Controllable acid vapor oxidation growth of complex SnO₂ nanostructures for ultrasensitive ethanol sensing

Controllable assembly from one-dimensional (1-D) and two-dimensional (2-D) nanoscale structures to three-dimensional (3-D) complex nanostructures has attracted great interest. For the first time, nanorods and nanosheets were controllably assembled into 3-D SnO₂ nanoflower architectures based on a facile and shape-controlled acid vapor oxidation (AVO) method from the substrate in a simple reaction system. The as-prepared 3-D SnO₂ nanoflowers have diameters ranging from 625 to 875 nm and are self-assembled by many nanorods and nanosheets with diameters and thicknesses of 33 nm. The growth of SnO₂ with different morphologies was studied by controlling the reaction temperature and hydrochloric acid concentration. Their application in gas sensing was evaluated, indicating that the 3-D SnO₂ nanoflower-based sensor is ultrasensitive to ethanol with a response of 2.54–50 ppb at the optimal working temperature of 230 °C. This work offers a facile, shape-controlled, and efficient route to synthesize complex SnO₂ nanoflowers for gas detection with high performance, including ultrahigh sensitivity, good selectivity, and reversibility.