Synthesis of monodisperse ZnO hollow six-sided pyramids and their high gas-sensing properties

• The ZnO hollow six-sided pyramids are synthesized by a low-cost and simple hydrothermal approach.
• Our sample has highly selectivity and sensitivity to 200 ppm ethanol at 240 °C.
• The possible growth mechanism of ZnO hollow six-sided pyramids is proposed.

Monodisperse ZnO hollow six-sided pyramids were successfully synthesized by a low-cost and simple hydrothermal method at 160 °C for 20 h without the use of any surfactant or template. The sodium citrate (Na3C6H5O7·2H2O) and glycerol (C3H8O3) played a pivotal role in the growth of hollow six-sided pyramid, and the possible growth mechanism was also proposed based on the experimental facts. Moreover, the gas sensor based on this structure displayed excellent gas sensing properties to ethanol at the optimum operating temperature of 240 °C. The response was about 187 and the response-recovery time was around 11 and 9 s for 200 ppm ethanol, respectively, which indicated that this structure had high sensitivity, fast response-recovery time and good selectivity to ethanol.