title: Graphene nanoelectrodes: fabrication and size-dependent electrochemistry.
abstract: The fabrication and electrochemistry of a new class of graphene electrodes are presented. Through high-temperature annealing of hydrazine-reduced graphene oxides followed by high-speed centrifugation and size-selected ultrafiltration, flakes of reduced graphene oxides (r-GOs) of nanometer and submicrometer dimensions, respectively, are obtained and separated from the larger ones. Using n-dodecanethiol-modified Au ultramicroelectrodes of appropriately small sizes, quick dipping in dilute suspensions of these small r-GOs allows attachment of only a single flake on the thiol monolayer. The electrodes thus fabricated are used to study the heterogeneous electron transfer (ET) kinetics at r-GOs and the nanoscopic charge transport dynamics at electrochemical interfaces. The r-GOs are found to exhibit similarly high activity for electrochemical ET reactions to metal electrodes. Voltammetric analysis for the relatively slow ET reaction of Fe(CN)6(3-) reduction produces slightly higher ET rate constants at r-GOs of nanometer sizes than at large ones. These ET kinetic features are in accordance with the defect-dominant nature of the r-GOs and the increased defect density in the nanometer-sized flakes as revealed by Raman spectroscopic measurements. The voltammetric enhancement and inhibition for the reduction of Ru(NH3)6(3+) and Fe(CN)6(3-), respectively, at r-GO flakes of submicrometer and nanometer dimensions upon removal of supporting electrolyte are found to significantly deviate in magnitude from those predicted by the electroneutrality-based electromigration theory, which may evidence the increased penetration of the diffuse double layer into the mass transport layer at nanoscopic electrochemical interfaces.
authors.affiliation: Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), Hubei Key Laboratory of Electrochemical Power Sources, Department of Chemistry, Wuhan University, Wuhan, People's Republic of China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Lixin
authors.initials: L
authors.lastname: Fan
authors.forename: Huawei
authors.initials: H
authors.lastname: Zhong
authors.forename: Yuwen
authors.initials: Y
authors.lastname: Liu
authors.forename: Shengli
authors.initials: S
authors.lastname: Chen
mesh_terms: D055664:Electrochemical Techniques; D004566:Electrodes; D006108:Graphite / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D010316:Particle Size; D013499:Surface Properties
chemical_list: D006834:Hydrazines; D010087:Oxides; C029424:hydrazine; D006108:Graphite