Highly toluene sensing performance based on monodispersed Cr2O3 porous microspheres

Monodispersed chromium oxide (Cr2O3) precursor microspheres have been synthesized by an ethanol solvothermal process without using a template or surfactant. Porous Cr2O3 microspheres consisting of nanoparticles have been obtained from a thermal treatment of the precursor microspheres in air. Compositions of the precursor microspheres and the porous microspheres have been characterized by XRD, IR, TG–DTA and XPS; structures of the porous microspheres have been investigated in detail by SEM, TEM, HRTEM and N2 adsorption–desorption; the structure analysis ascertains that the porous microspheres with diameters of 1.0–1.2 μm are constructed from nanoparticles with sizes of 40–70 nm. Aggregation of the nanoparticles results in the formation of pores with sizes of 20–80 nm in the microspheres. Thick film sensors, made from these porous Cr2O3 microspheres, exhibit excellent toluene sensing performance with a detection limit of 1 ppm at 170 °C.