Electrochemical-atomic force microscopy (EC-AFM) methods offer a unique vista into the sub-micron scale chemical and biochemical processes. With a hybrid scanning probe microscopy method called scanning electrochemical-atomic force microscopy (SECM-AFM), the AFM probe serves as the working electrode in a three-electrode cell. To function as a working electrode, the AFM probe contains an ultramicroelectrode at the tip apex or slightly recessed from the tip. In SECM-AFM topographic images and faradaic current maps can be obtained independently and simultaneously if a bias is applied to the AFM probe sufficient to oxidize or reduce a species of interest in solution. We have an Agilent 5500 AFM interfaced with a Nikon eclipse Ti inverted microscope and a CH Instruments potentiostat for combined AFM, electrochemical and optical imaging capabilities. In the Baker group, we fabricate gold, platinum and carbon SECM-AFM probes through the insulation of conductive AFM probe with parylene C, an excellent insulative coating, and the definition of a ring-shaped electrode with focused ion beam milling. Our interest in the field has turned to the development of a potentiometric EC-AFM instrument, to the creation of new types of SECM-AFM probes and to the study of electrochemical events in cellular systems. Presently, we are working on mapping the oxidation of dopamine in differentiated PC12 cells with SECM-AFM probes fabricated from a conductive, amorphous carbon coating, pyrolyzed parylene C.
An example SECM-AFM experiment in which the diffusion of a redox probe through etched pores in a poly-imide membrane is monitored electrochemically (see Derylo et al., Langmuir, 2011 for details). The scheme of the experiment is shown in a. The contact-mode topography and electrochemical images are shown in b and c, respectively.
Baker group publications associated with this research topic:
Morton, K.C.; Derylo, M.A.; Baker, L.A. Conductive Atomic Force Microscopy Probes from Pyrolyzed Parylene C. J. Electrochem. Soc., 2012, 159, H662-H667. (http://dx.doi.org/10.1149/2.061207jes).
Derylo, M.A.; Morton, K.C.; Baker, L.A. Parylene insulated probes for electrochemical atomic force microscopy. Langmuir, 2011, 27, 13925-13930 (http://dx.doi.org/10.1021/la203032u).
Morton, K. C.; Morris, C. A.; Derylo, M. A.; Thakar, R.; Baker, L. A. Carbon electrode fabrication from pyrolyzed parylene c. Anal. Chem., 2011, 83, 5447-5452. (http://dx.doi.org/10.1021/ac200885w).