pH-mediated hydrothermal synthesis of SnO2 for enhanced ethanol sensing: Structural regulation and performance optimization

Abstract

Developing high-performance gas sensors through facile synthesis remains challenging. Here, a pH-mediated hydrothermal strategy for precisely engineering SnO₂ nanostructures toward exceptional ethanol sensing is reported. By systematically tuning hydrothermal pH from 2 to 13, hierarchical control of crystallinity (XRD), particle morphology (SEM/TEM), and band structure (UV-Vis) are achieved. The strong alkaline condition (pH=13) yielded monodisperse 5–10 nm nanoparticles with optimized (101) facet exposure, delivering record-high response of 97.2 toward 400 ppm ethanol at 300°C, improvements over acidic (pH=2) and neutral (pH=7) counterparts, respectively. Mechanistic studies reveal that extreme pH conditions promote charge-driven crystallization kinetics, suppressing particle agglomeration while increasing oxygen vacancies. The obtained sensitivity (20.64 ppm⁻¹) and linearity (96.95 %) surpass some multifactor-modified SnO₂ sensors reported. This single-variable approach demonstrates cost reduction compared to composite modification methods, establishing a generalizable paradigm for transition metal oxide optimization. The fundamental insights into pH-dependent growth mechanisms provide new design principles for scalable nanofabrication.