Besides harvesting sunlight over a broad wavelength range as much as possible, the efficient separation of photo-generated electron–hole pairs is vital for the development of high-quality photocatalysts. In this work, we design FeTiO₃ (FTO) and Fe₂O₃ (FO) nanocomposites (xFTO–(1 − x)FO), which are simply prepared using a hydrothermal method. The FTO is epitaxially grown on FO nanoparticles, and with the increasing concentration of FTO, the band gaps decrease from 2.43 eV (x = 1.00) to 1.56 eV (x = 0.60). The photocatalytic capability is significantly improved such that xFTO–(1 − x)FO (x = 0.60) shows the highest value, which is about 8 times that of FO and 4 times that of FTO. Furthermore, strong ferromagnetism with saturated magnetization larger than 6 emu g⁻¹ is observed in xFTO–(1 − x)FO with x ≥ 0.60. xFTO–(1 − x)FO (x = 0.60) is further annealed at various temperatures. After annealing at 300 °C, the photocatalytic capability and ferromagnetism are both improved, by 38% and 31%, respectively, but drastically decrease with further increase of the annealing temperature to higher than 400 °C. The mechanism of the enhanced photocatalytic capability has been ascribed to the interdiffusion between FTO and FO at interfaces inside the nanocomposite particles, resulting in the formation of p–n junctions, which may facilitate the separation of photo-generated electron–hole pairs by the built-in-electric field. A significant enhancement of ferromagnetism occurs at the interdiffusion region with higher concentrations of FTO.

Sulfur is easy to be incorporated into ZnO nanoparticles by the solution-combustion method. Herein, the magnetic and adsorption properties of a series of ZnO_1−xS_x (x = 0, 0.05, 0.1, 0.15, and 0.2) nanoparticles were systematically investigated. The X-ray diffraction patterns show that the as-prepared ZnO_1−xS_x nanoparticles have the hexagonal wurtzite structure of ZnO with a low sulfur content that gradually transforms into the zinc blende structure of ZnS when the x value is greater than 0.1. PL spectra show several bands due to different transitions, which have been explained by the recombination of free excitons or defect-induced transitions. The introduction of sulfur not only modifies the bandgap of ZnO, but also impacts the concentration of Zn vacancies. The as-prepared ZnO shows weak room-temperature ferromagnetism, and the incorporation of sulfur improves the ferromagnetism owing to the increased concentration of Zn vacancies, which may be stabilized by the doped sulfur ions. The adsorption capability of ZnO_1−xS_x nanoparticles has been significantly improved, and the process can be well described by the pseudo-first-order kinetic model and the Freundlich isotherm model. The mechanism has been confirmed to be due to the active sulfate groups existing in zinc oxysulfide nanoparticles.