One-dimensional self-assembly of gold nanoparticles for tunable surface plasmon resonanceproperties

Abstract

The localized surface plasmon resonance (LSPR) is a collective oscillation of thenanoparticle conduction electrons. LSPR excitation in silver and gold nanoparticlesproduces strong extinction and scattering spectra that in recent years have been usedfor important sensing and spectroscopy applications. Tuning the optoelectronicproperties by controlling coupled SP modes in metals is one of the major challenges inthe area of metal nanomaterials. Here we develop a simple method to fabricatelinear-chainlike aggregates of gold nanoparticles (so-called nanochains), tuning the linearoptical properties in a wide wavelength range from visible to the near infrared. Theaggregation behaviour and linear self-assembly mechanism of citrate-stabilizedgold colloids as provoked by the addition of cetyltrimethylammonium bromide(CTAB) are also analysed. The CTAB with appropriate concentration serves as the‘glue’ that can link the {100} facets of two neighbour Au NPs, which leads to ananisotropic distribution of the residual surface charge, and this extrinsic electric dipoleformation is responsible for the linear organization of the gold NPs into short chains.