It is evident that the rise of the absorption edge near the band edge for the pure ZnO nanorods (sample S1) increased gradually, while it becomes sharper for the Cu-doped ZnO nanorods (samples S2 to S5), indicating the presence of localized states within the bandgap. The undoped ZnO nanorods (sample S1)

showed lower transmittance (approximately 70%) compared to the Cu-doped ZnO nanorods. This could be attributed to the scattering either from the unfilled inter-columnar volume and voids or from the inclined nanorods. Using BMS202 chemical structure Cu(CH3COO)2 as the Cu source (samples S2 and S3), the total transmittance increased, reaching approximately 80%, and was found to be independent on the amount of Cu dopants. Comparatively, using Cu(NO3)2 as the Cu precursor (samples S4 and S5), the total transmittance increased further, reaching approximately 90%. Lin et al. [37] related the presence of Gilteritinib solubility dmso oxygen vacancies to the transmittance ratio, where lower transmittance indicates that there are AG-881 datasheet more oxygen vacancies and vice versa.

However, in the study reported here, we can attribute the reduction in the total transmittance to the increase in the rod diameter for the samples doped with Cu(CH3COO)2. It can be seen that at the absorption edge for Cu-doped ZnO nanorods, the slight blueshift indicates that the bandgap was tuned by the incorporation of the Cu dopants. It may be observed that there are obvious interference fluctuations in the transmission spectra when Cu(CH3COO)2 was used as the Cu precursor (samples S2 and S3). These fluctuations can be attributed to the presence of scattering centers [36]. Figure 6 Total transmittance spectra of undoped and the Cu-doped ZnO nanorods. Conclusions In conclusion, we explored the effect of Cu precursors (Cu(CH3COO)2 and Cu(NO3)2) and concentration on the structural, morphological, and optical properties of the hydrothermally synthesized Cu-doped

ZnO nanorods. The XRD results revealed that the slight changes in the lattice parameters have occurred due to the substitution of Zn2+ by Cu2+ and the formation of PTK6 defect complexes. The nanorods doped with Cu(NO3)2 had less crystallinity than the nanorods doped with Cu(CH3COO)2, where the maximum compressive lattice strain (−0.423%) was obtained when 2 at.% of Cu was added from Cu(NO3)2. From the SEM studies, Cu(CH3COO)2 was found to be an effective precursor for the formation of Cu-doped ZnO nanorods with large diameter. Conversely, Cu-doped ZnO nanorods with a small diameter (approximately 120 nm when 2 at.% was added) can be obtained when Cu(NO3)2 is used as a Cu precursor due to the lack of hydrolysis process. UV and green emission peaks at 378 and 544 nm were observed for all samples and are attributed to the near-band edge UV emission and the defect-related emission, respectively.