Sensing performance and mechanism of shape-tunable CuO nanocrystals for monohydric alcohol gases

Abstract

In this work, a variety of CuO architectures, including cubes, truncated cubes, cubooctahedrons, truncated octahedrons, and octahedrons were achieved using Cu₂O nanocrystals as a sacrificial template. In the gas sensitivity test, the CuO nanocrystals with different shapes were tested for specific gases, such as monohydric alcohols, including methanol, ethanol, n-propanol, n-butanol, n-pentanol, and n-hexanol, belonging to the class of straight-chain alcohols (C1–C6). An interesting phenomenon could be observed where the gas response of the CuO sensors increased as the number of carbon atoms increased. However, when the number of carbon atoms was C5 (n-pentanol), the response values of CuO sensors reached the maximum. In these CuO architectures, the CuO-truncated octahedron-2 sensor and the CuO-octahedron sensor exhibited better performance than alcohols. The CuO-octahedron sensor exhibited the best sensitivity and selectivity to n-pentanol gas and possessed good long-time stability. In addition, the response and recovery times of the CuO-octahedron sensor to 100 ppm n-pentanol gas are 8 s and 16 s, respectively. In addition, the gas sensing mechanism of a CuO-truncated octahedron-2 sensor for n-pentanol was explored through theoretical calculations. Compared with the adsorption energy, the dissociation adsorption energy plays a more important role in the response of monobasic alcohol molecules on the (110) crystal surface of CuO.