Investigation on Metal Nanoparticles: Nickel Oxide, Cuprous Oxide and Tin Ferrite with Their Humidity Sensing at Room Temperature

This paper deals with the facile approach to the synthesis of different metal oxide nanoparticles and their comparative study for humidity sensing application at room temperature. The synthesis of these metal oxide nanoparticles is through co-precipitation method for nickel oxide and tin ferrite and hydrothermal route for cuprous oxide. The SEM and EDX reveal the porous morphology and confirmed composition of the synthesized metal oxides. FTIR detects the presence of functional groups like -OH and confirms the inverse spinal structure in tin ferrite. The optical band gap was determined by UV spectroscopy: 3.86 eV for NiO, 4.13 eV for Cu2O, and 4.07 eV for SnFe2O4. XRD gives the information about the average crystallite size for tin ferrite 2.42 nm, cuprous oxide 12.88 nm and nickel oxide 22.51 nm as the size comes to nano range the surface area increases, which is a good indication for humidity sensing. The humidity sensing of materials was detected by electrical modes. The deposited thin films were prepared by spin coater and observed sensitivity of these films was 0.72 M Omega/%RH for NiO, 1.59 M Omega/%RH for Cu2O, and 2.07 M Omega/% RH for SnFe2O4. The experiments were repeated after few weeks and the aging effects of samples were found negligible which makes the sensor stable.