Mid-infrared spectroscopy; dispersion spectroscopy; Mach-Zehnder interferometer; quantum cascade laser; refractive index sensing; protein analysis
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Abstract:
Novel laser light sources in the mid-infrared region enable new spectroscopy schemes beyond classical absorption spectroscopy. Herein, we introduce a refractive index sensor based on a Mach-Zehnder interferometer and an external-cavity quantum cascade laser that allows rapid acquisition of high-resolution spectra of liquid-phase samples, sensitive to relative refractive index changes down to 10−7. Dispersion spectra of three model proteins in deuterated solution were recorded at concentrations as low as 0.25 mg mL−1. Comparison with Kramers-Kronig-transformed Fourier transform infrared absorbance spectra revealed high conformance, and obtained figures of merit compare well with conventional high-end FTIR spectroscopy. Finally, we performed partial least squares-based multivariate analysis of a complex ternary protein mixture to showcase the potential of dispersion spectroscopy utilizing the developed sensor to tackle complex analytical problems. The results indicate that laser-based dispersion sensing can be successfully used for qualitative and quantitative analysis of proteins.
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Project title:
Advancing QCL-IR spectroscopy of proteins for DSP monitoring mid infraREd Fully Integrated CHemical sensors
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Project ID:
P 32644-N 780240
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Funder:
Fonds zur Förderung der wissenschaftlichen Forschung (FWF) European Commission