Deborah Vidick

Comparison of functionalized carbon nanofibers and multi-walled carbon nanotubes as supports for Fe–Co nanoparticles

Multi-walled carbon nanotubes (MWCNT) and nanofibers (CNF) have been functionalized at their surfaces with chelating phosphine (PPh2) and ammonium (NMe3+) groups, as anchoring sites for metal complexes. The surface functionalization has been monitored by XPS, elemental analyses, N2 physisorption and/or SEM surface morphology analysis at each step. Bimetallic Fe–Co nanoparticles from two different starting cluster complexes, [HFeCo3(CO)12] (1) and (NEt4)[FeCo3(CO)12] (2), have been deposited onto the surfaces of the functionalized MWCNT and CNF as well as their pristine forms for comparison. The samples have been fully characterized before and after thermal treatment. The obtained nanoparticles were shown by TEM to be better dispersed and of smaller size on functionalized than on pristine supports. Magnetic characterization revealed blocked superparamagnetic Fe–Co nanoparticles together with paramagnetic ions on CNF as well as MWCNT.

Heterometal nanoparticles from Ru-based molecular clusters covalently anchored onto functionalized carbon nanotubes and nanofibers

Summary Heterometal clusters containing Ru and Au, Co and/or Pt are anchored onto carbon nanotubes and nanofibers functionalized with chelating phosphine groups. The cluster anchoring yield is related to the amount of phosphine groups available on the nanocarbon surface. The ligands of the anchored molecular species are then removed by gentle thermal treatment in order to form nanoparticles. In the case of Au-containing clusters, removal of gold atoms from the clusters and agglomeration leads to a bimodal distribution of nanoparticles at the nanocarbon surface. In the case of Ru–Pt species, anchoring occurs without reorganization through a ligand exchange mechanism. After thermal treatment, ultrasmall (1–3 nm) bimetal Ru–Pt nanoparticles are formed on the surface of the nanocarbons. Characterization by high resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) confirms their bimetal nature on the nanoscale. The obtained bimetal nanoparticles supported on nanocarbon were tested as catalysts in ammonia synthesis and are shown to be active at low temperature and atmospheric pressure with very low Ru loading.

Clusters as precursors of nanoparticles supported on carbon nanofibers

Abstract Carbon nanofibers were functionalized following two distinct strategies, in order to introduce anchors for the grafting of clusters at their surface. In the first case, chelating phosphine groups were built using a multi-step synthesis, while in the second case, ammonium groups were introduced to create positive charges at the surface. To prove the success of the functionalization, a [Ru 5 PtC(CO) 14 (COD)] cluster was covalently grafted onto CNF-PPh 2 while a negatively charged (NEt 4 )[FeCo 3 (CO) 12 ] cluster was incorporated on CNF - NMe 3 + . Nanometer-sized RuPt and FeCo particles were evidenced by TEM.