Strain sensors based on individual ZnO piezoelectric fine-wires (PFWs; nanowires, microwires) have been fabricated by a simple, reliable, and cost-effective technique. The electromechanical sensor device consists of a single electrically connected PFW that is placed on the outer surface of a flexible polystyrene (PS) substrate and bonded at its two ends. The entire device is fully packaged by a polydimethylsiloxane (PDMS) thin layer. The PFW has Schottky contacts at its two ends but with distinctly different barrier heights. The I-V characteristic is highly sensitive to strain mainly due to the change in Schottky barrier height (SBH), which scales linear with strain. The change in SBH is suggested owing to the strain induced band structure change and piezoelectric effect. The experimental data can be well-described by the thermionic emission-diffusion model. A gauge factor of as high as 1250 has been demonstrated, which is 25% higher than the best gauge factor demonstrated for carbon nanotubes. The strain sensor developed here has applications in strain and stress measurements in cell biology, biomedical sciences, MEMS devices, structure monitoring, and more.

A low-cost high-performance solid-state flexible asymmetric supercapacitor (ASC) with α-MnO2 nanowires and amorphous Fe2O3 nanotubes grown on flexible carbon fabric is first designed and fabricated. The assembled novel flexible ASC device with an extended operating voltage window of 1.6 V exhibits excellent performance such as a high energy density of 0.55 mWh/cm(3) and good rate capability. The ASC devices can find numerous applications as effective power sources, such as powering color-switchable sun glasses and smart windows.

Dendrite growth and by-products in Zn metal aqueous batteries have impeded their development as promising energy storage devices.W eu tilize al ow-cost additive, glucose,t om odulate the typical ZnSO 4 electrolyte system for improving reversible plating/stripping on Zn anode for highperformance Zn ion batteries (ZIBs). Combing experimental characterizations and theoretical calculations,weshow that the glucose in ZnSO 4 aqueous environment can simultaneously modulate solvation structure of Zn 2+ and Zn anode-electrolyte interface.T he electrolyte engineering can alternate one H 2 O molecule from the primary Zn 2+ -6H 2 Os olvation shell and restraining side reactions due to the decomposition of active water.Concomitantly,glucose molecules are inclined to absorb on the surface of Zn anode,suppressing the random growth of Zn dendrite.A saproof of concept, as ymmetric cell and Zn-MnO 2 full cell with glucose electrolyte achieve boosted stability than that with pure ZnSO 4 electrolyte.

Although MnO2 is a promising material for supercapacitors (SCs) due to its excellent electrochemical performance and natural abundance, its wide application is limited by poor electrical conductivity. Inspired by our results that the electrochemical activity and electrical conductivity of ZnO nanowires were greatly improved after hydrogenation, we designed and fabricated hydrogenated single-crystal ZnO@amorphous ZnO-doped MnO2 core-shell nanocables (HZM) on carbon cloth as SC electrodes, showing excellent performance such as areal capacitance of 138.7 mF/cm(2) and specific capacitance of 1260.9 F/g. Highly flexible all-solid-state SCs were subsequently assembled with these novel HZM electrodes using polyvinyl alcohol/LiCl electrolyte. The working devices achieved very high total areal capacitance of 26 mF/cm(2) and retained 87.5% of the original capacitance even after 10 000 charge/discharge cycles. An integrated power pack incorporating series-wound SCs and dye-sensitized solar cells was demonstrated for stand-alone self-powered systems.

UV response of ZnO nanowire nanosensor has been studied under ambient condition. By utilizing Schottky contact instead of Ohmic contact in device fabrication, the UV sensitivity of the nanosensor has been improved by four orders of magnitude, and the reset time has been drastically reduced from ϳ417 to ϳ0.8 s. By further surface functionalization with function polymers, the reset time has been reduced to ϳ20 ms even without correcting the electronic response of the measurement system. These results demonstrate an effective approach for building high response and fast reset UV detectors. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3133358͔ Ultraviolet ͑UV͒ photon detectors have a wide range of applications from environmental monitoring, missile launching detection, space research, high temperature flame detection to optical communications.1 For these applications, fast response time, fast reset time, high selectivity, high responsivity, and good signal-to-noise ratio are commonly desired characteristics.2 For UV photon detector based on polycrystalline ZnO thin film, a slow response time ranging from a few minutes to several hours is commonly observed.3,4 Due to large surface-to-volume ratio and reduced dimensionality of the active area, ZnO nanostructures are expected to have high photon conductance.5 Kind et al. 6 reported the photon response of a single ZnO nanowire ͑NW͒ under UV illumination, which has also been studied by other groups.7-9 Most of the studies have been focused on the mechanism investigation 10,11 and improving the sensitivity. 9,12 For example, Lao et al. 9 have improved the sensitivity of the ZnO NW UV nanosensor ͑NS͒ for five orders of magnitude by functionalizing the surface of ZnO nanobelts using polymers that have a high absorption at the UV range. However, little attention has been paid on improving the response and recovery time 13 especially the reset time ͑defined as the time need to recovery to 1 / e ͑37%͒ of the maximum photocurrent͒.In this letter, we demonstrate effective ways for improving both the sensitivity and reset time of ZnO NW NSs. By fabricating Schottky type ͑ST͒ devices instead of Ohmic type ͑OT͒ devices, the UV sensitivity of ZnO NW NS has been improved for four orders of magnitude, and the reset time has been decreased from ϳ417 to ϳ0.8 s. By further surface coating with positive charged poly͑diallydimethylammonium chloride͒ ͑PDADMAC͒ and negative charged poly͑sodium 4-styrenesulfonate͒ ͑PSS͒, the reset time has been decreased to ϳ20 ms even without correcting the electronic response of the measurement system. The ZnO NWs for the NS fabrication were synthesized by thermal evaporation of ZnO powders without using any catalyst.14 UV response of our devices was characterized by a portable UV lamp ͑Spectroline, Model ENF-280C, 365 nm͒. The photon-response spectrum measurement was carried out in a PTI QuantaMaster Luminescence ͑QM 3PH͒ system. All of the measurements were carried out at room temperature in ambient condition.We first studied the performance of...

A previously unknown rigid helical structure of zinc oxide consisting of a superlattice-structured nanobelt was formed spontaneously in a vapor-solid growth process. Starting from a single-crystal stiff nanoribbon dominated by the c-plane polar surfaces, an abrupt structural transformation into the superlattice-structured nanobelt led to the formation of a uniform nanohelix due to a rigid lattice rotation or twisting. The nanohelix was made of two types of alternating and periodically distributed long crystal stripes, which were oriented with their c axes perpendicular to each other. The nanohelix terminated by transforming into a single-crystal nanobelt dominated by nonpolar (0110) surfaces. The nanohelix could be manipulated, and its elastic properties were measured, which suggests possible uses in electromechanically coupled sensors, transducers, and resonators.

All-solid-state flexible supercapacitors based on a carbon/MnO(2) (C/M) core-shell fiber structure were fabricated with high electrochemical performance such as high rate capability with a scan rate up to 20 V s(-1), high volume capacitance of 2.5 F cm(-3), and an energy density of 2.2 × 10(-4) Wh cm(-3). By integrating with a triboelectric generator, supercapacitors could be charged and power commercial electronic devices, such as a liquid crystal display or a light-emitting-diode, demonstrating feasibility as an efficient storage component and self-powered micro/nanosystems.

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