CAREER: Development of Single Molecule Infrared and Visible Absorption Spectroscopies using Optical Trapping Force Detection

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Ganim at Yale University is building microscopes that combine sensitivity (down to one molecule) with broad compatibility (any molecule, any solvent environment, bio/non-biological reactivity, etc.) and produce straightforward spectral data that any chemist can interpret. Professor Ganim uses a combination of ultrafast infrared spectroscopy with precision force microscopy to help scientists to watch the distribution of intermediates occurring in a chemical reaction one at a time. The results could provide new experimental and theoretical insights to comprehensively quantify distributions of molecular structures that naturally occur. Professor Ganim also works with three educational initiatives on campus. Exemplary projects include interactive demonstrations for students to pull and push at the microscopic world using a research-grade optical trap and workshops to build and take home a functional spectrometer and microscope.The support project is motivated by the transformative progress that will be possible when measuring reaction kinetics in complex mixtures is simple enough that chemists will apply it to study the mechanisms of failed reactions. Professor Ganim builds on the recent development of force-detected nanoscale absorption spectroscopy in solution and develops single molecule (SM) infrared spectroscopy suitable for chemical kinetics experiments. Specifically Professor Ganim and his group develop a predictive model to explain the photoinduced signal magnitude and to guide the synthesis of custom nanostructured force probes. Traditional SM fluorescence is used to independently verify single molecule sensitivity. These enhancements are then used in conjunction with a multiplexed, time-domain implementation and maximum-likelihood signal processing to realize SM infrared spectroscopy. The technique is then used to observe real-time ligand exchange in single iridium(III) hydride complexes, which are known for their catalytic hydrogenation and dehydrogenation properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.