Figure 6

Plan-view SEM images of ZnO nanostructures. They are grown (a) without surfactants, (b) with 0.1 ml PEI, and (c) with 2.5 mg of sodium citrate (per 40 ml of reaction solution), at 0.05 M, 80°C for 5 h. (d) PL spectra of ZnO nanostructures in (a), (b), and (c). It is well known that the optical properties of ZnO nanostructures are crucially dependent on their morphology. In addition, the optical properties of ZnO nanostructures would be improved due to surface passivation effects of polymer surfactants [27, 28]. Thus, the PL measurements were performed to evaluate the GSK872 molecular weight optical quality of the obtained ZnO nanostructures, and the corresponding results were shown in Figure 6d. It can be seen that the PL spectrum of the ZnO nanorods grown with no surfactant exhibits a dominant UV emission at 377 nm, along with a weak visible emission around 520 nm. Generally, the UV emission is due to the near-band edge (NBE) emission of ZnO, and the visible emission can be attributed to intrinsic defects such as oxygen vacancies [29, 30]. For the ZnO nanoneedles or platelets, grown with the addition of PEI or sodium citrate, the PL spectrum presents a unique UV emission (377 nm),

LY2874455 manufacturer but the defect-related visible emission is suppressed, which is attributed to the surface passivation effects of surfactants via the adsorption in different crystal faces and modification of the surface free energy. Furthermore, the intensity of NBE emission varies greatly with the morphology of ZnO nanostructures

(nanorods, nanoneedles, or nanoplatelets), demonstrating that the photoluminescence property of ZnO nanostructures is adjusted by introducing different surfactants. Conclusions In conclusion, the morphology evolution of the ZnO nanostructures was well monitored by tuning the hydrothermal growth parameters, such as seed layer, solution concentration, reaction temperature, and surfactant. It was found that both next deposition methods and thickness of the seed layer could affect the orientation and morphology of the resulting ZnO nanorods; moreover, the length of ZnO nanorods depended mainly on the reaction temperature, while the diameter was closely related with the solution concentration. In addition, the morphology, as well as the optical properties, was tuned effectively by introducing various surfactants. The ease of synthesis, ability to control morphology, and optical properties make this approach promising in LEDs, sensors, and other applications. Acknowledgements This work was financially supported by ‘the Fundamental Research Funds for the Central Universities’ (grant no. 2652013067). References 1. Wu WB, Hu GD, Cui SG, Zhou Y, Wu HT: Epitaxy of DNA Damage inhibitor vertical ZnO nanorod arrays on highly (001)-oriented ZnO seed monolayer by a hydrothermal route. Cryst Growth Des 2008, 8:4014–4020.CrossRef 2.