title: Interfacial electron-shuttling processes across KolliphorEL monolayer grafted electrodes.
abstract: Covalently grafted KolliphorEL (a poly(ethylene glycol)-based transporter molecule for hydrophobic water-insoluble drugs; MW, ca. 2486; diameter, ca. 3 nm) at the surface of a glassy-carbon electrode strongly affects the rate of electron transfer for aqueous redox systems such as Fe(CN)6(3-/4-). XPS data confirm monolayer grafting after electrochemical anodization in pure KolliphorEL. On the basis of voltammetry and impedance measurements, the charge transfer process for the Fe(CN)6(3-/4-) probe molecule is completely blocked after KolliphorEL grafting and in the absence of a "guest". However, in the presence of low concentrations of suitable ferrocene derivatives as guests, mediated electron transfer across the monolayer via a shuttle mechanism is observed. The resulting amplification of the ferrocene electroanalytical signal is investigated systematically and compared for five ferrocene derivatives. The low-concentration electron shuttle efficiency decreases in the following sequence: (dimethylaminomethyl)ferrocene > n-butyl ferrocene > ferrocene dimethanol > ferroceneacetonitrile > ferroceneacetic acid.
authors.affiliation: †Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom.|‡Department of Chemistry, University of Mohaghegh Ardabili, Ardabil 56199-11367, Iran.|§Laboratory of Green Chemistry, School of Engineering Science, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli, Finland.
authors.forename: Khadijeh
authors.initials: K
authors.lastname: Nekoueian
authors.affiliation: †Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Hotchen
authors.affiliation: ‡Department of Chemistry, University of Mohaghegh Ardabili, Ardabil 56199-11367, Iran.
authors.forename: Mandana
authors.initials: M
authors.lastname: Amiri
authors.affiliation: §Laboratory of Green Chemistry, School of Engineering Science, Lappeenranta University of Technology, Sammonkatu 12, FI-50130 Mikkeli, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Sillanpää
authors.affiliation: ∥Imperial College London, Department of Materials, Royal School of Mines, Exhibition Road, London SW7 2AZ, United Kingdom.
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Nelson
authors.affiliation: ⊥Chemistry Research Laboratories, Oxford University, South Parks Road, Oxford OX1 3TA, United Kingdom.
authors.forename: John S
authors.initials: JS
authors.lastname: Foord
authors.affiliation: #Department of Materials, Oxford University, Begbroke Science Park, Begbroke Hill, Oxford OX5 1PF, United Kingdom.
authors.forename: Philip
authors.initials: P
authors.lastname: Holdway
authors.affiliation: †Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom.
authors.forename: Antoine
authors.initials: A
authors.lastname: Buchard
authors.affiliation: †Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Parker
authors.affiliation: †Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom.
authors.forename: Frank
authors.initials: F
authors.lastname: Marken
keywords: Cremophor; PEGylation; amplification; sensor; tunneling; voltammetry