Project Summary/Abstract The goal of this project is to develop a sensor for monitoring of per- and polyfluoroalkyl substances (PFAS) in water for remediation applications. PFAS have received particular attention in the past decade due to their persistent and bio-accumulative nature and high toxicity. The proposed sensor is based on infrared (IR) spectroscopy that incorporates advanced membrane materials coated on surfaces of infrared waveguides for trapping of contaminants to achieve high selectivity and sensitivity. The proposed technology can be adapted for portable, automatable, and cost-effective screening of water in field conditions and for in-line water quality monitoring in water treatment trains. The