Nanoparticles as a support:: CaO deposits on MgO cubes

MgO nanocubes with an average particle size of 8 nm were used to support thermally stable CaO deposits. Energy-filtered transmission electron microscopy (EFTEM) reveals their unprecedented high dispersion with sizes significantly below 4 nm. CaO-specific photoluminescence emission results from the photoexcitation of oxygen anions in edges and oxygen-terminated corners that, for the first time, are available at a sufficiently high concentration to be detected by ensemble averaging techniques. The presented approach can be easily extended to a variety of other thermally labile oxides that find important applications in optics, sensing, and catalysis and, on this base, can be incisively characterized.