[Zurück]

B. Lendl, W. Ritter, H. Moser, Paul Waclawk, J. Ofner, C. Reidl-Leuthner, G. Ramer:
"Mid-IR Quantum Cascade Lasers: New Opportunities for Analytical Chemistry";
Hauptvortrag: Analysdagarna 2014, Djurönäset (eingeladen); 09.06.2014 - 11.06.2014.

Mid-IR quantum cascade lasers (QCLs) hold promise to revolutionize the way mid-IR spectroscopy is employed in analytical chemistry. Due to their highly attractive properties which include high spectral power densities (>100mW/cm-1), small size (e.g. TO8), room temperature operation and recently also increased tunability, a range of new measurement concepts can be realized.
This presentation will review the current state-of-the-art of Quantum Cascade Lasers and report on their spectroscopic properties as revealed by step-scan FTIR spectroscopy (time res.: 2 ns, spectral res.: 0.1 cm-1). Then, a range of applications which take advantage of the unique features of QCLs will be introduced. These will cover the analysis of liquids and gases as well as a new concept for near-field mid-IR imaging.
Concerning the analysis of liquids a new method for measuring oil-in-water and employing narrow distributed feedback (DFB) QCLs will be presented and an analyser for point-of-care measurements of human serum or plasma based on broadly tunable external cavity (EC) QCLs introduced (analytes: glucose, lactate, triglycerides, total protein, albumin, fibrinogen, total cholesterol, urea).
In the field of stack gas monitoring the simultaneous determination of NO and NO2 in the flue gas of a calorific power plant will be presented and compared to results obtained using a standard extractive method based on chemiluminescence. For gas monitoring in small volumes (2 ml) the concept of quartz enhanced photo-acoustic spectroscopy with ppb sensitivities will be shown on the example of SO2.
For near field mid-IR imaging (spatial res.: ~50 nm) a combination of pulsed EC-QCLs and atomic force microscopy (AFM) operated in the contact mode is used. Here the AFM cantilever is used to probe the photothermal expansion of sample caused by a periodic irradiation with the mid-IR laser light. The overall concept and first results will be shown.