Dispersion Curve Engineering of TiO₂/Silver Hybrid Substrates for Enhanced Surface Plasmon Resonance Detection

As surface plasmon resonance (SPR)-based biosensors are well translated into biological, chemical, environmental, and clinical fields, it is critical to further realize stable and sustainable systems, avoiding oxidation susceptibility of metal films-in particular, silver substrates. We report an enhanced SPR detection performance by incorporating a TiO₂ layer on top of a thin silver film. A uniform TiO₂ film fabricated by electron beam evaporation at room temperature is an effective alternative in bypassing oxidation of a silver film. Based on our finding that the sensor sensitivity is strongly correlated with the slope of dispersion curves, SPR sensing results obtained by parylene film deposition shows that TiO₂/silver hybrid substrates provide notable sensitivity improvement compared to a conventional bare silver film, which confirms the possibility of engineering the dispersion characteristic according to the incidence wavelength. The reported SPR structures with TiO₂ films enhance the sensitivity significantly in water and air environments and its overall qualitative trend in sensitivity improvement is consistent with numerical simulations. Thus, we expect that our approach can extend the applicability of TiO₂-mediated SPR biosensors to highly sensitive detection for biomolecular binding events of low concentrations, while serving a practical and reliable biosensing platform.