Abstract
The development of WO3-based gas sensors for analysis of acetone in exhaled breath is significant for noninvasive diagnosis of diabetes. A series of Fe-doped hexagonal and monoclinic WO3 phase−junction (Fe−h/m−WO3) sensors were synthesized by the hydrothermal calcination method, and the influences of operating temperature and light irradiation on the response were studied. Under light emitting diode (LED) illumination, Fe−h/m−WO3 exhibited higher responses to acetone than those of the undoped WO3-based sensors at an operating temperature of 260 °C with 90% relative humidity, and good linearity between response and acetone concentration (0.5 to 2.5 ppm) was achieved under the 90% relative humidity condition. Meanwhile, the optimal Fe−h/m−WO3 sensor exhibited high selectivity and stability for a duration of three months. The excellent sensing performance of Fe−h/m−WO3 was attributed to the formation of phase−junction and Fe doping, and these were beneficial for the separation of photon−generated carriers and oxygen adsorption on the WO3 surface, promoting the generation of superoxide radicals, which was demonstrated by electron paramagnetic resonance and photocurrent tests. Additionally, the Fe−doped WO3 phase−junction sample also showed good photocatalytic performance for rhodamine B degradation. This study may provide some insights into rational design of new types of gas sensors and offer an alternative for noninvasive diagnosis of diabetes.
Highlights
Over the last few years, breath analysis, as a rapid, cheap and non−invasive biological method, has attracted much attention in diagnosing and monitoring medical fields [1,2,3]
Li et al [22,23] reported that the anatase−rutile phase junction of TiO2 greatly enhanced the photocatalytic activity, and they demonstrated that efficient charge separation and transfer were achieved across the α−β phase junction of Ga2O3 leading to enhanced photocatalytic performance
A series of Fe-doped hexagonal and monoclinic WO3 phase junction materials were synthesized by the hydrothermal−calcination method
Summary
Over the last few years, breath analysis, as a rapid, cheap and non−invasive biological method, has attracted much attention in diagnosing and monitoring medical fields [1,2,3]. Li et al [18] reported that the gas-sensing property of a Co-doped monoclinic phase WO3 for acetone molecules was significantly improved due to the effect of lattice defect and Co doping, which facilitated gas adsorption. Apart from the carrier separation in semiconductors, the acetone-sensing property of the semiconductors relies heavily on the surface conductivity induced by chemical reactions between the target gases and oxygen species adsorbed onto the surface [17]. As for the general acetone-sensing mechanism (Equations (1)–(4)) [18], the oxygen ions were formed by drawing electrons from the conduction band of metal oxide, and different oxygen species (O2−, O− and O2−) were formed depending on the operating temperature [16]. The enhancement of oxygen adsorption ability was a positive approach for increasing gas-sensing performance of semiconductors.
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