MoS2 nanostructures for electrochemical sensing of multidisciplinary targets: A review

High performance Pt-anchored MoS2based chemiresistive ascorbic acid sensor

Ascorbic acid (AA), known as vitamin C, is a vital bioactive compound that plays a crucial role in several metabolic processes, including the synthesis of collagen and neurotransmitters, the removal of harmful free radicals, and the uptake of iron by cells in the human intestines. As a result, there is an absolute need for a highly selective, sensitive, and economically viable sensing platform for AA detection. Herein, we demonstrate a Pt-decorated MoS2for efficient detection of an AA biosensor. MoS2hollow rectangular structures were synthesized using an easy and inexpensive chemical vapor deposition approach to meet the increasing need for a reliable detection platform. The synthesized MoS2hollow rectangular structures are characterized through field effect scanning electron microscopy (FESEM), energy-dispersive spectroscopy elemental mapping, Raman spectroscopy, and x-ray photoelectron spectroscopy. We fabricate a chemiresistive biosensor based on Pt-decorated MoS2that measures AA with great precision and high sensitivity. The experiments were designed to evaluate the response of the Pt-decorated MoS2biosensor in the presence and absence of AA, and selectivity was evaluated for a variety of biomolecules, and it was observed to be very selective towards AA. The Pt-MoS2device had a higher response of 125% against 1 mM concentration of AA biomolecules, when compared to that of all other devices and 2.2 times higher than that of the pristine MoS2device. The outcomes of this study demonstrate the efficacy of Pt-decorated MoS2as a promising material for AA detection. This research contributes to the ongoing efforts to enhance our capabilities in monitoring and detecting AA, fostering advancements in environmental, biomedical, and industrial applications.

A sandwich electrochemiluminescence immunoassay based on 1T-MoS2@dual MOFs for detecting CA153

A "signal-on" electrochemiluminescence (ECL) immunosensor has been proposed for detecting carbohydrate antigen 153 (CA153) based on the dual MOFs sandwich strategy. The conductive and porous substrate consisting of 1T-MoS2 and two-dimensional conductive metal-organic framework (MOF, Ni-HAB) was anchored onto the glassy carbon electrode (GCE) to label the capture antibody (Ab1), and the luminescence-functionalized MOF (Ru(bpy)32+@UiO-66-NH2) was utilized to immobilize the detection second antibody (Ab2) to construct a "signal-on" responsive sandwich-type electrochemiluminescence immunoassay. Meanwhile, tripropylamine (TPA) acts as the co-reactant and provides a luminescence system for Ru(bpy)32+@UiO-66-NH2. The luminescence-functionalized MOFs showed excellent ECL activity owing to the tunable structure of MOFs. The remarkable enhancement in ECL intensity was obtained by the immunoreaction of antigen and antibody. Under the optimized conditions, the biosensor exhibited a detection limit of 0.0001 U mL-1 (S/N = 3) with a wide range from 0.001 to 50 U mL-1. The proposed ECL immunosensor was applicable for detecting human serum samples with a recovery of 99.83 ∼ 101 % (RSD < 5 %). This work demonstrates that the advantage of multifunctional MOFs could be applied to construct highly selective ECL immunosensor, and it may facilitate the diagnosis of breast cancer in clinics.

Novel MoS2-decorated Cu2O hybrid nanoparticles for enhanced non-enzymatic electrochemical cholesterol detection

Precise identification of cholesterol levels is crucial for the early diagnosis of cardiovascular risk factors. This paper presents a novel approach for cholesterol detection that circumvents the reliance on enzymatic processes. Leveraging the unique properties of advanced materials and electrochemical principles, our non-enzymatic approach demonstrates enhanced sensitivity, specificity, and limit of detection in cholesterol analysis. A non-enzymatic electrochemical biosensor for Cholesterol, employing a nanohybrid comprising Cu2O nanoparticles decorated with MoS2, is presented. The cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry techniques were employed to investigate the electrochemical behaviour of the glassy carbon electrode modified with the Cu2O/MoS2nanohybrid. The modified electrode exhibited an excellent sensitivity of 111.74μAμM-1cm-2through the CV method and showcased a low detection limit of 2.18μM and an expansive linear range spanning 0.1-180μM when employing the DPV method. The electrode also showed good selectivity to various interfering components in 0.1 M NaOH and a satisfied stability of about 15 days at room temperature. The study demonstrates the potential for broader applications in clinical diagnostics and monitoring cardiovascular health, paving the way for a paradigm shift in cholesterol detection methodologies and offering a more efficient and cost-effective alternative to traditional enzymatic assays.

Exceptionally large fracture strength and stretchability of 2D ReS2 and ReSe2

Two-dimensional rhenium disulfide (ReS2) and rhenium diselenide (ReSe2) have gained popularity due to their outstanding optoelectronic properties. However, their mechanical behavior has not been investigated experimentally and many of their mechanical parameters are still unexplored. Here we conducted atomic force microscopy (AFM) indentation experiments and extracted their Young's moduli and found that it is thickness-independent. In addition, we found that both materials are capable of sustaining large pretension. Importantly, fracture tests showed that these materials exhibit exceptionally large fracture strength (32.9 ± 2.4 GPa and 27.7 ± 3.9 GPa for ReS2 and ReSe2, respectively) and stretchability (up to 24.2% for ReS2 and 23.0% for ReSe2). Therefore, this study shows the superior mechanical properties of ReS2 and ReSe2. Thus, it will open the path for their future integration into advanced applications that will benefit from their outstanding mechanical durability and attractive optoelectronic properties, such as flexible photodetectors, stretchable photonic devices, and strain-engineered electronics.

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.

Recent Progress in Transition Metal Dichalcogenides for Electrochemical Biomolecular Detection

Advances in the field of nanobiotechnology are largely due to discoveries in the field of materials. Recent developments in the field of electrochemical biosensors based on transition metal nanomaterials as transducer elements have been beneficial as they possess various functionalities that increase surface area and provide well-defined active sites to accommodate elements for rapid detection of biomolecules. In recent years, transition metal dichalcogenides (TMDs) have become the focus of interest in various applications due to their considerable physical, chemical, electronic, and optical properties. It is worth noting that their unique properties can be modulated by defect engineering and morphology control. The resulting multifunctional TMD surfaces have been explored as potential capture probes for the rapid and selective detection of biomolecules. In this review, our primary focus is to delve into the synthesis, properties, design, and development of electrochemical biosensors that are based on transition metal dichalcogenides (TMDs) for the detection of biomolecules. We aim to explore the potential of TMD-based electrochemical biosensors, identify the challenges that need to be overcome, and highlight the opportunities for further future development.

A photoelectrochemical aptasensor for tetracycline based on the self-assembly of 2D MoS2 on a 3D ZnO/Au/ITO electrode

Two-dimensional (2D) layered MoS2 has good dispersion and adsorption properties, but being a narrow bandgap semiconductor limits its application in photoelectric sensing. In this study, a homogeneous photoelectrochemical sensor based on three-dimensional (3D) ZnO/Au/2D MoS2 is proposed for the ultrasensitive detection of tetracycline (TET). MoS2 is uniformly embedded on the 3D ZnO/Au surface by ordered self-assembly. The physical method of π-π interaction of MoS2 replaces the conventional use of chemically modifying aptamers on the electrode material surface. Under optimal conditions, this method has been successfully applied to the detection of TET in milk, honey, pig kidney and pork samples with reliable results. We believe that this study presents a method for the preparation of sensing carriers and target detection with great potential for application.

Heteroatom-Doped Molybdenum Disulfide Nanomaterials for Gas Sensors, Alkali Metal-Ion Batteries and Supercapacitors

Molybdenum disulfide (MoS2) is the second two-dimensional material after graphene that received a lot of attention from the research community. Strong S-Mo-S bonds make the sandwich-like layer mechanically and chemically stable, while the abundance of precursors and several developed synthesis methods allow obtaining various MoS2 architectures, including those in combinations with a carbon component. Doping of MoS2 with heteroatom substituents can occur by replacing Mo and S with other cations and anions. This creates active sites on the basal plane, which is important for the adsorption of reactive species. Adsorption is a key step in the gas detection and electrochemical energy storage processes discussed in this review. The literature data were analyzed in the light of the influence of a substitutional heteroatom on the interaction of MoS2 with gas molecules and electrolyte ions. Theory predicts that the binding energy of molecules to a MoS2 surface increases in the presence of heteroatoms, and experiments showed that such surfaces are more sensitive to certain gases. The best electrochemical performance of MoS2-based nanomaterials is usually achieved by including foreign metals. Heteroatoms improve the electrical conductivity of MoS2, which is a semiconductor in a thermodynamically stable hexagonal form, increase the distance between layers, and cause lattice deformation and electronic density redistribution. An analysis of literature data showed that co-doping with various elements is most attractive for improving the performance of MoS2 in sensor and electrochemical applications. This is the first comprehensive review on the influence of foreign elements inserted into MoS2 lattice on the performance of a nanomaterial in chemiresistive gas sensors, lithium-, sodium-, and potassium-ion batteries, and supercapacitors. The collected data can serve as a guide to determine which elements and combinations of elements can be used to obtain a MoS2-based nanomaterial with the properties required for a particular application.

2D-ReS2 & diamond nanoparticles-based sensor for the simultaneous determination of sunset yellow and tartrazine in a multiple-pulse amperometry FIA system

We present a flow injection system with a multiple pulse amperometric detection (FIA-MPA)-based methodology for the simultaneous analysis of sunset yellow and tartrazine. As transducer, we have developed a novel electrochemical sensor based on the synergistic effect of ReS₂ nanosheets and diamond nanoparticles (DNPs). Among several transition dichalcogenides for the sensor development, we have selected ReS₂ nanosheets since it yields a better response towards both colourants. Scanning probe microscopy characterization shows that the surface sensor is composed by scattered and stacked ReS₂ flakes and large aggregates of DNPs. With this system, the gap between the oxidation potential values of sunset yellow and tartrazine is wide enough to allow the simultaneous determination of both dyes. Under the optimum potential pulse conditions (0.8 and 1.2 V) during 250 ms, a flow rate of 3 mL/min and a volume injection of 250 μL, detection limits of 3.51 × 10^-7 M and 2.39 × 10^-7 M for sunset yellow and tartrazine, respectively, were obtained. This method exhibits good accuracy and precision with Er minor than 13% and RSD lower than 8% with a sampling frequency of 66 samples per hour. Pineapple jelly samples were analyzed by the standard addition method, obtaining 53.7 mg/kg and 29.0 mg/kg of sunset yellow and tartrazine, respectively. From the analysis of fortified samples, recoveries of 94% and 105% were obtained.

Recent Progress in Micro- and Nanotechnology-Enabled Sensors for Biomedical and Environmental Challenges

Micro- and nanotechnology-enabled sensors have made remarkable advancements in the fields of biomedicine and the environment, enabling the sensitive and selective detection and quantification of diverse analytes. In biomedicine, these sensors have facilitated disease diagnosis, drug discovery, and point-of-care devices. In environmental monitoring, they have played a crucial role in assessing air, water, and soil quality, as well as ensured food safety. Despite notable progress, numerous challenges persist. This review article addresses recent developments in micro- and nanotechnology-enabled sensors for biomedical and environmental challenges, focusing on enhancing basic sensing techniques through micro/nanotechnology. Additionally, it explores the applications of these sensors in addressing current challenges in both biomedical and environmental domains. The article concludes by emphasizing the need for further research to expand the detection capabilities of sensors/devices, enhance sensitivity and selectivity, integrate wireless communication and energy-harvesting technologies, and optimize sample preparation, material selection, and automated components for sensor design, fabrication, and characterization.

MoS2-ZnO Nanocomposite Mediated Immunosensor for Non-Invasive Electrochemical Detection of IL8 Oral Tumor Biomarker

In order to support biomolecule attachment, an effective electrochemical transducer matrix for biosensing devices needs to have many specialized properties, including quick electron transfer, stability, high surface area, biocompatibility, and the presence of particular functional groups. Enzyme-linked immunosorbent assays, gel electrophoresis, mass spectrometry, fluorescence spectroscopy, and surface-enhanced Raman spectroscopy are common techniques used to assess biomarkers. Even though these techniques provide precise and trustworthy results, they cannot replace clinical applications because of factors such as detection time, sample amount, sensitivity, equipment expense, and the need for highly skilled individuals. For the very sensitive and targeted electrochemical detection of the salivary oral cancer biomarker IL8, we have created a flower-structured molybdenum disulfide-decorated zinc oxide composite on GCE (interleu-kin-8). This immunosensor shows very fast detection; the limit of detection (LOD) for interleukin-8 (IL8) detection in a 0.1 M phosphate buffer solution (PBS) was discovered to be 11.6 fM, while the MoS₂/ZnO nanocomposite modified glassy carbon electrode (GCE) demonstrated a high catalytic current linearly from 500 pg to 4500 pg mL^-1 interleukin-8 (IL8). Therefore, the proposed biosensor exhibits excellent stability, high accuracy sensitivity, repeatability, and reproducibility and shows the acceptable fabrication of the electrochemical biosensors to detect the ACh in real sample analysis.

Multifunctional role of tannic acid in improving the mechanical, thermal and antimicrobial properties of natural rubber-molybdenum disulfide nanocomposites

Natural rubber is the only biosynthesized rubber and the most prominent of all the elastomers. Insertion of nanofillers into natural rubber matrix has received much research interest because of the enhanced mechanical, thermal, electrical, antibacterial, etc. properties of the final natural rubber nanocomposite. Molybdenum disulfide (MoS₂), an important member in transition metal dichalcogenides (TMD) is having excellent optical, thermal, mechanical, electronic and antibacterial properties. The inherent properties of this novel filler was exploited through the preparation of natural rubber-MoS₂ nanocomposites via latex dipping method in which tannic acid (TA), naturally occurring macromolecule was used as an exfoliating agent for MoS₂. MoS₂:TA dispersions were prepared in 1:2, 1:4 and 1:6 ratios by mechanical stirring followed by sonication method for analyzing the optimum amount of exfoliating agent for the preparation of NR-MoS₂ nanocomposite. MoS₂:TA in 1:4 ratio was found to be the optimum loading for the NR nanocomposite preparation with improved mechanical, thermal and antibacterial properties. The enhanced properties of the NR composites could be attributed to the synergistic effect of both MoS₂ and TA. The current study shows the role of TA in tuning the properties of NR/MoS₂ nanocomposites that enable their potential utilization in various biomedical applications.

Synthesis of recyclable SERS platform based on MoS2@TiO2@Au heterojunction for photodegradation and identification of fungicides

Surface-enhanced Raman spectroscopy (SERS) substrates based on metal/semiconductors have attracted much attention due to their excellent photocatalytic activity and SERS performance. However, they generally exhibit low light utilization and photocatalytic efficiencies. Herein, molybdenum disulfide coated titanium dioxide modified with gold nanoparticles (MoS₂@TiO₂@Au) as a heterojunction-based recyclable SERS platform was fabricated for the efficient determination of fungicides. Results showed that the MoS₂@TiO₂@Au platform could rapidly degrade 90.7% crystal violet in 120 min under solar light irradiation and enable reproducible and sensitive SERS analysis of three fungicides (methylene blue, malachite green, and crystal violet) and in-situ monitor of the photodegradation process. The platform could also be reused five times due to the unique integrated merits of the MoS₂@TiO₂@Au heterojunction. Meanwhile, experiments in determining methylene blue in prawn protein solution achieved a limit of detection of 1.509 μg/L. Therefore, it is hoped that this work could expand detection applications of photocatalytic materials.

Recent Trends in Metal Nanoparticles Decorated 2D Materials for Electrochemical Biomarker Detection

Technological advancements in the healthcare sector have pushed for improved sensors and devices for disease diagnosis and treatment. Recently, with the discovery of numerous biomarkers for various specific physiological conditions, early disease screening has become a possibility. Biomarkers are the body's early warning systems, which are indicators of a biological state that provides a standardized and precise way of evaluating the progression of disease or infection. Owing to the extremely low concentrations of various biomarkers in bodily fluids, signal amplification strategies have become crucial for the detection of biomarkers. Metal nanoparticles are commonly applied on 2D platforms to anchor antibodies and enhance the signals for electrochemical biomarker detection. In this context, this review will discuss the recent trends and advances in metal nanoparticle decorated 2D materials for electrochemical biomarker detection. The prospects, advantages, and limitations of this strategy also will be discussed in the concluding section of this review.

Development of MoS2-ZnO heterostructures: an efficient bifunctional catalyst for the detection of glucose and degradation of toxic organic dyes

The heterostructure catalyst MoS2-ZnO possesses binary properties and provides a novel platform for the remediation of environmental as well as health issues.

A novel sandwich impedimetric immunosensor for detection of apolipoprotein-A1 based on the gold nanoparticle-hybridized mercapto-β-cyclodextrin-Pb(II) metal-organic framework

A novel sandwich electrochemical impedimetric immunosensor was proposed to detect apolipoprotein-A1 (Apo-A1), a common biomarker for bladder cancer. The molybdenum disulfide/graphene quantum dot (MoS₂/GQD) nanocomposites were modified on the surface of a glassy carbon electrode (GCE) and used to immobilize the biotinylated antibody (Ab₁) with the help of chitosan and glutaraldehyde (denoted as BSA/Ab₁/CHIT/MoS₂/GQD/GCE). Pb(II)-thiol-β-cyclodextrin metal-organic framework (denoted as Pb-MOF) was synthesized with lead metal ions and thiol-β-cyclodextrin ligands by a one-pot solvothermal method, and then, gold nanoparticles were modified on the surface of Pb-MOF (Pb-MOF-AuNPs) by Au-S bond, which was used as signal label for the recombinant antibody (Ab₂). When the immunosensor of BSA/Ab₁/CHIT/MoS₂/GQD/GCE reacted with Apo-A1, Pb-MOF-AuNPs-Ab₂/BSA was connected to the electrode when immunoreaction occurred, and an immune sandwich structure was formed, which led to significantly increased charge transfer resistance of electrochemical probe for ferrocyanide (II)/(III) within the frequency range 10^-1 ~ 10⁵ Hz at 5 mV amplitude and the potential of 0.180 V (vs. SCE). Based on this principle, the quantitative detection of Apo-A1 was established. The relative change of electrochemical resistance and the logarithmic value of Apo-A1 concentration showed a linear relationship with a linear coefficient of 0.9989 in the range 1.00 pg mL^-1 and 1.00 μg mL^-1 with the limit of detection of 0.30 pg mL^-1. The selectivity, repeatability, and other performance of the proposed immunosensor were also investigated. The immunosensor was successfully applied to the detection of real serum and urine samples with recovery in the range 96.4 ~ 109.1% (RSD < 3.8%), indicating that it could be helpful for the clinical diagnosis of bladder cancer.

Enhanced Separation Performance of Polyamide Thin-Film Nanocomposite Membranes with Interlayer by Constructed Two-Dimensional Nanomaterials: A Critical Review

Thin-film composite (TFC) polyamide (PA) membrane has been widely applied in nanofiltration, reverse osmosis, and forward osmosis, including a PA rejection layer by interfacial polymerization on a porous support layer. However, the separation performance of TFC membrane is constrained by the trade-off relationship between permeability and selectivity. Although thin-film nanocomposite (TFN) membrane can enhance the permeability, due to the existence of functionalized nanoparticles in the PA rejection layer, the introduction of nanoparticles leads to the problems of the poor interface compatibility and the nanoparticles agglomeration. These issues often lead to the defect of PA rejection layers and reduction in selectivity. In this review, we summarize a new class of structures of TFN membranes with functionalized interlayers (TFNi), which promises to overcome the problems associated with TFN membranes. Recently, functionalized two-dimensional (2D) nanomaterials have received more attention in the assembly materials of membranes. The reported TFNi membranes with 2D interlayers exhibit the remarkable enhancement on the permeability, due to the shorter transport path by the "gutter mechanism" of 2D interlayers. Meanwhile, the functionalized 2D interlayers can affect the diffusion of two-phase monomers during the interfacial polymerization, resulting in the defect-free and highly crosslinked PA rejection layer. Thus, the 2D interlayers enabled TFNi membranes to potentially overcome the longstanding trade-off between membrane permeability and selectivity. This paper provides a critical review on the emerging 2D nanomaterials as the functionalized interlayers of TFNi membranes. The characteristics, function, modification, and advantages of these 2D interlayers are summarized. Several perspectives are provided in terms of the critical challenges for 2D interlayers, managing the trade-off between permeability, selectivity, and cost. The future research directions of TFNi membranes with 2D interlayers are proposed.

Facile fabrication of screen-printed MoS2 electrodes for electrochemical sensing of dopamine

Molybdenum disulfide (MoS₂) screen-printed working electrodes were developed for dopamine (DA) electrochemical sensing. MoS₂ working electrodes were prepared from high viscosity screen-printable inks containing various concentrations and sizes of MoS₂ particles and ethylcellulose binder. Rheological properties of MoS₂ inks and their suitability for screen-printing were analyzed by viscosity curve, screen-printing simulation and oscillatory modulus. MoS₂ inks were screen-printed onto conductive FTO (Fluorine-doped Tin Oxide) substrates. Optical microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDX) analysis were used to characterize the homogeneity, topography and thickness of the screen-printed MoS₂ electrodes. The electrochemical performance was assessed through differential pulse voltammetry. Results showed an extensive linear detection of dopamine from 1 µM to 300 µM (R² = 0.996, sensitivity of 5.00 × 10^-8 A μM^-1), with the best limit of detection being 246 nM. This work demonstrated the possibility of simple, low-cost and rapid preparation of high viscosity MoS₂ ink and their use to produce screen-printed FTO/MoS₂ electrodes for dopamine detection.

An integrated nanoflower-like MoS2@CuCo2O4 heterostructure for boosting electrochemical glucose sensing in beverage

Excessive glucose in food poses a non-negligible threat to its inherent quality and human health, which makes it imperative to develop a highly sensitive sensor for real-time glucose detection. In this work, an integrated electrochemical glucose sensor based on a nanoflower-like MoS₂@CuCo₂O₄ heterostructure was carefully constructed. Under optimal conditions, the as-fabricated sensor exhibited a high sensitivity of 1,303 μA mM^-1 cm^-2 over a wide range of 0.5-393.0 μmol/L, accompanied by a low determination limit (0.5 μmol/L) and short response time (2.1 s). The favorable sensing performance of the MoS₂@CuCo₂O₄ nanocomposite-modified electrode in electrochemical analyses was attributed to the introduction of unique nanoflower-like heterostructure and the synergistic effects between MoS₂ and CuCo₂O₄. Furthermore, the satisfactory applicability of this sensor in beverages was confirmed. These results demonstrate that the MoS₂@CuCo₂O₄/GCE may be a promising platform for sensitive monitoring of glucose content in food samples.

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

Two-dimensional transition metal dichalcogenides (2D TMDs) have gained considerable attention due to their distinctive properties and broad range of possible applications. One of the most widely studied transition metal dichalcogenides is molybdenum disulfide (MoS₂). The 2D MoS₂ nanosheets have unique and complementary properties to those of graphene, rendering them ideal electrode materials that could potentially lead to significant benefits in many electrochemical applications. These properties include tunable bandgaps, large surface areas, relatively high electron mobilities, and good optical and catalytic characteristics. Although the use of 2D MoS₂ nanosheets offers several advantages and excellent properties, surface functionalization of 2D MoS₂ is a potential route for further enhancing their properties and adding extra functionalities to the surface of the fabricated sensor. The functionalization of the material with various metal and metal oxide nanostructures has a significant impact on its overall electrochemical performance, improving various sensing parameters, such as selectivity, sensitivity, and stability. In this review, different methods of preparing 2D-layered MoS₂ nanomaterials, followed by different surface functionalization methods of these nanomaterials, are explored and discussed. Finally, the structure-properties relationship and electrochemical sensor applications over the last ten years are discussed. Emphasis is placed on the performance of 2D MoS₂ with respect to the performance of electrochemical sensors, thereby giving new insights into this unique material and providing a foundation for researchers of different disciplines who are interested in advancing the development of MoS₂-based sensors.

An electrochemical molecularly imprinted sensor based on CuBi2O4/rGO@MoS2 nanocomposite and its utilization for highly selective and sensitive for linagliptin assay

The molecularly imprinted polymers (MIP) is an outstanding electrochemical tool that demonstrates good chemical sensitivity and stability. These main advantages, coupled with the material's vast microfabrication flexibility, make molecularly imprinted sensors an attractive sensing device. Herein, it was aimed to develop a state-of-art molecularly imprinted sensor based on CuBi₂O₄/rGO@MoS₂ nanocomposite to be utilized for the detection of linagliptin (LNG), a novel hypoglycemic drug. The electrochemical characterizations of linagliptin on the surface of the modified electrode was examined via cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Several characterization methods including transmission electron microscope (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and Energy-dispersive X-ray spectroscopy(EDX), were utilized for electrode characterization. The LNG imprinted voltammetric sensor was developed in 80.0 mM phenol containing 20.0 mM LNG. CuBi₂O₄/rGO@MoS₂ nanocomposite on LNG imprinted screen-printed carbon electrode (SPCE) (MIP/CuBi₂O₄/rGO@MoS₂ nanocomposite/SCPE) exhibited a linear relationship between peak current and LNG concentration in the range 0.07-0.5 nM with a detection limit of 0.057 nM. In the existence of interfering substances, an LNG imprinted electrode was utilized to analyze urine, human plasma, and tablet samples with adequate selectivity. The developed sensor was also illustrated for stability, repeatability, reproducibility, and reusability.

A portable wireless intelligent electrochemical sensor based on layer-by-layer sandwiched nanohybrid for terbutaline in meat products

The aim of this study is to develop a portable wireless intelligent nanosensor (PWIN) for rapid cost-effective on-site determination of terbutaline (TRA) residue in meat products outdoors in comparison with traditional nanosensor and high-performance liquid chromatography (HPLC). The layer-by-layer sandwiched nanohybrid fabricated by platinum-palladium nanoparticles, carboxylated graphene and graphene-like molybdenum disulfide displayed a wide linear range of 0.55-14.9 μmol/L using the portable potentiostat with smartphone, and the result was almost close to the linear range (0.4-14 μmol/L) using the traditional potentiostat with desktop computer for TRA. The limit of detections were identified as 0.44 μmol/L and 0.18 μmol/L, respectively. PWIN displayed satisfactory recovery (91%-98.43%) of TRA in samples by the standard addition method and in comparison with both traditional sensor (93.79%-98%) and HPLC (93.4%-98.6%), revealing that PWIN for rapid cost-effective on-site analysis in the food safety field is feasible.

MXene-based electrochemical and biosensing platforms to detect toxic elements and pesticides pollutants from environmental matrices

Fabricating new biosensing constructs with high selectivity and sensitivity is the most needed environmental detection tool. In this context, several nanostructured materials have been envisaged to construct biosensors to achieve superior selectivity and sensitivity. Among them, MXene is regarded as the most promising to develop biosensors due to its fascinating attributes, like high surface area, excellent thermal resistance, good hydrophilicity, unique layered topology, high electrical conductivity, and environmentally-friendlier properties. MXenes-based materials have emerged as a prospective for catalysis, energy storage, electronics, and environmental sensing and remediation applications thanks to the above-mentioned exceptional characteristics. This review elaborates on the contemporary and state-of-the-art advancements in MXene-based electrochemical and biosensing tools to detect toxic elements, pharmaceutically active residues, and pesticide contaminants from environmental matrices. At first, the surface functionalization/modification of MXenes is discussed. Afterwards, a particular focus has been devoted to exploiting MXene to construct electrochemical (bio) sensors to detect various environmentally-related pollutants. Lastly, current challenges in this arena accompanied by potential solutions and directions are also outlined.

Voltammetric Determination of Isoniazid in the Presence of Acetaminophen Utilizing MoS2-Nanosheet-Modified Screen-Printed Electrode

We used MoS₂ nanosheets (MoS₂ NSs) for surface modification of screen-printed electrode (MoS₂NSs-SPE) aimed at detecting isoniazid (INZ) in the presence of acetaminophen (AC). According to analysis, an impressive catalytic performance was found for INZ and AC electro-oxidation, resulting in an appreciable peak resolution (~320 mV) for both analytes. Chronoamperometry, differential pulse voltammetry (DPV), linear sweep voltammogram (LSV), and cyclic voltammetry (CV) were employed to characterize the electrochemical behaviors of the modified electrode for the INZ detection. Under the optimal circumstances, there was a linear relationship between the peak current of oxidation and the various levels of INZ (0.035–390.0 µM), with a narrow limit of detection (10.0 nM). The applicability of the as-developed sensor was confirmed by determining the INZ and AC in tablets and urine specimens, with acceptable recoveries.

The electronic properties and water desalination performance of a photocatalytic TiO2/MoS2 nanocomposites bilayer membrane: a molecular dynamic simulation

Due to the rapid depletion of water resources, more interest is paid for the efficient desalination process in recent years. MoS₂ membrane aroused attention due to its high mechanical stability and electronic properties, which can sustain extra-large strains. In this study, the electronic properties and water desalination performance of TiO₂/MoS₂-hexagonal, and TiO₂/MoS₂-rhombohedral nanocomposites bilayer membranes were studied and simulated for the first time. The effect of TiO₂ in the performance of MoS₂ was observed in water desalination under the defined applied pressure ranging from 50 to 250 MPa with a 6.4 Å pore diameter. The membrane structure is created and optimized. The energy minimized for TiO₂ from - 19,596.4282 kcal/mol for the initial structure to - 19,605.1611 kcal/mol for the final structure. For TiO₂/MoS₂-hexagonal, the energy minimized from - 4955.54271 eV) to - 4955.62091 eV and TiO₂/MoS₂-rhombohedral from - 6042.26925 eV to - 6046.91835 eV. A molecular dynamic (MD) simulation was performed using Material Studio 2019 to study the electronic properties under 0-1 eV electric field using the CASTEP code. The results showed a better photocatalytic performance under the external electric field. The effect of external electric field significantly intensifies absorption in the visible range and achieved a high photocatalytic activity on TiO₂/MoS₂. TiO₂, TiO₂/MoS₂-hexagonal and TiO₂/MoS₂-rhombohedral nanocomposites bilayer membranes are simulated and evaluated for the water desalination using ReaxFF software. Both MoS₂ phases with TiO₂ have achieved a high salt rejection up to 97% (P-value = 0.0036, R² = 0.958), while TiO₂/MoS₂-rhombohedral achieved the highest permeability (6.0*10^-8 mm g cm^-2 s^-1 bar^-1) (P-value = 0.000296, R² = 0.972) under 250 MPa applied pressure.

Direct Detection of Inhomogeneity in CVD-Grown 2D TMD Materials via K-Means Clustering Raman Analysis

It is known that complex growth environments often induce inhomogeneity in two-dimensional (2D) materials and significantly restrict their applications. In this paper, we proposed an efficient method to analyze the inhomogeneity of 2D materials by combination of Raman spectroscopy and unsupervised k-means clustering analysis. Taking advantage of k-means analysis, it can provide not only the characteristic Raman spectrum for each cluster but also the cluster spatial maps. It has been demonstrated that inhomogeneities and their spatial distributions are simultaneously revealed in all CVD-grown MoS₂, WS₂ and WSe₂ samples. Uniform p-type doping and varied tensile strain were found in polycrystalline monolayer MoS₂ from the grain boundary and edges to the grain center (single crystal). The bilayer MoS₂ with AA and AB stacking are shown to have relatively uniform p-doping but a gradual increase of compressive strain from center to the periphery. Irregular distribution of 2LA(M)/E2g1 mode in WS₂ and E2g1 mode in WSe₂ is revealed due to defect and strain, respectively. All the inhomogeneity could be directly characterized in color-coded Raman imaging with correlated characteristic spectra. Moreover, the influence of strain and doping in the MoS₂ can be well decoupled and be spatially verified by correlating with the clustered maps. Our k-means clustering Raman analysis can dramatically simplify the inhomogeneity analysis for large Raman data in 2D materials, paving the way towards direct evaluation for high quality 2D materials.

Electrochemical Studies of Biofunctionalized MoS2 Matrix for Highly Stable Immobilization of antibodies and Detection of Lung Cancer Protein Biomarker

To address the issue of lack of stable immobilization of antibodies on the biosensing matrix for repeated cycles of measurement, chitosan (CS) bio-functionalized MoS2 is prepared to serve as a...

MoS2 quantum dots and titanium carbide co-modified carbon nanotube heterostructure as electrode for highly sensitive detection of zearalenone

A novel electrochemical sensor has been fabricated for sensitive determination of zearalenone (ZEA) in food samples based on molybdenum disulfide quantum dots (MoS₂ QDs) and two-dimensional titanium carbide (2D-Ti₃C₂T_x MXene) co-modified multi-walled carbon nanotube (MWCNT) heterostructure. Physical and electrochemical characterizations reveal that 2D-Ti₃C₂T_x and MoS₂ QDs co-modified MWCNTs yields synergistic signal amplification effect, together with large specific surface area and excellent conductivity for the heterostructure, endowing the developed sensor with high detection performance to ZEA. Under optimized conditions, the sensor shows a wide linear range from 3.00 to 300 ng mL^-1 and a low limit of detection (LOD) of 0.32 ng mL^-1_, which is far lower than the maximum residue limits (MRLs) settled by the European Commission. In addition, it exhibits excellent selectivity, high reproducibility with a relative standard deviation (RSD) of 1.1%, and good repeatability (RSD 1.1%). In real sample analysis recoveries ranged from 94.8 to 105% showing the proposed electrochemical sensor has high potential in practical applications. This work presents an effective and valuable pathway for the use of novel heterostructure in the biosensing field.

Advances in Nanomaterials-Based Electrochemical Biosensors for Foodborne Pathogen Detection

Electrochemical biosensors utilizing nanomaterials have received widespread attention in pathogen detection and monitoring. Here, the potential of different nanomaterials and electrochemical technologies is reviewed for the development of novel diagnostic devices for the detection of foodborne pathogens and their biomarkers. The overview covers basic electrochemical methods and means for electrode functionalization, utilization of nanomaterials that include quantum dots, gold, silver and magnetic nanoparticles, carbon nanomaterials (carbon and graphene quantum dots, carbon nanotubes, graphene and reduced graphene oxide, graphene nanoplatelets, laser-induced graphene), metal oxides (nanoparticles, 2D and 3D nanostructures) and other 2D nanomaterials. Moreover, the current and future landscape of synergic effects of nanocomposites combining different nanomaterials is provided to illustrate how the limitations of traditional technologies can be overcome to design rapid, ultrasensitive, specific and affordable biosensors.

MoS2/PPy Nanocomposite as a Transducer for Electrochemical Aptasensor of Ampicillin in River Water

We report the design of an electrochemical aptasensor for ampicillin detection, which is an antibiotic widely used in agriculture and considered to be a water contaminant. We studied the transducing potential of nanostructure composed of MoS2 nanosheets and conductive polypyrrole nanoparticles (PPyNPs) cast on a screen-printed electrode. Fine chemistry is developed to build the biosensors entirely based on robust covalent immobilizations of naphthoquinone as a redox marker and the aptamer. The structural and morphological properties of the nanocomposite were studied by SEM, AFM, and FT-IR. High-resolution XPS measurements demonstrated the formation of a binding between the two nanomaterials and energy transfer affording the formation of heterostructure. Cyclic voltammetry and electrochemical impedance spectroscopy were used to analyze their electrocatalytic properties. We demonstrated that the nanocomposite formed with PPyNPs and MoS2 nanosheets has electro-catalytic properties and conductivity leading to a synergetic effect on the electrochemical redox process of the redox marker. Thus, a highly sensitive redox process was obtained that could follow the recognition process between the apatamer and the target. An amperometric variation of the naphthoquinone response was obtained regarding the ampicillin concentration with a limit of detection (LOD) of 10 pg/L (0.28 pM). A high selectivity towards other contaminants was demonstrated with this biosensor and the analysis of real river water samples without any treatment showed good recovery results thanks to the antifouling properties. This biosensor can be considered a promising device for the detection of antibiotics in the environment as a point-of-use system.

Recent Progress on Semiconductor-Interface Facing Clinical Biosensing

Semiconductor (SC)-based field-effect transistors (FETs) have been demonstrated as amazing enhancer gadgets due to their delicate interface towards surface adsorption. This leads to their application as sensors and biosensors. Additionally, the semiconductor material has enormous recognizable fixation extends, high affectability, high consistency for solid detecting, and the ability to coordinate with other microfluidic gatherings. This review focused on current progress on the semiconductor-interfaced FET biosensor through the fundamental interface structure of sensor design, including inorganic semiconductor/aqueous interface, photoelectrochemical interface, nano-optical interface, and metal-assisted interface. The works that also point to a further advancement for the trademark properties mentioned have been reviewed here. The emergence of research on the organic semiconductor interface, integrated biosensors with Complementary metal–oxide–semiconductor (CMOS)-compatible, metal-organic frameworks, has accelerated the practical application of biosensors. Through a solid request for research along with sensor application, it will have the option to move forward the innovative sensor with the extraordinary semiconductor interface structure.

Highly exfoliated functionalized MoS2 with sodium alginate-polydopamine conjugates for electrochemical sensing of cardio-selective β-blocker by voltammetric methods

Molybdenum disulfide (MoS₂) surface functionalization was performed with a catechol-containing polymer sodium alginate (SA) and dopamine (DA) through simultaneous MoS₂ exfoliation and self-polymerization of DA. The MoS₂/SA-PDA nanocomposite was characterized using spectroscopic, microscopic, and electroanalytical techniques to evaluate its electrocatalytic performance. The electrocatalytic behavior of the MoS₂/SA-PDA nanocomposite modified electrode for the detection of acebutolol (ACE), a cardio-selective β-blocker drug was explored  through cyclic voltammetric and differential pulse voltammetric techniques. The influence of scan rate, concentration, and pH value on the oxidation peak current of ACE was investigated  to optimize the deducting condition. The electrochemical activity of the MoS₂/SA-PDA nanocomposite electrode was attributed to the existence of reactive functional groups being contributed from SA, PDA, and MoS₂ exhibiting a synergic effect. The MoS₂/SA-PDA nanocomposite modified electrode exhibits admirable electrocatalytic activity with a wide linear response range (0.009 to 520 μM), low detection limit (5 nM), and high sensitivity (0.354 μA μM^-1 cm^-2) also in the presence of similar (potentially interfering) compounds. The fabricated MoS₂/SA-PDA nanocomposite modified electrode can be useful for the detection of ACE in pharmaceutical analysis.

Graphene/MoS2 Nanohybrid for Biosensors

Graphene has been studied a lot in different scientific fields because of its unique properties, including its superior conductivity, plasmonic property, and biocompatibility. More recently, transition metal dicharcogenide (TMD) nanomaterials, beyond graphene, have been widely researched due to their exceptional properties. Among the various TMD nanomaterials, molybdenum disulfide (MoS2) has attracted attention in biological fields due to its excellent biocompatibility and simple steps for synthesis. Accordingly, graphene and MoS2 have been widely studied to be applied in the development of biosensors. Moreover, nanohybrid materials developed by hybridization of graphene and MoS2 have a huge potential for developing various types of outstanding biosensors, like electrochemical-, optical-, or surface-enhanced Raman spectroscopy (SERS)-based biosensors. In this review, we will focus on materials such as graphene and MoS2. Next, their application will be discussed with regard to the development of highly sensitive biosensors based on graphene, MoS2, and nanohybrid materials composed of graphene and MoS2. In conclusion, this review will provide interdisciplinary knowledge about graphene/MoS2 nanohybrids to be applied to the biomedical field, particularly biosensors.

MoS2-based composite nanozymes with superior peroxidase-like activity for ultrasensitive SERS detection of glucose

An ultrasensitive biosensor with high peroxidase-like catalytic activity and excellent SERS properties is developed based on PANI@MoS2@Fe3O4@Au nanozymes.

Electrochemical Determination of Hydroxyurea in a Complex Biological Matrix Using MoS2-Modified Electrodes and Chemometrics

Hydroxyurea, an oral medication with important clinical benefits in the treatment of sickle cell anemia, can be accurately determined in plasma with a transition metal dichalcogenide-based electrochemical sensor. We used a two-dimensional molybdenum sulfide material (MoS₂) selectively electrodeposited on a polycrystalline gold electrode via tailored waveform polarization in the gold electrical double layer formation region. The electro-activity of the modified electrode depends on the electrical waveform parameters used to electro-deposit MoS₂. The concomitant oxidation of the MoS₂ material during its electrodeposition allows for the tuning of the sensor’s specificity. Chemometrics, utilizing mathematical procedures such as principal component analysis and multivariable partial least square regression, were used to process the electrochemical data generated at the bare and the modified electrodes, thus allowing the hydroxyurea concentrations to be predicted in human plasma. A limit-of-detection of 22 nM and a sensitivity of 37 nA cm⁻² µM⁻¹ were found to be suitable for pharmaceutical and clinical applications.

Insight the process of hydrazine gas adsorption on layered WS2: a first principle study

The process of hydrazine gas adsorption on layered WS₂ has been systematically studied from first principle calculations. Our results demonstrate that this adsorption process is exothermic, and hydrazine molecules are physically adsorbed. The layer-dependent adsorption energy and interlayer separation induced by van der Waals interaction exerted by hydrazine molecules lead to the difficulty in desorbing hydrazine molecules from layered WS₂ as the number of layers increases. The most interesting finding is the emergence of localized impurity states below the Fermi level upon the hydrazine adsorption, irrespective of the number of WS₂ layers, resulting in a significant effect on the band structures and subsequently changing its electrical conductivity. Furthermore, a layer-dependent small charge transfer occurs between hydrazine and layered WS₂, leading to a charge redistribution and considerable polarization in the adsorbed systems. The existence of defects and the humidity, on the other hand, influences the sensitivity of layered WS₂ to the hydrazine adsorption. Obtained results show that a perfectly layered WS₂ might be a promising candidate as an efficient nanosensor to detect such toxic gas in dry environment.