Synthesis of Absorption-Dominant Small Gold Nanorodsand Their Plasmonic Properties.

Absorption-dominant small Au nanorodswith diameters of less than10 nm are prepared using a facile seed-mediated growth method. Thediameters of the small gold nanorods range from 6 to 9 nm, and theirlengths vary from 16 to 45 nm. Their aspect ratios can be tailoredfrom 2.7 to 4.7. As a result, the longitudinal plasmon resonance wavelengthsare readily tunable from ∼720 nm to ∼830 nm by changingthe seed-to-Au(III) molar ratio in the growth solution. The fractionsof the scattering in the total extinction of the small Au nanorodsare found to be in the range of 0.005 to 0.025 with finite-differencetime-domain simulations, confirming that the extinction values ofthese small Au nanorods are dominantly contributed to by the lightabsorption. Moreover, the small Au nanorod sample is coated with adense silica layer for photothermal therapy with three cell lines.It shows improved photothermal therapy performance compared to a largeAu nanorod sample for the same cellular Au contents. Our study suggeststhat small Au nanorods are promising light absorbers and photothermaltherapy agents. [ABSTRACT FROM AUTHOR]