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C. Koch, B. Zachhuber, B. Lendl:
"Innovative Sensing Strategies based on Vibrational Spectroscopy for Explosive Detection and (Bio)process Monitoring";
Hauptvortrag: Europtrode XI, Barcelona (eingeladen); 01.04.2012 - 04.04.2012.

Advances in technology for infrared and Raman spectrometry are of key importance in the development of innovative analysis systems for use in applied environmental and process monitoring as well as in basic (bio)chemical research. These advances can include novel optical components such as light sources, detectors and fiber optics, but also supporting technologies for enabling new measurement concepts. These are needed to meet the increasing demands for reliable chemical information in our industrialized society. This presentation reports on recent developments which make use of such technological advances in the field of bioprocess monitoring and detection of explosives from a distance.

A standing MHz ultrasound field established between the plane ATR surface of a fiber optic probe and a piezo-ceramic element placed at a distance of a few millimeters can be used to manipulate particles in a suspension. Particles such as microorganisms are captured in the nodes of the standing pressure waves. By controlling the frequency of the standing waves the particles can either be kept away from the ATR surface or pressed against it. Based on this idea a mid-IR fiber optic fiber sensor has been developed which is capable to discriminate between particles (micro-organism) and solutes (substrates and products) in a given suspension (fermentation). Using this sensor, in-line spectra of yeast in a stirred (up to 800 rpm) semi-industrial fermenter have been recorded successfully. From these spectra changes in the chemical composition of yeast could be detected. Especially, detailed information on the carbohydrate content of yeast could be monitored successfully.

Detection of hazardous substances like explosives at a distance of 100 m is shown by stand-off Raman scattering. The developed instrumentation employs a pulsed (4 ns at 10 Hz) frequency doubled (532 nm) or tripled (355 nm) Nd:YAG laser, a 6 inch telescope to collect the inelastically scattered light, appropriate fiber optics and a fast (500 ps) gated iCCD camera. Analysis of sub-mg amounts of PETN, TNT, RDX and inorganic explosives as well as H2O2 solutions of different concentrations at a distance will be shown. By applying the concept of spatial off-set Raman scattering to stand-off measurements it is also possible to characterize the content of concealed objects from a distance up to 12-40m [1]. References should be listed at the end of the abstract.






[1] B. Zachhuber, C. Gasser, E. T.H. Chrysostom, B. Lendl, "Stand-off Spatial Offset Raman Spectroscopy for the detection of concealed content in distant objects", Analytical Chemistry (2011) DOI: 10.1021/ac2021008