Synthesis of sodium acetate oriented Ni (II)-doped iron oxide nanospheres for efficient acetone sensing

Monodisperse pure and nickel-doped iron oxide Ni_xFe_3-xO₄ (x ​= ​0.00, 0.02, 0.04, and 0.06) nanospheres were synthesized by hydrothermal method. The synthetic method was featured by using a structure directing agent, namely, anhydrous sodium acetate and ferric ions source, iron (III) chloride in an ethylene glycol solution without any kind of surfactant or template involved. The molar ratio of salts to anhydrous sodium acetate was optimized to 1:4 to get monodispersed and uniform spherical nanostructures. The sensing response of nickel doped iron oxide to different gases such as acetone, ammonia, sulphur dioxide, hydrogen sulphide, ethanol and methanol are accomplished at room temperature with the gas concentration of 5 ​ppm and was found selective towards acetone with response 29.9%. The response of Ni_xFe_3-xO₄ (x ​= ​0.06) nanospheres were found to be 29.9%, 46%, 66%, 106%, and 174% towards 5, 10, 15, 20 and 25 ​ppm acetone concentration respectively. The response and recovery time at 5 ​ppm acetone concentration was found to be 94 ​s and 68 ​s respectively. Based on the reproducibility and stability test, it was observed that the fabricated sensor based on nickel doped iron oxide is highly reliable. The energy band diagram of the sensing mechanism of Ni_xFe_3-xO₄ (x ​= ​0.06) nanospheres upon exposure to air and acetone atmosphere are presented.