High-sensitivity spectroscopic detection of vapor mixtures using sorbent films on hyper-bounce ATR crystals

Robert Furstenberg; Christopher J. Breshike; Tyler J. Huffman; Christopher A. Kendziora; R. A. McGill

doi:10.1117/12.2618950

30 May 2022 High-sensitivity spectroscopic detection of vapor mixtures using sorbent films on hyper-bounce ATR crystals

Robert Furstenberg, Christopher J. Breshike, Tyler J. Huffman, Christopher A. Kendziora, R. A. McGill

Proceedings Volume 12116, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXIII; 121160C (2022) https://doi.org/10.1117/12.2618950
Event: SPIE Defense + Commercial Sensing, 2022, Orlando, Florida, United States

Abstract

While infrared spectroscopy is often used for chemical vapor identification, it has two major disadvantages: relatively low sensitivity and the inability to reliably identify components in a complex mixture. This paper presents a method that overcomes the low sensitivity challenge. The low-sensitivity is overcome by using a thin germanium wafer in an ATR configuration, providing 10 to 20 times more bounces per centimeter than commercially available multi-bounce ATR crystals. By using a 25 mm long crystal, we can detect nanogram amounts of analyte which is adequate for possible applications in detecting CWA threats, environmental monitoring and medicine (e.g. breath analysis). While not specifically discussed in this paper, the mixture challenge can be overcome by using a “cocktail problem” algorithm which requires multiple spectra with differing concentration ratios of analytes. This is provided by collecting the sampled vapor on either a single spin-coated sorbent film layer or several parallel sorbent strips with differing chemistries to separate the mixture into classes. In both cases, temperature ramping of the sorbent-coated crystal provides additional unique spectral data through boiling point separation. Full gas chromatography column separation is also possible and this is the main topic of a companion paper. In the current experimental setup, we use a tunable quantum cascade laser as the light source and a TE cooled MCT detector.

Conference Presentation

Citation Download Citation

Robert Furstenberg, Christopher J. Breshike, Tyler J. Huffman, Christopher A. Kendziora, and R. A. McGill "High-sensitivity spectroscopic detection of vapor mixtures using sorbent films on hyper-bounce ATR crystals", Proc. SPIE 12116, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XXIII, 121160C (30 May 2022); https://doi.org/10.1117/12.2618950

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