Noble metal/silica “raspberry” type hybrids: Synthesis and functionalization

• Ru NPs were adsorbed on bare and amine functionalized silica NPs by simple mixing.
• Extent of Ru NPs binding can be controlled through zeta potential of silica NPs.
• Order of adsorption of Ru on SiO2 was: SiO2-arg > SiO2-lys > SiO2.

Metal decorated SiO2 nanoparticles (NPs) were prepared by adsorption of Ru NPs on bare SiO2 NPs and amine functionalized SiO2 NPs. The Ru NPs were synthesized by a microwave method and the amine functionalized SiO2 NPs were prepared by an amino acid catalyzed reaction. The hybrid system of smaller Ru NPs and larger SiO2 NPs obtained by simple mixing was studied by transmission electron microscopy (TEM), which shows that the adsorbed smaller Ru NPs decorate the SiO2 NPs. The amount of adsorbed Ru NPs was determined by using energy dispersive X-ray (EDX) spectroscopy and the size of the hybrid colloids (<100 nm hydrodynamic diameter) was measured by dynamic light scattering (DLS). The Ru NPs were found to be adsorbed with a highest content on arginine, compared to lysine-functionalized SiO2 and this fact can be rationalized via the zeta potential. This means that the extent of decoration can be controlled by the extent of amino acid functionalization, thereby allowing for a rational design of these hybrid materials.

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