Nickel oxide nanosheets grown on amorphous and porous zinc-tin-oxide microcubes as heterojunctions for effective sensing of triethylamine gas.

Nanosized heterojunctions were designed and assembled into gas sensors for triethylamine through a series of processes. Amorphous and porous ZnSnO microcubes were first synthesized via aqueous chemical reactions followed by calcination. Then crystalline NiO nanosheets with a narrow thickness distribution of 16.0–28.0 nm were anchored on their surfaces dispersedly. The as-prepared NiO/ZnSnO heterojunctions possessed an increased specific surface area of 118.18 m2/g and an average pore diameter of 4.11 nm. Compared to the amorphous ZnSnO microcubes, the NiO/ZnSnO heterojunctions exhibited higher sensitivity and selectivity toward triethylamine in gas sensing tests. The optimal operating temperature was 180 °C with fast response/recovery time of approximately 7/16 s and excellent repeatability. The enhanced sensing performance was attributed to the synergistic effects of the large surface area, the strong catalytic activity of NiO, and the efficient charge transfer at the interfaces between the amorphous and crystalline metal oxides.