Soft-templated formation of double-shelled ZnO hollow microspheres for acetone gas sensing at low concentration/near room temperature

Abstract The synthesis of well-defined and complex porous hollow structures via a simple method is still a major challenge. In this work, a unique double-shelled ZnO hollow microsphere with a porous surface is successfully synthesized by a facile soft-templated solvothermal method followed by calcination. The presence of ethylene glycol (EG) as soft template leads to the formation of initial single-layered hollow microspheres and then a time-dependent evolution transforms them into uniform ZnO hollow microspheres with tunable shell numbers and void space. When used as sensing materials for detecting acetone, the double-shelled ZnO hollow microsphere sensor exhibits high response toward 100 ppm acetone (101.1) and achieves a rapid response rate and recovery process (within 1/7 s) at 300 °C, which are superior over those for ZnO microparticle and single shelled ZnO hollow microsphere. In addition, this sensor exhibits low detection limit (0.5 ppm), low operating temperature (40 °C), high selectivity to acetone, and long term stability, suggesting their potential applications as advanced gas sensing materials. Such outstanding gas sensing properties of double-shelled ZnO hollow microsphere is due to the larger Brunauer-Emmett-Teller (BET) surface area (76.11 m2 g−1), porous and double-shelled hollow structure, and excellent capabilities of surface adsorbed oxygen.