Fabrication of nanocrater-decorated anodic aluminum oxide membranes as substrates for reproducibly enhanced SERS signals

Abstract

Despite the potential sensitivity and the wide range of applications for surface-enhanced Raman spectroscopy (SERS), it is not used as a routine detection tool due mainly to the poor reproducibility of the enhanced SERS signals. In order to obtain reproducibly strong SERS data, both lithographic and non-lithographic approaches are intensively investigated to produce large-area nanopatterned SERS substrates displaying periodically arranged arrays of nanostructures. Herein, we report a facile method for the non-lithographic fabrication of plasmonic nanoparticle arrays by utilizing the barrier sides of anodized aluminum oxide (AAO) membranes. The nanobump-decorated surfaces (NBDS) of AAO barrier sides were treated with wet etching to create periodic arrays of nanocraters. Upon coating with an optimized thickness of Au, the nanocrater decorated surfaces (NCDS) displayed intensified SERS signals compared with the NBDS counterparts. This result was also confirmed with simulation studies and it was related to the increased surface roughness for the NCDS substrates. The fabricated Au@NCDS nanoplatforms were stable for extended periods and allowed enhanced and reproducible SERS signals with relative standard deviation values ∼10% from independently prepared samples. Our current studies are focused on the potential use of these SERS substrates for sensing biomarker molecules including myoglobin and troponin-T.