Effect of Colloidal Medium on the Shelf-Life and Stability of Gold Nanorods Prepared by Seed-Mediated Synthesis.

Gold nanorods (GNRs) owing to their tunable longitudinal surface plasmon resonance in tissue transparent near infrared region have potential applications (like cancer imaging, surface enhanced Raman spectroscopy, cancer targeting, drug delivery and optical hyperthermia) in nanomedicine. Success of these diagnosis/therapy options depends on the plasmonic properties of gold nanorods, which are influenced by the interaction of GNRs with the colloidal medium. In this article, a systematic study is performed to evaluate the effect of colloidal medium on shelf life and stability of gold GNRs. As-synthesized GNRs are preserved in four aqueous media (deionized water, pluronic F-127, CTAB solution and growth solution) and their stability is investigated by closely monitoring the changes in the plasmonic signatures by UV-Visible spectroscopy and variation in hydrodynamic size by photon correlation spectroscopy for 30 days. As-synthesized GNRs are most stable in deionized water followed by pluronic F-127, CTAB and growth solution. The vast difference in the colloidal stability of GNRs in different media is due to the differences in surface driven unzipping of gold in these aqueous media.