Nitrogen doped In2O3-ZnO nanocomposite mesoporous thin film based highly sensitive and selective ethanol sensors

Nanocomposite metal oxide thin films exhibit promising qualities in the field of gas sensors due to the opportunities provided by the heterointerface formation. In this work, we present the synthesis of nitrogen doped mesoporous In₂O₃-ZnO nanocomposite thin films by a simple wet chemical method using urea as the nitrogen precursor. SEM investigation suggests the formation of mesoporous nanocomposite thin films, where the uniformity of the surface pore distribution depends on the relative proportion of In₂O₃ and ZnO in the composites. HRTEM investigation suggests the formation of sharp interfaces between N-In₂O₃ and N-ZnO grains in the nanocomposite thin films. The nanocomposite thin films have been tested for their ethanol sensing performance over an extensive range of temperatures, ethanol vapor concentrations and relative humidities. Nitrogen doped nanocomposite thin films with an equal proportion of In₂O₃ and ZnO exhibit excellent ethanol sensing performance at a reasonable operating temperature (∼94% at 200 °C for 50 ppm of ethanol), fast response time (∼two seconds), stability over time, enhanced resilience against humidity and selectivity to ethanol over various other volatile organic compounds. All the results indicated that nitrogen doped In₂O₃/ZnO nanocomposite thin films portray great possibilities in designing improved performance ethanol sensors.

Adsorption of SF6 Decomposed Products over ZnO(101̅0): Effects of O and Zn Vacancies

We carried out a density functional theory study to investigate the adsorption behavior of four kinds of SF₆ decomposed products over the ZnO(101̅0) surface. The effects of O and Zn vacancies on the surface were also considered. For perfect ZnO(101̅0) surface, the adsorption of SO₂ and H₂S exhibits stronger chemical interactions compared to the adsorption of SOF₂ and SO₂F₂. For SO₂ and H₂S adsorption, there may exist new chemical bond formation between the molecule and the surface and the H₂S molecule experiences one H-S broken bond. The introduction of O vacancy cannot obviously enhance the chemical interactions between these four molecules and the surface. However, the Zn vacancy on the surface can significantly elevate the chemical interactions between SO₂/H₂S and the surface. The two-coordinated O atom (O_2c) on the surface plays an important role. For SO₂ and H₂S adsorption, the S atom in SO₂ or H₂S tends to bond to the O_2c atom, bringing much larger adsorption energy compared to the adsorption over the perfect ZnO(101̅0) surface. This work can provide a basis for surface modification of ZnO in applications to detecting SF₆ decomposed products by theoretical evaluation.