In this study, a hollow malposition structure (HMS) optical fiber 2-butanone gas sensor based on double-layer WO 3 @CQDs porous film is proposed, and realizes the ppb detection of 2-butanone gas at room temperature. The HMS can excite the evanescent field and sense the gas adsorption on the fiber surface. The experimental results show sensitivity of 3.09 pm/ppm for this HMS optical fiber gas sensor based on double-layered WO 3 @CQDs porous film, which is 6.05 times higher than that of the sensor coated with single-layer WO 3 @CQDs porous film. In addition, a limit of detection (LOD) reaches 500 ppb. The response time is 11.7 s and the recovery time is 5.72 s. Density functional theory (DFT) results show that the modification of CQDs improves the adsorption capacity of WO 3 @CQDs for 2-butanone gas molecules and changes the refractive index of the material. The sensor has the advantages of small volume, high sensitivity and a low LOD, which is of great significance for the detection of trace 2-butanone gas.
Bingcai Chen,Pengpeng Li,Lian Sun,Yingde Wang,Bing Wang
To selectively detect trace carbon monoxide (CO typically lower than 100 ppb) at low temperature is still a great challenge for chemiresistive gas sensors. In this work, we introduce In2O3 nanocubes with exposed {001} facets to couple with MOF-derived porous Co3O4 nanosheets (NSs) forming p–n heterojunction for trace CO detection. Benefiting from the vacancy storing effect of the sub-valent band on In2O3 nanocube {001} facets and the p–n heterojunction effect, the electron–hole recombination is effectively inhibited, and the carrier lifetime is prolonged. As a result, the prepared CoIn0.1-based gas sensor shows a good selectivity and ultralow detection limitation of 25 ppb toward CO at relatively low temperature of 175 °C. In addition, the CoIn0.1-based CO sensor also exhibits high response (272.89%) and ultrafast response/recovery time (2 s/13 s) to 100 ppm CO, which can be ascribed to the fast gas diffusion in the porous Co3O4 NSs and the high-index facet effect of In2O3 nanocubes. This work provides a method to design and synthesize trace CO gas sensors via modulating the band structure of p–n heterojunctions constructed by two-dimensional metal oxide NSs and oxide-exposed high-index facets.
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