One-Dimensional CdS/α-Fe₂O₃ and CdS/Fe₃O₄ Heterostructures: Epitaxial and Nonepitaxial Growth and Photocatalytic Activity

One-dimensional (1D) heterostructures of uniform CdS nanowires separately decorated with hematite (α-Fe 2 O 3 ) nanoparticles or magnetite (Fe 3 O 4 ) microspheres were successfully synthesized via a two-step solvothermal deposition method. Each CdS nanowire had a uniform diameter of 40−50 nm and a length ranging from several to several tens of micrometers. Quasicubic α-Fe 2 O 3 nanoparticles, with edge lengths up to about 30 nm, and Fe 3 O 4 microspheres, with diameters of about 200 nm, anchored on nanowires free from any surface pretreatment form 1D dimer-type CdS/α-Fe 2 O 3 semiconductor heterostructures or CdS/Fe 3 O 4 semiconductor magnetic functionally assembled heterostructures. It was also found that α-Fe 2 O 3 nanoparticles with a smooth surface were well-crystallized, and Fe 3 O 4 microspheres with a relatively rough surface showed a polycrystalline nature. The relationship between the crystal structures and effects of lattice mismatch on the formation of heterojunctions were systematically investigated. The magnetic and optical properties and photocatalytic activities of the as-obtained heterostructures were separately investigated. The 1D CdS/Fe 3 O 4 nanostructures displayed ferromagnetic properties of the Fe 3 O 4 microspheres, and the photoluminescence behaviors of CdS nanowires were conserved in both heterostructures. The enhanced photocatalytic activity under visible light (λ > 420 nm) was observed in 1D CdS/α-Fe 2 O 3 heterostructures due to fast charge separation.