High-resolution transmission electron microscopy (HRTEM) micrographs of the samples were taken via a JEOL HRTEM (JEM-2100F), operating at an accelerating voltage

of 200 kV. Characterization by X-ray diffraction and photoluminescence have been previously performed and published [17, 18] (see Additional file 1). A preliminary PEC cell testing has been carried out to characterize the photocurrent. The find protocol prepared NSs on ITO-coated glass substrate were used as working electrode. The test was done by using a VersaSTAT 3 potentiostat (Ametek Princeton Applied Research, Oak Ridge, TN). A solar light simulator (Oriel Instrument) was used to generate an equivalent intensity of one sunlight (100 mWcm−2) AM 1.5 G radiation. A conventional three-electrode cell was constructed

with the samples as working electrode, a platinum wire as counter electrode, and Ag/AgCl (in 3 M KCl) as reference electrode. The AG-881 supplier electrodes were immersed in a 1 M KCl electrolyte solution throughout the test. Since it was a PEC cell, the area of illumination is the same as the area which was immersed in the electrolyte, which was 1 cm × 2 cm2 for the sample of ZnO NRs as working electrode. While for Si/ZnO sample, this website it was 1 × 1 cm2. Current density was calculated in each case for comparison purpose. Results and discussion As shown by the FESEM images in Figure 2, both of the ZnO NRs grown by HTG and VTC methods show no difference in terms of general appearance. A well-defined hexagonal shape indicates crystalline structure of the ZnO NRs grown by both methods. But basically, the VTC-grown NRs are higher in diameters and lengths because the growth rate is higher for VTC method. Both of them show hexagonal structures while HTG-grown sample provides higher number

of density. Figure 2 Morphologies of the planar ZnO NRs. Surface and cross-section FESEM images of the (a, b) HTG- and (c, d) VTC-grown Baf-A1 ic50 ZnO NR arrays. Figure 3 shows the photocurrent-time plots of the as-grown ZnO NRs prepared on ITO-coated glass substrate using VTC and HTG methods. Despite of their similar morphologies, the VTC-grown ZnO NRs showed a higher significant photocurrent density (about 0.06 mA/cm2) compared to HTG-grown ZnO NRs (about 0.01 mA/cm2). Our results are comparable to the photocurrent density of the VTC-grown ZnO NWs (0.01 to 0.07 mA/cm2) [19] and HTG prepared-nitrogen-doped ZnO NRs (about 0.01 mA/cm2) [20] reported by other groups. The reason of the higher photocurrent effect for VTC-grown ZnO NRs could be due to the high temperature growth process, thus, resulted in the less structure defects in the ZnO NRs. However, the photocurrent response of the VTC-grown ZnO NRs was slower, which took more than 30 s for the current to reach its optimum value under illumination.