Interfacial Bilayer Engineering Enables Year-Long Stable Gold Nanorods with Enhanced Plasmonic Sensing

Gold nanorods (GNRs) are widely applied in optical sensing owing to their tunable plasmonic response, but conventional cetyltrimethylammonium bromide (C₁₆TAB) bilayers readily desorb and induce self-etching, severely impairing long-term stability and sensing sensitivity. Here we propose an interfacial engineering strategy that reconstructs a denser and more robust bilayer using octadecyltrimethylammonium bromide (C₁₈TAB). Enhanced adsorption and increased surface charge density enable GNRs to achieve, for the first time, long-term colloidal and optical stability in aqueous solution for up to 330 days, far surpassing previous reports. C₁₈TAB also lowers the Gibbs free energy for forming complexes between gold and etchants, accelerating etching kinetics and amplifying plasmonic optical responses. This strategy exhibits simultaneous improvements in stability and responsiveness across diverse gold nanostructures and multiple oxidative etchants. Sensing arrays constructed from C₁₈TAB-stabilized GNRs achieve nanomolar-level antioxidant detection and high-resolution discrimination, providing a generalizable design principle for reliable plasmonic sensing under complex conditions.