3D-Geometrical and chemical quantification of Au@SiO_x nano-composites in HAADF-STEM imaging mode

Abstract

Hybrid gold and Silica nano-composites (Au@SiO_x) can be used for photonic, optical and biomedical applications, for example for the development of novel contrast agents in magnetic resonance imaging (e.g. [1]). According to the synthesis conditions, these nano-hybrids can adopt various configurations, such as core-shell structures, distribution of Au nano-particles exclusively inside, or at the surface of the silica-based particles. The synthesis involves micro-emulsions; the native micellar structure (oil in water, presence of surfactant, co-surfactant) defines the final silica morphology, and the localization of gold particles with respect to the silica ones depends on the order of adding nano-reactors. An optimised feedback on the synthesis conditions requires a detailed geometrical and chemical analysis of the final products. According to the nanometric size of these objects (see figure 1), a stereoscopy approach in HAADF (High Angle Annular Dark Field) imaging in a Transmission Electron Microscope appears to be an elegant way for that purpose.