Mapping surface chemistry and molecular orientation with combinatorial near-edge X-ray absorption fine structure spectroscopy

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 adsorption fine structure (NEXAFS) spectroscopy. These spatially resolved NEXAFS maps have been made by utilizing synchrotron-based NEXAFS spectroscopy in conjunction with a computer controlled precision sample manipulator. The NEXAFS 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: (1) the concentration and molecular orientation of semifluorinated molecules in molecular gradients; (2) the concentration of amino groups in molecular gradients used for nanoparticle templating and (3) the rehybridation of propylene intermediates on zeolite catalyst arrays used for measuring solid-state acidity and catalyst activity.