Functionalization of small platinum nanoparticles with amines and phosphines: Ligand binding modes and particle stability.
We report the binding mode of amines and phosphines on platinum nanoparticles. Protective ligands comprising different functional groups are systematically studied for the elucidation of ligand binding at different functionalization conditions. From the functionalization conditions it is concluded that the binding of amines to the nanoparticles occurs via the formation of a PtHN moiety or electrostatic interaction, which is supported by spectroscopic evidences. In particular from complex chemistry such a binding mode is surprising, as amines are expected to bind via their electron pair to the metal. Similar results from functionalization are observed for phosphine-protected nanoparticles, which suggest similar binding modes in these systems. In contrast to the strong covalent bond of the protection with thiols, considerable weakly binding systems result. The characteristics of the binding mode are reflected by the stability of the colloids and their catalytic properties. In the selective hydrogenation of 3-hexyne to 3-hexene thiolate-stabilized Pt particles are highly stable, but exhibit the lowest activity. On the other hand, amine- and phosphine-capped platinum nanoparticles show a significantly higher activity, but rapidly agglomerate.
Chair of Physical Chemistry, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany; Chair of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany.
Patricia
P
Wand
Chair of Physical Chemistry, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany.
Johannes D
JD
Bartl
Chair of Physical Chemistry, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany.
Ueli
U
Heiz
Chair of Physical Chemistry, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany. Electronic address: tschurl@tum.de.
Martin
M
Tschurl
Chair of Inorganic Chemistry/Molecular Catalysis, Department of Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, D-85747 Garching bei München, Germany. Electronic address: mirza.cokoja@tum.de.
Mirza
M
Cokoja
Functionalization; Ligand binding; Nanoparticle; Platinum; Stability