title: Microfluidic channel flow cell for simultaneous cryoelectrochemical electron spin resonance.
abstract: A novel microfluidic electrochemical channel flow cell has been constructed for in situ operation in a cylindrical TE011 resonant ESR cavity under variable temperature conditions. The cell has a U-tube configuration, consisting of an inlet and outlet channel which run parallel and contain evaporated gold film working, pseudo-reference, and counter electrodes. This geometry was employed to permit use in conjunction with variable temperature apparatus which does not allow a flow-through approach. The cell is characterized qualitatively and quantitatively using the one-electron reduction of p-bromonitrobenzene in acetonitrile at room temperature as a model system, and the ESR signal-flow rate response is validated by use of three-dimensional digital simulation of the concentration profile for a stable electrogenerated radical species under hydrodynamic conditions. The cell is then used to obtain ESR spectra for a number of radical species in acetonitrile at 233 K, including the radical anions of m- and p-iodonitrobenzene, o-bromonitrobenzene, and m-nitrobenzyl chloride, the latter three being unstable at room temperature. Spectra are also presented for the radical anion of 2-chloranthraquinone and the crystal violet radical, which display improved resolution at low temperatures.
authors.affiliation: Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wain
authors.forename: Richard G
authors.initials: RG
authors.lastname: Compton
authors.forename: Rudolph
authors.initials: R
authors.lastname: Le Roux
authors.forename: Sinead
authors.initials: S
authors.lastname: Matthews
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Fisher