Eco-friendly facile synthesis of Co 3 O 4 –Pt nanorods for ethylene detection towards fruit quality monitoring

Ethylene, a biomarker widely employed for evaluating fruit ripening during storage, exists at extremely low concentrations. Therefore a gas sensor with high sensitivity and a sub-ppm detection limit is needed. In this work, porous Co 3 O 4 nanorods were synthesized through a hydrothermal method involving Co(NO 3 ) 2, Na 2 C 2 O 4, H 2 O and ethylene glycol (EG), followed by annealing at 400 °C in air. The surface of the porous Co 3 O 4 nanorods was functionalized with Pt nanoparticles to enhance the ethylene sensing performance. The effect of Co 3 O 4 surface functionalisation with Pt nanoparticles was investigated by adding different amounts of nanoparticles. The sensor’s outstanding performance at the optimum working temperature of 250 °C is attributed to the synergy between the high catalytic activity of Pt nanoparticles and the extensive surface area of the porous Co 3 O 4 nanorods. Compared to pure Co 3 O 4, the 0.031 wt% Pt sensor showed better ethylene sensing performance with a response 3.4 times that of pristine Co 3 O 4. The device also demonstrated high selectivity, repeatability, long-term stability and a detection limit of 0.13 ppm for ethylene, which is adequate for fruit quality monitoring. The gas sensing mechanism of porous Co 3 O 4 nanorods and the influence of Pt decoration on sensor performance are discussed.