronic devices. 相似文献
The Kirkendall effect is a consequence of the different diffusivities of atoms in a diffusion couple causing a supersaturation of lattice vacancies. This supersaturation may lead to a condensation of extra vacancies in the form of so-called \"Kirkendall voids\" close to the interface. On the macroscopic and micrometer scale these Kirkendall voids are generally considered as a nuisance because they deteriorate the properties of the interface. In contrast, in the nanoworld the Kirkendall effect has been positively used as a new fabrication route to designed hollow nano-objects. In this Review we summarize and discuss the demonstrated examples of hollow nanoparticles and nanotubes induced by the Kirkendall effect. Merits of this route are compared with other general methods for nanotube fabrication. Theories of the kinetics and thermodynamics are also reviewed and evaluated in terms of their relevance to experiments. Moreover, nanotube fabrication by solid-state reactions and non-Kirkendall type diffusion processes are covered. 相似文献
Gas and liquid phase chemical reactions cover a broad range of research areas in materials science and engineering, including the synthesis of nanomaterials and application of nanomaterials, for example, in the areas of sensing, energy storage and conversion, catalysis, and bio‐related applications. Environmental transmission electron microscopy (ETEM) provides a unique opportunity for monitoring gas and liquid phase reactions because it enables the observation of those reactions at the ultra‐high spatial resolution, which is not achievable through other techniques. Here, the fundamental science and technology developments of gas and liquid phase TEM that facilitate the mechanistic study of the gas and liquid phase chemical reactions are discussed. Combined with other characterization tools integrated in TEM, unprecedented material behaviors and reaction mechanisms are observed through the use of the in situ gas and liquid phase TEM. These observations and also the recent applications in this emerging area are described. The current challenges in the imaging process are also discussed, including the imaging speed, imaging resolution, and data management. 相似文献
Porous hollow iron oxide nanoparticles (PHNPs) supported on carbon nanotubes (CNTs) were facilely synthesized by etching Fe@FexOy/CNT with dilute nitric acid aqueous solution at ambient temperature without the assistance of any surfactants and ligands. The mean diameter of hollow iron oxide nanoparticles was about 17 nm, with a wall thickness of about 4 nm. The formation mechanism of PHNPs is discussed based on the characterization results from TEM, XRD and H2-TPR. The combination of nanoscale Kirkendall effect and selective acid etching is proposed to be responsible for the formation of CNT supported PHNPs, through a transformation from core/void/shell structures to hollow nanoparticles. 相似文献
Formic acid oxidation is an important electrocatalytic reaction in protonexchange membrane (PEM) fuel cells, in which both active sites and species adsorption/activation play key roles. In this study, we have developed hollow Pd-Ag alloy nanostructures with high active surface areas for application to electrocatalytic formic acid oxidation. When a certain amount of Ag is incorporated into a Pd lattice, which is already a highly active material for formic acid oxidation, the electrocatalytic activity can be significantly boosted. As indicated by theoretical simulations, coupling between Pd and Ag induces polarization charges on Pd catalytic sites, which can enhance the adsorption of HCOO* species. As a result, the designed electrocatalysts can achieve reduced Pd usage and enhanced catalytic properties at the same time. This study represents an approach that simultaneously fabricates hollow structures to increase the number of active sites and utilizes interatomic interactions to tune species adsorption/activation towards improved electrocatalytic performance.
In this work, a facile salt‐templated approach is developed for the preparation of hollow FeSe2/graphitic carbon composite microspheres as sodium‐ion battery anodes; these are composed of interconnected multicavities and an enclosed surface in‐plane embedded with uniform hollow FeSe2 nanoparticles. As the precursor, Fe2O3/carbon microspheres containing NaCl nanocrystals are obtained using one‐pot ultrasonic spray pyrolysis in which inexpensive NaCl and dextrin are used as a porogen and carbon source, respectively, enabling mass production of the composites. During post‐treatment, Fe2O3 nanoparticles in the composites transform into hollow FeSe2 nanospheres via the Kirkendall effect. These rational structures provide numerous conductive channels to facilitate ion/electron transport and enhance the capacitive contribution. Moreover, the synergistic effect between the hollow cavities within FeSe2 and the outstanding mechanical strength of the porous carbon matrix can effectively accommodate the large volume changes during cycling. Correspondingly, the composite microsphere exhibits high discharge capacity of 510 mA h g?1 after 200 cycles at 0.2 A g?1 with capacity retention of 88% when calculated from the second cycle. Even at a high current density of 5.0 A g?1, a high discharge capacity of 417 mA h g?1 can be achieved. 相似文献
This current research progress on the fabrication of hollow nanostructures by using self‐templating methods is reviewed. After a brief introduction to the unique properties and applications of hollow nanostructures and the three general fabrication routes, the discussions are focused on the five main self‐templating strategies, including galvanic replacement, the Kirkendall effect, Ostwald ripening, dissolution–regrowth, and the surface‐protected hollowing process. Some newly developed synthetic routes are selected and discussed in detail. In conclusion, a summary and the perspectives on the directions that might lead the future development of this exciting field are presented. 相似文献
Nitrogen oxides are one of the major sources of air pollution. To remove these pollutants originating from combustion of fossil fuels remains challenging in steel, cement, and glass industries as the catalysts are severely deactivated by SO2 during the low‐temperature selective catalytic reduction (SCR) process. Here, a MnOX/CeO2 nanorod catalyst with outstanding resistance to SO2 deactivation is reported, which is designed based on critical information obtained from in situ transmission electron microscopy (TEM) experiments under reaction conditions and theoretical calculations. The catalysts show almost no activity loss (apparent NOX reaction rate kept unchanged at 1800 µmol g?1 h?1) for 1000 h test at 523 K in the presence of 200 ppm SO2. This unprecedented performance is achieved by establishing a dynamic equilibrium between sulfates formation and decomposition over the CeO2 surface during the reactions and preventing the MnOX cluster from the steric hindrance induced by SO2, which minimized the deactivation of the active sites of MnOX/CeO2. This work presents the ultralong lifetime of catalysts in the presence of SO2, along with decent activity, marking a milestone in practical applications in low‐temperature selective catalytic reduction (SCR) of NOX. 相似文献
Redox-induced interconversions of metal oxidation states typically result in multiple phase boundaries that separate chemically and structurally distinct oxides and suboxides. Directly probing such multi-interfacial reactions is challenging because of the difficulty in simultaneously resolving the multiple reaction fronts at the atomic scale. Using the example of CuO reduction in H2 gas, a reaction pathway of CuO → monoclinic m-Cu4O3 → Cu2O is demonstrated and identifies interfacial reaction fronts at the atomic scale, where the Cu2O/m-Cu4O3 interface shows a diffuse-type interfacial transformation; while the lateral flow of interfacial ledges appears to control the m-Cu4O3/CuO transformation. Together with atomistic modeling, it is shown that such a multi-interface transformation results from the surface-reaction-induced formation of oxygen vacancies that diffuse into deeper atomic layers, thereby resulting in the formation of the lower oxides of Cu2O and m-Cu4O3, and activate the interfacial transformations. These results demonstrate the lively dynamics at the reaction fronts of the multiple interfaces and have substantial implications for controlling the microstructure and interphase boundaries by coupling the interplay between the surface reaction dynamics and the resulting mass transport and phase evolution in the subsurface and bulk. 相似文献
Liquid-phase transmission electron microscopy (TEM) offers a real-time microscopic observation of the nanometer scale for understanding the underlying mechanisms of the growth, etching, and interactions of colloidal nanoparticles. Despite such unique capability and potential application in diverse fields of analytical chemistry, liquid-phase TEM studies rely on information obtained from the limited number of observed events. In this work, a novel liquid cell with a large-scale array of highly ordered nanochambers is constructed by sandwiching an anodic aluminum oxide membrane between graphene sheets. TEM analysis of colloidal gold nanoparticles dispersed in the liquid is conducted, employing the fabricated nanochamber array, to demonstrate the potential of the nanochamber array in quantitative liquid-phase TEM. The independent TEM observations in the multiple nanochambers confirm that the monomer attachment and coalescence processes universally govern the overall growth of nanoparticles, although individual nanoparticles follow different growth trajectories. 相似文献
Modern aberration corrected transmission electron microscopes offer the potential for electron beam sensitive materials, such as graphene, to be examined with low energy electrons to minimize, and even avoid, damage while still affording atomic resolution, and thus providing excellent characterization. Here in this review, the exploits in which the electron beam interactions, which are often considered negative, are explored to usefully drive a wealth of chemistry in and around graphene, importantly, with no other external stimuli. After introducing the technique, this review covers carbon phase reactions between amorphous carbon, graphene, fullerenes, carbon chains, and carbon nanotubes. It then explores different studies with clusters and nanoparticles, followed by coverage of single atom and molecule interactions with graphene, and finally concludes and highlights the anticipated exciting future for electron beam driving chemistry in and around graphene. 相似文献
