Fabrication of designed architectures of Au nanoparticles on solid substrate with printed self-assembled monolayers as templates

This paper provides a convenient method for fabricating architectures of Au nanoparticles on solid substrate, with precise position and density control. Our strategy is to modify Au substrate with self-assembled monolayers (SAMs) terminated with different functional groups. They were chosen to be -CH₃/-NH₂ or -CH₃/-SH according to their affinities to Au nanoparticle. Au nanoparticles assemble selectively on -NH₂ or -SH terminated locations, the -NH₂ functional group binding electrostatically to the nanoparticles whereas the -SH groups bonding chemically. The SAMs, acting as guiding templates for Au nanoparticles, were fabricated by the microcontact printing (μCP) technique. A patterned or unpatterned SAM was prepared by using patterned or unpatterned poly(dimethyl)siloxane (PDMS) stamp, respectively. The coverage of -CH₃ terminated SAM in the contact region is controlled by changing the concentration of `ink' solution for the stamp. After immersing the printed SAM into -SH or -NH₂ thiol solutions for 2 h, a mixed SAM with a predetermined coverage of -SH or -NH₂ was formed in the contact regions, and a pure -SH or -NH₂ SAM was formed in the intervening area. The position and density of nanoparticles on the surface were determined by the distribution of the underlying functional groups.