Issue Date: April 20, 2009
Single-Molecule Fluorescence Events Seen In Real Time
By designing a fluorescence-generating reaction that is mediated by single-walled carbon nanotubes (SWNTs), researchers at Cornell University now have in hand a method to monitor electrocatalytic events on SWNTs in real time at the single-molecule level (Nano Lett., DOI: 10.1021/nl900988f). The detection method provides a nanoscale probe for studying the electronic properties of carbon nanotubes, which is critical for solar-cell technology and other energy-harvesting applications. The method also provides a way to measure electron-transfer processes at solid-liquid interfaces, which are central to fuel cells and batteries. Weilin Xu, Hao Shen, Peng Chen, and coworkers developed their microscopy method specifically to probe the solution-phase catalytic reduction of the indicator compound resazurin to resorufin on the surface of SWNTs—fluorescent light bursts mark each catalytic event. On the basis of the technique's roughly 20-nm spatial resolution, the team reports that the reactions occur at discrete catalytically active sites and not along the entire length of the nanotubes. By coupling the microscopy study with a kinetics analysis, the researchers formulated a mechanism for the electrocatalytic reactions and determined the associated rate constants for each SWNT reactive site.
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