Recent advances in ZnO nanostructures and thin films for biosensor applications: review.

We report on the effects of post-growth hydrothermal treatment and thermal annealing on properties of vertically aligned ZnO nanowires arrays (NWs). The samples were electrochemically deposited (ECD) on indium–tin oxide (ITO)-coated glass substrates and subjected to post-growth hydrothermal treatment (HT) at 150 °C and, for the purpose of comparison, to conventional thermal annealing (CTA) in a furnace at 150, 400, and 600 °C in air. Sample characterization was realized using X-ray diffraction (XRD), SEM, TEM, selected-area electron diffraction (SAED) and photoluminescence (PL). Thermal annealing does not induce significant changes of morphology, but influences the structural and optical properties. At the same time we found that the HT induces more significant improvement of properties of ZnO nanowires arrays (ZnO NWs) on ITO. The results show that the ECD ZnO NWs are single-crystalline with hexagonal structure and c-axis perpendicular to ITO substrate. Only one peak at about 379 nm was observed in the photoluminescence spectra at room temperature which showed an intensity increase after hydrothermal treatment. This corresponds to the increase of the optical quality of ZnO NWs. The best optical quality for ZnO NWs was found after the hydrothermal treatments at 150 °C in our experiment. The high-quality electrodeposited NW layers have been used, after sensitization with the highly absorbing D149 dye, as a photoanode in dye sensitized solar cells (DSCs) and the impact of post-growth treatment of the nanowires on DSCs performances has been evaluated. The photocurrent of the solar cells increased significantly after HT or CTA at 150 °C leading to a maximum overall photovoltaic conversion efficiency (PCE) of 0.66% at 100 mW/cm2, based on short-circuit photocurrent density, open-circuit voltage and fill factor of 3.283 mA/cm2, 0.606 V and 33.3%, respectively. The obtained results are interesting in view of the low layer roughness and pave the way for implementation of high-quality electrodeposited ZnO NW arrays in DSCs fabrication.

Well-aligned arrays of vertically oriented ZnO nanowires electrodeposited on ITO-coated glass and their integration in dye sensitized solar cells

Synthesis and characterization of ZnO, CuO and a mixed Zn and Cu oxide

A systematic study of the role of KCl on the electrodeposition of ZnO nanowire arrays from the reduction of oxygen in ZnCl2 solutions was performed. Besides its role as a supporting electrolyte, other major effects were found. An increase of KCl concentration ([KCl]) considerably decreased the rate of O2 reduction. The consequent decrease in OH- production rate resulted in an augmentation of the ZnO deposition efficiency, from a value around 3% for [KCl] = 5 × 10-2 M to more than 40% for [KCl] = 3.4 M. The increase of the deposition efficiency mainly resulted in an enhancement of the longitudinal growth rate. However, high [KCl] (>1 M) also favored the lateral growth of the ZnO nanowires, resulting in diameters as big as 300 nm (in comparison to the diameter of 80 nm obtained for [KCl] < 1 M). The observed effects were discussed in terms of Cl- ion adsorption on the cathode surface. The possible preferential adsorption of the anion on the (0001) ZnO surface was emphasized. Transmission electron microscopy...

G. Y. Wang

Papers

Structure study of electrodeposited ZnO nanowires

Study on the microstructure and growth mechanism of electrochemical deposited ZnO nanowires