In this work, hierarchical ZnO (H-ZnO) and Au decorated hierarchical ZnO (Au-H-ZnO) microstructures have been successfully fabricated for improved gas-sensing and photocatalytic properties. Particularly, the H-ZnO microstructures are synthesized by a low temperature (60 degrees C) aqueous growth followed by a heat treatment process. The growth mechanism of the ZnO architecture is related to the concentration of sodium hydroxide. Gas sensing measurements reveal that the ZnO microstructures decorated with Au nanoparticles exhibited outstanding sensing properties toward acetone and ethanol, including the fast response and recovery rate, high sensitivity and low optimum working temperature, these test results are much better than that of pure ZnO sensor. Also, the UV-vis and photocatalytic measurements of the as-synthesized Au-H-ZnO microstructures displayed remarkable enhancement of photocatalytic properties. The improvement of the gas sensing and optical properties should be ascribed to the reality that the complex structure supplied a high absorption surface area and sufficient oxygen vacancies, and Au nanoparticles play the role as a catalyst to facilitate the absorption and desorption of gas molecules. (C) 2018 Elsevier B.V. All rights reserved.