Metal-organic frameworks-derived hollow nanotube La2O3-In2O3 heterojunctions for enhanced TEA sensing at low temperature

The rational construction of metal oxides heterojunctions is an effective method to enhance their gas-sensing performance of metal oxide semiconductors. However, La2O3-In2O3 heterojunctions can be hardly obtained by conventional impregnation and thermal treatment because the harsh conditions are required for the ex-solution of La3+ in In2O3 lattice. Herein, MOF-derived synthesis method is applied to synthesize the La2O3-In2O3 heterojunctions, and the uniform hollow La2O3-In2O3 nanotube can be obtained after annealing at 450 °C. Additionally, the La2O3-In2O3 heterojunctions are further fabricated as gas sensors to monitor the accurate concentration of TEA molecules. Compared with the pristine In2O3 and La doped In2O3 (La-In2O3-RW) samples, La2O3-In2O3 heterojunctions exhibit the best sensing performance for 50 ppm TEA at low working temperature of 120 °C (Ra/Rg=458.13), which is 4.8 times and 1.9 times higher than pristine In2O3 and La-In2O3-RW. Moreover, the sensors also exhibit good long-term stability and high selectivity at low working temperature. The excellent sensing performance can be attributed to the synergistic effect between La2O3 and In2O3 species including the modified electronic structure, the formation of electron depletion layer, the wide distribution of acid sites and O2-(ad) and O-(ad) species.