CO sensing properties of Ga-doped ZnO prepared by sol–gel route

• Nanostructured Ga-doped ZnO were synthesized by the sol–gel method.
• The effects of Ga doping level on the structural, morphological and sensing properties of ZnO were investigated.
• Ga doping promotes the enhancement of CO sensing allowing to detect CO at sub-ppm concentrations in air.

The microstructural and functional characterization of pure and Ga (1–5 at.%)-doped ZnO nanoparticles synthetized by sol–gel method is reported. All the samples, characterized by XRD and TEM, showed the nanocrystalline ZnO wurtzite structure. However, depending on the Ga content, the morphological, microstructural and electrical properties of doped samples changed markedly with respect to the undoped ZnO. The effect of gallium dopant on sensing properties of thick films of ZnO nanoparticles, deposited on alumina substrates provided with Pt interdigited electrodes for the application as CO resistive sensors, have been investigated. Sensors based on Ga-doped ZnO exhibited a higher response (R0/R = 9, to 50 ppm of CO at the operating temperature of 250 °C) and lower response/recovery time (8 and 35 s, respectively) than the pure ZnO sample, allowing to detect CO at sub-ppm concentrations in air.

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