High‐Temperature Large‐Scale Self‐Assembly of Highly Faceted Monocrystalline Au Metasurfaces

Localized surface plasmon resonance (LSPR) devices based on resonant metallic metasurfaces have shown disruptive potential for many applications including biosensing and photocatalysis. Despite significant progress, highly performing Au plasmonic nanotextures often suffer of suboptimal electric field enhancement, due to damping effects in multicrystalline domains. Fabricating well-defined Au nanocrystals over large surfaces is very challenging, and usually requires time-intensive multi-step processes. Here, presented are first insights on the large-scale self-assembly of monocrystalline Au nano-islands with tunable size and separation, and their application as efficient LSPR surfaces. Highly homogeneous centimeter-sized Au metasurfaces are fabricated by one-step deposition and in situ coalescence of hot nanoparticle aerosols into a discontinuous monolayer of highly faceted monocrystals. First insights on the mechanisms driving the high-temperature synthesis of these highly faceted Au nanotextures are obtained by molecular dynamic and detailed experimental investigation of their growth kinetics. Notably, these metasurfaces demonstrat high-quality and tunable LSPR, enabling the fabrication of highly performing optical gas molecule sensors detecting down to 3 × 10−6 variations in refractive index at room temperature. It is believed that these findings provide a rapid, low-cost nanofabrication tool for the engineering of highly homogenous Au metasurfaces for large-scale LSPR devices with application ranging from ultrasensitive optical gas sensors to photocatalytic macroreactors.