Preparation and Stability of Template-Synthesized Metal Nanorod Sols in Organic Solvents

Abstract

Gold and silver nanorods of diameter 40 and 90 nm and having a variety of aspect ratios (length/diameter) were prepared using the template synthesis approach. After template synthesis, the nanorods were freed from the template membrane and dispersed in either hexafluoro-2-propanol (HFIP) or CHCl 3 . The stability of these nanorod sols was monitored using visible absorption spectroscopy. For both the Au and Ag nanorods (in both solvents), sols prepared from the 90-nm diameter nanorods were found to be less stable than sols prepared from the 40-nm diameter nanorods. The addition of the polymeric stabilizers poly(vinylpyridine) or poly(vinylpyrrolidone) did not enhance the stability of these nanorod sols. In addition to these studies of sol stability, UV−vis absorption spectroscopy was used to investigate the plasmon absorption band of these sols. The wavelength of maximum absorbance of the plasmon resonance band (λ max ) for both Ag and Au sols was shifted to higher wavelengths when the nanorod diameter was increased from 40 to 90 nm. In addition, the λ max values for sols prepared in CHCl 3 were red-shifted relative to analogous sols prepared in HFIP.