Different morphologies hierarchical flower-like tin dioxide (SnO2) nanostructures were fabricated by changing the volume ratio of glycol and de-ionized water (V-g:V-w=0, 1:2, 1:1 and 2:1) under a template-free and low-cost hydrothermal method and subsequent calcinations. The architectures, morphologies and gas sensing performances of the products were characterized by X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and gas-sensing measurement device. It can be observed that all the nanoflowers were composed of two-dimensional (2D) nanosheets, and the thickness of nanosheets is only about 9 nm when V-g:V-w = 1:1. The sensor based on the product of Vg:Vw = 1:1 exhibited excellent gas sensing performance toward 500 ppm acetic acid at 260 degrees C, and the response value of this sensor was about 153.6, which was above 7.5 times higher than that of ammonia (about 20.3). In addition, the 3D flower-like SnO2 nanostructures exhibited not only high response and selectivity to ppm level acetone, but also fast response and recovery time within 10 s, demonstrating it can be used as a potential candidate for detecting acetic acid. Finally, the possible formation mechanism was proposed, too. (C) 2015 Elsevier B.V. All rights reserved.