Mapping Surface Chemistry and Molecular Orientation With Combinational Near-Edge X-Ray Absorption Fine Structure Spectroscopy
Daniel A. Fischer, K Efimenko, R R. Bhat, S Sambasivan, Jan Genzer
Mapping the bond chemistry and molecular orientation of self-assembled monolayer gradients on flat surfaces and reaction intermediates in catalyst arrays is made possible using combinatorial near-edge X-ray absorption fine structure (NEXAFS). These spatially resolved NEXAFS maps have been made by utilizing synchrotron-based NEXAFS spectroscopy and a computer controlled precision sample manipulator. The maps reveal bond concentration, rehybridization and orientation of the surface-bound molecules with sub-millimeter planar spatial resolution and sub-monolayer molecular sensitivity. The wide applicability of the combinatorial NEXAFS method is illustrated by mapping the (1) concentration and molecular orientation of semifluorinated molecules in molecular gradients, (2) concentration of amino groups in molecular gradients used for nanoparticle templating, and (3) rehydridization of propylene intermediates on zeolite catalyst arrays used for measuring solid state acidity and catalyst activity.