  We demonstrate the first successful functionalization of epitaxial
three-dimensional graphene with metal nanoparticles. The functionalization is
obtained by immersing the 3D graphene in a nanoparticle colloidal solution.
This method is versatile and here is demonstrated for gold and palladium, but
can be extended to other types and shapes of nanoparticles. We have measured
the nanoparticle density on the top-surface and in the porous layer volume by
Scanning Electron Microscopy and Scanning Transmission Electron Microscopy.
Samples exhibit a high coverage of nanoparticles with minimal clustering. High
quality graphene has been demonstrated to promote the functionalization leading
to higher nanoparticle density, both on the surface and in the pores. X-ray
Photoelectron Spectroscopy allowed to verify the absence of contamination after
the functionalization process. Moreover, it confirmed the thermal stability of
the Au- and Pd-functionalized three-dimensional graphene up to 530{\deg}C. Our
approach opens up new avenues for utilizing three-dimensional graphene as a
versatile platform for catalytic applications, sensors, and energy storage and
conversion.
