In this study, a facile hydrothermal method was adopted to fabricate SnO2 and CuO–SnO2 nanoparticles. The CuO content was chosen as 5 mol.-% (sample 1), 10 mol.-% (sample 2) and 15 mol.-% (sample 3). Microstructures and surface morphologies for all samples were characterised by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). A systematic comparison study reveals an enhanced gas sensing performance for the CuO–SnO2 gas sensor towards CO gas. The improved gas sensing properties are attributed to the formation of p–n junctions and the absorbed oxygen species as well as to the heterojunctions of the CuO to the SnO2 nanoparticles which provide additional reaction rooms. The results represent an advance of heterojuction nanostructures in further enhancing the functionality of gas sensors, and this simple method could be applicable to many sensing materials.
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