A fluorescence-based imaging-fiber electrode chemical sensor for hydrogen peroxide

The fabrication and characterization of imaging fiber electrodes (IFEs) is presented, and the concept of an electrochemically-modulated, fluorescence- based, imaging-fiber electrode chemical sensor (IFECS) is demonstrated. In brief, an imaging fiber distal tip was sputter-coated with a semi-transpare nt gold layer to create an IFE, and a fluorescent redox dye was immobilized across the IFE face to create an IFECS. An electroactive analyte was image d by monitoring the change in the immobilized redox dye's fluorescence foll owing its homogeneous electron transfer reaction with the electroactive ana lyte. Fluorescence images were collected through the IFECS and detected by an epi-fluorescence microscope/CCD imaging system. Cyclic voltammetry and f luorescence microscopy were utilized to characterize the electrochemical an d fluorescence properties of IFECSs. Reversible voltammetry was observed fo r the rhodamine B isothiocyanate (RBITC) redox couple at IFEs. IFECSs using RBITC as the fluorescent redox dye and Nafion as the immobilization polyme r were fabricated to detect hydrogen peroxide. The IFECS's RBITC-fluorescen ce was decreased by similar to 27% upon exposure to 250 mu M hydrogen perox ide and similar to 95% of the original fluorescence was observed following the electrochemical regeneration of the Nafion-immobilized RBITC. These IFE CSs represent the first union in which remote fluorescence imaging of an el ectroactive analyte can be performed through the actual fiber-optic electro de itself. (C)2000 Elsevier Science B.V. All rights reserved.