Sensitivity Analyses of Cu/Chitosan and Ag/Chitosan Based SPR Biosensor for Glucose Detection

This study investigates the sensitivity performance between hybrid thin films of Copper (Cu)/Chitosan and silver (Ag)/Chitosan for glucose biosensing applications. Ag and Cu with refractive indices of n=0.1351+3.9853k and n=0.2388+3.4156k are coated onto the flat surface of hemispherical prism prior 10nm thickness of chitosan (n=1.54+0.015k). The thicknesses of metal are varied between 35nm until 49nm. To generate SPR, a red laser of 633nm p-polarized light is incident onto the Cu/Chitosan and Ag/Chitosan coated prism. Light incident angles are varied from 40° to 60° via the angular interrogation technique. Glucose solution with a concentration of 70mg/dl and 235mg/dl (1.38 RIU and 1.53 RIU, respectively) are flown along with the flow cell during SPR to investigate the sensing ability of the proposed sensors. The relationship between hybrid thin film thicknesses and the value of minimum reflectance shows a polynomial pattern as the thicknesses increased. Based on Q² analysis, the deployment of Ag/Chitosan results in 18.51% poorer stability performance of R_min value than Cu/Chitosan SPR sensor. The Cu/Chitosan SPR sensor at total thicknesses within the range from 46nm to 49nm and from 53nm to 56nm exhibits 67% better potential than Ag/Chitosan due to its sensitivity and selectivity in differentiating dissimilar concentration of glucose with a maximum sensitivity of 6°/RIU. We believe the utilization of Cu/Chitosan as plasmonic sensing material offers a low-cost sensor that easy to handle, cheap, miniaturized and excellent sensitivity. (paper)