46878-AC5
Imaging Single Molecule Catalysis at the Solid-Liquid Interface
Spatially correlated single molecule fluorescence spectrsocopy and atomic force microscopy (AFM) are being used to study the kinetics of single molecule catalysis at the solid-liquid interface. These studies are being carried out to explore the relationship between the catalytic activity of the surface and its nanometer scale structure and topography. To accomplish this research, we are developing advanced experimental techniques that allow precise spatial registry of single molecule fluorescence and AFM images. The fluorescence images allow us to determine the precise position of the catalytic sites with nanometer scale precision, as well as the catalytic activity of the site. The corresponding AFM images show us the nanometer scale structure of the surface surrounding the catalytic site. Using this information, we can resolve surface defects or other topographical features and see if such features enhance or supress the catalytic activity. To date, we have been developing our AFM and fluorescence instrumentation that will be applied to this project by examining single fluorescent nanocrystals dispersed on mica substrates. Our studies have included individual isolated nanocrystals and small ensembles of nanocrystals that are clustered together. We have made progress toward identifying the nanometer scale positions of the nanocrystals in both the fluorescence and AFM images, and we have shown that we can characterize the local topography of the surface surrounding each nanocrystal. We have also examined the fluorescence intermittency of the nanocrystals, which resembles the time-dependent fluorescence signals that will be observed in the study of catalytic activity. In so doing, we have uncovered some interesting comparisons between individual isolated nanocrystals and clusters of nanocrystals. This has led to a submitted manuscript describing a redshift in the fluorescence emission of a nanocrystal cluster compared to that of individual isolated nanocrystals.
