Mid-Infrared standoff spectroscopy using Quantum Cascade Lasers has been a focus of on-going research for many years. When attempting to detect trace analyte residues, the greatest challenge facing this technology is not in the lasers, but the difficulty in creating a spectroscopic background reference for an unknown surface. Such techniques as Differential Location Measurements fail when analyte concentrations are below 1 μg/cm². To overcome this challenge of unknown surface backgrounds, we propose a technique to alter the IR absorption peaks of a target analyte by exposing the surface to a high intensity, alternating electric field in a standoff fashion. The high intensity electric field generates ozone radicals from the local air, oxidizing organic compounds on the surface. A spectrum of the surface before and after the ozone radicals is obtained. The ozone altered spectrum acts as the reference background and is compared against the un-altered spectrum, generating a differential signal used to identify the target analyte.

Date Published: 22 May 2015
PDF: 5 pages
Proc. SPIE 9467, Micro- and Nanotechnology Sensors, Systems, and Applications VII, 94672P (22 May 2015); doi: 10.1117/12.2178606

Published in SPIE Proceedings Vol. 9467:
Micro- and Nanotechnology Sensors, Systems, and Applications VII
Thomas George; Achyut K. Dutta; M. Saif Islam, Editor(s)