Room temperature single molecule absorption spectroscopy detected by STM

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With this award, funded by the Chemical Measurement and Imaging Program of the Division of Chemistry, Professor Gruebele and his students will develop single molecule absorption spectroscopy detected by a scanning tunneling microscope. In this experiment, a laser beam excites a single molecule deposited on a semiconductor or metal surface, and a nanometer-sized metal tip detects the change of the molecular shape caused by the laser excitation. The laser wavelength is then scanned to measure an absorption spectrum of the molecule, while simultaneously visualizing the shape of the molecule's excited state. The technique will also be used to study complex surfaces with defects, such as conductive glasses. Absorption spectroscopy allows for the measurement and visualization of molecules that do not fluoresce, and that cannot be detected by single molecule fluorescence techniques. The broader goal of this research is to understand how the excited states of large molecules used in molecular electronics are tuned by defects and by a complex surface environment. The carbon nanotubes, quantum dots and metallic glasses studied in this project have applications ranging from displays to cell phone shells; however, much of the fundamental physical chemistry needed to harness the properties of these materials remains to be discovered. The undergraduate and graduate students supported by this research project will acquire the knowledge and hands-on skills needed to advance U.S. chemical technology and teaching in the area of nanodevices.