Facile synthesis and ultrahigh ethanol response of hierarchically porous ZnO nanosheets

Zinc oxide (ZnO) nanosheets were successfully synthesized through a facile, economic, and low-temperature hydrothermal process, followed by annealing of the zinc carbonate hydroxide hydrate precursors. The nanosheets are single crystals with hexagonal wurtzite and mesoporous structures. Gas sensors based on these ZnO nanosheets exhibited ultrahigh response, fast response–recovery, and good selectivity and stability to 0.01–1000 ppm (parts per million) ethanol at 400 °C. Extremely low concentration ethanol (down to 10 ppb (parts per billion)) can be readily detected (S = 3.05 ± 0.21), which is the lowest detection limit to ethanol utilizing pure ZnO as sensing materials in a one-side heated gas sensor hitherto. The excellent ethanol-sensing performance of ZnO, particularly the ppb-level response, is mainly attributed to its novel hierarchical structure, which has a large specific surface area, abundant mesopores, single-crystal structure, plane-contact between sheets, three-dimensional network architecture, and characteristically small thickness.