Optical Constant Determination of Crosslinked Chitosan-Polyethylene Glycol (PEG) using Attenuated Total Reflection Method by Surface Plasmon Resonance Phenomenon

Abstract

Application of chitosan as a sensing layer for heavy metal ions in surface plasmon resonance (SPR)-based sensor with Kretschmann configuration has been done extensively using polypyrrole and gruteraldehid. The deposition methods that are very widely used in depositing chitosan onto the sensing surface are spin coating, electrodeposition and dip coating (for SPR based fiber optic sensor). The deposition technique of chitosan-polyethylene glycol (PEG) composite material as sensing layer in SPR based sensor by using the drop-casting method has not been done to the best of our knowledge. In order to use chitosan-PEG composite material as a sensing layer for heavy metal ion detection, it is necessary to determine the optical constant of chitosan-PEG which is deposited by the drop-casting method. The refractive index of chitosan-PEG with mass composition 0.4 grams chitosan and 0.04 grams PEG was determined by attenuated total reflection (ATR) method by utilizing surface plasmon resonance phenomenon on the prism/silver/chitosan-PEG interfaces in Kretschmann configuration. The refractive index then was extracted from the ATR curve by using Winspall software. Based on the experimental result, it was found that the ATR curve was shifted from 44.3° to 68.9° with the presence of a chitosan-PEG layer deposited onto the silver surface, about 0.01 ml in solution form. From the fitting result, it was found that the refractive index of chitosan-PEG was n = 1.32.