The role of halide adsorption on the localized surface plasmon resonance (LSPR) of thermally assembled surfactant-free Au nanostructures is investigated. Previously, it was shown that the exposure of surfactant stabilized, solution dispersed, metallic nanostructures to ions results in a red shift and a dramatic dampening of the LSPR. A major drawback of such studies is that solution phase templates, upon exposure to ions, are (i) susceptible to aggregation and (ii) provide a surface which is much different from that of the intrinsic interface formed between halides and a Au nanostructure. The use of thermally assembled Au nanostructures circumvents these problems and provides access to the interaction of Au nanoparticles with the ions exclusively. Our results show that the adsorption of halogen ions (e.g. F-, Cl-, Br-, I-) on surfactant-free Au nanostructures induces the expected dampening of the LSPR, but where, in contrast to surfactant coated nanoparticles, the resonance is blue shifted. We attribute these observations to an increase in the electron density of the nanostructure upon exposure to halogen ions. Scanning electron micrographs confirmed that the morphology of these nanostructures were conserved before and after the exposure to ions.

Localized surface plasmon (LSPR) based optical detection of ions in aqueous solution

249th National Meeting (2015)

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