One-dimensional nanostructure ZnO nanorods (NRs) with controlled lengths and diameters were synthesized by the growth of colloidal nanoparticles and then characterized by XRD, TEM, Raman, PL and UVâVis. The growth time parameter plays an important role in the formation process of ZnO NRs. The as-prepared nanoparticles has spherical shape with size about 4Â nm, and formed single-crystalline NRs of length up to 150Â nm and 16â20Â nm in diameters. Raman spectra of the as-grown ZnO nanorods revealed the existence of Raman silent modes B1(low) and B1(high) at 273 and 538Â cmâ1 respectively. Photoluminescence (PL) and UVâvisible absorption measurements have been performed at room temperature. The PL spectrum showed that the relative intensity of ultraviolet (UV) and defect bands depend on the length of ZnO nanorods. The peak of photoluminescence of UV band around 395Â nm is strongly enhanced when the length of ZnO nanorods is reduced and the humps around 580Â nm decreases. Keywords: ZnO nanorods, Raman spectroscopy, UVâVis spectroscopy, Photoluminescence spectroscop

ZnO nanocrystals with various sizes were prepared and characterized. Their photoluminescence dynamics has been investigated at low temperatures. For the smallest particles (3 nm), a defect-induced long-lived photoluminescence occurs around 2.5 eV which is slowed down at decay times longer than 3 ns when sample temperature T decreases. From thermal quenching of the 2.5 eV band, the exciton dissociation energy at defect centers is estimated around ∼11.8 meV. For larger crystallites (10 and 20 nm), the ultraviolet emission observed at 3.32 eV decays in less than 85 ps and follows a Varshni law [Y. P. Varshni, Physica (Amsterdam) 34, 149 (1967)].