Controllable synthesis of a nanoparticle-modified thin-layer 3D flower-like CuZnAl-LDHs material with high NO2 gas sensing performance at room temperature

To optimise the morphology and properties of LDH materials, 3D flower-like CuZnAl-LDHs were controllably synthetized by a hydrothermal method. The as-obtained CuZnAl-LDHs were assembled successfully by ultra-thin nanosheets. The optimal sensor (CZA-2) has a high sensitivity and a fast response to 100 ppm NO2 at room temperature (RH = 26%), and its response value and response/recovery time are 22.30 and 2.66/57.60 seconds, respectively. At the same time, it also has a high selectivity and significant long-term stability of up to 8 weeks at RT. The excellent performance of the sensor is attributed to the abnormal phenomenon of octahedral coordination of divalent copper ions in an excess alkaline environment with Zn2+, which increases the LDH layer spacing and is conducive to electron transport. Moreover, the metal hydroxides exhibit a nanosheet morphology under the induction of NH4F and are self-assembled into flower-like hierarchical structures. The existence of nano-islands and ultra-thin 2D layered structures synergistically constructs a fast transmission channel for the electrons, which effectively improves the gas sensing performance of NO2 at room temperature.