Au 4f spin-orbit coupling effects in supported gold nanoparticlesElectronic supplementary information (ESI) available: Detailed description of Au/TiO2 catalysts, XRD spectrum of synthesized TiO2, TEM images and Au particle size distributions, ToF-SIMS spectra and sodium impurity. See DOI: 10.1039/c6cp03362h

Using X-ray photoelectron spectroscopy we examine the Au 4f spin-orbit components in Au 4f spectra of nanosized Au particles on a TiO 2 support. In general, the peak ratios of the Au 4f 7/2 and 4f 5/2 excitations are found to deviate from the statistical ratio of 4 : 3 and their linewidths (FWHM) are not equal. We reveal that both the FWHM and the Au 4f 7/2 -to-4f 5/2 peak ratios increase appreciably as the Au atomic concentration on the surface of the TiO 2 support and the size of Au nanoparticles decrease. On the contrary, the Au 4f spin-orbit splitting remains essentially unchanged. Our findings are discussed in terms of alterations in the electronic band structure. We reveal that the ratio of spin-orbit components in X-ray photoelectron Au 4f spectra of titania-supported gold nanoparticles deviates from the statistical ratio 4 : 3 and demonstrates an appreciable dependence on the concentration of Au atoms on the surface of TiO 2 support and size of Au nanoparticles.