Multi-analyte hybrid plasmonic dual grating biosensor hetereostructured by convexing slit width geometrical corrugation and its potentiality for noninvasive salivary glucose monitoring

A novel and self referenced multi-analyte Hybrid Plasmonic Dual Grating Biosensor is proposed. The grating structure is composed of gold and corrugations are filled with dielectric ZnS. A thin layer of ZnS with slit is spread over grating thus making it dual grating structure. The influence of convexing of slit walls is modeled by parameter alpha in analytical equation. The reflectance characteristics are rigorously investigated using wavelength interrogation method for different values of parameter alpha, it is observed that wavelength varies from 722.2 to 729.6 nm for surface refractive index in the slit varying from 1.3 to 1.4 respectively at alpha equal to 0. The surface sensitivity obtained is about 74 nm/RIU. The surface sensitivity is also investigated by intensity interrogation and is equal to 0.2637 R/RIU or 26.37% R/RIU. It is observed that for higher values of alpha, the sensor is ideal for sensing gaseous analytes while at lower values of alpha can be used for liquid analytes. Refractive index range of surface analyte is correlated with the refractive index of blood by using linear refractive index model and Gladstone-Dale law for blood. It is observed that for alpha equal to 0, the grating biosensor can be used for invasive blood glucose monitoring with very high sensitivity of about 0.02641 nm/mg/dl. Linear regression model relating blood glucose and salivary glucose is used. The proposed sensor can also be used for noninvasive salivary glucose monitoring with surface sensitivity of 0.7410 nm/mg/dl.