A sensitive method to determine dopamine in the presence of uric acid based on In2O3 nanosheet arrays grown on 3D graphene.

A nonenzymatic voltammetric assay for dopamine (DA) was developed based on the combination of three-dimensional graphene (3D Gr) and indium oxide nanosheet arrays (In2O3 NSAs). 3D Gr was prepared by chemical vapor deposition (CVD), and In2O3 NSAs were grown on its surface by hydrothermal synthesis. The results show that 3D Gr maintains a good porous structure (200 µm), and the pore size of In2O3 NSAs is 0.50 µm. Differential pulse voltammetry (DPV) is mainly used to determine the electrochemical properties of In2O3 NSAs/3D Gr. It possesses a sensitivity of 2.69 µA·µM-1·cm-2 towards DA (5-60 µM) at 0.14 V, and the detection limit (LOD) is 0.10 µM (S/N = 3). The recoveries obtained for spiked samples in the real sample detection is 105 (± 8)%. Graphical abstractSchematic representation of DA sensitive detection by growing In2O3 nanosheets arrays on three-dimentional graphene modified ITO.

Influence of the carrier concentration on the piezotronic effect in a ZnO/Au Schottky junction.

The piezotronic effect, which utilizes the piezopotential to engineer the interface characteristics, has been widely exploited to design novel functional device or to optimize the device performance, which is intimately related to the carrier concentration. Here, by constructing a general Schottky diode, the piezotronic effect dependence on the carrier concentration was investigated systematically using ultraviolet (UV) illumination. Scanning Kelvin Probe Microscopy was employed to quantify the carrier concentration in ZnO nanorods under UV illumination. The results showed that the carrier concentration increases with increasing light intensity and an average value of up to 5.6 × 10(18) cm(-3) under 1.2 mW cm(-2) light illumination was obtained. Furthermore, with increasing UV light intensity, an increasingly imperceptible variation in the current-voltage characteristics under strain was observed, which finally disappeared under 1.2 mW cm(-2) light illumination. This phenomenon was attributed to the weakened modulation ability of the piezopotential due to the strengthened screening effect. In addition, the gradual disappearing in the barrier also contributed to the gradual disappearance of the piezotronic effect. This study provides an in-depth understanding of piezotronics, which could be extended to other piezoelectric devices and guide the design and optimization of piezotronic and even piezophototronic devices.

Piezotronic interface engineering on ZnO/Au-based Schottky junction for enhanced photoresponse of a flexible self-powered UV detector.

Exploiting piezoelectric effect to engineer material interface has been confirmed as a promising way to optimize the performance of optoelectronic devices. Here, by using this effect, we have greatly improved the photoresponse of the fabricated ZnO/Au Schottky junction based self-powered UV detector. A 440% augment of photocurrent, together with 5× increased sensitivity, was obtained when the device was subjected to a 0.580% tensile strain. The enhancement can be attributed to the facility separation and extraction of photoexcites due to the formation of the stronger and expanding built-in field, which is a result of charge redistribution induced by piezoelectric polarization at the ZnO/Au interface. This study not only can strengthen the understanding of piezoelectric effects on energy devices but also can be extended to boost performances of optoelectronic devices made of piezoelectric semiconductor materials.

A self-powered ultraviolet detector based on a single ZnO microwire/p-Si film with double heterojunctions.

Recently, self-powered devices based on a p-n heterojunction have been widely reported, but there are few reports about self-powered UV detectors based on a single ZnO microwire/p-Si film with double heterojunctions. Compared with the common p-n heterojunction type devices, the fabricated devices with double heterojunctions based on a single n-type ZnO microwire and a p-type Si film exhibited excellent electrical performance such as an ideal rectification behaviour and a low turn-on voltage. At zero bias, the fabricated device can deliver a photocurrent of 71 nA, a high photosensitivity of about 3.17 × 10(3) under UV light (0.58 mW cm(-2)) illumination and a fast rising and falling time of both less than 0.3 s. Furthermore, the photocurrent increased with the rising of the optical intensity at low power intensities. The physical mechanism has been explained by energy band diagrams.

Investigation on the mechanism of nanodamage and nanofailure for single ZnO nanowires under an electric field.

The electrical service behavior of ZnO nanowires (NWs) with various diameters was investigated by a nanomanipulation technique. The nanodamage and nanofailure phenomena of the ZnO NWs were observed when external voltages were applied. The threshold voltages of the ZnO NWs increased linearly from 15 to 60 V with increasing diameter. The critical current densities were distributed from 19.50 × 10(6) to 56.90 × 10(6) A m(-2), and the reciprocal of the critical current density increased linearly with increasing diameter as well. The thermal core-shell model was proposed to explain the nanodamage and nanofailure mechanism of ZnO NWs under an electric field. It can be expected that the investigation on the nanodamage and nanofailure of nanomaterials would have a profound influence on practical applications of photoelectric, electromechanical, and piezoelectric nanodevices.

Size dependence of dielectric constant in a single pencil-like ZnO nanowire.

Scanning conductance microscopy (SCM) is used to measure the dielectric constant of a single pencil-like zinc oxide (ZnO) nanowire with the diameters ranging from 85 to 285 nm. As the diameter decreases, the dielectric constant of ZnO nanowire is found to decrease from 6.4 to 2.7, which is much smaller than that of the bulk ZnO of 8.66. A core-shell composite nanowire model in terms of the surface dielectric weakening effect is proposed to explore the origin of the size dependence of dielectric constant, and the experimental results are well explained.