Fabrication of Twin-Linked Gold Nanoparticles and Their Linear/Nonlinear Optical Properties

We developed a new method for the preparation of connected-spherical gold nanoparticles (GNPs), which exhibited surface plasmon resonance properties different from those of spherical GNPs. In this method, citrate-stabilized GNPs in spherical form were connected to each other by use of cetyltrimethylammonium bromide, and then the progressing connection of GNPs in solution was restrained by the coverage of thin silica layer on them. The connectivity of GNPs was analyzed by transmission electron microscopy images and optical absorption spectra. The modulus of the third-order nonlinear optical susceptibility of the twin-linked GNPs film was estimated as 1.61 × 10−9 esu (the real and imaginary parts were 1.55 × 10−9 and −4.24 × 10−10 esu, respectively).