Preparation of TiO2/VOx, TiO2/SiO2, and VOx/SiO2 nanostructures by hydrothermal methods and determination of their magnetic properties

Abstract

New nanostructures of TiO₂/VO_x, TiO₂/SiO₂, and VO_x/SiO₂ have been prepared via hydrothermal methods at different temperatures and times. They were characterized using scanning electron microscopy-energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and powder X-ray diffraction, whilst their magnetic properties were determined using a Physical Property Measurement System. According to the obtained results, the synthesized nanostructures can be used as magnetic detectors. The X-ray diffraction results for each titanium dioxide structure doped with vanadium or silica showed an increase the anatase structure. This proves that the photocatalytic properties of the synthesized nanostructures improve under optimum conditions. Temperature dependent magnetization (M–T) measurements were carried out for the composites under field-cooled and zero field-cooled conditions by applying a 500 Oe magnetic field. The M–T results indicate that all composites have weak ferromagnetic coupling, and they show a blocking temperature (T_B), except for the TiO₂/VO_x and SiO₂/VO_x composites due to their strong paramagnetic signals. Magnetic field dependent magnetization (M–H) measurements were performed on the composites in fields up to ±6 T at 5, 40, 90, and 300 K. From the resulting hysteresis curves, it is observed that all composites show weak ferromagnetic behavior with a coercive field. The highest saturation magnetization (M_s) and coercive field (H_c) were found to be 0.963 emu g⁻¹ and 764 Oe in the TiO₂/VO_x composite at 5 K while a maximum M_s of 0.126 emu g⁻¹ is recorded for the composite with the formula Ti_1.35Si₀.₃₂O_1.33 at room temperature.