Self-assembly of Au nano-islands with tuneable organized disorder for highly sensitive SERS

Abstract

Aggregates of disordered metallic nano-clusters exhibiting long-range organized fractal properties are amongst the most efficient scattering enhancers, and they are promising as high performance surfaceenhanced Raman scattering (SERS) substrates. However, the low reproducibility of the disordered structures hinders the engineering and optimization of well-defined scalable architectures for SERS. Here, a thermophoretically driven Au aerosol deposition process is used for the self-assembly of thin films consisting of plasmonic nano-islands (NIs) with a controllable and highly reproducible degree of disorder. The intrinsic Brownian motion of the aerosol deposition process results in long-range periodicity with self-similar properties and stochastically distributed hot-spots, providing a facile means for the reliable fabrication of crystalline Au substrates with uniform disorder over large-surfaces. These morphological features result in the generation of a high density of hot-spots, benefitting their application as SERS substrates. NI substrates with an optimal uniform disorder demonstrate a SERS enhancement factor (EF) of 107 –108 with nanomolar concentrations of Rhodamin-6G. These findings provide new insights into the investigation of light scattering with disordered structures, paving the way toward low-cost scalable selfassembly optoelectronic materials with applications ranging from ultrasensitive spectroscopy to random lasing and photonic devices.