3.2.1. DR-UV–Vis analysis
The DR-UV–Vis spectra of Cu-doped TiO2 and blank TiO2 are shown in Fig. 3. The spectra of TiO2 show an PHA-739358 peak at 350 nm in the UV region. When 1.0% copper was doped onto TiO2, considerable shift of the peak towards the visible range of about 400–800 nm occurred (red-shift).
Fig. 3. Diffuse reflectance spectra for blank TiO2 and Cu-doped TiO2.Figure optionsDownload full-size imageDownload as PowerPoint slide
It has been reported that the band at 210–270 nm would indicate the O2−(2p)→Cu2(3d) ligand to metal charge transfer transition, where the copper ions occupy isolated sites over the support. A band at 350 nm would indicate the formation of (Cu–O–Cu)2+ clusters in a highly dispersed state. The broad band between 400 nm and 600 nm is attributed to the presence of Cu1+ clusters in partially reduced CuO matrix as well as (Cu–O–Cu)2+ clusters. The absorption band at 600–800 nm indicates the crystalline and bulk CuO in octahedral symmetry . The incorporation of copper ion causes a red shift and increases the absorption band to the visible or even near-infrared range and this promotes the photocatalytic activity.