title: Redox cycling in nanoscale-recessed ring-disk electrode arrays for enhanced electrochemical sensitivity.
abstract: An array of nanoscale-recessed ring-disk electrodes was fabricated using layer-by-layer deposition, nanosphere lithography, and a multistep reactive ion etching process. The resulting device was operated in generator-collector mode by holding the ring electrodes at a constant potential and performing cyclic voltammetry by sweeping the disk potential in Fe(CN)6(3-/4-) solutions. Steady-state response and enhanced (~10×) limiting current were achieved by cycling the redox couple between ring and disk electrodes with high transfer/collection efficiency. The collector (ring) electrode, which is held at a constant potential, exhibits a much smaller charging current than the generator (disk), and it is relatively insensitive to scan rate. A characteristic feature of the nanoscale ring-disk geometry is that the electrochemical reaction occurring at the disk electrodes can be tuned by modulating the potential at the ring electrodes. Measured shifts in Fe(CN)6(3-/4-) concentration profiles were found to be in excellent agreement with finite element method simulations. The main performance metric, the amplification factor, was optimized for arrays containing small diameter pores (r < 250 nm) with minimum electrode spacing and high pore density. Finally, integration of the fabricated array within a nanochannel produced up to 50-fold current amplification as well as enhanced selectivity, demonstrating the compatibility of the device with lab-on-a-chip architectures.
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Chaoxiong
authors.initials: C
authors.lastname: Ma
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Contento
authors.forename: Larry R
authors.initials: LR
authors.lastname: Gibson
authors.forename: Paul W
authors.initials: PW
authors.lastname: Bohn
mesh_terms: D017097:Electric Impedance; D004563:Electrochemistry; D004566:Electrodes; D036103:Nanotechnology / Q000295:instrumentation*; D010084:Oxidation-Reduction