Combination of plasmonic and dielectric properties by multivariate analysis for enhanced sensing

We present a highly sensitive plasmonic sensing approach in Kretschmann configuration that additionally includes dielectric features from Fresnel reflections and combines multiple sensitive features of the reflectance curve by multivariate analysis. The sensor consists of periodic gold nanostructures, which are integrated into a microfluidic chamber composed of several dielectric layers. We operate the sensor at single wavelength with angular scan using a p-polarized HeNe laser. The excitation of the whole device in Kretschmann configuration leads to complex multiple plasmonic resonances, generally with localized surface plasmon resonances, plasmonic surface lattice resonances, and resonances related with the evanescent field beyond total internal reflection. Additionally, characteristic features generated due to Fresnel reflections from the stack of different dielectric interfaces of the whole sensing device, including a microfluidic chamber, contribute in a sensitive way to the sensing performance. These dielectric features can be exploited additionally as sensitive sensing characteristics with respect to refractive index changes of the analyte under test. The increased number of features obtained from the plasmonic response together with the multiple reflections at the dielectric interfaces reveal strongly enhanced sensing capabilities when we combine them as input for multivariate analysis. By mathematically including a variety of characteristic features of the reflectance curve, the analytical sensitivity and the sensor resolution are improved by 200% and 23%, respectively; moreover, the prediction error is reduced by around 38% compared to a standard plasmonic sensor based on a continuous gold layer.