Light-induced in situ active tuning of the LSPR of gold nanorods over 90 nm.

We demonstrate an easy and controllable method for light-induced active tuning of the longitudinal surface plasmon resonance (LSPR) of gold nanorods (AuNRs) over ∼94nm. The red-shift of the LSPR can be controlled by varying the time of exposure to a 532 nm laser. The tuning is achieved by photo-induced dissolution of individual AuNRs by sodium dodecyl sulfate (SDS) under continuous illumination. The dissolution of the AuNRs increases the aspect ratio, and consequently the LSPR exhibits a gradual but large redshift. A key feature is that it is possible to selectively tune the LSPR of a specific AuNR in a group while leaving the others totally unaffected. Such controllable, light-induced, post-synthesis fine-tuning of the LSPR is useful for tailoring the plasmonic response of individual AuNRs for a wide range of applications.

Synthesis of Complex Nanoparticle Geometries via pH-Controlled Overgrowth of Gold Nanorods.

We show that many complex gold nanostructures such as the water chestnut, dog bone, nanobar, and octahedron, which are not easily accessible via a direct seed-growth synthesis approach, can be prepared via overgrowth of the same gold nanorods by varying pH and Ag concentrations in the growth solution. Overgrown nanostructures' shapes were determined by the rate of gold atom deposition, which is faster at higher pH. In the presence of AgNO3, codeposition of gold and silver atoms affects the shapes of overgrown nanostructures, particularly at high pH.