Miniaturised Flexible Sensors Empowered by MoS₂/rGO 2D Materials for Enhanced Ammonia Detection.

In this work, we synthesised MoS₂-nanoflakes using a hydrothermal method and rGO via a modified Hummer's method, followed by preparing 3 distinct composites. Conductive inks were formulated with an appropriate binder, and NH₃ sensors were fabricated using a simple, low-cost screen-printing technique on a flexible PET substrate. The influence of the active material, its density, and the number of overprints on NH₃ sensing properties was systematically investigated. The NH₃ sensor with a 1:1 MoS₂/rGO ratio and three overprints exhibited a linear response within the NH₃ gas concentration range of 1 ppm to 100 ppm, with a regression coefficient 0.97. The sensor demonstrated superior performance, achieving a maximum response of 28.3% at 100 ppm NH₃ gas concentration at room temperature. The fastest response and recovery times recorded were 56s and 106s, respectively, at the same gas concentration. Additionally, the sensor exhibited remarkable repeatability and high selectivity towards NH₃ compared to other gases. The observed response is attributed to the synergistic effect of MoS₂ and rGO, which enhances charge transfer and surface interaction, with a proposed sensing mechanism that highlights the roles of both materials.