Noninvasive confocal Raman imaging of immiscible liquids in a porous medium

The physical properties of a porous medium impregnated by a liquid or vapor are dictated in part by the spatial distribution of these phases within the solid host matrix and by physicochemical interactions at the solid−liquid−vapor boundaries. We report on a novel 3-D imaging technique based on the high spatial resolution and chemical specificity of the confocal Raman microscope, which allows for the first time the in situ study and visualization of these processes. Images showing the topology of immiscible liquids (trichloroethylene−water) in a natural porous sandstone demonstrate the potential of the technique and reveal a rich variety of interfacial phenomena.