Advances in Mid-Infrared Spectroscopy for Chemical Analysis

Abstract

Infrared spectroscopy in the 3-20 μm spectral window has evolved from a routine laboratory technique into a state-of-the-art spectroscopy and sensing tool by benefitting from recent progress in increasingly sophisticated spectra acquisition techniques and advanced materials for generating, guiding, and detecting mid-infrared (MIR) radiation. Today, MIR spectroscopy provides molecular information with trace to ultratrace sensitivity, fast data acquisition rates, and high spectral resolution catering to demanding applications in bioanalytics, for example, and to improved routine analysis. In addition to advances in miniaturized device technology without sacrificing analytical performance, selected innovative applications for MIR spectroscopy ranging from process analysis to biotechnology and medical diagnostics are highlighted in this review.

Portable Infrared Laser Spectroscopy for On-site Mycotoxin Analysis

“…In particular, infrared attenuated total reflection (IR-ATR) spectroscopy has emerged as a viable strategy for rapid analysis for mycotoxin-contaminated commodities, as reported for maize, wheat, raisins, and peanuts13. While infrared spectra provide inherent molecular information, the evaluation of individual absorption bands is of limited utility, as IR spectroscopic techniques usually rely on the detection of matrix changes due to physical alterations caused by fungal contaminations (i.e., content of fatty acids, proteins) rather than detection of individual metabolites14.…”

“…Due to their exceedingly compact dimensions, high output power, operational stability, and broad tunability (>400 cm −1 per device), QCLs are unambiguously accepted as the most advanced light source facilitating compact and portable MIR spectroscopy and sensing schemes1325. Thin-film waveguides with a thickness on the order of or below the propagating wavelength ideally complement these light sources ensuring single mode light propagation behavior.…”

Gas-phase broadband spectroscopy using active sources: progress, status, and applications [Invited]

“…These cells have the potential to operate from the visible to the THz. In another approach, hollow mid-IR waveguides have been fabricated with interaction paths on the order of 10 cm and small sample volumes [328, 329]. Finally, resonant optical cavities can be miniaturized, including mm-scale fiber Fabry-Perot cavities formed between mirrors machined on the tips of optical fibers [330, 331].…”

III-V on CaF2: a possible waveguiding platform for mid-IR photonic devices

“…On one hand, in the field of optoelectronics, the control of material deposition at the atomic scale has revolutionized industrial applications, leading for instance to quantum cascade lasers (QCLs, from the mid-IR up to the THz spectral region) and quantum-well infrared photodetectors (QWIPs); on the other hand, by engineering plasmonic nanostructures, the ability to confine light down to the micro-and nano-scales has further boosted technological applications. To cite a few, enhanced optoelectronics [1] and energy-transfer [2], biochemical spectroscopy [3][4][5][6], electrochemical and photochemical catalysis [7], photovoltaics [8], and more. Novel materials have at last differentiated the possible platforms, allowing great manufacturing flexibility and possibilities [6,9,10].…”