This study reports on a new method for manipulating the size and shape of silver nanostructures using supercritical carbon dioxide (CO2) in the presence of polyvinyl pyrrolidone (PVP) and ethylene glycol (EG). The temperature and pressure of CO2 as well as the ratio of the capping agent PVP to the precursor of silver nitrate are used to control the growth of the silver nuclei and grains during the synthesis of silver nanostructures in ethylene glycol. The as-synthesized nanostructures were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray powder diffraction (XRD). The results indicate that the aspect ratio of silver nanostructures, in particular, increases with an increase in the temperature and pressure of supercritical CO2 from 3.5 to 50. (C) 2010 Elsevier B.V. All rights reserved.