Layered MXene heterostructured with In2O3 nanoparticles for ammonia sensors at room temperature

The MXene/In2O3 heterostructure was formed through a facile hybridization process which enables the In2O3 nanoparticles to be coated dispersively on the surface and also partly intercalated into the interlayers of the layered MXene. The MXene/In2O3 hybrids based chemiresistive-type gas sensor exhibited good sensitivity and selectivity toward NH3 at room temperature. The response of the MXene/In2O3 hybrids based sensors to 20 ppm ammonia increased remarkably from 3.6% to 100.7% at room temperature in comparison to the pristine MXene-based one. Moreover, it was found that the gas response of the MXene/In2O3 based sensors to ammonia increased with the increase of relative humidity in the gas mixture. Furthermore, the wireless-type response of the MXene/In2O3 based sensors coupled with a LC antenna fabricated by a LTCC (low temperature co-fired ceramic) technology has also been examined. The wireless-type sensors displayed an excellent sensing performance with a significantly improved response/recovery time less than 2 s and a long-term stability toward ammonia. The in-situ infrared spectroscopy of MXene/In2O3 exposed to NH3 indicated the production of gaseous nitric oxides during the sensing process. The a.c. impedance spectroscopy shows that the bulk resistance of MXene/In2O3 heterostructured particles was mainly responsible for the generation of the sensor signals.