Molybdenum disulfide (MoS2) and reduced graphene oxide (rGO) nanocomposite based electrochemical sensor for detecting mercury(II) ions

In this study, a two-dimensional (2D) layered nanocomposite of molybdenum disulfide and reduced graphene oxide (rGO) was synthesized through a facile single-step hydrothermal method. Internal structure and morphological studies have shown that the vertical layered structure of MoS2 has grown over the horizontally aligned layer of reduced graphene oxide. The XRD analysis proved that the structure is multi-layered with 68.8 % crystallinity. Despite the highly crystalline nanocomposite structure, very few defects are also present in the network, as shown through Raman spectroscopy. Further, the presence of CS, RSR, CO, CO, MoO and MoS bonds, identified through XPS, indicates the successful synthesis of the MoS2-rGO nanocomposite. The nanocomposite was further evaluated for its electrochemical properties and applications regarding the sensing of mercury ions. Cyclic voltammetry shows that the oxidation peak current response increased by ∼103 % with the MoS2-rGO modified electrode compared to a bare electrode. The sensor has shown an excellent detection limit (LOD) of 1.6 μM, while the sensitivity and limit of quantification obtained from the sensor are 76.302 μM μA−1 cm−2 and 5.4 μM, respectively. The enhanced sensing performance of the MoS2-rGO modified sensor is attributed to the synergistic effect of MoS2 and rGO. The as-synthesized sensor also exhibits excellent stability, as only a 13% drop in current was observed after 60 days. This work proves that MoS2-rGO possesses enormous potential for developing next-generation heavy metal ion sensors.