The template-free synthesis of square-shaped SnO2 nanowires:: the temperature effect and acetone gas sensors

Square-shaped single-crystalline SnO2 nanowires and their sphere-like hierarchical structures were synthesized successfully with a template-free hydrothermal approach. It was found that an intermediate phase-Na2Sn(OH)(6)-is first produced because it is slow to dissolve in ethanol/water media. The intermediate phase gradually decomposes and converts into SnO2 at temperatures higher than 200 degrees C. The reaction temperature also affects the microstructure of SnO2 nanomaterials. Uniform square-shaped SnO2 nanowires, which form sphere-like hierarchical structures in 100% structure yield, can be produced at 285 degrees C on a large scale. The diameter of the nanowires shows a decrease accompanying the increase of the reaction temperature. The temperature effect could be a result of the faster and oriented growth of SnO2 nanowires along their < 001 > direction at higher temperature. Chemical sensors constructed with square-shaped SnO2 nanowires exhibit excellent stability, good sensitivity and selectivity, as well as a quick response and short recovery times under exposure to acetone gas in practical applications.