Synthesis and nonlinear optical characterization of nanostructured gold/polymer composites and suspensions

Nanometric gold particles were synthesized by a liquid/liquid phase-transfer reaction. Composites of these particles were prepared by free-radical polymerization of suspensions of the particles in styrene and methyl methacrylate monomer. Concentrations of 1.0, 1.3, and 4.4 mg/ml were prepared, with no noticeable agglomeration of particles during processing. These composites and toluene suspensions (0.18 mg/ml) showed a linear absorption peek at 530 nm, which is characteristic of nanosized gold. High-resolution electron microscopy measurement showed that the particle diameters varied from 5 to 10 nm. Degenerate four-wave mixing experiments at 532 nm yielded, on 10-micron films, a maximum value of 1.0 x 10(-10) e.s.u. for the third-order nonlinear optical susceptibility. The toluene suspension had a susceptibility of 7.7 x 10(-12) e.s.u.