Molecular selectivity development of Teflon® AF1600-coated gold-deposited surface plasmon resonance-based glass rod sensor

Abstract

• A Teflon AF1600-coated gold-deposited SPR-based glass rod sensor was developed. • The PEG spacer between Au and Teflon was studied via the sensor response and XPS. • The Teflon coating selectivity was evaluated using aqueous alcohol solutions. • The Teflon-coated sensor is unaffected by interference compounds in the samples. A gold (Au)-deposited surface plasmon resonance (SPR)-based glass rod sensor coated with an α-mercaptoethyl-ω-methoxy polyoxyethylene (PEG thiol) layer and a Teflon AF1600 overlayer with high selectivity for small molecules in aqueous solutions was developed. The PEG thiol layer forms a space (approximately 13 nm thick) for analytes between the Au film (45 nm thick) and the Teflon layer (25 μm thick). Small molecules in sample solutions pass selectively through the porous Teflon, accumulate in the PEG thiol layer and are detected using the SPR phenomenon. PEG thiol adsorption on the Au films was confirmed by the sensor response and X-ray photoelectron spectroscopy. Teflon overlayer thicknesses on the Au films were measured using cross-sectional scanning electron microscope images of the sensor. The sensor's selectivity was evaluated using aqueous solutions of methanol, ethanol, propanol, ethylene glycol, glycerin, pentaerythritol, and glucose. Only the monohydric alcohols pass through the Teflon overlayer, while the polyhydric alcohols do not pass through the layer. This sensor thus allows us to measure the ethanol concentrations directly in aqueous ethanol solutions mixed with interference compounds. The sensor is unaffected by glucose, tartaric acid, and glutamic acid in the solutions.