Rapid Vibrational Circular Dichroism – Opportunities through the combination of External Cavity Quantum Cascade lasers and balanced detection

Abstract

Chirality is a property of molecules that so far has been challenging to study, as enantiomers are similar with regards to most properties except their interaction with polarized light and other chiral substances. Vibrational circular dichroism (VCD) is an established technique for detection/analysis of chiral molecules. Unfortunately, this technique is slow (with measurement times typically stated to be in the order of hours). Our innovation is a novel approach to VCD sensing based on a broadly tunable, mid-IR External Cavity Quantum Cascade Laser (EC-QCL) for high optical power and a custom optical setup that counters its main draw backs (pulse to pulse fluctuation, long term intensity drifts). This approach reduces typical measurement times for VCD from hours to minutes while improving signal to noise ratios (SNRs). This novel technique can enable VCD, which is currently mainly used for basic research on chiral molecules, to be used routinely to measure enantiomeric excess or identify a specific enantiomer in laboratory or process analytical settings.