Scalable decoration of Au nanoparticles on Al nanoconcavity arrays for highly enhanced SERS detection

Abstract

Highly sensitive Raman signal enhancement of target molecules is achieved by developing effective surface-enhanced Raman spectroscopy (SERS) sensing platforms created by a unique combination of plasmonic gold nanofractals and highly ordered nanostructured aluminum arrays. Under efficient laser illumination, the SERS-active substrates formed by Al nanoconcavities of less than 100 nm, each decorated with a single Au nanoparticle, trigger localised surface plasmon resonance. 4-Mercaptopyridine (4-Mpy) successfully interferes on the surface of Au nanofractals, proving the method's utility. As a result, the SERS signal from the 4-MPy adsorbed on Au nanostructures is long-range electromagnetically amplified. The designed and developed substrate brings about a high enhancement factor (EF), over 10⁷ increase in intensity when approaching 4-Mpy adsorbed on Au nanostructures. A considerable increase in the SERS signal is found when the excitation origin is determined to be vibrant with the charge transfer (CT) state formed at the interface of the Al nanoconcavities and organic molecules. This approach, which does not need nanopatterning, provides an alternative strategy for conducting SERS investigations on molecules with remarkably weak Raman signals.