A novel array of optoelectrochemical submicrometer sensors for remote electrochemiluminescence (ECL) imaging is presented. This device was fabricated by chemical etching of a coherent optical fiber bundle to produce a nanotip array. The surface of the etched bundle was sputter-coated with a thin layer of indium tin oxide in order to create a transparent and electrically conductive surface that is insulated eventually by a new electrophoretic paint except for the apex of the tip. These fabrication steps produced an ordered array of optoelectrochemical sensors with submicrometer dimensions that retains the optical fiber bundle architecture. The electrochemical behavior of the sensor array was independently characterized by cyclic voltammetry and ECL experiments. The steady-state current indicates that the sensors are diffusively independent. This sensor array was further studied with a co-reactant ECL model system, such as Ru(bpy)(3)(2+)/TPrA. We clearly observed an ordered array of individual ECL micrometer spots, which corresponds to the sensor array structure. While the sensors of the array are not individually addressable electrochemically, we could establish that the sensors are optically independent and individually readable. Finally, we show that remote ECL imaging is performed quantitatively through the optoelectrochemical sensor array itself.

We describe the development of a new type of high-resolution atomic force electrochemical microscopy (AFM-SECM), labeled Tarm (for tip-attached redox mediator)/AFM-SECM, where the redox mediator, a ferrocene (Fc), is tethered to the AFM-SECM probe via nanometer long, flexible polyethylene glycol (PEG) chains. It is demonstrated that the tip-attached ferrocene-labeled PEG chains effectively shuttle electrons between the tip and substrate, thus acting as molecular sensors probing the local electrochemical reactivity of a planar substrate. Moreover the Fc-PEGylated AFM-SECM probes can be used for tapping mode imaging, allowing simultaneous recording of electrochemical feedback current and of topography, with a vertical and a lateral resolution in the nanometer range. By imaging the naturally nanostructured surface of HOPG, we demonstrate that Tarm/AFM-SECM microscopy can be used to probe the reactivity of nanometer-sized active sites on surfaces. This new type of SECM microscopy, being, by design, free of the diffusional constraints of classical SECM, is expected to, in principle, enable functional imaging of redox nanosystems such as individual redox enzyme molecules.