Pure TiO2 , Ti 0.75 Fe0.25 O2, Ti0.75 Ni0.25 O2, Ti0.75 Co0.25 O2 nanocrystals were prepared by low temperature sol-gel method. The samples were characterized by using transmission electron microscope, X-ray diffractometer and ultraviolet-visible spectrophotometer to study the effect of transition metal ions on the photocatalytic properties of TiO2 nanocrystals. The results show that the pure TiO2 and Ti0.75 Fe0.25 O2, Ti0.75 Ni0.25 O2, Ti0.75 Co0.25 O2 nanocrystals were granular and the size of which is 3.5, 2.9, 3.6, 3.9 nm, respectively. The titania anatase phases appear in the pure TiO2 , the Ti0.75 Fe0.25 O2, Ti0.75 Ni0.25 O2, Ti0.75 Co0.25 O2. The absorption edge of Ti0.75 Fe0.25 O2occur red shift comparing with that of pure TiO2 and the absorption edge of Ti0.75 Fe0.25 O2and Ti0.75 Fe0.25 O2occur blue shift comparing with that of pure TiO2. The photocatalytic properties of pure TiO2, Ti0.75 Fe0.25 O2, Ti0.75 Fe0.25 O2, Ti0.75 Fe0.25 O2nanocrystals synthesized at low temperature by sol-gel method were investigated by degrading the methyl orange solution under ultraviolet irradiation. The degradation rate of Ti0.75 Fe0.25 O2is the highest (60%) and that of Ti0.75Co0.25O2 (10%) is the lowest among these catalysts after degradation for 120min.The result shows that the photocatalytic property ofTi0.75 Fe0.25 O2nanocrystals synthesized at low temperature is obviously better than that of pure TiO2 and Ti0.75 Fe0.25 O2, Ti0.75 Fe0.25 O2.
