Localized Surface Plasmon Resonance-Mediated Fabry-Pérot Interferometer for Enzyme-Free Glucose Detection

The well-known Fabry-Pérot (F-P) cavity serves as a crucial element of complex optical devices, offering distinctive functionalities. However, modifying reflection properties by altering the underlying optical structure remains challenging. Inspired by the optical modulation ability of plasmonic nanoparticles (NPs) and the sensitivity of reflective interferometric Fourier transform spectroscopy (RIFTS) of the F-P cavity to effective optical thickness (EOT), herein, a local surface plasmon resonance (LSPR) effect-mediated F-P interferometer with improved sensing ability is proposed. Using glucose as a model analyte, the TiO₂ nanotube (NT)-based F-P interferometer is constructed by integrating a pH-responsive block copolymer (BCP) film and LSPR-mediated enzyme-like reactions in interferometric TiO₂ NTs. The high-energy hotspots generated by the Au-LSPR effect can accelerate glucose oxidation in NTs, which generates gluconic acid and H₂O₂ as the products. By combining the experimental results with COMSOL simulations, it is found that the satisfactory response achieved in reflective interferometric Fourier transform spectroscopy (RIFTS) not only relates to the enhanced reflectivity induced by AuNPs but also depends on the EOT changes mediated by the Au-LSPR effect. The plasmon-mediated F-P interferometer offers sensitive glucose quantification with satisfactory performance in real samples, suggesting a new route to design an F-P cavity with a highly sensitive response for boosting target sensing performance.