Highly sensitive hierarchical MoS2 nanoflowers for in-situ soil moisture sensing

Abstract

In this work, we explored hierarchical MoS2 nanomaterials for soil moisture sensing (SMS) and tested their efficacy considering the operational aspects of the sensor. Carnation and marigold flower-like MoS2 nanostructures were prepared via facile hydrothermal processes with varying synthesis temperatures. The synthesized MoS2 nanostructures were well characterized by XRD, FTIR, FESEM, EDS, and HRTEM and it is evident that the variation in the hydrothermal temperatures has a significant impact on the crystallinity, morphology, stoichiometry, dimensions, and lattice spacing. We found that hierarchical MoS2 marigold flower-like nanostructures offer the highest sensitivity of about 2000 %, when gravimetric water content (GWC) is varied from 1 % to 20 % GWC, which is one of the highest reported SMS. The sensors exhibit hysteresis of about ± 4 % and response times of about 500 s. They were highly selective to moisture compared to the other salts like Na, K, Cd, and Cu present in the soil. The sensors were also unaffected by changing temperatures with a small 2–4 % between 20 °C and 65 °C.