Vertically aligned undoped ZnO nanowires and Sn doped ZnO nanonails are synthesized on a silicon substrate using vapor-solid technique, without using a catalyst or predeposited buffer layers. The structure and morphology of the as-synthesized nanonails and nanowires are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and electron dispersive X-ray spectroscopy. The results showed that the use of SnCl(2) is critical for the formation of nanonails. Without it, only ZnO nanowires can be obtained. The photoluminescence properties are also investigated at room temperature. The UV peaks of undoped ZnO nanowires and doped nanonails are located at 379.5 and 385.4 nm, respectively. This red shift of 6 nm in the Sn doped samples indicates a reduction of the ZnO band gap caused by the Sn doping. The dominance of the green emission in the nanowires sample indicates that it exhibits a much higher defect concentration than the nanonails. (C) 2011 Elsevier B.V. All rights reserved.