Spontaneous Salt-Preventing Solar-Thermal Water Evaporator with a High Evaporation Efficiency through Dual-Mode Water Transfer.

Benefiting from the abundant solar energy and the emergence of photothermal conversion equipment, solar-driven water evaporation has shown great potential in seawater desalination. One common problem for solar-thermal evaporation is that the salt crystallized on the surface of solar absorbers during the seawater evaporation process will significantly deteriorate the continuity and efficiency of the evaporation process. In most reports, efforts have been made to transfer the accumulated salts, while the studies on preventing salt crystallization, which leads to better continuity of the production, are limited. Herein, a spontaneous salt-preventing solar-thermal water evaporator was designed, utilizing a dual-mode water transfer structure consisting of in-plane diffusion and in-tube migration. The dual-mode structural system gave rise to uniform and continuous water transfer, efficiently suppressing the salt concentration in the evaporator. As a result, salt crystallization was scarcely found on the surface of the evaporator under 1 sun irradiation for an ultralong time (200 h), demonstrating its high efficiency in inhibiting salt crystallization. In addition, the small contact area between the water and the evaporator could reduce the heat loss during the solar-thermal evaporation process, which further improved the water evaporation rate (1.64 kg m-2 h-1).

Rolled-up single-layered vanadium oxide nanomembranes for microactuators with tunable active temperature.

Multilayer vanadium dioxide (VO2) actuators are a widespread concern as these micro/nano-actuators present a fast and efficient dynamic response when VO2 occurs in metal-insulator transition (MIT) at 68 °C. By tuning the O2 flow rate during oxide deposition and rolled-up nanotechnology, a microactuator based on a single-layered vanadium oxide nanomembrane with vertical component gradient is fabricated. Upward bending of the nanomembrane is driven by the release of the compressive strain gradient which is revealed through the difference in Raman shift of the vibration mode. Combining strain engineering, the initial curvature of microactuators is tuned in a wide range by the thickness of the nanomembranes. The actuation behavior from low curvature to high final curvature across the MIT is observed which depends on the nanomembrane thickness. Initial compressive strain distribution of the rolled-up nanomembrane decreases the MIT temperature simultaneously. Thus, taking advantage of the tunable MIT and reversible shape transformation, micro/nano-actuators with tunable triggering temperature, controllable initial curvature and large-displacement actuation are fabricated for curvature engineering in micromechanical systems.

Controllable etching-induced contact enhancement for high-performance carbon nanotube thin-film transistors.

Semiconducting single-walled carbon nanotubes (s-SWNTs) show great promises in advanced electronics. However, contact resistance between the nanotubes and metal electrode has long been a bottleneck to the development of s-SWNTs in high-performance electronic devices. Here we demonstrate a simple and controllable strategy for enhancing the electrode contact and therefore the performance of s-SWNT thin film transistors by plasma etching treatment, which effectively removes the polymer residues, including the photoresist and the conjugated molecules, adsorbed on the surface of s-SWNTs. As a result, the contact resistance is reduced by 3 times and the carrier mobility rises by up to 70%. Our method is compatible with current silicon semiconductor processing technology, making it a viable effective approach to large-scale application of s-SWNTs in the electronics industry.

ZnO Nanomembrane/Expanded Graphite Composite Synthesized by Atomic Layer Deposition as Binder-Free Anode for Lithium Ion Batteries.

A zinc oxide (ZnO)/expanded graphite (EG) composite was successfully synthesized by using atomic layer deposition with dimethyl zinc as the zinc source and deionized water as the oxidant source. In the composite structure, EG provides a conductive channel and mechanical support to ZnO nanomembranes, which effectively avoids the electrode pulverization caused by the volume change of ZnO. The anodes made from the flexible composite films without using binder, conductive agent, and current collector show high stable capacities especially for that with a moderate ZnO concentration. The highest capacity stayed at 438 mAh g-1 at a current rate of 200 mA g-1 after 500 cycles. The good performance is considered to be due to the co-effects of the high capacity of ZnO and the support of the EG framework. Such composite structures may have great potential in low-cost and flexible batteries.

Reducing and Uniforming the Co3 O 4 Particle Size by Sulfonated Graphenal Polymers for Electrochemical Applications.

A novel two-dimensional (2D) nanomaterial, namely sulfonated graphenal polymer (SGP), is used to tune the hydrothermal growth of Co3O4 nanoparticles. SGP provides abundant nucleation sites to grow Co3O4 nanoparticles and effectively reduces the particle size and dimension. As a result, with considering the improved size uniformity of Co3O4 and the tight wrapping of SGP around Co3O4 as well, the Co3O4/SGP hybrid electrode exhibits a high specific electrochemical capacitance of 234.28 F/g at a current density of 0.2 A/g, 237% higher than that of the pure Co3O4 electrode. By using the hybrid as the anode of an all-solid-state asymmetric supercapacitor, the capacitance can be well maintained up to 93% after 5000 cycles even at 2 A/g.

An Extraordinary Sulfonated-Graphenal-Polymer-Based Electrolyte Separator for All-Solid-State Supercapacitors.

Sulfonated graphenal polymers can be assembled up by poly(vinyl alcohol) adhesion. The porous assembly structure results in a remarkably improved ionic conductivity and thus enhances electrochemical performances such as specific capacitance, capacitance retention, and cycling stability.

Atomic Layer Deposition of Pt Nanoparticles for Microengine with Promoted Catalytic Motion.

Nanoparticle-decorated tubular microengines were synthesized by a combination of rolled-up nanotechnology and atomic layer deposition. The presence of Pt nanoparticles with different sizes and distributions on the walls of microengines fabricated from bilayer nanomembranes with different materials results in promoted catalytic reaction efficiency, which leads to an ultrafast speed (the highest speed 3200 µm/s). The motion speed of the decorated microengines fits the theoretical model very well, suggesting that the larger surface area is mainly responsible for the acceleration of the motion speed. The high-speed nanoparticle-decorated microengines hold considerable promise for a variety of applications.

Programmable writing of graphene oxide/reduced graphene oxide fibers for sensible networks with in situ welded junctions.

Direct spinning of the graphene oxide (GO) dispersions from a moveable spinneret along the programmed track, i.e., a "programmable writing" technique, was developed to make nonwoven, nonknitted, graphene-based networks with excellent mechanical properties. The resulting GO networks can be successfully converted into reduced GO (RGO) ones with better mechanical properties as well as excellent electrical conductivity via thermal/chemical reduction. In situ welded junctions formed during processing of the spun fibers have made the resulting networks with the integral structure, and outstanding mechanical properties and high electrical conductivities of the spun fibers and their web integrations have provided a great opportunity to remotely sense the external mechanical stimuli via electrical signal monitoring.