Highly sensitive C2H5OH sensors using Fe-doped NiO hollow spheres

NiO and Fe-doped NiO hollow spheres with the shell thickness of ∼12 nm have been prepared by applying uniform coatings of Ni- and Fe-precursors onto Ni spheres, partial oxidation of Ni spheres near their surfaces at 300 °C, the dissolution of core Ni using dilute HCl aqueous solution, and subsequent heat treatment at 500 °C, and their gas sensing characteristics at 300–400 °C were compared. The response to 100 ppm C2H5OH of Fe-doped NiO hollow spheres at 350 °C (Rg/Ra = 172.5; Rg, resistance in gas; Ra, resistance in air) was 31.4 times higher than that of NiO hollow spheres (Rg/Ra = 5.5). The reasons for the significant enhancement of C2H5OH response by doping Fe into NiO hollow spheres were discussed in relation to the incorporation of Fe components into the NiO lattice and their consequent impact on the gas sensing reaction.