Dynamically driven perovskite La-Fe-modified SrTiO 3 nanocubes and their improved photoresponsive activity under visible light: influence of alkaline environment.

Visible-light active La-Fe-SrTiO 3 (La 0.01 Sr 0.99 Fe 0.01 Ti 0.99 O 3 ) photocatalysts were synthesized via a dynamic hydrothermal route under different NaOH concentrations (2, 3, 4, 5, and 6 M). The results showed that altering NaOH concentrations changed the physicochemical characteristics of the materials. Namely, the decrease in particle size was observed when the NaOH levels were increased. The specific surface area of the photocatalysts changed with an increased concentration of NaOH, and the maximum value was 17.10 m 2 /g in 5 M of NaOH. The crystal structure of all prepared samples remained unaffected when altered the NaOH concentration or when incorporated La and Fe in the lattice of SrTiO 3 . Namely, all samples synthesized under various NaOH concentrations crystallized and maintained in the standard cubic perovskite structure of SrTiO 3 . The increased NaOH concentration slightly altered the absorption wavelength towards a longer wavelength region. The La atom, replacing some Sr 2+ in the structure of modified SrTiO 3 , was confirmed to be in the La 3+ valence state. Simultaneously, Fe atoms demonstrating oxidation states of Fe 3+ can also be incorporated into the SrTiO 3 network. The photocatalytic degradation of ciprofloxacin antibiotic revealed that the highest performance was approximately 75% within 9 h over the La 0.01 Sr 0.99 Fe 0.01 Ti 0.99 O 3 sample prepared at 5 M of NaOH via the dynamic hydrothermal process. Meanwhile, this photocatalyst also displayed greater activity than the pristine SrTiO 3 , the single-doped samples (SrFe 0.01 Ti 0.99 O 3 and La 0.01 Sr 0.99 TiO 3 ), and the La 0.01 Sr 0.99 Fe 0.01 Ti 0.99 O 3 sample prepared through a static hydrothermal technique under the same synthesis condition.