Acquisition and Application of Multimodal Sensing Information, volume II

As a promising sensing material, Molybdenum disulfide (MoS₂) nanosheets is being increasingly studied for Nitrogen dioxide (NO₂) gas sensing. However, the MoS₂ nanosheets is prone to the stacking effect that compromises the sensing performances. Here, the stacking effect is mitigated by engineering MoS₂ nanosheets into a three dimensional (3D) network microstructure, which was fabricated by method of electrostatically self-assembling of MoS₂/SiO₂ microspheres. The fabricated sensor based on 3D MoS₂ network observed a significantly improved response of 15% to 12.3 ppm NO₂, which is a 75-fold increase compared to the control sensor with pure MoS₂ nanosheets. In addition, the sensitivity of the sensor with 3D MoS₂ network was 6.15 times larger than that of the control sensor with pure MoS₂ nanosheets. The detection limit of our sensor was 0.297 ppm, lower than most of reported MoS₂-based NO₂ sensors. The enhanced sensitivity and dynamic response stem from the improved interaction between NO₂ molecules and MoS₂ network, thanks to its increased surface area per footprint of MoS₂ nanosheets compared to pure 2D MoS₂ film (single- or few-layer). This work presents a new approach to enhancing the performance of gas sensors based on 2D materials.

A photoacoustic module based on a novel 273 nm deep-ultraviolet light-emitting diode (DUV-LED) was developed for sulfur dioxide (SO₂) detection. The DUV-LED with an emission angle of 60° emitted a power of 10 mW. A high-sensitivity non-resonant photoacoustic cell with a gas chamber volume of only 0.39 mL was introduced to reduce the thermal noise generated by the contact of scattered DUV light with the photoacoustic cell. Assembly of the DUV-LED with the non-resonant photoacoustic cell resulted in a robust and portable photoacoustic module without any moving parts. The minimum detection limit of 725 ppb was achieved with 1s integration time at room temperature and atmospheric pressure. Furthermore, the photoacoustic module performance was evaluated in terms of DUV modulation frequency, linearity and the long-term stability.