Publication 652

ACS Nano 3, 2927–2940, 2009 . DOI: 110.1021/nn9009054
Electrochemical atomic force microscopy using a tip-attached redox mediator for topographic and functional imaging of nanosystems.

Laboratoire d'Electrochimie Moléculaire, Université Paris Diderot, UMR CNRS 7591, 15, rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France, Laboratoire de Photonique et de Nanostructures (LPN/CNRS), Route de Nozay, 91460 Marcoussis, France

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.