Fabrication and Structure of Alginate Gel Incorporating Gold Nanorods

The gelation of sodium alginate incorporating gold nanorods was investigated. The hybrid gel was obtained by mixing calcium ions with a gel precursor (alginate + nanorod). The gel displayed two plasmon bands in the visible and near-infrared region. The shapes of the hybrid gel grains were controllable, like sphere, ring, and rod. Furthermore, the release of the gold nanorods from the gel phase was observed in a saline solution, accompanying the gel collapse to alginate fibers. Moreover, in the structural investigation of the hybrid gel using small-angle X-ray scattering, it was confirmed that alginate fibers were tightly condensed on the nanorod and formed a shell on it. Such condensation or shell formation resulted from the electrostatic interaction of alginate with hexadecyltrimethylammonium bromide, which protects the nanorods. The hybrid gel retained the same amount of water as the neat gel, although the water content (30 wt %) in a shell on a nanorod was far less than that (98 wt %) of bulk gel.