Functionalization of 2D MoS2 Nanosheets with Various Metal and Metal Oxide Nanostructures: Their Properties and Application in Electrochemical Sensors

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.

Bacillus subtilis DNA fluorescent sensors based on hybrid MoS2 nanosheets

Although sensor technology has advanced with better materials, biomarkers, and fabrication and detection methods, creating a rapid, accurate, and affordable bacterial detection platform is still a major challenge. In this study, we present a combination of hybrid-MoS2 nanosheets and an amine-customized probe to develop a fast, sensitive biosensor for Bacillus subtilis DNA detection. Based on fluorescence measurements, the biosensor exhibits a detection range of 23.6-130 aM, achieves a detection limit of 18.7 aM, and was stable over four weeks. In addition, the high selectivity over Escherichia coli and Vibrio proteolyticus DNAs of the proposed Bacillus subtilis sensors is demonstrated by the fluorescence quenching effect at 558 nm. This research not only presents a powerful tool for B. subtilis DNA detection but also significantly contributes to the advancement of hybrid 2D nanomaterial-based biosensors, offering substantial promise for diverse applications in biomedical research and environmental monitoring.

2D-MoS2-supported copper peroxide nanodots with enhanced nanozyme activity: application in antibacterial activity

Peroxidase (POD)-like nanozymes are an upcoming class of new-generation antibiotics that are efficient for broad-spectrum antibacterial action. The POD-like activity employs the generation of reactive oxygen species (ROS), which have been utilized for bactericidal action. However, their intrinsic low catalytic activity and stability limit their bactericidal properties. In this study, we prepared a MoS2-based nanocomposite with copper peroxide nanodots (MoS2@CP) to achieve pH-dependent light-induced nanozyme-based antibacterial action. It has shown superior peroxidase and antibacterial activity at low pH. The mechanism behind the enhanced POD-like activity and high antibacterial activity was established. The mechanistic pathway involves estimating ROS generation, membrane depolarization, inner membrane permeabilization, metal ion release, and the effect of NIR on photothermal and photodynamic activities. Overall, our work highlighted the combinatorial approach for eradicating bacterial infections using enzyme-based antibacterial agents.

Pencil Graphite Electrocatalytic Sensors Modified by Pyrene Coated Reduced Graphene Oxide Decorated with Molybdenum Disulfide Nanoroses for Hydrazine and 4-Nitrophenol Detection in Real Water Samples

Novel nanostructured platforms based on Pencil Graphite Electrodes (PGEs), modified with pyrene carboxylic acid (PCA) functionalized Reduced Graphene Oxide (rGO), and then decorated by chronoamperometry electrodeposition of MoS2 nanoroses (NRs) (MoS2NRs/PCA-rGO/PGEs) were manufactured for the electrocatalytic detection of hydrazine (N2H4) and 4-nitrophenol, pollutants highly hazardous for environment and human health. The surface morphology and chemistry of the MoS2NRs/PCA-rGO/PGEs were characterized by scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS), assessing the coating of the PCA-rGO/PGEs by dense multilayers of NRs. N2H4 and 4-nitrophenol have been monitored by Differential Pulse Voltammetry (DPV), and the MoS2NRs/PCA-rGO/PGEs electroanalytical properties have been compared to the PGEs, as neat and modified by PCA-rGO. The MoS2NRs/PCA-rGO/PGEs demonstrated a higher electrochemical and electrocatalytic activity, due to their high surface area and conductivity, and very fast heterogeneous electron transfer kinetics at the interphase with the electrolyte. LODs lower than the U.S. EPA recommended concentration values in drinking water, namely 9.3 nM and 13.3 nM, were estimated for N2H4 and 4-nitrophenol, respectively and the MoS2NRs/PCA-rGO/PGEs showed good repeatability, reproducibility, storage stability, and selectivity. The effectiveness of the nanoplatforms for monitoring N2H4 and 4-nitrophenol in tap, river, and wastewater was addressed.

In-situ mechanochemically tailorable 2D gallium oxyselenide for enhanced optoelectronic NO2 gas sensing at room temperature

The adverse effects of NO₂ on the environment and human health promote the development of high-performance gas sensors to address the need for monitoring. Two-dimensional (2D) metal chalcogenides have been considered an emerging group of NO₂-sensitive materials, while incomplete recovery and low long-term stability are the two major hurdles for their practical implementation. The transformation into oxychalcogenides is an effective strategy to alleviate these drawbacks, but usually requires multiple-step synthesis and lacks controllability. Here, we prepare tailorable 2D p-type gallium oxyselenide with the thicknesses of 3-4 nm, through a single-step mechanochemical synthesis that combines the in-situ exfoliation and oxidation of bulk crystals. The optoelectronic NO₂ sensing performances of such 2D gallium oxyselenide with different oxygen contents are investigated at room temperature, in which 2D GaSe_0.58O_0.42 exhibits the largest response magnitude of 82.2% towards 10 ppm NO₂ at the irradiation of UV, with full reversibility, excellent selectivity, and long term stability for at least one month. Such overall performances are significantly improved over those of reported oxygen-incorporated metal chalcogenide-based NO₂ sensors. This work provides a feasible approach to prepare 2D metal oxychalcogenides in a single-step manner and demonstrates their great potential for room-temperature fully reversible gas sensing.

Recent Developments and Future Perspective on Electrochemical Glucose Sensors Based on 2D Materials

Diabetes is a health disorder that necessitates constant blood glucose monitoring. The industry is always interested in creating novel glucose sensor devices because of the great demand for low-cost, quick, and precise means of monitoring blood glucose levels. Electrochemical glucose sensors, among others, have been developed and are now frequently used in clinical research. Nonetheless, despite the substantial obstacles, these electrochemical glucose sensors face numerous challenges. Because of their excellent stability, vast surface area, and low cost, various types of 2D materials have been employed to produce enzymatic and nonenzymatic glucose sensing applications. This review article looks at both enzymatic and nonenzymatic glucose sensors made from 2D materials. On the other hand, we concentrated on discussing the complexities of many significant papers addressing the construction of sensors and the usage of prepared sensors so that readers might grasp the concepts underlying such devices and related detection strategies. We also discuss several tuning approaches for improving electrochemical glucose sensor performance, as well as current breakthroughs and future plans in wearable and flexible electrochemical glucose sensors based on 2D materials as well as photoelectrochemical sensors.