Cd-Doped Biphase In₂O₃ Nanospheres with High Sensitivity and Selectivity for Acetic Anhydride Sensors

Drugs emerge in an endless stream; the global drug supply is increasing, and the number of drug users is steadily rising, so the detection of acetic anhydride, a raw material for drug preparation, is of great significance for controlling the spread of drugs. The crystal phase of semiconductor metal oxides has an important impact on oxygen vacancy, microscopic morphology, specific surface area, and high-energy surface exposure, which in turn affect the catalytic and gas-sensing effects of materials. Ion doping can sometimes achieve the purpose of changing the crystal phase. In this study, Cd-doped biphase (cubic phase and hexagonal phase) In 2 O 3 nanospheres sensitive to acetic anhydride were synthesized via one easy hydrothermal process and the proportion of cubic phase and hexagonal phase is controlled by the amount of Cd element. The ion-doped biphase structure can save the consumption of expensive metals and provide a heterojunction structure as well as more oxygen vacancy to enhance gas sensing properties. The fabricated sensors not only have high sensitivity (372) to 100 ppm of acetic anhydride in the dry environment of 220 °C but also keep excellent selectivity and good stability. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) analysis, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to observe the crystal phase, elemental information, nanoscale appearance, and existing state of the elements of the prepared compounds. The gas-sensitive mechanism was briefly analyzed according to the characterization information. The enhancing acetic anhydride sensing properties are owing to the change of internal electronic channels, abundant oxygen vacancy, and the crystal structure of In 2 O 3 material caused by Cd doping.