Design of Au@WO3 core−shell structured nanospheres for ppb-level NO2 sensing

As motivated by the driving force of the urgent demand for high-performance nitrogen dioxide (NO2) sensor, in this work, a novel structure of [email protected]3 core–shell nanospheres (CSNSs) was designed and successfully prepared for NO2 detection. The techniques of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller measurement, and elemental mapping analysis were used for the characterizations of the obtained samples. The results demonstrated that Au nanoparticles with 25–50 nm in diameter were successfully encapsulated by WO3 shells with the thickness of 30–50 nm. The NO2 sensing performance of the [email protected]3 CSNSs as well as the pure WO3 nanospheres were systematically investigated. Compared with the pure WO3 nanospheres, [email protected]3 CNNSs exhibited overall enhanced NO2 sensing performances in terms of response, detection limit, and response/recovery times. At the optimal operating temperature of 100 °C, [email protected]3 CSNSs showed excellent NO2 selectivity and long-term stability. Notably, the excellent NO2 sensing performance of [email protected]3 CSNSs was slightly affected by humidity. The possible sensing mechanism of the enhanced NO2 sensing properties of the [email protected]3 CSNSs was discussed.