We present results from our investigations into correlating the styrene-oxidation catalysis of atomically precise mixed-ligand biicosahedral-structure [Au25(PPh3)10(SC12H25)5Cl2](2+) (Au25-bi) and thiol-stabilized icosahedral core-shell-structure [Au25(SCH2CH2Ph)18](-) (Au25-i) clusters with their electronic and atomic structure by using a combination of synchrotron radiation-based X-ray absorption fine-structure spectroscopy (XAFS) and ultraviolet photoemission spectroscopy (UPS). Compared to bulk Au, XAFS revealed low Au-Au coordination, Au-Au bond contraction and higher d-band vacancies in both the ligand-stabilized Au clusters. The ligands were found not only to act as colloidal stabilizers, but also as d-band electron acceptor for Au atoms. Au25-bi clusters have a higher first-shell Au coordination number than Au25-i, whereas Au25-bi and Au25-i clusters have the same number of Au atoms. The UPS revealed a trend of narrower d-band width, with apparent d-band spin-orbit splitting and higher binding energy of d-band center position for Au25-bi and Au25-i. We propose that the differences in their d-band unoccupied state population are likely to be responsible for differences in their catalytic activity and selectivity. The findings reported herein help to understand the catalysis of atomically precise ligand-stabilized metal clusters by correlating their atomic or electronic properties with catalytic activity.

Colón Santana, J. A.; and Dowben, Peter A., "The surface relaxation and band structure of Mo (112) (112) are compared. This surface band structure mapping is presented with corrections included for the lattice relaxation of the Mo(112) surface. Quantitative low energy electron diffraction (LEED) has been used to determine the details of the Mo(112) surface structure. The first layer contraction is 14.9% by LEED intensity versus voltage analysis and is in general agreement with the 17.6% contraction found from total surface energy optimization. The electronic band structure is mapped out alonḡ -X and¯ -Ȳ of the surface Brillouin zone (SBZ). There is strong evidence of electron-phonon coupling particularly in the region of the Fermi level band crossing at 0.54Å −1 .

Gd 2 O 3 and Gd-doped HfO 2 films were deposited on p-type silicon substrates in a reducing atmosphere. Gd 4f photoexcitation peaks at roughly 7 and 5 eV below the valence band maximum have been identified using the resonant photoemission of Gd 2 O 3 and Gd-doped HfO 2 films, respectively. In the case of Gd 2 O 3 , strong hybridization with the O 2p band is demonstrated, and there is evidence that the Gd 4f weighted band exhibits dispersion in the bulk band structure. The rectifying (diode-like) properties of Gd-doped HfO 2 -silicon and Gd 2 O 3 -silicon heterojunctions are demonstrated.

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Lozova, N.; Manno, M.; Leighton, C.; and Dowben, Peter A., "The minority spin surface bands of CoS 2 (001)" (2009 Abstract Angle-resolved photoemission was used to study the surface electronic band structure of high quality single crystals of ferromagnetic CoS 2 (below 120 K). Strongly dispersing Co t 2g bands are identified along the 100 k direction, the¯ -X line of the surface Brillouin zone, in agreement with model calculations. The calculated surface band structure includes corrections for the previously determined surface structure of CoS 2 (001) and is in general agreement with the experimental photoemission spectra in the region of the Fermi level. There is evidence of the existence of several minority spin surface states, falling into a gap of the projected minority spin bulk CoS 2 (001) band structure.