Waveguide-enhanced Raman spectroscopy for characterizing sorbent-analyte binding (Conference Presentation)

Abstract

Waveguide-enhanced Raman spectroscopy (WERS) enables the detection and identification of trace concentrations of vapor-phase analytes using a chip-scale photonic circuit coated with a sorbent material. Previous demonstrations of WERS utilized a hydrogen-bond acidic hyperbranched carbosilane fluoroalcohol-based sorbent polymer and focused on detection limits for different nerve agent simulants. In this work, we examine the Raman spectra of a number of new sorbent materials obtained using WERS. By comparing the spectra pre-exposure to the modified spectra measured during analyte exposure, the effects of hydrogen-bonding on the sorbent and analyte molecules are observed. Changes to the Raman transition strength or frequency of individual lines due to analyte binding shed light on the partitioning of vapor-phase molecular agents into the sorbent, and can be used to design sorbent materials with even higher sensitivity. We examine two new types of sorbents: Fluorinated bisphenol-based materials that increase the steric bulk of the substituents ortho- to the hydroxyl group, designed to reduce self-binding; and carbosilane fluoroalcohol polymers synthesized with a novel hydrosilylation reaction. The WERS detection limits for these new sorbents are measured for nerve-agent simulants and compared to previous generation materials.