Tunable Raman scattering enhancement due to self-assembled Au nanoparticles layer on porous AAO: The influence of the alumina support

In this investigation, SERS substrates were synthesized based on the growth of Au nanoparticles (AuNPs) layer over porous support of anodized aluminum oxide (AAO). The enhancement factor (EF) of the SERS substrates was determined by the measurement of Rhodamine 6G (R6G) allowed a detection limit of 10⁻¹¹ (measured over molar concentration). The AAO was grown by a two-stage anodizing method, and subsequently, an Au precursor layer in different thicknesses was sputtered on each alumina support. The coated samples were heat-treated under nitrogen to promote different spatial distributions of AuNPs on the surface. Au-Np layer was achieved with disordered pore-like as demonstrated by low-pressure Nitrogen adsorption and BET analysis (isotherm curve type IV-H₃). The sample that exhibited the strongest SERS effect consisted of a 50 nm Au precursor layer on the AAO support. The method reported in this work is highly reproducible, given its simplicity, with a homogeneous size distribution compared to other methods and other substrates such as Silicon.