Direct or Indirect Sonication in Ecofriendly MoS₂ Dispersion for NO₂ and NH₃ Gas-Sensing Applications

Unlike the most used, this study explores the effects of direct and indirect sonication methods on the dispersion and gas sensing performance of MoS₂ nanoflakes. The obtained dispersions are characterized using various techniques, such as field emission scanning electron microscopy, high resolution transmission electron microscopy, atomic force microscopy, dynamic light scattering, and Raman and X-ray diffraction, to evaluate their morphological and structural properties. Gas sensing measurements are conducted using exfoliated MoS₂ on interdigitated electrode structures, and the response to multiple gases is recorded. The sensitivity and selectivity of the sensors are analyzed and compared between the direct and indirect sonication methods. The results demonstrate that both direct and indirect methods lead to the formation of well-dispersed MoS₂ multilayer nanosheets, whereas the indirect approach exhibits a uniform and bigger flake size. Gas sensing experiments reveal that the MoS₂ nanoflakes prepared via indirect sonication have enhanced sensitivity by 17 and 46% toward NO₂ and NH₃ gases, respectively, compared to the ones achieved by the direct sonication method. Both methods demonstrated its selectivity for NO₂ and NH₃ and the preferential temperature to detect NO₂ and NH₃ gas are 50 and 100 °C, respectively. This research contributes to the development of eco-friendly MoS₂-based gas sensors by providing insights into the influence of direct (probe) and indirect (bath) sonication methods on dispersion quality and gas sensing performance. The findings highlight the potential of indirect sonication as a reliable technique for fabricating high-performance MoS₂ gas sensors, opening venues for the design and optimization of eco-friendly sensing platforms for environmental monitoring and industrial applications.