Gold nanorod surface preparation for enhanced EC-SERS: a comparison of two electrochemical CTAB removal protocols

Gold nanorods (AuNRs) present a promising alternative to silver nanoparticles (AgNPs) for surface-enhanced Raman spectroscopy (SERS) applications due to their improved biocompatibility, chemical stability, and tunable optical properties. However, the cetyltrimethylammonium bromide (CTAB) surfactant typically required for AuNR synthesis introduces significant spectral and physical interferences that inhibit analyte detection. This study systematically compares reductive and oxidative electrochemical cleaning protocols to remove CTAB from AuNR-modified screen-printed electrodes. Electrochemical cleaning effectively removes CTAB, enabling detection of metabolites such as uric acid (0.15 mM) and nicotinic acid (10.0 mM). Reductive cleaning preserves the AuNR morphology, while oxidative cleaning induces surface restructuring that alters molecular adsorption behaviour on the metal surface. Both cleaning methods retain strong SERS activity originating from the AuNRs, which is improved compared to uncleaned substrates. Oxidative cleaning enhances SERS intensity by increasing surface roughness and hot-spot density, thereby improving electrochemical SERS (EC-SERS) performance relative to AgNP-based platforms.