Ethanol gas sensor based on CoFe2O4 nano-crystallines prepared by hydrothermal method

CoFe2O4 nano-crystallines were prepared by a hydrothermal method at 120–220 °C. CoFe2O4 sensors were fabricated from the CoFe2O4 nano-crystallines and their gas sensing properties were investigated. Spinel CoFe2O4 nano-crystallines could be obtained when the pH value was in the range of 8–14, and the morphology of the particles obtained under different conditions was almost spherical. The CoFe2O4 nano-crystallines obtained at a pH of 8–10 exhibited n-type response to gases at low temperatures and p-type response to gases at high temperatures, while CoFe2O4 nano-crystallines obtained at a pH of 11–14 exhibited p-type response to gases. It was found that the sensor based on the CoFe2O4 nano-crystallines prepared at 180 °C for 48 h (pH 8) exhibited good performance, characterized by high responses to dilute C2H5OH and very low responses to petrol, C6H6 and C6H5CH3 when operating at 150 °C. If there was no ethanol in the atmosphere, the sensor based on nano-CoFe2O4 (180 °C, 48 h, pH 8) could be used to detect triethylamine at 190 °C. The sensor is a promising candidate for practical detector for dilute C2H5OH and triethylamine.