Room-temperature acetone gas sensing using Sm-doped Co–Zn ferrite nanoparticles: role of mesoporosity and oxygen vacancies in enhancing sensor response

This study presents the synthesis, structural characterization, and acetone gas sensing behavior of nanocrystalline Co-Zn-Sm ferrites (CZSmF) with the general formula Co_0.7Zn_0.3Sm _<i>x</i> Fe_2-<i>x</i> O₄ (<i>x</i> = 0-0.04), synthesized <i>via</i> the sol-gel auto-combustion method. Rietveld-refined X-ray diffraction (XRD) analysis confirms the formation of a single-phase spinel structure (space group <i>Fd</i>3̄<i>m</i>), with crystallite sizes ranging between 31 and 43 nm as determined by the Williamson-Hall method. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) reveal well-defined nanocrystals with predominantly oval morphology and an average particle size of ∼28 nm. Brunauer-Emmett-Teller (BET) analysis indicates mesoporous behavior with surface areas ranging from 6.2 to 15.2 m² g^-1 and pore sizes in the range of 16-22 nm. X-ray photoelectron spectroscopy (XPS) confirms the oxidation states of Co²⁺, Zn²⁺, Fe²⁺/Fe³⁺, and Sm³⁺ ions and reveals significant oxygen vacancies contributing to the gas sensing mechanism. The CZSmF sample with <i>x</i> = 0.01 (CZSmF01) demonstrates superior acetone sensing performance at ambient temperature (296 K), exhibiting high selectivity, a swift response time of 84 s, and a rapid recovery time of 24 s for 100 ppm acetone. The optimized sensing performance is attributed to a synergistic combination of favorable crystallite size, pore architecture, and oxygen vacancy-induced n-type conduction. Additionally, CZSmF01 shows high stability and reproducibility across multiple cycles and maintains linear response characteristics across a concentration range of 25-100 ppm, establishing its applicability for quantitative detection. Notably, the sensor also demonstrates humidity sensing with low response (10 s) and recovery (8 s) times, indicating multifunctionality. The results highlight the potential of CZSmF01 for commercial acetone detection applications.