fig7

Figure 7. (A) Time-dependent ethanol gas sensing performances of TiO₂ and C₄₀-TiO₂ sensor performances at 150 °C (A₁); Ethanol gas sensing mechanism on pristine TiO₂ and C₄₀-TiO₂. Figure 7A is quoted with permission from Raghu et al.^[147]; (B) molecular structure of N-doped In₂O₃ (B₁); SEM (B₂) and TEM (B₃) image of N-doped In₂O₃; The response transients of sensors to 10 ppm NO₂ (B₄); The linear fitting to the relationship between response and concentrations for In₂O₃ and N-doped In₂O₃ (B₅). Figure 7B is quoted with permission from Mo et al.^[150]; (C) Acetone sensing performance and mechanism of 3D cross-stacked Si-doped WO₃ nanowire arrays. Figure 7C is quoted with permission from Ren et al.^[153]; (D) Schematic illustration of the synthesis of the Ti₃C₂T_x MXene, sulfur-doped Ti₃C₂T_x MXene, and preparation of the MXene sensors (D₁); Dynamic response curve of sulfur-doped Ti₃C₂T_x sensors for toluene at room temperature (D₂). Figure 7D is quoted with permission from Shuvo et al.^[156]. VOC: Volatile organic compound; TEM: transmission electron microscopy; SEM: scanning electron microscope; ppm: parts-per-million.