AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP26
Size-Dependent Resonant Inelastic X-ray Scattering of Ligand-Stabilized Cobalt Nanoparticles in Liquid Suspension

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: H. Liu, Lawrence Berkeley National Laboratory
Authors: H. Liu, Lawrence Berkeley National Laboratory
G. Thornton, University College London, UK
J.-H. Guo, Lawrence Berkeley National Laboratory
Y.D. Yin, University of California, Berkeley
A. Augustsson, Lawrence Berkeley National Laboratory
C.L. Dong, Lawrence Berkeley National Laboratory
A.P. Alivisatos, University of California, Berkeley
D.F. Ogletree, Lawrence Berkeley National Laboratory
M. Salmeron, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
The electronic properties of cobalt nanoparticles suspended in liquid have been investigated using synchrotron-based resonant inelastic x-ray scattering (RIXS) spectroscopy. Cobalt nanoparticles of 3, 4, 5, 6, and 9 nm were synthesized using wet-chemical methods. Liquid suspensions of the samples were then sealed into a vacuum-compatible cell closed with an x-ray transparent silicon nitride window, which separated the liquid from the surrounding vacuum during measurements. The experiments were carried out at beamline 7.0.1 of the Advanced Light Source (ALS). Particle oxidation was prevented by performing spectroscopy under the conditions of synthesis. RIXS spectra revealed two main features with energy losses of 1.8 eV and 6 eV. The 1.8 eV feature was assigned to excitations from the ground state to a final state dominated by the 3d@super n@ configuration electrons (dd transition), while the 6 eV feature was assigned to charge transfer from the ligand/solvent molecules to metal atoms with a 3d@super n+1@L@super -1@ final state. RIXS spectra excited at the Co 2p@sub 3/2@ XAS peak position showed that the intensity of the 1.8 eV peak (dd excitation) decreased with decreasing particle size. The charge transfer feature also shifted significantly, from ~ 6.9 eV for 9 nm nanoparticles to ~ 6.0 eV for smaller particles. This difference can be attributed to changes in the interaction between the metal core and the ligand/solvent molecules with nanoparticle size.