Size-Controlled Synthesis and Optical Properties of Small-Sized ZnO Nanorods

One-dimensional ZnO nanorods with very small diameters in the range of 10 +/- 2 nm were fabricated by facile sol-gel and hydrothermal methods. The structural, morphologic and optical properties of ZnO nanorods were investigated using X-ray diffraction, electron microscopy, and photoluminescence (PL). A strong ultraviolet (UV) near-band-edge emission peak at 373 nm (3.32 eV) was observed, while the deep-level emission band was too weak to observe at room temperature. The UV emission peak has an obvious blue shift compared to the samples with a larger size, which was attributed to the size-decreased nanorods. The large ratio of the UV emission to visible emissions in PL spectra can be obtained in small-sized ZnO nanorods. Furthermore, the morphologic and optical properties of ZnO nanorods can be adjusted by controlling the reactant concentration and reaction time. The possible growth mechanism of the nanorods is proposed.