Illumination impact on monolayer MoS2 chemical sensor arrays

Molybdenum disulfide (MoS2) is a promising nanomaterial for chemical sensing due to its exceptional properties. However, it is extremely sensitive to illumination and converts the energy of photons absorbed into photocurrent, which has hampered efforts to explore the sensing performance and underlying transduction mechanism of intrinsic MoS2. Here we systematically explored the sensing behavior of intrinsic MoS2 and the impact of illumination. In dark environment, MoS2 demonstrated record-high sensitivity reaching 1030 for pH change by 1 unit. Its photoresponsivity (1300 A/W) can be tuned by ions in electrolyte. Photon absorption not only substantially reduced the response of intrinsic MoS2 by up to 95%, but also changed its sensing mechanism. After revealing the remarkable sensing performance of intrinsic MoS2, we demonstrated the possibility of the integration of MoS2 sensors functionalized with ionophore. Multiplex trace detection of Na+, Hg2+, and Cd2+ was realized on a 1 cm×1 cm chip with tunable sensitivity by illumination. The ion sensing results demonstrated outstanding selectivity, repeatability, detection limit (50 nM), response rate (10 s), and the capability of detecting target ions in environmental water samples. Our results show the prominent advantages of intrinsic MoS2 as a chemical sensing material.