Spacial Sensitivity and Time Dependence of Evanescent-Wave Cavity Ring-Down Spectroscopy
Authors:Claire Berchiolli, Allison Vander Wall
Mentor:Michael Everest, Professor of Chemistry, Westmont College
Evanescent-wave cavity ring-down spectroscopy (EW-CRDS) is a highly sensitive, absorption-based technique. The spatial sensitivity and time dependence of EW-CRDS may be demonstrated by measuring changes in absorption as substances adsorb to chemically modified silica surfaces. In this study, the adsorption of methyl red to a surface modified with (3-aminopropyl)trimethoxysilane (APTMS) was monitored as a function of both position and time. As a function of position, surface modifications with distinct geometries were observed with sub-millimeter spatial resolution. The adsorption and desorption kinetics of methyl red were also observed, displaying time constants on the order of 20 seconds.