Highly sensitive and selective gas-phase ethanolamine sensor by doping sulfur into nanostructured ZnO

The chronic and prolonged exposure to ethanolamine (EA), which is widely used in various commercial and industrial applications, can compromise human health and cause even death. Thus, sensors that can rapidly and efficiently detect EA in air, especially where EA is widely produced or used, is of paramount importance. Herein, we report the synthesis of sulfur-doped, flower-shaped ZnO (SFZO) microparticles that can serve as highly sensitive sensors for the detection of gas-phase EA. The materials are synthesized by a facile synthetic route, involving hydrolysis, precipitation and calcination. The composition, morphology and structure of the materials are characterized by various analytical techniques. The results show that, while the sulfur atoms introduced by substituting some of the oxygen atoms of ZnO do not change the morphology of the ZnO particles, they slightly affect the crystal structure, such as lattice parameters and cell volume, of ZnO, as also confirmed by DFT calculation. More importantly, the sulfur dopant atoms in ZnO create interstitial lattice defects and vacancies that can absorb O₂ and form reactive oxygen species on the material better, thereby facilitating the reaction between oxygen and EA. As a result, SFZO-based sensor exhibits a very high sensitivity to EA, with a detection limit of up to 89 ppb and about four times higher sensitivity than its undoped counterpart (FZO-based sensor). SFZO-based sensor also shows a high selectivity to EA, a fast response time (1 s) and a fast recovery time (40 s) to various concentrations of gas phase EA at various temperatures. Additionally, the sensor exhibits a linear detection response with respect to the concentration of EA vapor in a wide concentration range, a property that is highly desirable in gas sensors.