PL spectra of undoped ZnO and Zn1−x Cu x O samples with the Cu contents of 7%, 18%, and 33%. As can be clearly observed from Figure 6, the undoped ZnO possesses a strong near-band-edge UV emission together with a weak visible emission, indicating that the undoped ZnO nanostructures have a fairly high quality with low defect concentration (its PL intensity was 10 times magnified). After Cu is introduced, the UV emission is rapidly suppressed while the visible luminescence is greatly enhanced compared with the undoped

counterpart, suggesting the poorer crystallinity and greater level of structural defects introduced by Cu ion incorporation into ZnO. The intensity ratio of the visible band emission to the UV peak increases from approximately 0.2 to approximately 150 with the Cu content change from 0% to 33%, demonstrating AG-014699 in vitro that the Cu doping strongly increases the concentration of defects. Nevertheless, selleck chemical the defects are believed to significantly improve a variety of surface properties, such as heterogeneous catalysis, corrosion inhibition, and gas sensing, which have been addressed by theoretical calculation and experimental data [38–40]. Furthermore, we have also presented in the inset the

enlarged view of the UV peak between 360 and 405 nm. It is obvious that the introduction of Cu will cause a little redshift of the UV peak (34 meV under Cu contents from 0% to 33%) compared with the undoped one, i.e., a reduction of ZnO bandgap Isoconazole caused by the Cu doping. We have also employed the high-spatial resolution CL technique at various locations within the same cross structure to explore the defect distribution and the local optical properties in an individual Zn1−x Cu x O micro-cross. A typical secondary electron (SE) image of such an individual micro-cross is shown in Figure 7a. Clearly, there is a 200-nm square hole in the center of the stem, which confirms that the central zone is a cubic prism.

Figure 7b presents the corresponding panchromatic CL image at the same place. Interestingly, the cross structure exhibits inhomogeneous luminescence. The strong CL emissions are mainly focused on the middle of the four-folded branched nanorod according to the intense distribution curve obtained along the axial line (yellow curve). Figure 7 SE and CL images of a single micro-cross structure with its corresponding spectra. (a) SE image of the Zn1−x Cu x O micro-cross. (b) CL panchromatic image padded with the brightness distribution curve along the axial line of the sample. (c) Corresponding CL spectra at five different locations along the axial line of one branched nanorod. (d) CL ratio and Cu content variation with different positions of the branched nanorod. Figure 7c illustrates the typical CL spectra, which are acquired at the center stem (noted as ‘0’ on the axis in Figure 7b) and four different locations along one branched nanorod.