The electronic d-band properties are important factors for the emerging catalytic activity of Au nanoclusters of sub-5-nm size. We analyzed the d-band properties of Au nanoclusters grown on amorphous carbon supports by photoelectron spectroscopy using synchrotron-radiation light coupled with high-resolution ion scattering spectrometry which enables us to estimate the size and shape of Au nanoclusters. The d-band width (Wd), d-band center position (Ed), and apparent 5d3/2-d5/2 spin-orbit splitting (ESO) were determined as a function of a number of Au atoms per cluster (nA) and an average coordination number (nC) in a wide range (11<nA<1600). The Wd and ESO values decrease steeply with decreasing nA below ~150 owing to band narrowing which is caused by hybridization of fewer wave functions of the valence electrons. However, Ed shifts to the higher binding energy side with decreasing cluster size. The rapid movement of E d is attributed to the dynamic final-state effect, which results in higher binding energy shifts of core and valence states due to a positive hole created after photoelectron emission. We have estimated the contribution from the final-state effect and derived the approximated initial-state spectra. Modified data, however, still show a slight movement of the d-band center away from the Fermi level (EF) although the Ed values for Au nanoclusters are closer to EF compared to the bulk value. This behavior is ascribed to the contraction of average Au-Au bond length with decreasing cluster size.
|ジャーナル||Physical Review B - Condensed Matter and Materials Physics|
|出版ステータス||出版済み - 4月 20 2011|
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