Fig. 8

Detection of Cu(II) and Cu(I) by XPS experiments. a To 3a when X = I and b to 3u when X = Cl. XPS Instrument type: Thermo ESCALAB 250Xi; X-ray excitation source: monochromatic Al Ka (hv = 1486.6 eV), power 150 W, X-ray beam 500 μm; Energy analyzer fixed transmission energy: 30 eV