The US nanoparticles have been assembled into US nanorods and arrayed nanorod bundles by a thioglycolic acid (TGA) assisted hydrothermal processes using sodium sulfide (Na2S) and thiourea ((NH2)(2)CS) as the sulfur source, respectively. High-resolution transmission electron microscopy (HRTEM) shows that the US nanorods are single crystalline and the arrayed nanorod bundles are polycrystalline in nature. It is believed that the US nanorods were formed through the cluster-to-cluster oriented attachment mechanism, while the US nanorods bundles were formed through the particle-to-particle oriented attachment mechanism. In addition, the optical properties of US nanostructures were characterized by photoluminescence spectra (PL) and Raman spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.