Photocatalytic Activity and Humidity Sensor Studies of Magnetically Reusable FeWO₄-WO₃ Composite Nanoparticles

Different mole ratios of (8:2, 6:4, 4:6 and 2:8) iron tungstate-tungsten trioxide (FeWO₄-WO₃) composite nanoparticles were synthesized by solid state method. The synthesized composite nanoparticles were characterized by powder X-ray diffraction analysis (XRD), field-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) studies. The crystalline nature and particle size of the samples were characterized by powder X-ray diffraction analysis (XRD). The morphology was confirmed by field-emission scanning electron microscopy (FE-SEM) analysis and transmission electron microscope (TEM). The energy dispersive X-ray spectroscopy (EDX) proved the purity of nanocomposites. Vibrating sample magnetometer reveals that the sample shows paramagnetic property based on the metal present in the prepared nanocomposites at room temperature. The magnetic property is due to the structural defects rather than the impurity phase. Magnetization saturation value (M_s = 398.7 emu/g) of FWWO-46 composite nanoparticles is high enough to be magnetically removed by applying a magnetic field. The composites were subjected to DC conductance measurement as a function of relative humidity in the range of 5-98%, achieved by different water vapour buffers thermostated at room temperature. The sensitivity factor, S_f (R_5%/R_98%) measured at 25 °C revealed that FWWO-46 shows the highest humidity sensitivity factor S = 3956, with a response and recovery time of 45 s and 100 s respectively. Photocatalytic degradation of methylene blue (MB) from aqueous solution has been carried out using FeWO₄-WO₃ composite nanoparticles as photocatalyst under Ultraviolet radiation.