Self-Assembly of a Two-Dimensional Au-Nanocluster Superlattice and Its Photoluminescence Spectra

A solution of dodecanethiol-capped Au nanoparticles (diameter ∼ 2 nm), prepared through reduction of hydrogen tetrachloroaurate, was coated on a patterned cross-linked polydimethylsiloxane (PDMS) film (thickness ≥ 1 m) comprising array of square pillars, by either spin- or dip coating. Drying in ambient conditions for about 5 days resulted in the self-assembly of a superlattice (300 nm × 300 nm × 90 nm) of monodisperse nanoparticle clusters for the dip-coated samples, the clusters occupying the interstitial locations between four adjacent pillars on the polymer surface. Initial patterning of the PDMS is found to give rise to new photoluminescence bands in the near ultraviolet and visible regions, which the nanoclusters quench.