Scalable Fabrication of Cataluminescent Sensing Films with Enhanced Selectivity for <i>Iso</i> -Butanol over Structural Isomers

The broad use of gas sensors requires high selectivity and sensitivity together with scalable, reproducible fabrication of sensing films. Here, we report a slurry blade-coating route to thick-film MgO, SiO₂, and MgO-SiO₂ composite cataluminescence (CTL) sensing layers with controlled thickness and consistent performance. The MgO-SiO₂ composite exhibited enhanced markedly selectivity for <i>iso</i>-butanol (IBA) over its structural isomers, while maintaining rapid and reversible response characteristics. The calibration was linear from 15 to 580 mg/m³, with a detection limit of 8.4 mg/m³ (<i>S</i>/<i>N</i> = 3). Practical applicability was demonstrated by online monitoring of IBA production during <i>Saccharomyces cerevisiae</i> fermentation, where the sensor outputs closely matched gas chromatography-mass spectrometry measurements. Mechanistic investigations revealed that acid-base bifunctional ensembles formed at interfacial Mg-O-Si domains can moderate the surface basicity of MgO, tune adsorption energetics, and redirect the oxidation pathway, which potentially contribute to the observed enhancement in selectivity. This work pioneers a scalable route to high-performance CTL sensor fabrication and provides molecular-level insights into selective gas sensing, paving the way for next-generation sensors tailored for complex environments.