The synthesis method we used enables the homogeneous deposition of both relatively large and small Fe₂O₃ nanoparticles on the surface of TiO₂. SAED analysis shows that TiO₂ NCs crystallize in anatase form and Fe₂O₃ as hematite in all cases. The formation of a TiO₂@Fe₂O₃ heterostructure leads to an increase in photocatalytic activity (in the presence of H₂O₂) compared to pure titanium and iron oxides. Mössbauer spectra confirm the existence of the hematite structure of Fe₂O₃ and, together with XPS, the presence of Fe³⁺ only. Fe₂O₃ nanoparticles on the surface of TiO₂ nanocrystals are in the paramagnetic/superparamagnetic state. Magnetization curves under ZFC and FC conditions also indicate the effect of the size of Fe₂O₃ particles on the magnetic properties of TiO₂@Fe₂O₃ nanostructures. The magnetic properties of the TiO₂@Fe₂O₃ heterostructure exhibit sensitivity to the size of nanometric Fe₂O₃ grains. The energies of optical transitions in nanometric Fe₂O₃ reveal the occurrence of a quantum-size effect. The heterostructures forms a complex structure; on the one hand, at the TiO₂ acceptor level associated with the incorporation of Fe³⁺ into the structure of TiO₂ anatase there is present on the other hand, the microstructure differentiation responsible for the occurrence of three optical transitions in Fe₂O₃.