Core-shell structures of silica-organic pigment nanohybrids visualized by electron spectroscopic imaging.

Energy-filtering electron transmission spectroscopy observation has been achieved to elucidate the nanostructures of powdery nanohybrids, which were produced by the dry mechanical milling of organic pigments and silica nanoparticles. The hybrids possess core-shell structures, irrespective of the levels of aggregation of primary particles, whereas hollow sites of aggregates of primary silica particles were filled with the pigment, leading to the locally concentrated distribution of the pigment to reduce the surface areas of the hybrids. The results imply that nanohybridization is referred to as the buildup method, although mechanical tools and procedures are quite the same as those for the conventional breakdown method.