Influence of Cd, Mn, and Co addition on the structural and optical properties of TiO₂ crystal

Synthesis of TiO₂-M (M = Cd, Mn, Co) has been done by the sol gel method. Solution of titanium (IV) isopropoxide was hydrolyzed using a solution of glacial acetic acid at a temperature range of 10-15 °C to obtain a sol, subsequently heated to form a white gel. Ion solution Cd (II), Mn (II) and Co (II) each added to the gel TiO₂ with Ti:M mole ratio (M= Cd, Mn, Co) = 3:1 (mol/mol). After calcination process at a temperature of 400 °C, we have obtained TiO₂ and TiO₂-M (Cd, Mn, Co). Characterization of the samples with XRD showed TiO₂-M (M = Cd, Mn, Co) produces crystalline of anatase TiO₂ phase. SEM-EDX results showed differences in the amount of metal contained within TiO₂-M (M= Cd, Mn, Co) that is equal to 8.62% (w/w) Cd; 3.26% (w/w) Mn; 0.721% (w/w) Co. The addition of transition metals ion as impurities as Cd (II), Mn (II), or Co (II) have inhibited the growth of TiO₂ crystals. The insertion of metal ions in the TiO₂ were also affected the optical properties shown by the energy band gap (Eg) shift in order of Eg TiO₂ (3.35 eV)>TiO₂-Cd (3.10 eV)>TiO₂-Co (3.00 eV)>TiO₂-Mn (2.5 eV). The eletronic structures of TiO₂ doped 3d transition metals showed that an electron occupied level energy occurs. Electron from dopand are somewhat delocalized, thus significantly contributing to the formaton of the valece band with O p and Ti 3d electrons. Based on a comparation with the absorption data, we show that t₂g state of the dopand plays a significant role in the photoresponse of TiO₂ under visible irradiaton.