Figure 3 shows the reflectance UV-Vis absorption spectra of the P25 TiO2 and Cu/P25 TiO2 samples. The unmodified P25 TiO2 sample has white colour as can be reflected in its UV-Vis absorption spectrum that displayed very low absorption intensity in the visible region of the spectrum (Fig. 3(a)). The addition of copper oxide resulted in the colour change from white to green. The colour became darker with the increase of the copper oxide loading. These changes could be observed in Figure 2, in which the Cu/P25 TiO2 samples gave additional absorption in the visible light region and the absorbance increased with the increase of the copper oxide loading amount. The absorbance in the visible light region would be originated from the d-d transitions of the Cu2+ system [19], which were present on the surface of copper oxide modified TiO2. While the Cu/P25 TiO2 samples with low loadings of copper oxide did not much influence the band gap of the TiO2, sample with high loading 5 mol% Cu/P25 TiO2 slightly shifted the band edge absorption of P25 TiO2 to longer wavelength. The shift indicated that some copper metal ions might alter the band gap of TiO2 [16, 17].