Ag/Au bi-metallic film based color surface plasmon resonance biosensor with enhanced sensitivity, color contrast and great linearity

In wavelength surface plasmon resonance (SPR) biosensor, the manipulation of SPR dispersion relation by Ag/Au bi-metallic film was first time implemented. Due to the enhanced resonant wavelength shift and the sharper SPR slope of using Ag/Au bi-metallic film, the illuminated color of reflection shows one order of magnitude greater contrast than conventional SPR biosensors. Such an Ag/Au bi-metallic film based color SPR biosensor (CSPRB) allows the detail bio-interactions, for example 100 nM streptavidin, to be distinguished by directly observing the color change of reflection through naked eyes rather than the analysis of spectrometer. In addition to the enhanced sensitivity and color contrast, this CSPRB also possesses a great linear detection range up to 0.0254 RIU, which leading to the application of point-of-care tests.

► Among angle, intensity, phase, and wavelength SPR interrogations, only wavelength interrogation performs a sensitivity enhancement without decreasing the linear detection range when applying Ag/Au bi-metallic film as sensing layer.
► The enhanced sensitivity of wavelength SPR by Ag/Au bi-metallic film further promote the color contrast of resonant reflections up to 10 folds.
► This enhanced color contrast allows the streptavidin concentration as low as 100 nM being discernible by naked eyes, leading this Ag/Au bi-metallic film based color SPR biosensor to point-of-care applications.