4,218 publications from this institution
Contact electrification exists everywhere and between every phase of matter. However, its mechanism still remains to be studied. The recent triboelectric nanogenerator serves as a probe and provides some new clues about the mechanism present in solid–solid, solid–liquid, and liquid–liquid contact electrification. The gas–solid model still remains to be exploited. Here, we investigated the contact electrification between gases and solids based on the single-electrode triboelectric nanogenerator. Our work shows that the amount of transferred charges between gas and solid particles increases with surface area, movement distance, and initial charges of particle increase. Furthermore, we find that the initial charges on the particle surface can attract more polar molecules and enhance gas collisions. Since ions in gas–solid contact are rare, we speculate that gas–solid contact electrification is mainly based on electron transfer. Further, we propose a theoretical model of gas–solid contact electrification involving the gas collision model and initial charges of the particle. Our study may have great significance to the gas–solid interface chemistry.
Wearable and implantable electronics (WIEs) are more and more important and attractive to the public, and they have had positive influences on all aspects of our lives. As a bridge between wearable electronics and their surrounding environment and users, sensors are core components of WIEs and determine the implementation of their many functions. Although the existing sensor technology has evolved to a very advanced level with the rapid progress of advanced materials and nanotechnology, most of them still need external power supply, like batteries, which could cause problems that are difficult to track, recycle, and miniaturize, as well as possible environmental pollution and health hazards. In the past decades, based upon piezoelectric, pyroelectric, and triboelectric effect, various kinds of nanogenerators (NGs) were proposed which are capable of responding to a variety of mechanical movements, such as breeze, body drive, muscle stretch, sound/ultrasound, noise, mechanical vibration, and blood flow, and they had been widely used as self-powered sensors and micro-nanoenergy and blue energy harvesters. This review focuses on the applications of self-powered generators as implantable and wearable sensors in health monitoring, biosensor, human-computer interaction, and other fields. The existing problems and future prospects are also discussed.
In this study, we examined the fine structure of the compound eyes of a household fly and precisely replicated its entire structure using a low-temperature atomic layer deposition technique. The surface of the fly eye is found to be covered by highly packed protuberances, which potentially increases visual efficiency through increased photon capture for a given stimulus. The alumina replica was achieved by removing the fly compound eye template at high temperature, and the alumina coating was crystallized simultaneously. Besides the morphology, the unique antireflection property was also inherited by the alumina replica. By measuring the reflective spectra of the replica, we demonstrated that the alumina replica of a fly eye was an efficient antireflection structure of visible light at an incident angle up to 80°. Such a grating would be particularly useful on a cured corneal surface since it could increase the transmission of incident light through the cornea compared with a smooth surface.
Abstract Of recent interest in the science of nano-scale materials is the production and characterization of substances composed of ordered lattices of up to millions of identical nanometer scale particles. Silver nanocrystals of ∼ 4.5 nm diameter passivated with dodecanthiol surfactant were produced in the aerosol phase. Characterization of the individual particles and the subsequent supercrystals (SXs) resulting from their periodic packing was brought about using Mass Spectrometry, Transmission Electron Microscopy (TEM)/Electron Diffraction (ED), Scanning Electron Microscopy and Atomic Force Microscopy (AFM). It was determined that the micrometer and greater sized faceted SXs exhibited an hexagonal-close-packed (HCP) superstructure (fig.l) resulting in triangular shapes bounded by ﹛1100﹜ facets (fig. la); their platlet-like nature (∼20 nanocrystal layers thick) owing to their particular growth pattern. Knowledge of the growth mechanism is important to production of these materials on a macroscopic scale. Here we report a proposed growth model for these supercrystals.
This paper focuses on the growth mechanism of the multiwalled carbon nanotubes exhibiting helical and zigzag growth morphologies. Our data support a kinetically controlled growth model in which the creation rates of the pentagon and heptagon carbon rings determine the geometrical shapes of the nanotubes. The carbon nanotube is believed to be grown from a carbon cluster that is nucleated from a pentagon carbon ring followed by a spiral shell growth. The pairing of pentagonal−heptagonal (P−H) carbon rings is essential in forming the helical and zigzag structures. If there is no twist in the P−H orientation along the body of the carbon nanotube, a planar-spiral structure would be formed. If the P−H pairs twist their orientations along the growth direction of the nanotube, a helical structure would be formed. The periodicity and the coiling diameter of the helix are determined by the angle of the twist and the distance between the adjacent P−H pairs. If the P−H pairs are densely accumulated at a local region and the interpair distance is small, a node is formed, thus, the zigzag growth morphology.
