4,218 publications from this institution
A novel wet chemical technique for the site-selective growth of ZnO nanorod arrays on polymer substrates is described. Electron beam lithography is employed to define nanorod positions using a polymethylmethacrylate (PMMA) mask on a Kapton polyimide substrate with a Au intermediate layer. An applied potential is utilized to enhance the nucleation process and achieve ZnO nanorods with a base diameter of 200 nm. The technique does not require a ZnO seed layer and can be carried out at temperatures as low as 70 °C. Structural characterization of the as-grown ZnO nanorods has been investigated by scanning electron microscopy and X-ray diffraction. This technique represents a new low-cost method for integrating ZnO nanorods into flexible electronic devices.
Contact electrification (CE) is a common physical phenomenon, and its mechanisms for solid-solid and liquid-solid cases have been widely discussed. However, the studies about liquid-liquid CE are hindered by the lack of proper techniques. Here, a contactless method is proposed for quantifying the charges on a liquid droplet based on the combination of electric field and acoustic field. The liquid droplet is suspended in an acoustic field, and an electric field force is created on the droplet to balance the acoustic trap force. The amount of charges on the droplet is thus calculated based on the equilibrium of forces. Further, the liquid-solid and liquid-liquid CE are both studied by using the method, and the latter is focused. The behavior of negatively precharged liquid droplet in the liquid-liquid CE is found to be different from that of the positively precharged one. The results show that the silicone oil droplet prefers to receive negative charges from a negatively charged aqueous droplet rather than positive charges from a positively charged aqueous droplet, which provides a strong evidence about the dominant role played by electron transfer in the liquid-liquid CE.
Abstract In order to improve the accuracy of on-site facility monitoring in power infrastructure, a node fusion method based on wireless sensor collection for on-site facility monitoring in power infrastructure is proposed. This method collects monitoring data of power infrastructure on-site facilities through wireless sensors. It combines data fusion technology with the least squares integration method to remove abnormal data, such as noise in the environment of power infrastructure on-site. Using an adaptive genetic algorithm and floating search algorithm to extract the optimal feature subset of power infrastructure site monitoring data and implementing node fusion of power infrastructure site monitoring data collected by multiple sensors based on an adaptive weighted average algorithm. Through experimental verification, this method can strengthen the accuracy and reliability of monitoring systems data while reducing energy consumption and increasing data throughput. This node fusion method can effectively improve the performance of the on-site facility monitoring system for power infrastructure construction, providing strong support for the safe operation of power facilities.
The coexistence of decomposition, phase segregation, and alloying behaviors of Au@Cu2O core–shell nanoparticles were found through in situ heating transmission electron microscopy imaging and spectral-analysis techniques. Thermally induced compositional variations (from Cu2O to Cu) were observed to be present in the nanoparticle shells, which was followed by a spontaneous occurrence of Au–Cu alloying. The higher-Cu loading (1:10 Au/Cu) sample displays a clear Cu/Cu2O phase segregation driven by the internal stresses resulting from lattice mismatch. Cu extrusions also occur in this sample after storage in ethanol for 10 days. These in situ observations/findings may help enhance a fundamental understanding of remarkable experimental aspects arising in catalytic processes and other applications as well as provide a valuable reference for testing/refining potential models of hybrid nanoparticles in theoretical calculations.
An experimental procedure is presented for the controlled synthesis and manipulation of ZnO nanorings and nanobows at high purity and large yield. Atomic force microscopy manipulation of the nanostructures demonstrates their mechanical toughness and flexibility. Extensive bending of the nanorings and nanobows suggests an extremely high deformation limit with the potential for building ultrasensitive electromechanical coupled nanoscale sensors, transducers, and resonators.
Multiwalled carbon nanotubes are shown to be ballistic conductors at room temperature, with mean free paths of the order of tens of microns. The measurements are performed both in air and in high vacuum in the transmission electron microscope on nanotubes that protrude from unprocessed arc-produced nanotube-containing fibers that contact with a liquid metal surface. These experiments follow and extend the original experiments by Frank et al. (Science 1998, 280 1744), which demonstrated for the first time the large current carrying capability, very low intrinsic resistivities, and evidence for quantized conductance. This indicated 1D transport, that only the surface layer contributes to the transport, and ballistic conduction at room temperature. Here, we follow up on the original experiment including in-situ electron microscopy experiments and a detailed analysis of the length dependence of the resistance. The per unit length resistance ρ < 100 Ω/μm, indicating free paths l > 65 μm, unambiguously demonstrates ballistic conduction at room temperature up to macroscopic distances. The nanotube−metal contact resistances are in the range from 0.1 to 1 kΩμm. Contact scattering can explain why the measured conductances are about half of the expected theoretical value of 2 G0. For V > 0.1 V, the conductance rises linearly (dG/dV∼0.3 G0/V) reflecting the linear increase in the density-of-states in a metallic nanotube above the energy gap. Increased resistances (ρ = 2−10 kΩ/μm) and anomalous I−V dependences result from impurities and surfactants on the tubes. Evidence is presented that ballistic transport occurs in undoped and undamaged tubes for which the top layer is metallic and the next layer is semiconducting. The diffusive properties of lithographically contacted multiwalled nanotubes most likely result from purification and other processing steps that damage and dope the nanotubes, thereby making them structurally and electronically different than the pristine nanotubes investigated here.
Zinc oxide is an important semiconducting and piezoelectric material. Structurally, due to the three types of fast growth direction: <0001>, <01 0> and <2 0> as well as the ±(0001) polar surfaces, a diversity group of ZnO nanostructures have been grown in our laboratory: including nanocombs, nanosaws, nanosprings, nanorings, nanobows and nanopropellers. This article reviews our recent progress in the synthesis and characterization of the polar surface induced ZnO nanostructures and their growth mechanisms.
