Gold Nanoparticle Plasmonic Superlattices as Surface-Enhanced Raman Spectroscopy Substrates

Metal colloids are of great interest in the field of nanophotonics, mainly due to their morphology-dependent optical properties, but also because they are high-quality building blocks for complex plasmonic architectures. Close-packed colloidal supercrystals not only serve for investigating the rich plasmonic resonances arising in strongly coupled arrangements but also enable tailoring the optical response, on both the nano- and the macroscale. Bridging these vastly different length scales at reasonable fabrication costs has remained fundamentally challenging, but is essential for applications in sensing, photovoltaics or optoelectronics, among other fields. We present here a scalable approach to engineer plasmonic supercrystal arrays, based on the template-assisted assembly of gold nanospheres with topographically patterned polydimethylsiloxane molds. Regular square arrays of hexagonally packed supercrystals were achieved, reaching periodicities down to 400 nm and feature sizes around 200 nm, over areas u...