Scanning Electrochemical Microscopy and Ultramicroelectrode Studies Electrochemistry of Single Molecules and Nanoparticles

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With this award, the Chemical Measurement and Imaging Program is supporting the research of Allen J. Bard of the University of Texas at Austin to continue his development of a special type of microscope. The instrument, which uses a technique known as scanning electrochemical microscopy, or SECM, has been developed in the investigator's lab over a number of years and utilizes a tiny electrified probe hovered just above the sample of interest. As this probe is moved across the surface, electrical signals are detected through it and an image of the sample surface revealed. The current project is investigating various types of electrified tips, or ultramicroelectrodes, interacting with different types of surfaces, including very soft ones. such as emulsions. The work is having a broad impact through the direct development of new scientific instrumentation that will find application in a wide variety of fields from biology to manufacturing. It is having a further broad impact on the training of the next generation of scientists through the participation of student researchers in the project.The central thrust of this project is the development of further extensions of the SECM method and improved fundamental understanding of single nanoparticle events. This is accomplished by the detection and measurement of collisions between different types of single nanoparticles (NPs) and a variety of electrodes. New areas of electrochemical study in this work include: (1) Improved and advanced understanding of NP responses; (2) Investigation of new NP systems, e.g. soft particles, by the collision technique; and (3) Application of tunneling layers with nm-size ultramicroelectrodes (UMEs) with the ability to characterize large molecules by collision measurements. Knowledge gained from this work regarding the nature of nanoparticle/surface interactions at electrodes can reveal subtle phenomena not observable in ensemble studies, such as the effects of current density variations across UME surfaces, motion of particles on surfaces, deactivation effects by trace impurity adsorption, and single nanoparticle dynamics. Stochastic electrochemistry could potentially challenge current understanding of inner-sphere heterogeneous electron transfer, and provide a pathway to advances in inter-conversion of chemical and electrical energy. The experiments being carried out are providing new insights and a novel tool for the study of emulsions, micelles and vesicles.