Cation effects and nanocomposite architectures in spinel-ferritechemiresistive gas sensors: A critical review

NH₃, H₂S, and NO₂ detection below occupational and environmental thresholds remains constrained bypoor selectivity, elevated operating temperatures, and humidity interference in single-phase ferritechemiresistors. Spinel ferrite nanocomposites introduce two design variables absent from single-phaseconfigurations: ferrite cation-site occupancy and composite junction architecture. This critical reviewcovers 2015-2026 cation-engineered MFe₂O₄ nanocomposite literature across four compositearchitectures for NH₃, NO₂, H₂S, ethanol, acetone, and toluene.

ZnO/ZnFe₂O₄ hollow nanocages resolved acetone to 1 ppm at 290°C with response 25.8, outperformingboth phases under matched conditions. Ni substitution produced Fe/Ni-ratio-dependent barriersensitivity; Co substitution restricted grain growth above 200°C. Cu-bearing composites showedmorphology and transport changes determined by partner phase. Ferrite/carbon composites achieved0.02 ppm acetone at room temperature but showed unsatisfactory long-term stability. Ferrite/polymercomposites enabled room-temperature NH₃ detection, operationally limited to below 150°C. Bi-ferriteheterojunctions produced no chemiresistive sensing data across any analyte in the reviewed period.

Within the reviewed period, no study links Möössbauer-confirmed A/B-site occupancy to compositejunction behaviour and sensing outcome in a single experimental design. Zn/Ni co-doped ferritenanocomposites with confirmed site occupancy and humidity-controlled testing define the primaryunresolved experimental target.