Traditionally, supported catalysts have been synthesized by precursor reduction, ion exchange and chemical vapor/fluid deposition. In these techniques, it is challenging to control the metal cluster size and surface morphology. It would be highly desirable to design well-defined metal nanocrystals with well-defined metal-support interactions to understand fundamental mechanisms in catalyst activity and selectivity. Alternatively, pre-synthesized metal nanocrystals, with controlled properties, may be infused into ordered mesoporous materials by tuning the interactions of the nanocrystals with the pore walls. The decoupling of the nanocrystal synthesis step and the infusion step, leads to exquisite control of the nanocrystal size, morphology, binding and dispersibility within the pores.

FePt nanocrystals, stabilized with oleic acid and oleylamine ligands and dispersed in toluene, have been infused within mesoporous silica. The objective is to synthesize highly loaded and highly stable metal-metal oxide nanocomposites with precise control over the nanocrystal size and morphology. The nanocrystals are highly dispersed within the pores as can be visualized by Z-contrast STEM. The surface coverage and the binding strength of the stabilizing ligands on the nanocrystals have been designed to facilitate the adsorption of nanocrystals onto the surface. A simple model of the van der Waals and electrostatic interactions between the metal nanocrystals and the silica under predicted the adsorption of nanocrystals onto the silica surface. Thus, the short range interactions between the nanocrystals and the silanol groups may be expected to play a key role in driving high metal loadings. Supported nanocrystals are very stable and do not show any aggregation, sintering or desorption up to 700 C indicating strong metal metal-oxide interactions.

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