fig3

Figure 3. Structural characterization and proposed sensing mechanisms of MOF-based and noble-metal-sensitized H₂S sensors. (A) Cross-sectional SEM images of thickness-controlled Ni₃(HITP)₂/NUS-8 films (A₁-A₄); KPFM maps of pristine NUS-8 (A₅) and Ni₃(HITP)₂/NUS-8 (A₆), S 2p and N 1s XPS spectra before and after exposure to 10 ppm H₂S (A₇-A₈); EPR spectra (A₉); and the proposed redox sensing mechanism (A₁₀). Reproduced with permission from Ref.^[46]. Copyright 2024, Wiley-VCH; (B) Proposed sensing mechanism of Ag nanoparticle-decorated TiO₂ nanosheets, including Ag-to-TiO₂ electron transfer, defect-assisted electron transport, and potential-barrier formation. Reproduced from Ref.^[138], under CC BY 4.0 license; (C) Proposed Au/SnO₂ interfacial dipole effect under low bias(C₁); O 1s XPS spectra of pristine SnO₂ (C₂) and Au/SnO₂ (C₃); and the proposed surface-reaction and charge-transport mechanisms (C₄). Adapted from Ref.^[48], under CC BY 4.0 license. MOF: Metal-organic framework; SEM: scanning electron microscope; KPFM: Kelvin probe force microscopy; NUS: National University of Singapore; XPS: X-ray photoelectron spectroscopy; EPR: electron paramagnetic resonance.