title: SECM study of solute partitioning and electron transfer at the ionic liquid/water interface.
abstract: Molecular partitioning and electron-transfer kinetics have been studied at the ionic liquid/water (IL/water) interface by scanning electrochemical microscopy (SECM). The ionic liquid C8mimC1C1N is immiscible with water and forms a nonpolarizable interface when in contact with it. Partitioning of ferrocene (Fc) across the IL/water interface was studied by SECM and found to be kinetically fast with a partition coefficient CIL/CW of 2400:1. The partition coefficient value was measured by SECM under quasi-steady-state conditions without waiting for complete solute equilibration. To investigate the kinetics of the electron transfer (ET) between aqueous ferricyanide and Fc dissolved in IL, a new approach to the analysis of the SECM current-distance curves was developed to separate the contributions of Fc partitioning and the ET reaction to the tip current. Several combinations of different aqueous and nonaqueous redox species were investigated; however, only the Fc/Fe(CN)63- system behaved according to the Butler-Volmer formalism over the entire accessible potential range.
authors.affiliation: Department of Chemistry and Biochemistry, Queens College-CUNY, Flushing, New York 11367, USA.
authors.forename: François O
authors.initials: FO
authors.lastname: Laforge
authors.forename: Takashi
authors.initials: T
authors.lastname: Kakiuchi
authors.forename: Fumiko
authors.initials: F
authors.lastname: Shigematsu
authors.forename: Michael V
authors.initials: MV
authors.lastname: Mirkin