Chemical Tuning versus Microstructure Features in Solid-State Gas Sensors: LaFe_1‑xGa_<i>x</i>O₃, a Case Study

A simple and cheap wet chemical approach is exploited to synthesize LaFe_1‑<i>x</i>Ga_<i>x</i>O₃ (<i>x</i> = 0–1) crystalline perovskites. Ga doping level deeply influences not only the microstructure, but also the iron chemical features and consequently the responses to external chemicals. Sensitivity toward gases (NO₂, CO, and ethanol), in fact, is driven by both Fe/Ga ratio and iron oxidation states, which are demonstrated playing a role much stronger than morphological parameters, such as grain size and specific surface area, usually dominating the performances of metal oxide based gas sensors. Results highlight that sensing behavior is tunable within a large extent by a simple and effective modulation of the chemical composition, obtaining sensitivities comparable with state of the art perovskite based gas sensors

Tin Oxide Nanowires Decorated with Ag Nanoparticles for Visible Light-Enhanced Hydrogen Sensing at Room Temperature: Bridging Conductometric Gas Sensing and Plasmon-Driven Catalysis

We demonstrate that conductometric gas sensing at room temperature with SnO₂ nanowires (NWs) is enhanced by visible and supraband gap UV irradiation when and only when the metal oxide NWs are decorated with Ag nanoparticles (NPs) (<i>diameter</i> < 20 nm); no enhancement is observed for the bare SnO₂ case. We combine the spectroscopic techniques with conductometric gas sensing to study the wavelength dependency of the sensors’ response, showing a strict correlation between the Ag-loaded SnO₂ optical absorption and its gas response as a function of irradiation wavelength. Our results lead to the hypothesis that the enhanced gas response under UV–vis light is the effect of plasmonic hot electrons populating the Ag NPs surface. Finally, we discuss the chemiresistive properties of Ag-loaded SnO₂ sensor in parallel with the theory of plasmon-driven catalysis, to propose an interpretative framework that is coherent with the established paradigma of these two separated fields of study