Fig. 4. XPS Cu 2p detail spectra of the (a) Cu(NO3)2/TiO2 and (b) Cu(ac)2/TiO2 composites subjected to various temperature treatments. (c) Cu LMM Auger spectra for both composites non-calcined (RT) and at 250 °C. The Cu2+, Cu+ and Cu0 reference values were taken from literature reports.33–35 (d) Elemental Cu contents (Cu-to-Ti ratio in at%) derived from bulk sensitive XRF and surface-sensitive XPS survey data. Absolute values are shown in Table S5.† (e) Ti 2p spectra of the composites and (f) graphical representation of the proposed thermally induced diffusion mechanism and depth penetration of XPS and XRF.
