Selective Growth of Patterned Monolayer Gold Nanoparticles on SU-8 through Photoreduction for Plasmonic Applications

This paper presents a simple approach for the selective growth of patterned monolayer gold nanoparticles (AuNPs) and bulk gold nanostructures through photoreduction. Photoreduction can occur on the surface of SU-8 but not on the surface of poly(methyl methacrylate) (PMMA). Therefore, a PMMA mask was introduced to the SU-8 surface to confine the area for AuNP production. We developed a residual layer-free nanotransfer printing process to transfer the PMMA mask from a perfluoropolyether mold onto the SU-8 surface. After the exposure of a drop of HAuCl4 over the SU-8 surface masked by PMMA to UV light, AuNPs formed on the uncovered SU-8 surface. Gold nanostructures with various shapes, including nanodisks, nanorings, nanorod dimers, and asymmetric U-shaped split-ring resonators, were produced through the proposed approach. The optical properties of the fabricated nanostructures were investigated and found to be consistent with the simulation. Overall, this study provides a reliable and predictable process for fabricating gold nanostructures with various shapes, which can be beneficial for plasmonic applications.