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Molybdenum disulfide (MoS2) quantum dots (QDs) are a type of nanomaterial with unique electronic and optical properties. This abstract explores how these dots are made and what they look like, and how they can be used in different kinds of sensing platforms. The review covers their use in gas sensing, biosensing, and environmental monitoring, and explains how MoS2QDs are particularly good at detecting things with high sensitivity and selectivity. By integrating these nanomaterials into sensing devices, we can create new and more effective sensing technologies that can be used in a variety of fields. In addition to their sensing capabilities, MoS2QDs have other advantages too, like being easy to modify, having a stable structure, and being able to change their bandgap. All these things make MoS2QDs adaptable to different sensing platforms, which means they can perform well even in challenging environments. This abstract goes into more detail about the different ways MoS2QDs can be made, how we can study them, and what new developments are happening in the world of sensing technologies. We will also talk about what challenges there are and what the future of MoS2QDs might look like. MoS2, when reduced to a nanoscale, exhibits various applications in the quantum and electronic fields. It is available with both covalent and Van der Waals bonding, allowing MoS2to be utilized in an optimal way for sensing different gases. However, studies related to the sensing characteristics of MoS2are currently insufficient in fields such as optoelectronics, hydrogen testing and evolution, biomedicines, and IOT-based areas. Nevertheless, MoS2can be introduced harmlessly into internal organs as it does not undergo any harmful biological interaction. These numerous features of MoS2make it ideal for use in various sensing approaches.

Adsorption of arsenic by graphene-based adsorbents is widely applied to remove arsenic from water and has become a promising technology. However, most of the reported studies were conducted at a relatively higher concentration of arsenic in As (V) oxidative form, whereas the As (III) is more difficult to remove from water and more toxic, which prompted us to conduct the study at a lower concentration of 1 ppm in As (III). A Facile and controlled synthesis of graphene-based metal/metal oxide nanomaterials and adsorptive removal of aqueous As (III) is reported here. Adsorbents were characterized using spectroscopy (FTIR, XPS and Raman) and microscopy (TEM). The maximum uptake of arsenic obtained was 88.8% from the RGO-Fe3O4composite among all the adsorbents. The pseudo-second-order model and Intra-particle mass transfer diffusion model were applied to determine the adsorption kinetics with varying contact time between the adsorbents and the As (III) in water to interact. Experimental results suggest that the adsorption of As (III) onto the adsorbents was a multi-step process involving external adsorption to the surface followed by diffusion to the interior. A simple spectrophotometric method also was used for the detection and quantification of As (III).

A series of composites were synthesized having graphene oxide (GO)/reduced graphene oxide (RGO), decorated with Ag halide within inert poly(vinyl alcohol) (PVA) matrix. A calculated amount of cuprous iodide was also synthesized with Ag halide. On exposure to light, due to the photochromic effect, Ag halide converts into Ag nanoparticles as a donor, whereas cuprous iodide acts as a hole trapper to introduce a band gap in graphene. With increasing exposure time, the Ag nanoparticles increase in size and number and composites become increasingly dark. The appearance of the plasmonic peak in ultraviolet–visible plots after exposure to light confirms the presence of Ag nanoparticles in these composites. The apparent red shift of the surface plasmon resonance peak, reduction of its intensity, and broadening of the peak are dependent on the dielectric constant of the surrounding matrix and the distance between the GO/RGO sheet and the Ag nanoparticles. The increasing number and size of Ag nanoparticles introduce tunable n-type doping in the GO/RGO–PVA composites, as determined directly by Raman spectroscopy, without the necessity of electrically gated device.