Soft X-ray spectromicroscopy on solid-stabilized emulsions

Oil-water emulsions stabilized by solids have been imaged with sub-100 nm s patial resolution and analyzed spectroscopically using a scanning transmiss ion X-ray microscope. The emulsions are stabilized by particle heterocoagul ate cages surrounding the oil droplets. These cages form due to the interac tion of negatively charged clay mineral particles (sodium montmorillonite, Wyoming) and positively charged particles of calcium/aluminum layered doubl e hydroxide (LDH). The emulsions were studied at atmospheric pressure, with out any pretreatment using carbon K and calcium L X-ray absorption edges. O il- and calcium-rich LDH were separately mapped, and the clay mineral dispe rsions were also imaged. Applying X-ray absorption-edge contrast, oil could be distinguished from water in the emulsion near the carbon K absorption e dge (284 eV, 4.4 nm). Spectromicroscopy near the calcium L absorption edge (346 eV, 3.6 nm) allowed the structural details of heterocoagulate formatio n to be revealed.