title: Attenuated total reflection-infrared nanofluidic chip with 71 nL detection volume for in situ spectroscopic analysis of chemical reaction intermediates.
abstract: We present a micromachined silicon attenuated total reflection-infrared (ATR-IR) crystal with integrated nanofluidic glass channels which enables infrared spectroscopic studies with only 71 nL sample volume. Because of the short path length through silicon, the system allows IR spectroscopy down to 1200 cm(-1), which covers the typical fingerprint region of most organic compounds. To demonstrate proof-of-principle, the chip was used to study a Knoevenagel condensation reaction between malononitrile and p-anisaldehyde catalyzed by different concentrations of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in solvent acetonitrile. By in situ measurement, it was demonstrated for the first time that at certain concentrations of DBU, reaction intermediates become stabilized, an effect that slows down or even stops the reaction. This is thought to be caused by increased ionic character of the solvent, in which protonated DBU stabilizes the intermediates. This clearly demonstrates that infrared mechanistic studies of chemical reactions are feasible in volumes as little as 71 nL.
authors.affiliation: Photo Catalytic Synthesis Group, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands. e.karabudak@utwente.nl
authors.forename: Engin
authors.initials: E
authors.lastname: Karabudak
authors.forename: Barbara L
authors.initials: BL
authors.lastname: Mojet
authors.forename: Stefan
authors.initials: S
authors.lastname: Schlautmann
authors.forename: Guido
authors.initials: G
authors.lastname: Mul
authors.forename: Han J G E
authors.initials: HJ
authors.lastname: Gardeniers