title: Electrochemical studies of guanosine in DMF and detection of its radical cation in a scanning electrochemical microscopy nanogap experiment.
abstract: This communication reports the findings of the investigation of the electrochemical (EC) oxidation of the important bimolecular guanosine (Gs) by scanning electrochemical microscopy (SECM) using carbon fiber ultramicroelectrodes (CF-UMEs) as the probe and substrate. The first attempt is to try to gain a steady-state voltammogram for EC oxidation of Gs at the CF-UME probe in aqueous buffer solutions with three different pH values. Experimental results indicate that due to serious adsorption of Gs on the CF-UME surface, an "S-shaped" steady-state voltammetric curve, which is required for SECM studies, cannot be obtained in aqueous solutions. To solve this adsorption problem, a series of experiments for studying the EC behavior of Gs in DMF are carried out. A well-defined "S-shaped" steady-state cyclic voltammogram (CV) could be achieved at the CF-UME in DMF containing 0.1M TBAPF6 as the supporting electrolyte. By combining several EC techniques, including cyclic voltammetry at glassy carbon (GC) macroelectrode and CF-UMEs, and chronoamperometry, the general chemical characteristics and EC behavior of Gs in DMF solution are studied. Furthermore, SECM detection of Gs*+, the radical cation of Gs electrogenerated in its first oxidation, is carried out by using feedback and tip generation/substrate collection modes in a nanogap configuration. Gs*+ has been electrochemically detected for the first time, with an estimated lifetime of </=40 mus and E degrees = 1.55 V versus NHE for the Gs/Gs*+ couple.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Shuping
authors.initials: S
authors.lastname: Bi
authors.forename: Biao
authors.initials: B
authors.lastname: Liu
authors.forename: Fu-Ren F
authors.initials: FR
authors.lastname: Fan
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Bard
mesh_terms: D002412:Cations / Q000737:chemistry; D004126:Dimethylformamide / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods; D005609:Free Radicals / Q000737:chemistry; D006151:Guanosine / Q000737:chemistry*; D008853:Microscopy / Q000379:methods; D036103:Nanotechnology / Q000379:methods; D010084:Oxidation-Reduction
chemical_list: D002412:Cations; D005609:Free Radicals; D006151:Guanosine; D004126:Dimethylformamide