Synthesis of TiO2@alpha-Fe2O3 core-shell heteronanostructures by thermal decomposition approach and their application towards sunlight-driven photodegradation of rhodamine B

TiO2@alpha-Fe2O3 core-shell heteronanostructures with different shell thickness have been synthesized by a thermal decomposition approach. The thickness of the shell (alpha-Fe2O3) could be controlled by simply varying the amount of iron-urea complex, which was used as a precursor for iron oxide. The formation of core-shell TiO2@alpha-Fe2O3 was confirmed by various analytical techniques. XRD analysis confirms the presence of anatase and hematite in the TiO2@alpha-Fe2O3 core-shell heteronanostructures. Scanning electron microscopy studies confirm deposition of the alpha-Fe2O3 shell on the surface of TiO2 spheres and TEM analysis proves the formation of a uniform alpha-Fe2O3 shell on the TiO2 spheres. The XPS measurements prove the presence of Ti4+, Fe3+, and oxygen in the lattice and surface hydroxyls. From UV-visible DRS spectroscopy, it was observed that the TiO2@alpha-Fe2O3 core-shell heteronanostructures absorb in both the UV and visible range of the electromagnetic spectrum. Field-dependent (M-H) magnetic measurements indicate the weak ferromagnetic behaviour of the TiO2@alpha-Fe2O3 core-shell nanoparticles at 300 K and superparamagnetic behaviour at 5 K. Temperature-dependent magnetic studies (M-T) show the characteristic Morin transition of alpha-Fe2O3 in all the core-shell nanoparticles. The synthesized TiO2@alpha-Fe2O3 core-shell heteronanostructures were explored as a catalyst for the photodegradation of rhodamine B (RhB) in an aqueous solution in the presence of sunlight and it was found that TiO2@alpha-Fe2O3 core-shell nanoparticles act as a better photocatalyst compared to pure TiO2 and alpha-Fe2O3. Kinetic studies indicate that the photodegradation follows first-order kinetics.