A templating effect of carbon nanomaterials on the synthesis of Pd nanoparticles by covalent grafting onto surface O-groups

Abstract

Carbon nanotubes and nanofibers were functionalized with HNO₃ in order to introduce surface carboxyl groups. These were used as anchoring points for the grafting of metal complexes. Pd carboxylates were selected to graft Pd(II) fragments by Pd–O bonds after ligand exchange. Blank experiments conducted with non-functionalized nanocarbons demonstrated that these specific interactions occur only in the presence of surface O-groups. The stoichiometry of the expected molecular fragments was confirmed by XPS analyses, and the absence of agglomerates verified by SEM. After thermal ligand removal, Pd(II) atoms coalesced into Pd nanoparticles, whose sizes were controlled by the diameter of the supporting nanocarbons. Indeed, particles of sizes 7.2 ± 2.8 nm were observed by TEM on nanofibers and 2.1 ± 0.6 nm on MWNTs.