VOC Sensors Based on Nanoparticles and Nanorods of Nickel Ferrite

Nanostructures with different morphologies have been widely used as the sensing material for the detection of volatile organic compounds (VOCs). This research investigated the response of fabricated sensors based on nickel ferrite nanorods and nanoparticles in various conditions. Both nanostructures were prepared through the hydrothermal technique. Nanorods were synthesized in the absence of any surfactant agents by annealing the as prepared precursor at 550 °C. The prepared nanostructures were characterized by field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) analysis, and UV-vis spectroscopy. By investigating the response of sensors to different VOCs, it was shown that the response to acetone is highest for each sensor. Therefore, the sensing performance of the proposed low-cost (based on glass substrate) sensors was evaluated at different temperatures and acetone concentrations (25 to 500 ppm). The measurements show that both sensors have p-type gas sensing behavior. The response value of nickel ferrite nanoparticle based sensor to 100 ppm acetone at the optimum temperature of 190 °C was 120%, while the maximum response value of 70% was obtained for the nanorod sensor at 310 °C. Due to the high response value, our sensors can also be utilized for the detection of methanol or ethanol. The higher response of the nanoparticle-based sensor is due to the lower bandgap, which increases the chemical reactivity. Long term chemical stability, repeatability, and easy recovery as well as the cheap and easy fabrication process are other advantages of the present sensors. Furthermore, the nanoparticle-based sensor can selectively detect acetone in the presence of dichloromethane, toluene, or xylene.