Novel irregular pore peripheral plasmonic mechanism of nanocomposite metal-nanoporous AAO using new facile one-step anodization and pore widening for high SERS enhancement

Conventional surface-enhanced Raman scattering (SERS) substrates are usually performed by Ag-or-Au metal nanoparticles (Ag,Au-MNPs) in suspension-or-solid substrates. The SERS mechanism is widely explained by the hot spots and shape of Ag,Au-MNPs. Here, the facile one-step irregular-nanopore anodic aluminum oxide (AAO) with platinum-metal-film (Pt-MF) coating as the new SERS substrate is proposed. A novel SERS mechanism based on the irregular Pore Peripheral Plasmonic Mechanism (3PM) of MF-AAO is interpreted. COMSOL (R) simulation shows the pore peripheral of AAO may gather a strong electric field for enhancing Raman signal. The irregular pores formed in the as-prepared one-step AAO and followed by pore-widening etching can generate additional hot spots at the small interpore gap and high-curvature tips for further enhancing SERS analytical enhancement factor (AEF). Using methylene blue (MB) as a probe molecule that was generally used to practically detect industry-pollution S2- and to sanitize water for fish health, the Pt-MF-AAO SERS substrate can reach a high AEF up to 1.88 x 10(5), and low limit of detection (LOD) of 1 x 10(-9) M. A good linearity (R-2 of 0.9406) between the MB concentration and Raman intensity is achieved. The large-area (several cm(2)) uniformity of is good with relative standard deviation (RSD) of 7.14%.

Automated summary

In this study, a new SERS substrate based on irregular nanopore anodic aluminum oxide with platinum-metal-film coating was proposed. The SERS mechanism was explained by the peripheral plasmonic mechanism of the substrate. Experimental results showed that the substrate achieved high enhancement factor and low limit of detection for detecting pollutants and sanitizing water.