Water-evaporation-induced electricity with nanostructured carbon materials.

Water evaporation is a ubiquitous natural process that harvests thermal energy from the ambient environment. It has previously been utilized in a number of applications including the synthesis of nanostructures and the creation of energy-harvesting devices. Here, we show that water evaporation from the surface of a variety of nanostructured carbon materials can be used to generate electricity. We find that evaporation from centimetre-sized carbon black sheets can reliably generate sustained voltages of up to 1 V under ambient conditions. The interaction between the water molecules and the carbon layers and moreover evaporation-induced water flow within the porous carbon sheets are thought to be key to the voltage generation. This approach to electricity generation is related to the traditional streaming potential, which relies on driving ionic solutions through narrow gaps, and the recently reported method of moving ionic solutions across graphene surfaces, but as it exploits the natural process of evaporation and uses cheap carbon black it could offer advantages in the development of practical devices.

Three-tier rough superhydrophobic surfaces.

A three-tier rough superhydrophobic surface was fabricated by growing hydrophobic modified (fluorinated silane) zinc oxide (ZnO)/copper oxide (CuO) hetero-hierarchical structures on silicon (Si) micro-pillar arrays. Compared with the other three control samples with a less rough tier, the three-tier surface exhibits the best water repellency with the largest contact angle 161° and the lowest sliding angle 0.5°. It also shows a robust Cassie state which enables the water to flow with a speed over 2 m s(-1). In addition, it could prevent itself from being wetted by the droplet with low surface tension (mixed water and ethanol 1:1 in volume) which reveals a flow speed of 0.6 m s(-1) (dropped from the height of 2 cm). All these features prove that adding another rough tier on a two-tier rough surface could futher improve its water-repellent properties.

Paper-based supercapacitors for self-powered nanosystems.

Energy storage on paper: paper-based, all-solid-state, and flexible supercapacitors were fabricated, which can be charged by a piezoelectric generator or solar cells and then discharged to power a strain sensor or a blue-light-emitting diode, demonstrating its efficient energy management in self-powered nanosystems.

WO3­x@Au@MnO2 core­shell nanowires on carbon fabric for high-performance flexible supercapacitors.

WO3­x@Au@MnO2 core­shell nanowires (NWs) are synthesized on a flexible carbon fabric and show outstanding electrochemical performance in supercapacitors such as high specific capacitance, good cyclic stability, high energy density, and high power density. These results suggest that the WO3­x@Au@MnO2 NWs have promising potential for use in high-performance flexible supercapacitors.

Anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire.

We report a systematic study about the anisotropic third-order optical nonlinearity of a single ZnO micro/nanowire by using the Z-scan method with a femtosecond laser. The two-photon absorption coefficient and nonlinear refraction index, which are measured as a function of polarization angle and sample orientation angle, exhibit oscillation curves with a period of π/2, indicating a highly polarized optical nonlinearity of the ZnO micro/nanowire. Further studies show that the polarized optical nonlinearity of the ZnO micro/nanowire is highly size-dependent. The results indicate that ZnO nanowire has great potential in applications of nanolasers, all-optical switching and polarization-sensitive photodetectors.

Flexible solid-state supercapacitors based on carbon nanoparticles/MnO2 nanorods hybrid structure.

A highly flexible solid-state supercapacitor was fabricated through a simple flame synthesis method and electrochemical deposition process based on a carbon nanoparticles/MnO(2) nanorods hybrid structure using polyvinyl alcohol/H(3)PO(4) electrolyte. Carbon fabric is used as a current collector and electrode (mechanical support), leading to a simplified, highly flexible, and lightweight architecture. The device exhibited good electrochemical performance with an energy density of 4.8 Wh/kg at a power density of 14 kW/kg, and a demonstration of a practical device is also presented, highlighting the path for its enormous potential in energy management.

High-strain sensors based on ZnO nanowire/polystyrene hybridized flexible films.

A type of strain sensor with high tolerable strain based on a ZnO nanowires/polystyrene nanofibers hybrid structure on a polydimethylsiloxane film is reported. The novel strain sensor can measure and withstand high strain and demonstrates good performance on rapid human-motion measurements. In addition, the device could be driven by solar cells. The results indicate that the device has potential applications as an outdoor sensor system.

Three-dimensional WO3 nanostructures on carbon paper: photoelectrochemical property and visible light driven photocatalysis.

Three-dimensional (3D) WO(3) nanostructures were grown on carbon paper by a catalyst-free high temperature reactive vapor deposition process, which exhibit a good photoelectrochemical property and visible light driven photocatalytic performance.

Self-cleaning flexible infrared nanosensor based on carbon nanoparticles.

Highly flexible, robust, and sensitive infrared nanosensors were fabricated based on carbon nanoparticles that were synthesized through a simple and low-cost flame method. The infrared nanosensor devices showed sharp infrared photoresponse with a response time of ∼68 ms and a maximum photocurrent change of ∼52.9%. The devices showed a superhydrophobic property with a contact angle larger than 150° and a sliding angle of ∼4°. The mechanism for the enhanced infrared photoresponse from carbon nanoparticles is discussed.

High optical switching speed and flexible electrochromic display based on WO3 nanoparticles with ZnO nanorod arrays' supported electrode.

The electrochromic (EC) property of WO(3) nanoparticles grown on vertically self-aligned ZnO nanorods (ZNRs) is reported. An electrochromic character display based on WO(3) nanoparticle-modified ZnO nanorod arrays on a flexible substrate has been fabricated and demonstrated. The ZNRs were first synthesized on ZnO-seed-coated In(2)O(3):Sn (ITO) glass (1 cm(2) cell) and polyethylene terephthalate (PET) (4 cm(2) cell) substrates by a low temperature hydrothermal method, and then amorphous WO(3) nanoparticles were grown directly on the surface of the ZNRs by the pulsed laser deposition (PLD) method. The ZNR-based EC device shows high transparence, good electrochromic stability and fast switching speed (4.2 and 4 s for coloration and bleaching, respectively, for a 1 cm(2) cell). The good performance of the ZNR electrode-based EC display can be attributed to the large surface area, high crystallinity and good electron transport properties of the ZNR arrays. Its high contrast, fast switching, good memory and flexible characteristics indicate it is a promising candidate for flexible electrochromic displays or electronic paper.