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Water is one of the most abundant energy sources in our environment and hydroelectric power has been one of the main forms of macro-energy supply. However, for harvesting green micro-energy from water presented in our residential zone, industry or agricultural irrigation, traditional electromagnetic hydraulic turbine generator has limited applications due to its large size, complexity and high cost. Here we report a novel design of the multi-unit hydroelectric generator (HEG) for harvesting water-related energy based on contact electrification. The instantaneous output power density of the multi-unit HEG array is 0.07 W/m 2 , which is 9 times of that from the individual HEG with the same dimension. Moreover, the rational design of the multi-unit HEG can increase the safety for its future service. By integrating with the multi-unit HEG, the household faucet can be a power source to supply clean energy continuously. Given the compelling features, such as, highly efficient, easily implemented, lightweight and extremely cost-effective, the multi-unit HEG renders a promising approach toward clean energy harvesting from ambient environment.

We developed and demonstrated a ZnO/ZnS/Au composite photoanode with significantly enhanced photoelectrochemical water-splitting performance, containing a ZnS interlayer and Au nanoparticles. The solar-to-hydrogen conversion efficiency of this ZnO/ZnS/Au heterostructure reached 0.21%, 3.5 times that of pristine ZnO. The comparison of the incident photon-to-current efficiency (IPCE) and the photoresponse in the white and visible light regions further verified that the enhancement resulted from contributions of both UV and visible light. The modification of the Au NPs was shown to improve the photoelectrochemical (PEC) performance to both UV and visible light, as modification encouraged effective surface passivation and surface-plasmonresonance effects. The ZnS interlayer favored the movement of photogenerated electrons under UV light and hot electrons under visible light, causing their injection into ZnO; this simultaneously suppressed the electron-hole recombination at the photoanode-electrolyte interface. The optimized design of the interlayer within plasmonic metal/semiconductor composite systems, as reported here, provided a facile and compatible photoelectrode configuration, enhancing the utilization efficiency of incident light for photoelectrochemical applications.

Nowadays, the fabrication of photoanodes with high light-harvesting capability and charge transfer efficiency is a key challenge for photoelectrochemical (PEC) water splitting. In this paper, large-scale patterned ZnO nanorod arrays (NRAs) were designed and fabricated via two-beam laser interference lithography and hydrothermal synthesis, which were further applied as PEC photoanodes for the first time. By adopting the ZnO NRA photoanodes with square pattern, the PEC cells achieved a maximum efficiency of 0.18%, which was improved 135% compared to the control group with no patterned ZnO NRAs. The large-scale highly ordered ZnO NRAs have enhanced light-harvesting ability due to the light-scattering effect. In addition, the enlarged surface area of the patterned ZnO NRAs accelerated the charge transfer at the photoanode/electrolyte interface. This research demonstrates an effective mean to realize the efficient solar water splitting, and the results suggest that large-scale highly ordered nanostructures are promising candidates in the field of energy harvesting.

Developing photoanodes with high light-harvesting efficiency and great electronic transmission capacity remains a key challenge in photoelectrochemical (PEC) water splitting. In this paper, we reported an effective approach to enhance the PEC performance of ZnO nanowire arrays (NAs) photoanodes via overcoating ZnIn2S4 nanosheets onto the ZnO surfaces. The ZnIn2S4 electrocatalyst nanosheets were grown on the reduced graphene oxide (RGO) substrates by solvothermal synthesis and then grafted onto ZnO NAs, forming ZnO NAs/RGO/ZnIn2S4 heterojunctions. The ZnIn2S4 shells acted as visible light sensitizers, and the type-II band alignment between the ZnIn2S4 shells and the ZnO cores contributed to charge separation and transport. Meanwhile, the introduction of RGO nanosheets largely increased the surface area and accelerated the PEC process by reducing the energy barrier of interfacial electrochemical reaction. As a result, over 200% enhancement of photo-to-hydrogen conversion efficiency was achieved from the ZnO NAs/RGO/ZnIn2S4 heterojunctions compared to bare ZnO NAs. The results demonstrate that the RGO-based core/shell heterojunction arrays can provide a facile and compatible configuration for the potential applications in solar water splitting.

We demonstrated a sort of self-powered vibration sensor based on a triboelectric generator (TEG) using triboelectrification and electrostatic induction effects. The as-prepared TEG delivered an output voltage of 34.06 V and short-circuit current density of 22.5 mA/m 2 corresponding to a maximum power density of 0.77 W/m 2 , which was capable of driving five LEDs directly and continuously with working frequency of 50 Hz without any rectification circuit or energy storage unit. The vibration sensor has a detection range of 0–500 Hz, and high accuracy. Besides, it could realize detection under non-contact mode, which would protect the device and the detected object in operation. Moreover, the stability and repeatability could also be well retained. The TEG based vibration sensor possessed great potential in machines operation monitoring, process control, and security applications in unreachable and access-denied extreme environments.

One dimensional (1-D) nanostructures are envisioned as fundamental building blocks of future electronic, electromechanical, optoelectronic nanodevices and sensors, which will be integrated into nanosystems. We briefly introduce the advantages of 1-D nanostructure in the fabrication of energy conversion devices, followed by the recent developments in device designs, fabrication and some effective approaches for performance enhancement. This review will cover the major progress in three research fields. Firstly, we present the progresses on the fabrication and property modulation of wurtzite nanostructures. Then, we introduce the progresses on the piezotronic properties of wurtzite nano-materials and prototype piezotronic devices, including piezoelectric field effect transistors, piezoelectric diodes, strain sensors and nanogenerators. Finally, the investigations of property degrading and damage of nanomaterials, and functional degrading and failure of the nanodevices will be presented for future electronic applications.

Gold nanoparticle (Au NP)@ZnO nanorod (NR) (Au@ZnO) hybrids with various ZnO:Au molar ratios were developed to enhance the generation of reactive oxygen species (ROS) in photodynamic therapy (PDT) applications. Introducing a metal/semiconductor heterostructure interface between Au NPs and ZnO NRs modulated electron transfer under ultraviolet (UV) irradiation, which dramatically suppressed the electron-hole recombination in ZnO and simultaneously increased the amount of excited electrons with high energy at Au NP surfaces. Hence, the ROS yield of the nanohybrid was considerably improved over those of pristine Au NPs or ZnO NRs alone and demonstrated a “1 + 1 > 2 effect.” This enhancement was strengthened with increases in the proportion of Au in the hybrid. The results showed that the Au@ZnO nanohybrids with a ZnO:Au ratio of 20:1 generated the highest ROS yield because they had the largest interface area between Au and ZnO, which in turn led to the lowest cell viability for HeLa and C2C12 cells during PDT. Furthermore, both ROS generation and cell destruction were positively correlated with nanohybrid dosage. The Au@ZnO hybrid (20:1, 100 μg/mL) resulted in HeLa cell viability as low as 28% after UV exposure for 2 min, which indicated its promising potential to improve the therapeutic efficacy of PDT.

In this work, a high-performance, forming-free memristor based on Au/ZnO nanorods/AZO (Al-doped ZnO conductive glass) sandwich structure has been developed by rapid hydrogen annealing treatment. The Ron/Roff rate is dramatically increased from ∼10 to ∼10(4) after the surface treatment. Such an enhanced performance is attributed to the introduced oxygen vacancies layer at the top of ZnO nanorods. The device also exhibits excellent switching and retention stability. In addition, the carrier migration behavior can be well interpreted by classical trap-controlled space charge limited conduction, which verifies the forming of conductive filamentary in low resistive state. On this basis, Arrhenius activation theory is adopted to explain the drifting of oxygen vacancies, which is further confirmed by the time pertinence of resistive switching behavior under different sweep speed. This fabrication approach offers a useful approach to enhance the switching properties for next-generation memory applications.

Functional electrical devices have promising potentials in structural health monitoring system, human-friendly wearable interactive system, smart robotics, and even future multifunctional intelligent room. Here, a low-cost fabrication strategy to efficiently construct highly sensitive graphite-based strain sensors by pencil-trace drawn on flexible printing papers is reported. The strain sensors can be operated at only two batteries voltage of 3 V, and can be applied to variously monitoring microstructural changes and human motions with fast response/relaxation times of 110 ms, a high gauge factor (GF) of 536.6, and high stability >10 000 bending–unbending cycles. Through investigation of service behaviors of the sensors, it is found that the microcracks occur on the surface of the pencil-trace and have a major influence on the functions of the strain sensors. These performances of the strain sensor attain and even surpass the properties of recent strain sensing devices with subtle design of materials and device architectures. The pen-on-paper (PoP) approach may further develop portable, environmentally friendly, and economical lab-on-paper applications and offer a valuable method to fabricate other multifunctional devices.

Interface modulation for broad-band light trapping and efficient carrier collection has always been the research focus in solar cells, which provides the most effective way to achieve performance enhancement. In this work, solution-processed 3D ordered ZnO/Cu2O nanoheterojunctions, consisting of patterned n-ZnO nanorod arrays (NRAs) and p-Cu2O films, are elaborately designed and fabricated for the first time. By taking advantage of nanoheterojunctions with square patterned ZnO NRAs, solar cells demonstrate the maximum current density and efficiency of 9.89 mA cm(-2) and 1.52%, which are improved by 201% and 127%, respectively, compared to that of cells without pattern. Experimental analysis and theoretical simulation confirm that this exciting result originates from a more efficient broad-band light trapping and carrier collection of the 3D ordered ZnO/Cu2O nanoheterojunctions. Such 3D ordered nanostructures will have a great potential application for low-cost and all oxide solar energy conversion. Furthermore, the methodology applied in this work can be also generalized to rational design of other efficient nanodevices and nanosystems.

Here we design a nanostructure by embedding Au nanoparticles into ZnO/NiO core-shell composites as supercapacitors electrodes materials. This optimized hybrid electrodes exhibited an excellent electrochemical performance including a long-term cycling stability and a maximum specific areal capacitance of 4.1 F/cm(2) at a current density of 5 mA/cm(2), which is much higher than that of ZnO/NiO hierarchical materials (0.5 F/cm(2)). Such an enhanced property is attributed to the increased electro-electrolyte interfaces, short electron diffusion pathways and good electrical conductivity. Apart from this, electrons can be temporarily trapped and accumulated at the Fermi level (EF') because of the localized schottky barrier at Au/NiO interface in charge process until fill the gap between ZnO and NiO, so that additional electrons can be released during discharge. These results demonstrate that suitable interface engineering may open up new opportunities in the development of high-performance supercapacitors.

Piezoelectric materials can be applied into electromechanical conversion and attract extensive attention with potential applications in various sensors. Here, we present two types of piezotronic pressure sensors based on ZnO nanoarrays. By introducing an insulating MgO (i-MgO) nanolayer, the "on/off" current ratio of the sensor is significantly improved up to 10(5). Furthermore, the sensor shows a high sensitivity of 7.1 × 10(4) gf(-1), a fast response time of 128 ms. The excellent properties are attributed to the combination of piezoelectric effect of ZnO nanoarrays and electron-tunneling modulation of MgO nanolayer, and the reversible potential barrier height controlled by piezoelectric potential. We further investigate the service behavior of the sensor, which can detect force varying from 3.2 to 27.2 gf. Our research provides a promising approach to boost the performance of nanodevices.

The mechanical service behaviors of ZnO nanowires (NWs) with diameters ranging from 67 to 201 nm and different scanning angles at a scanning rate of 14.8 μm s−1 were studied by atomic force microscope (AFM). The force calibration equation was established between the actual forces applied on the surface of single ZnO NW, applied forces and scanning angles. It was proved that the actual forces strengthened when scanning angles exist. The actual fracture threshold forces increase linearly with the increase of diameters of the ZnO NWs, but do not dependent on the scanning angles. The force calibration is important and significant for applying forces accurately using AFM with scanning angles. The investigation provides a method for studying mechanical service behaviors of one dimensional nanomaterial under non-normal stress state and calibrating the actual force applied by AFM under different scanning angles.

We report fabrication of an all inorganic, self-powered and rapid-response ultraviolet (UV) photodetector using solution-processed p-NiO/ZnO-nanorod array heterojunction. The device exhibited a fast binary-response with a rise time of 0.23 s and decay time of 0.21 s. A large responsivity of 0.44 mA W−1 was achieved for a 0.4 mW cm−2 UV light irradiation at a zero-bias voltage. The self-powered performance could be attributed to the proper built-in electric field between ZnO and NiO arising from the well-aligned energy-band structure of the device, which gives rise to a photovoltaic effect.

During the investigation of mechanical properties of nanomaterials by atomic force microscope (AFM), a non-normal stress state with large scanning angles is a universal phenomenon. The mechanical service behaviors of ZnO nanowires (NWs) with diameters ranging from 177 to 386 nm under non-normal stress state were studied by AFM at a scanning rate of 14.8 μm s−1. We expanded the application scope of the threshold force equation determining the fracture threshold forces of ZnO NWs which was established in our previous work. The criterion equation for security service of ZnO NWs was established by the threshold force equation and force calibration equation. The criterion equation was used to predict the security service range of ZnO NWs successfully. The modulus and fracture strength of the ZnO NWs were also calculated through the fracture threshold force obtained from the threshold force equation. The results have important and meaningful consequences for security practical applications of ZnO NWs under non-normal stress state.

Biosensing has developed tremendously since it was demonstrated by Leland C. Clark Jr. in 1962. ZnO nanomaterials are attractive candidates for fabricating biosensors, because of their diverse range of nanostructures, high electron mobility, chemical stability, electrochemical activity, high isoelectric points which promote enzyme adsorption, biocompatibility, and piezoelectric properties. This review covers ZnO nanostructures applied in enzyme biosensors, in the light of electrochemical transduction and field effect transduction. Different assembly processes and immobilization methods have been used to load enzymes into various ZnO nanostructures, providing enzymes with favorable micro-environments and enhancing their sensing performance. We briefly describe recent trends in ZnO syntheses, and the analytical performance of the fabricated biosensors, summarize the advantages of using ZnO nanostructures in biosensors, and conclude with future challenges and prospects.

2D metallic TaS

To assess 24-hour fluctuations in Schlemm's canal (SC) parameters (cross-sectional area, perimeter) and intraocular pressure (IOP) and the relationship between these fluctuations in healthy individuals.SC and IOP were examined in 29 participants at 2:30, 5:30, 11:30, 17:30, and 23:30 within one day. The superior, inferior, nasal, and temporal SC quadrants were evaluated using 80-MHz ultrasound biomicroscopy.SC parameters and IOP fluctuated significantly within 24 hours (all P0.05). After age, gender, axial length, and central corneal thickness were adjusted, compared with the baseline (23:30) value, the change in SC cross-sectional area was negatively associated with the change in IOP at 2:30, 5:30, 11:30, and 17:30 (β = -0.072[-0.094, -0.049], -0.070[-0.102, -0.038], -0.046[-0.079, -0.013], and -0.033[-0.062, -0.004], respectively; P0.001,0.001, = 0.009, and = 0.028, respectively). The nasal (175.6 ± 36.0 pixels) and inferior (174.8 ± 36.0 pixels) SC cross-sectional areas were significantly larger than the superior area (156.2 ± 27.1 pixels) (P = 0.018 and 0.048, respectively) at 23:30. The observable SC proportion did not change among the quadrants or measurement time points (all P0.05).SC cross-sectional area fluctuated throughout the day and was negatively associated with changes in IOP.

Black silicon (b-Si) is a surface-nanostructured Si with extremely efficient light absorption capability and is therefore of interest for solar energy conversion. However, intense charge recombination and low electrochemical stability limit the use of b-Si in photoelectrochemical solar-fuel production. Here we report that a conformal, ultrathin, amorphous TiO2 film deposited by low-temperature atomic layer deposition (ALD) on top of b-Si can simultaneously address both of these issues. Combined with a Co(OH)2 thin film as the oxygen evolution catalyst, this b-Si/TiO2/Co(OH)2 heterostructured photoanode was able to produce a saturated photocurrent density of 32.3 mA cm−2 at an external potential of 1.48 V versus reversible reference electrode (RHE) in 1 M NaOH electrolyte. The enhanced photocurrent relative to planar Si and unprotected b-Si photoelectrodes was attributed to the enhanced charge separation efficiency as a result of the effective passivation of defective sites on the b-Si surface. The 8-nm ALD TiO2 layer extends the operational lifetime of b-Si from less than half an hour to four hours. Nanostructured black silicon can be used as a photoelectrode for solar-driven water splitting, but its high surface area can increase charge recombination and accelerate corrosion. Here the authors show that a thin, conformal film of TiO2 can increase both the photocurrent and the stability of black silicon.

To compare the choroidal area in different eye fundus sectors of subjects with normal eyes, early-stage primary open-angle glaucoma (POAG) eyes, and 10° tubular visual field POAG eyes using enhanced depth imaging optical coherence tomography. Twenty-five normal, 25 early-stage POAG, and 25 ten-degree tubular visual field POAG eyes were recruited. Enhanced depth imaging optical coherence tomography was used to measure the choroidal area in different fundus sectors (fovea; 10° superior, inferior, temporal, and 24° superior, inferior, temporal, nasal to the fovea) and the peripapillary sector. There were neither significant differences in the choroidal area at any of the 8 measured fundus sectors, nor significant differences in the percentage change between the choroidal area of the fovea and other 7 measured fundus sectors among the 3 groups (all P > 0.05). For the total peripapillary choroidal area, no significant difference was found among the 3 groups (P > 0.05); however, the temporal peripapillary choroidal area of 10° tubular visual field POAG eyes was significantly thicker than that of normal eyes (4,46,213 ± 1,16,267 vs 3,74,164 ± 1,21,658 μm2; P = 0.048). Our study showed that there was no significant difference in the choroidal area of the 8 measured fundus sectors among normal, early-stage POAG, and 10° tubular visual field POAG eyes, suggesting that there might be no blood redistribution from the peripheral choroid to the subfoveal choroid. However, the thicker temporal peripapillary choroidal area might play a role in the central visual acuity protection in patients with POAG.

A self-powered photodetector was fabricated by taking advantage of the band bending at the ZnO/electrolyte interface. And a 48% performance enhancement was achieved with the introduction of 0.15% compressive strain due to the generation of piezopolarization charges. This result could be extended to other solid-liquid reactions, such as photoelectrochemical or photocatalytic processes.

We report on an enzymatic electrochemical glucose biosensor based on the use of zinc oxide nanorods (ZnO NRs) modified with gold nanoparticles (Au-NPs) and arranged in the form of an array. The nanorods were obtained via a hydrothermal method, and the Au-NPs were synthesized by photo-reduction. The surface of the nanoarrays was then modified with Au-NPs via electrostatic self-assembly. GOx was immobilized onto the surface of Au-NPs modified ZnO nanoarrays by electrostatic adsorption. The performance of the resulting glucose biosensors were investigated by cyclic voltammetry and amperometry. Compared to biosensors based on ZnO nanoarrays without Au-NPs, the ones described here exhibit a higher sensitivity (43.7 nA cm−2 mM−1) and a lower K app,M (0.78 mM). It is obvious, therefore, that the Au-NPs play an important role with respect to the performance of this biosensor.

In this study, the potential predictability of the Northern America (NA) surface air temperature (SAT) was explored using an information-based predictability framework and two multiple model ensemble products: a one-tier prediction by coupled models (T1), and a two-tier prediction by atmospheric models only (T2). Furthermore, the potential predictability was optimally decomposed into different modes for both T1 and T2, by extracting the most predictable structures. Emphasis was placed on the comparison of the predictability between T1 and T2. It was found that the potential predictability of the NA SAT is seasonal and spatially dependent in both T1 and T2. Higher predictability occurs in spring and winter and over the southeastern US and northwestern Canada. There is no significant difference of potential predictability between T1 and T2 for most areas of NA, although T1 has higher potential predictability than T2 in the southeastern US. Both T1 and T2 display similar most predictable components (PrCs) for the NA SAT, characterized by the inter-annual variability mode and the long-term trend mode. The first one is inherent to the tropical Pacific sea surface temperature forcing, such as the El Nino-Southern Oscillation, whereas the second one is closely associated with global warming. In general, the PrC modes can better characterize the predictability in T1 than in T2, in particular for the inter-annual variability mode in the fall. The prediction skill against observations is better measured by the PrC analysis than by principal component analysis for all seasons, indicating the stronger capability of PrCA in extracting prediction targets.

Well-aligned ZnO nanorod (NR) arrays were grown on the indium-tin-oxide glass through a hydrothermal method. A novel and simple method was created to fabricate the high-performance ultraviolet (UV) photodetectors on the basis of the ZnO NR arrays. When the ZnO NRs device is under 365-nm UV illumination (2.01 mW/cm 2 ), it showed a photocurrent of ~308.04 μA, an on/off ratio of ~5.13×10 2 and a fast decay time constant of 1.69 s at 1 V applied bias. The performance of the ZnO NRs device was much better than that of the conventional ZnO film device. The superior photoresponse of the ZnO NRs device is due to the larger surface-to-volume ratio and better crystal quality of ZnO NRs. The ZnO NRs device has great potential for application in UV detection and is promising for large-scale production.

The ability to arbitrarily regulate semiconductor interfaces provides the most effective way to modulate the performance of optoelectronic devices. However, less work has been reported on piezo-modulated interface engineering in all-oxide systems. In this paper, an enhanced photoresponse of an all-oxide Cu2O/ZnO heterojunction was obtained by taking advantage of the piezotronic effect. The illumination density-dependent piezoelectric modulation ability was also comprehensively investigated. An 18.6% enhancement of photoresponse was achieved when applying a −0.88% compressive strain. Comparative experiments confirmed that this enhancement could be interpreted in terms of the band modification induced by interfacial piezoelectric polarization. The positive piezopotential generated at the ZnO side produces an increase in space charge region in Cu2O, thus providing an extra driving force to separate the excitons more efficiently under illumination. Our research provides a promising method to boost the performance of optoelectronics without altering the interface structure and could be extended to other metal oxide devices.

In this letter, the facial noncovalent adsorption of single-stranded DNA (ssDNA) provided single-walled carbon nanotubes (SWNTs) with biofunctionality while their superior properties were retained. In this case, we innovatively demonstrated the feasibility of employing the negative surface charge of ssDNA-SWNTs to realize layer-by-layer electrostatic self-assembly. On the basis of such a sandwichlike structure, an applicable glucose microbiosensor with direct electrochemistry and high performance was fabricated. The proposed protocol provided an ideal platform for various sensing applications, and might have profound influence on related nanotechnology.

High quality n-ZnO/p-GaN heterojunction was fabricated by growing highly crystalline ZnO epitaxial films on commercial p-type GaN substrates via radio frequency (RF) magnetron sputtering. Low-voltage blue light emitting diode with a turn-on voltage of ∼2.5 V from the n-ZnO/p-GaN heterojunction was demonstrated. The diode gives a bright blue light emission located at ∼460 nm and a low threshold voltage of 2.7 V for emission. Based on the results of the photoluminescence (PL) and electroluminescence (EL) spectra, the origins of the EL emissions were studied in the light of energy band diagrams of ZnO–GaN heterojunction, and may attribute to the radiative recombination of the holes in p-GaN and the electrons injected from n-ZnO, which almost happened on the side of p-GaN layer. These results may have important implications for developing short wavelength optoelectronic devices.

Ultraviolet (UV) photodetectors (PDs) based on ZnO micro/nanowire (MNW) networks with Pt contacts have been fabricated on glass substrates. The PDs exhibited a high photosensitivity (5×10 3 ) for 365 nm UV light with a fast recovery time (0.2 s) at a reverse bias voltage of 2 V. The light induced modulation of Schottky barrier and MNW–MNW junction barrier was employed to account for the results. It was also observed that the PD had a high on–off ratio of 800 without external bias. The photovoltaic effect was proposed to explain the self-powered phenomenon.

The change in predictability of monthly mean temperature in a future climate is quantified based on the Community Climate System Model, version 4. According to this model, the North Atlantic overtakes the El Niño–Southern Oscillation (ENSO) as the dominant area of seasonal predictability by 2095. This change arises partly because ENSO becomes less variable and partly because the ENSO teleconnection pattern expands into the Atlantic. Over land, the largest change in temperature predictability occurs in the tropics and is predominantly due to a decrease in ENSO variability. The southern peninsula of Africa and northeast South America are predicted to experience significant drying in a future climate, which decreases the effective heat capacity and memory, and hence increases variance independently of ENSO changes. Extratropical land areas experience enhanced precipitation in a future climate, which decreases temperature variance by the same mechanism. Finally, the model predicts that surface temperatures near the poles will become more predictable and less variable in a future climate, primarily because melting sea ice exposes the underlying sea surface temperature, which is more predictable owing to its longer time scale. Some of these results, especially the change in ENSO variance, are known to be model dependent. This paper also advances the use of information theory to quantify predictability, including 1) deriving a quantitative relation between predictability of the first and second kinds; 2) showing how differences in predictability can be decomposed in two dramatically different ways, facilitating physical interpretation; and 3) proposing a sample estimate of mutual information whose significance can be tested using standard techniques.

ZnO nanomaterials have been shown to have novel applications in optoelectronics, energy harvesting and piezotronics, due to their coupled semiconducting and piezoelectric properties. Here a functional nanogenerator (FNG) based on ZnO nanowire arrays has been fabricated, which can be employed to detect vibration in both self-powered (SP) and external-powered (EP) modes. In SP mode, the vibration responses of the FNG can be measured through converting mechanical energy directly into an electrical signal. The FNG shows consistent alternating current responses (relative error < 0.37%) at regular frequencies from 1 to 15 Hz. In EP mode, the current responses of FNG are significantly enhanced via the piezotronic effect. Under a forward bias of 3 V, the sensor presented a sensitivity of 3700% and an accurate measurement (relative error < 0.91%) of vibration frequencies in the range 0.05–15 Hz. The results show that this type of functional nanogenerator sensor can detect vibration in both SP and EP modes according to the demands of the applications.

Long-term changes in land–atmosphere interactions during spring and summer are examined over North America. A suite of models from phase 5 of the Coupled Model Intercomparison Project simulating preindustrial, historical, and severe future climate change scenarios are examined for changes in soil moisture, surface fluxes, atmospheric boundary layer characteristics, and metrics of land–atmosphere coupling. Simulations of changes from preindustrial to modern conditions show warming brings stronger surface fluxes at high latitudes, while subtropical regions of North America respond with drier conditions. There is a clear anthropogenic aerosol response in midlatitudes that reduces surface radiation and heat fluxes, leading to shallower boundary layers and lower cloud base. Over the Great Plains, the signal does not reflect a purely radiatively forced response, showing evidence that the expansion of agriculture may have offset the aerosol impacts on the surface energy and water cycle. Future changes show soils are projected to dry across North America, even though precipitation increases north of a line that retreats poleward from spring to summer. Latent heat flux also has a north–south dipole of change, increasing north and decreasing south of a line that also moves northward with the changing season. Metrics of land–atmosphere feedback increase over most of the continent but are strongest where latent heat flux increases in the same location and season where precipitation decreases. Combined with broadly elevated cloud bases and deeper boundary layers, land–atmosphere interactions are projected to become more important in the future with possible consequences for seasonal climate prediction.

Data from 15 models of phase 5 of the Coupled Model Intercomparison Project (CMIP5) for preindustrial, historical, and future climate change experiments are examined for consensus changes in land surface variables, fluxes, and metrics relevant to land–atmosphere interactions. Consensus changes in soil moisture and latent heat fluxes for past-to-present and present-to-future periods are consistent with CMIP3 simulations, showing a general drying trend over land (less soil moisture, less evaporation) over most of the globe, with the notable exception of high northern latitudes during winter. Sensible heat flux and net radiation declined from preindustrial times to current conditions according to the multimodel consensus, mainly due to increasing aerosols, but that trend reverses abruptly in the future projection. No broad trends are found in soil moisture memory except for reductions during boreal winter associated with high-latitude warming and diminution of frozen soils. Land–atmosphere coupling is projected to increase in the future across most of the globe, meaning a greater control by soil moisture variations on surface fluxes and the lower troposphere. There is also a strong consensus for a deepening atmospheric boundary layer and diminished gradients across the entrainment zone at the top of the boundary layer, indicating that the land surface feedback on the atmosphere should become stronger both in absolute terms and relative to the influence of the conditions of the free atmosphere. Coupled with the trend toward greater hydrologic extremes such as severe droughts, the land surface seems likely to play a greater role in amplifying both extremes and trends in climate on subseasonal and longer time scales.

We describe the use of individual zinc oxide (ZnO) micro/nanowires in an electrochemical biosensor for uric acid. The wires were synthesized by chemical vapor deposition and possess uniform morphology and high crystallinity as revealed by scanning electron microscopy, X-ray diffraction, and photoluminescence studies. The enzyme uricase was then immobilized on the surface of the ZnO micro/nanowires by physical adsorption, and this was proven by Raman spectroscopy and fluorescence microscopy. The resulting uric acid biosensor undergoes fast electron transfer between the active site of the enzyme and the surface of the electrode. It displays high sensitivity (89.74 μA cm−2 mM−1) and a wide linear analytical range (between 0.1 mM and 0.59 mM concentrations of uric acid). This study also demonstrates the potential of the use of individual ZnO micro/nanowires for the construction of highly sensitive nano-sized biosensors.

A ZnO nanowire (NW) array ultraviolet photodetector (PD) with Pt Schottky contacts has been fabricated on a glass substrate. Under UV light illumination, this PD showed a high photo-to-dark current ratio of 892 at 30 V bias. Interestingly, it was also found that this PD had a high sensitivity of 475 without external bias. This phenomenon could be explained by the asymmetric Schottky barrier height (SBH) at the two ends causing different separation efficiency of photogenerated electron–hole pairs, which resulted in the formation of photocurrent. It is anticipated to have potential applications in self-powered UV detection field.