Growth of gold nanorods in gelled surfactant solutions

Gold nanorods have been actively studied for new nanotechnological materials and industrial applications. It is well known that gold nanorods grow spontaneously in surfactant solutions, and a number of procedures for their preparation have been reported; however, the factors that determine the morphology have not been well understood. In this study, we observed the time series of the growth process of gold nanorods in gelled surfactant solutions by completely stopping the growth reaction. This growth process was compared to that in solution without gelation. The comparison indicates that the self-assembly of surfactant molecules affected the resulting shape, especially the short-axis length, of the nanorods. Small-angle neutron scattering (SANS) experiments revealed that the gelled solutions form lamellar structures, whereas nongelled systems form spherical micelles. On the bases of these results, we present a model showing that the short-axis length of gold nanorods is affected by a decrease in the spontaneous curvature of the outer surfactant layer and/or an increase in the bending modulus of the surfactant membrane neighboring the gold surface.

Relation between self-assembly of surfactant growth solution and thickness of gold nanorods.Figure optionsDownload high-quality image (87 K)Download as PowerPoint slideResearch highlights
► The growth of gold nanorods in gelled surfactant solutions was studied.
► SANS experiments revealed the gelled surfactant solutions self-assembled as lamellae.
► The lamellar structure affected the short-axis length of the gold nanorods.
► A curvature of surfactant layers around nanorods is important for the nanorod growth.