SYNTHESIS OF NANOSTRUCTURED METAL OXIDES FOR GAS SENSORS
Keywords:
Keywords: metal oxide; gas sensor; nanostructure; chemiresistive sensing; hydrothermal synthesis; grain-size effect.Abstract
Abstract. Semiconducting metal oxides are the dominant transduction
materials for chemiresistive gas sensors, and their performance is governed by the
surface-to-volume ratio, crystallite size and morphology that nanostructuring makes
accessible. This work reviews the principal vapour- and solution-phase routes used to
synthesise nanostructured metal oxides for gas sensing—sol–gel processing, spray
pyrolysis, chemical and physical vapour deposition, template filling, and hydro-
/solvothermal growth—and links each architecture to the underlying sensing physics.
Representative systems include template-grown SnO₂ nanotubes, carbothermal one-
dimensional In₂O₃ and Ga₂O₃, hydrothermal porous α-Fe₂O₃, ultrathin p-type CuO
nanoribbons, and Co₃O₄ hollow nanospheres. A compact mathematical framework—
the Debye-length depletion model, the double-Schottky-barrier grain-size effect, and
the Knudsen diffusion–reaction equation—rationalises the measured responses, which
are maximised when the feature size approaches twice the depletion-layer thickness
and gas access to interior sites is preserved by controlled porosity.
References
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