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Next-Generation Chemical Mapping on the Nanoscale

Schematic of coaxial probe for imaging a carbon nanotube (left) and chemical map of carbon nanotube with chemical (right) with topographical information available at each pixel.

A team of Molecular Foundry scientists led by Alexander Weber-Bargioni has pioneered a new chemical mapping method that provides unprecedented insight into materials at the nanoscale. Moving beyond traditional static imaging techniques, which provide a snapshot in time, these new maps will guide researchers in deciphering molecular chemistry and interactions at the nanoscale—critical for artificial photosynthesis, biofuels production and light-harvesting applications such as solar cells.

Using the Foundry's state-of-the-art focused ion beam tool, Weber-Bargioni and his team designed and fabricated a coaxial antenna capable of focusing light at the nanoscale. Consisting of gold wrapped around a silicon nitride atomic force microscope tip, this coaxial antenna serves as an optical probe for structures with nanometer resolution for several hours at a time.

What's more, unlike other scanning probe tips, it provides enough enhancement, or light intensity, to report the chemical fingerprint at each pixel while collecting an image. This data is then used to generate multiple composition-related "maps," each with a wealth of chemical information at every pixel, at a resolution of just twenty nanometers. The maps provide information that is critical for examining nanomaterials, in which local surface chemistry and interfaces dominate behavior.

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. Weber-Bargioni, A. Schwartzberg, M. Cornaglia, A. Ismach, J.J. Urban, YJ Pang, R. Gordon, J. Bokor, M.B. Salmeron, D.F. Ogletree, P. Ashby, S. Cabrini, and P.J. Schuck, "Hyperspectral nanoscale imaging on dielectric substrates with coaxial optical antenna scan probes," Nano Lett. 11, 1201 (2011).