Probing the surface of platinum nanoparticles with 13CO by solid-state NMR and IR spectroscopies

The synthesis and full characterization of platinum nanoparticles (Pt NPs) prepared by decomposition of the Pt(dba)(2) complex in the presence of CO and H-2 and stabilized either sterically by a polymer, polyvinylpyrrolidone or chemically by a ligand, diphenylphosphinobutane, are reported. In these studies, (CO)-C-13 was used as a probe molecule to investigate the surface of the particles, using IR and solid-state NMR spectroscopies with magic angle spinning (MAS-NMR). Three nanosystems with different sizes are described: Pt/PVP/(CO)-C-13 (monomodal: 1.2 nm), Pt/dppb/(CO)-C-13 (bimodal: 1.2 nm and 2.0 nm) and Pt/dppb/H-2 (monomodal: 2.0 nm) NPs. Spectroscopic data suggest a modification of the electronic state of the nanoparticles between 1.2 nm and 2.0 nm which can be related to the presence of Knight shift.