Optically active two-dimensional MoS₂-based nanohybrids for various biosensing applications: A comprehensive review

Following the discovery of graphene, there has been a surge in exploring other two-dimensional (2D) nanocrystals, including MoS₂. Over the past few decades, MoS₂-based nanocrystals have shown great potential applications in biosensing, owing to their excellent physico-chemical properties. Unlike graphene, MoS₂ shows layer-dependent finite band gaps (∼1.8 eV for a single layer and ∼1.2 for bulk) and relatively strong interaction with the electromagnetic spectrum. The tunability of the size, shape, and intrinsic properties, such as high optical absorption, electron mobility, mechanical strength and large surface area, of MoS₂ nanocrystals, make them excellent alternative probe materials for preparing optical, photothermal, and electrical bio/immunosensors. In this review, we will provide insights into the rapid evolutions in bio/immunosensing applications based on MoS₂ and its nanohybrids. We emphasized the various synthesis, characterization, and functionalization routes of 2D MoS₂ nanosheets/nanoflakes. Finally, we discussed various fabrication techniques and the critical parameters, including the limit of detection (LOD), linear detection range, and sensitivity of the biosensors. In addition, the role of MoS₂ in enhancing the performance of biosensors, the limitations associated with current biosensing technologies, future challenges, and clinical implications are addressed. The advantages/disadvantages of each biosensor technique are also summarized. Collectively, we believe that this review will encourage resolute researchers to follow up further with the state-of-the-art MoS₂-based biosensing technology.