The Rise of Xene Hybrids

Xenes, mono-elemental atomic sheets, exhibit Dirac/Dirac-like quantum behavior. When interfaced with other 2D materials such as boron nitride, transition metal dichalcogenides, and metal carbides/nitrides/carbonitrides, it enables them with unique physicochemical properties, including structural stability, desirable bandgap, efficient charge carrier injection, flexibility/breaking stress, thermal conductivity, chemical reactivity, catalytic efficiency, molecular adsorption, and wettability. For example, BN acts as an anti-oxidative shield, MoS2 injects electrons upon laser excitation, and MXene provides mechanical flexibility. Beyond precise compositional modulations, stacking sequences, and inter-layer coupling controlled by parameters, achieving scalability and reproducibility in hybridization is crucial for implementing these quantum materials in consumer applications. However, realizing the full potential of these hybrid materials faces challenges such as air gaps, uneven interfaces, and the formation of defects and functional groups. Advanced synthesis techniques, a deep understanding of quantum behaviors, precise control over interfacial interactions, and awareness of cross-correlations among these factors are essential. Xene-based hybrids show immense promise for groundbreaking applications in quantum computing, flexible electronics, energy storage, and catalysis. In this timely perspective, recent discoveries of novel Xenes and their hybrids are highlighted, emphasizing correlations among synthetic parameters, structure, properties, and applications. It is anticipated that these insights will revolutionize diverse industries and technologies.

Molybdenum Sulfide Nanoflowers as Electrodes for Efficient and Scalable Lithium-Ion Capacitors

Hybrid supercapacitors (HSCs) bridge the unique advantages of batteries and capacitors and are considered promising energy storage devices for hybrid vehicles and other electronic gadgets. Lithium-ion capacitors (LICs) have attained particular interest due to their higher energy and power density than traditional supercapacitor devices. The limited voltage window and the deterioration of anode materials upsurged the demand for efficient and stable electrode materials. Two-dimensional (2D) molybdenum sulfide (MoS2) is a promising candidate for developing efficient and durable LICs due to its wide lithiation potential and unique layer structure, enhancing charge storage efficiency. Modifying the extrinsic features, such as the dimensions and shape at the nanoscale, serves as a potential path to overcome the sluggish kinetics observed in the LICs. Herein, the MoS2 nanoflowers have been synthesized through a hydrothermal route. The developed LIC exhibited a specific capacitance of 202.4 F g-1 at 0.25 A g-1 and capacitance retention of >90 % over 5,000 cycles. Using an ether electrolyte improved the voltage window (2.0 V) and enhanced the stability performance. The ex-situ material characterization after the stability test reveals that the storage mechanism in MoS2-LICs is not diffusion-controlled. Instead, the fast surface redox reactions, especially intercalation/deintercalation of ions, are more prominent for charge storage.

Topochemically prepared tungsten disulfide nanostructures as a novel pseudocapacitive electrode for high performance supercapacitor

The topochemical preparation of nanostructured materials (NMs) has received significant attention in recent years due to the exceptional electrochemical properties exhibited by the resulting NMs. This work focuses on the preparation of two-dimensional tungsten di-sulfide (WS2) nanostructures through the topochemical conversion of tungsten trioxide (WO3) nanostructures and also evaluates their potential applications as electrode materials for supercapacitors (SCs). The X-ray diffraction and photoelectron studies conducted in this research reveal the conversion of hexagonal WO3 into hexagonal WS2 nanosheets, accompanied by changes in oxidation states. The FE-SEM and HR-TEM studies confirm the formation of WS2 in the sheet-like morphologies with lateral dimensions of 100 × 100 nm. The electrochemical investigation, using techniques such as CV, galvanostatic CD, and EIS, confirmed the presence of intercalation pseudocapacitance in the WS2 electrode, with a higher electrode-specific-capacitance (260 F g-1) than that of WO3 electrode. The WS2 symmetric SC delivered high device capacitance (59.17 F g-1), energy density (8.21 Wh kg-1) and power density (3,750 W kg-1) with better cyclic stability over 5000 cycles. These experimental findings show that the topochemically synthesized WS2as novel supercapacitor electrodes might be useful for the advancement of future-generation energy storage devices.

Enhanced electrochemical performance of the MoS2/Bi2S3 nanocomposite-based electrode material prepared by a hydrothermal method for supercapacitor applications

Supercapacitors are widely used energy storage systems in the modern world due to their excellent electrochemical performance, fast charging capability, easy handling, and high power density. In the present work, pure MoS2 and MoS2/Bi2S3 nanocomposites with different compositions of bismuth were synthesized by the hydrothermal method. The structural properties of the electrode materials were studied using the XRD technique, which confirmed the formation of MoS2 and the secondary phase of Bi2S3 while increasing Bi substitution. The morphological studies of the synthesized electrode materials were performed using SEM, TEM, and HRTEM techniques, which indicated the 3D layered hierarchical structure of MoS2 nanospheres and the nanosheet-like structure of Bi2S3. The electrochemical properties of pristine MoS2 and MoS2/Bi2S3 nanocomposites were analysed by CV, CP, and EIS techniques using a 2 M KOH electrolyte in a three-electrode system. The CV curves show evidence of significant improvement in the electrochemical performance of MoS2/Bi2S3 composites compared to that of pure MoS2. The calculated specific capacitances of MoS2/Bi2S3 nanocomposites were relatively higher than those of pristine MoS2. The 20 mol% Bi added sample showed a maximum specific capacitance of 371 F g-1, compared to pristine MoS2 and other samples at a current density of 1 A g-1. The kinetics of the electrochemical process was studied. The Nyquist plots indicated that the Bi-added nanocomposites had lower Resr and RCT values, which resulted in high electrochemical performance. The experimental results revealed that Bi-substitution can further enhance the electrochemical energy storage performance of MoS2 for supercapacitor applications.

Recent advancements in zero- to three-dimensional carbon networks with a two-dimensional electrode material for high-performance supercapacitors

Supercapacitors have gained significant attention owing to their exceptional performance in terms of energy density and power density, making them suitable for various applications, such as mobile devices, electric vehicles, and renewable energy storage systems. This review focuses on recent advancements in the utilization of 0-dimensional to 3-dimensional carbon network materials as electrode materials for high-performance supercapacitor devices. This study aims to provide a comprehensive evaluation of the potential of carbon-based materials in enhancing the electrochemical performance of supercapacitors. The combination of these materials with other cutting-edge materials, such as Transition Metal Dichalcogenides (TMDs), MXenes, Layered Double Hydroxides (LDHs), graphitic carbon nitride (g-C₃N₄), Metal-Organic Frameworks (MOFs), Black Phosphorus (BP), and perovskite nanoarchitectures, has been extensively studied to achieve a wide operating potential window. The combination of these materials synchronizes their different charge-storage mechanisms to attain practical and realistic applications. The findings of this review indicate that hybrid composite electrodes with 3D structures exhibit the best potential in terms of overall electrochemical performance. However, this field faces several challenges and promising research directions. This study aimed to highlight these challenges and provide insights into the potential of carbon-based materials in supercapacitor applications.

Drastic Gas Sensing Selectivity in 2-Dimensional MoS2 Nanoflakes by Noble Metal Decoration

Noble metal nanoparticle decoration is a representative strategy to enhance selectivity for fabricating chemical sensor arrays based on the 2-dimensional (2D) semiconductor material, represented by molybdenum disulfide (MoS₂). However, the mechanism of selectivity tuning by noble metal decoration on 2D materials has not been fully elucidated. Here, we successfully decorated noble metal nanoparticles on MoS₂ flakes by the solution process without using reducing agents. The MoS₂ flakes showed drastic selectivity changes after surface decoration and distinguished ammonia, hydrogen, and ethanol gases clearly, which were not observed in general 3D metal oxide nanostructures. The role of noble metal nanoparticle decoration on the selectivity change is investigated by first-principles density functional theory (DFT) calculations. While the H₂ sensitivity shows a similar tendency with the calculated binding energy, that of NH₃ is strongly related to the binding site deactivation due to preferred noble metal particle decoration at the MoS₂ edge. This finding is a specific phenomenon which originates from the distinguished structure of the 2D material, with highly active edge sites. We believe that our study will provide the fundamental comprehension for the strategy to devise the highly efficient sensor array based on 2D materials.

NiCo2S4/MoS2 Nanocomposites for Long-Life High-Performance Hybrid Supercapacitors

Metal sulfides (MS) and mixed metal sulfides (MTMS) have been considered potential candidates over their metal oxide/mixed metal oxide counterparts in recent years. Herein, one MTMS, i.e., NiCo₂S₄, was combined with 2D MS MoS₂ through a single-step solvothermal process with different morphologies (sheet-like and rod-like) for supercapacitor applications. The resulting electrode exhibited excellent coulombic efficiency, high specific capacitance, superior energy density, and, most importantly, ultra-high cycling stability. In particular, the electrode delivered a capacitance of 2594 F g^-1 at 0.8 A g^-1 after 45,000 charge/discharge cycles with a remarkable stability of 192%. Moreover, the corresponding hybrid supercapacitor device displayed an impressive coulombic efficiency of 123% after 20,000 cycles and 118% after 45,000 cycles. In addition, the device also exhibited a decent energy density of 31.9 Wh kg^-1 and good cycling stability of 102% over 15,000 cycles.

High-Performance Flexible Energy Storage Devices Based on Graphene Decorated with Flower-Shaped MoS2 Heterostructures

MoS₂, owing to its advantages of having a sheet-like structure, high electrical conductivity, and benign environmental nature, has emerged as a candidate of choice for electrodes of next-generation supercapacitors. Its widespread use is offset, however, by its low energy density and poor durability. In this study, to overcome these limitations, flower-shaped MoS₂/graphene heterostructures have been deployed as electrode materials on flexible substrates. Three-electrode measurements yielded an exceptional capacitance of 853 F g^-1 at 1.0 A g^-1, while device measurements on an asymmetric supercapacitor yielded 208 F g^-1 at 0.5 A g^-1 and long-term cyclic durability. Nearly 86.5% of the electrochemical capacitance was retained after 10,000 cycles at 0.5 A g^-1. Moreover, a remarkable energy density of 65 Wh kg^-1 at a power density of 0.33 kW kg^-1 was obtained. Our MoS₂/Gr heterostructure composites have great potential for the development of advanced energy storage devices.

Tailoring of 1T Phase-Domain MoS2 Active Sites with Bridging S22-/Apical S2- Phase-Selective Precursor Modulation for Enriched HER Kinetics

Molybdenum disulfide (MoS₂) is a promising alternative electrocatalyst for hydrogen evolution reaction (HER) due to its relatively near zero hydrogen adsorption free energy (ΔG_H = 0.08) and availability as a metallic (1T) phase. The superior catalytic activity of the 1T phase over 2H is owing to the availability of dense active sites, 10⁷ fold higher conductivity, and greater hydrophilicity. However, in the synthesis of 1T-MoS₂, a highly controlled proficient method is indispensable due to its metastable nature. Besides, phase enrichment is greatly sensitive to experimental parameters such as precursor, temperature, reaction time, and solvent. In the context of precursors, to date, no single precursor has been recognized as a selective precursor for the synthesis of 1T-MoS₂. In this work, MoS₂ with high content of 1T phase (79.4%) and excessive bridging S₂^2-/apical S^2- sites has been formulated from a single precursor, that is, ammonium tetrathiomolybdate ((NH₄)₂MoS₄), ATTM). In HER, it displayed an inspired activity, that is, achieving 10 mA cm^-2 current density, it requires just 248 mV overpotential with a minimal Tafel slope value (56 mV/dec). The maximum enrichment of the 1T phase, abundant accumulation of catalytically active bridging S₂^2-/apical S^2- sites, and the complete reduction of Mo⁺⁶ to Mo⁺⁴ (absence of Mo⁺⁶) are root causes for the outstanding activity of the synthesized 1T phase-domain MoS₂. To the best of our knowledge for the very first time, here, we declare that the single source, that is, ATTM is an exclusive precursor for the selective synthesis of 1T-MoS₂ with advantageous structural features. Moreover, this expedient precursor could be more pertinent for the industrial-scale preparation of 1T phase-domain MoS₂ in near future.

Recent progress in 2D hybrid heterostructures from transition metal dichalcogenides and organic layers: properties and applications in energy and optoelectronics fields

Atomically thin transition metal dichalcogenides (TMDs) present extraordinary optoelectronic, electrochemical, and mechanical properties that have not been accessible in bulk semiconducting materials. Recently, a new research field, 2D hybrid heteromaterials, has emerged upon integrating TMDs with molecular systems, including organic molecules, polymers, metal-organic frameworks, and carbonaceous materials, that can tailor the TMD properties and exploit synergetic effects. TMD-based hybrid heterostructures can meet the demands of future optoelectronics, including supporting flexible, transparent, and ultrathin devices, and energy-based applications, offering high energy and power densities with long cycle lives. To realize such applications, it is necessary to understand the interactions between the hybrid components and to develop strategies for exploiting the distinct benefits of each component. Here, we provide an overview of the current understanding of the new phenomena and mechanisms involved in TMD/organic hybrids and potential applications harnessing such valuable materials in an insightful way. We highlight recent discoveries relating to multicomponent hybrid materials. Finally, we conclude this review by discussing challenges related to hybrid heteromaterials and presenting future directions and opportunities in this research field.

Scanning electrochemical microscope as a tool for the electroporation of living yeast cells

In this study, a scanning electrochemical microscope (SECM) was for the first time adapted to perform the electroporation process of living yeast cells. We have demonstrated that relatively low voltage pulses of 1-2 V vs. Ag/AglCl,Cl^-_sat applied to gold-based ultramicroelectrode (Au-UME) are performing reversible electroporation of yeast cells immobilized on fluorine-doped tin oxide (FTO)/glass surface. SECM and electrochemical impedance spectroscopy (EIS) were used for the determination of quantitative electrochemical characteristics before and after the electroporation. The electrochemical impedance spectroscopy (EIS) illustrated significant electrochemical changes of electroporated yeast cells, while SECM feedback mode surface vertical scan current-distance curves showed that the diameter of the area affected by the electrical pulse is about 25 times larger than the diameter of the Au-UME used for the electroporation process. The results presented in this research open up a possibility to develop a targeted electroporation system which will affect only the selected area of tissue or some other cell-covered surface. Such model is promising for the selective treatment of selected cells in tissues and/or other sensitive biological systems while selecting the location and size of electroporated areas.

Potential transition and post-transition metal sulfides as efficient electrodes for energy storage applications: review

Electrochemical energy storage has attracted much attention due to the common recognition of sustainable energy development. Transition metal sulfides and post-transition metal sulfides have been intensively been focused on due to their potential as electrode materials for energy storage applications in different types of capacitors such as supercapacitors and pseudocapacitors, which have high power density and long cycle life. Herein, the physicochemical properties of transition and post-transition metal sulfides, their typical synthesis, structural characterization, and electrochemical energy storage applications are reviewed. Various perspectives on the design and fabrication of transition and post-transition metal sulfides-based electrode materials having capacitive applications are discussed. This review further discusses various strategies to develop transition and/or post-transition metal sulfide heterostructured electrode-based self-powered photocapacitors with high energy storage efficiencies.

Electrochemical energy storage has attracted much attention due to the common recognition of sustainable energy development.

A highly efficient rGO grafted MoS2 nanocomposite for dye adsorption and electrochemical detection of hydroquinone in wastewater

Scheme depicting the synthesis and the fabrication of rGO–MoS2 nanocomposite-based enzymatic biosensor for estimation of hydroquinone.

Insights into the Influence of Key Preparation Parameters on the Performance of MoS2/Graphene Oxide Composites as Active Materials in Supercapacitors

Advances in energy storage and energy conversion play an essential role nowadays because the energy demands are becoming greater than ever. To overcome the actual performances of the materials used to build supercapacitors, a combination of transition metal dichalcogenides (TMDCs) and graphene oxide (GO) or reduced graphene oxide (rGO) as graphene-based structures are often studied for their excellent properties, such as high specific area and good electrical conductivity. Nevertheless, synthesis pathways and parameters play key roles in obtaining better materials as components for supercapacitors with higher technical performances. Driven by the desire to understand the influence of the structural and morphological particularities on the performances of supercapacitors based on MoS2/graphene oxide (GO) composites, a survey of the literature was performed by pointing out the alterations induced by different synthesis pathways and key parameters to the above-mentioned particularities.

High-performance flexible transparent micro-supercapacitors from nanocomposite electrodes encapsulated with solution processed MoS2 nanosheets

Two-dimensional molybdenum disulfide (MoS2) nanosheets have emerged as a promising material for transparent, flexible micro-supercapacitors, but their use in electrodes is hindered by their poor electrical conductivity and cycling stability because of restacking. In this paper, we report a novel electrode architecture to exploit electrochemical activity of MoS2 nanosheets. Electrochemically exfoliated MoS2 dispersion was spin coated on mesh-like silver networks encapsulated with a flexible conducting film exhibiting a pseudocapacitive behavior. MoS2 nanosheets were electrochemically active over the whole electrode surface and the conductive layer provided a pathway to transport electrons between the MoS2 and the electrolyte. As the result, the composite electrode achieved a large areal capacitance (89.44 mF cm-2 at 6 mA cm-2) and high energy and power densities (12.42 µWh cm-2 and P = 6043 µW cm-2 at 6 mA cm-2) in a symmetric cell configuration with 3 M KOH solution while exhibiting a high optical transmittance of ~80%. Because the system was stable against mechanical bending and charge/discharge cycles, a flexible micro-supercapacitor that can power electronics at different bending states was realized.

Silver decorated 2D nanosheets of GO and MoS2serve as nanocatalyst for water treatment and antimicrobial applications as ascertained with molecular docking evaluation

In this work, synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) was realized through a modified Hummers route. Different concentrations (5 and 10 wt%) of Ag were doped in MoS₂and rGO using a hydrothermal technique. Synthesized Ag-MoS₂and Ag-rGO were evaluated through XRD that confirmed the hexagonal structure of MoS₂along with the transformation of GO to Ag-rGO as indicated by a shift in XRD peaks while Mo-O bonding and S=O functional groups were confirmed with FTIR. Morphological information of GO and formation of MoS₂nanopetals as well as interlayer spacing were verified through FESEM and HRTEM respectively. Raman analysis was employed to probe any evidence regarding defect densities of GO. Optical properties of GO, MoS₂, Ag-rGO, and Ag-MoS₂were visualized through UV-vis and PL spectroscopy. Prepared products were employed as nanocatalysts to purify industrial wastewater. Experimental results revealed that Ag-rGO and Ag-MoS₂showed 99% and 80% response in photocatalytic activity. Besides, the nanocatalyst (Ag-MoS₂and Ag-rGO) exhibited 6.05 mm inhibition zones againstS. aureusgram positive (G+) and 3.05 mm forE. coligram negative (G-) in antibacterial activity. To rationalize biocidal mechanism of Ag-doped MoS₂NPs and Ag-rGO,in silicomolecular docking study was employed for two enzymes i.e.β-lactamase and D-alanine-D-alanine ligase B (ddlB) from cell wall biosynthetic pathway and enoyl-[acylcarrier-protein] reductase (FabI) from fatty acid biosynthetic pathway belonging toS. aureus. The present study provides evidence for the development of cost-effective, environment friendly and viable candidate for photocatalytic and antimicrobial applications.

Synthesis of biocompatible chitosan functionalized Ag decorated biocomposite for effective antibacterial and anticancer activity

The transition-metal dichalcogenides (TMDCs) like MoS₂ and WS₂ are a new and interesting class of materials and show considerable promise for use in a wide variety of fields, including nanomedicine for cancer. The eco-friendly, biodegradability, toxicity, and antimicrobial activity remain an open issue. Herein, we focused on the current demands of two dimensional (2D) TMDCs and produced high-quality, few-layered MoS₂ nanosheets. Noble metal Ag incorporated into the 2D-CS/MoS₂ NC by the liquid exfoliated process. The manufactured CS/MoS₂/Ag hybrid NC showed excellent antibacterial activity against two microorganisms such as Gram-positive (21, 27, and 33 mm) and Gram-negative bacteria (23, 30, and 39 mm). The CS/MoS_2/Ag hybrid NC was designed to have significant antibacterial activity against E.coli bacteria than S.aureus. Furthermore, the hybrid NC has a 74.18% cell inhibition against MCF-7 cancer cells. According to the literature relevant, it is the first extensive experimental analysis on the nano-bio interaction of 2D TMDCs nanomaterials in MCF-7 breast cancer cells.

Catalytic activity of synthesized 2D MoS2/graphene nanohybrids for the hydrodesulfurization of SRLGO: experimental and DFT study

Hydrodesulfurization (HDS) of straight run light gas oil (SRLGO) using novel highly active two-dimensional (2D) MoS₂/graphene (G) nanohybrid catalysts is a precursor technology for the production of clean heavy fuel. The aim of this research is the synthesis of 2D MoS₂/G nanohybrid catalysts by use of exfoliation method from commercial bulky MoS₂ and graphite using hydrothermal ball milling system, which is a low-cost, high-yield, and scalable method. These nanohybrid catalysts were characterized by XRD, Raman spectroscopy, XPS, SEM, TEM, STEM, ICP, BET surface, TPR, and TPD techniques. Also, catalytic activities of 2D MoS₂/G nanohybrid catalysts were evaluated under different operating conditions such as temperature, pressure, LHSV, and H₂/Feed (SRLGO) ratio in the HDS reaction. The conversion of the HDS of SRLGO with 14000 ppm sulfur showed a considerably higher activity of 2D MoS₂/G nanohybrid catalyst (99.95% HDS efficiency) compared with the Co-Mo/γAl₂O₃ as a commercial catalyst (90% HDS efficiency) in the operation condition (340 °C, 40 bars, LHSV: 1 h^-1and H₂/oil: 600 NL L^-1) which is economically valuable. Using density functional theory calculations, the detailed mechanism of the HDS process over MoS₂/G catalyst was explored. It was found that sulfur coverage on the Mo edge of MoS₂ plays an important role in the hydrogenation of sulfur components.

Hierarchical structure of molybdenum disulfide-reduced graphene oxide nanocomposite for the development of a highly efficient serotonin biosensing platform

Molybdenum disulfide-reduced graphene oxide nanocomposite based immunosensor for the serotonin detection.

Synergistic lubrication performance by incommensurately stacked ZnO-decorated reduced graphene oxide/MoS2 heterostructure

Incommensurate stacking between two different types of two-dimensional layered materials furnished the weak interfacial interaction due to the mismatch of their lattice structure, which can be harnessed for development of new generation lubricant additives. Herein, a facile approach is presented to synthesize the ZnO-decorated reduced graphene oxide/MoS₂ (Gr-MS-Zn) nanosheets. The Fourier transform infrared, X-ray photoelectron spectroscopic, Raman, and transmission electron microscopic analyses confirmed the preparation of Gr-MS-Zn heterostructure. The MoS₂ nanosheets having 3-7 molecular lamellae are thoroughly distributed over the graphene skeleton via weak interfacial interaction. The curved and bent structure of MoS₂ nanosheets grown over the graphene lamellae subsidized the cohesive interaction and furnished the stable dispersion of Gr-MS-Zn in the fully formulated engine oil. The minute dose of Gr-MS-Zn as a nano-additive to engine oil significantly enhanced the tribological performance between the steel-steel tribopair by decreasing the friction (37%) and the wear volume (87%). The microscopic and spectroscopic analyses revealed the formation of a Gr-MS-Zn-based surface protective tribo thin film of low shear strength. The enhanced tribo performance is collectively attributed to (a) uninterrupted supply of ultrathin Gr-MS-Zn nanosheets to tribo-interfaces, (b) stable dispersion of Gr-MS-Zn, and (c) the significantly low shear strength, arising from weak interfacial interaction between the incommensurately stacked graphene and MoS₂ nanosheets.

Antimonene nanosheets with enhanced electrochemical performance for energy storage applications

Antimonene is an exfoliated 2D nanomaterial obtained from bulk antimony. It is a novel class of 2D material for energy storage applications. In the present work, antimonene was synthesized using a high-energy ball milling-sonochemical method. The structural, morphological, thermal, and electrochemical properties of antimonene were comparatively analyzed against bulk antimony. X-ray diffractometry (XRD) analysis confirms the crystal structure and 2D structure of antimonene, as a peak shift was observed. The Raman spectra show the peak shift for the E_g and A_1g modes of vibration of antimony, which confirms the formation of antimonene. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) images depict the exfoliation of antimonene from bulk antimony. Thermal analysis unveiled the thermal stability of antimonene up to 400 °C with only 3% weight loss. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of antimonene, which is free from contamination. The electrochemical properties of antimony and antimonene were investigated using cyclic voltammetry (CV) and chronopotentiometric (CP) analysis, using 2 M KOH as an electrolyte. Antimonene exhibited a relatively high specific capacitance of 597 F g^-1 compared to ball-milled antimony (101 F g^-1) at a scan rate of 10 mV s^-1. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that antimonene has a relatively low equivalence series resistance (RESR) and low charge transfer resistance (RCT) compared to bulk antimony, which favors high electrochemical performance. The cyclic stability of antimonene was studied for 3000 cycles, and the results show high cyclic stability. The electrochemical results demonstrated that antimonene is a promising material for energy storage applications.

Structural-Defect-Mediated Grafting of Alkylamine on Few-Layer MoS2 and Its Potential for Enhancement of Tribological Properties

Two-dimensional transition-metal dichalcogenides possess inherent structural characteristics that can be harnessed for enhancement of tribological properties by making them dispersible in lube media. Here, we present a hydrothermal approach to preparing MoS₂ nanosheets comprising 4-10 molecular lamellae. A structural-defect-mediated route for grafting of octadecylamine (ODA) on MoS₂ nanosheets is outlined. The unsaturated d orbitals of Mo at the sulfur vacancies on the MoS₂ surface are coupled with the electron-rich nitrogen center of ODA and yield ODA-functionalized MoS₂ (MoS₂-ODA). The MoS₂-ODA nanosheets exhibit good dispersibility in lube base oil and are used as an additive (optimized dose: 0.1 mg·mL^-1) to mineral oil. It is shown that even at low concentration, MoS₂-ODA nanosheets significantly reduce the friction (48%) and wear (44%). Microscopy (field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM)) and spectroscopy (Raman and elemental mapping) analyses of worn scars revealed the formation of MoS₂-based protective thin films for lowering of friction and wear. This work, therefore, presents a pathway for low-friction lubricants by deploying functionalized low-dimensional material systems.

Single-Step Synthesis of Mesoporous Carbon Nitride/Molybdenum Sulfide Nanohybrids for High-Performance Sodium-Ion Batteries

Molybdenum disulfide (MoS₂ ) is a promising candidate as a high-performing anode material for sodium-ion batteries (SIBs) due to its large interlayer spacing. However, it suffers from continued capacity fading. This problem could be overcome by hybridizing MoS₂ with nanostructured carbon-based materials, but it is quite challenging. Herein, we demonstrate a single-step strategy for the preparation of MoS₂ coupled with ordered mesoporous carbon nitride using a nanotemplating approach which involves the pyrolysis of phosphomolybdic acid hydrate (PMA), dithiooxamide (DTO) and 5-amino-1H-tetrazole (5-ATTZ) together in the porous channels of 3D mesoporous silica template. The sulfidation to MoS₂ , polymerization to carbon nitride (CN) and their hybridization occur simultaneously within a mesoporous silica template during a calcination process. The CN/MoS₂ hybrid prepared by this unique approach is highly pure and exhibits good crystallinity as well as delivers excellent performance for SIBs with specific capacities of 605 and 431 mAhg^-1 at current densities of 100 and 1000 mAg^-1 , respectively, for SIBs.

Synergistic effect of Bi-doped exfoliated MoS2 nanosheets on their bactericidal and dye degradation potential

Nanosheets incorporated with biological reducing agents are widely used to minimize the toxic effects of chemicals. Biologically amalgamated metal oxide nanomaterials have crucial importance in nanotechnology. In this study, bare and bismuth (Bi)-doped molybdenum disulfide (MoS2) nanosheets were synthesized via a hydrothermal method. Different Bi weight ratios of 2.5, 5, 7.5 and 10% were incorporated in a fixed amount of MoS2 to evaluate its catalytic and antimicrobial activities. Doped nanosheets were characterized using XRD, FTIR and UV-vis spectroscopy, FESEM, HRTEM, Raman, PL, DSC/TGA, EDX, XRF and XPS analysis. The XRD spectra confirmed that the doped nanosheets exhibit a hexagonal structure and their crystallite size increases gradually upon doping. The morphology and interlayer d-spacing of doped MoS2 were determined by FESEM and HRTEM. The presence of functional groups in the doped nanosheets was confirmed using FTIR, PL and Raman analysis. The absorption intensity increased and the corresponding measured band gap energy decreased with doping. The thermal stability and weight loss behaviour of the prepared samples were studied using DSC/TGA. The doped MoS2 nanosheets showed a higher catalytic potential compared to undoped MoS2. The doped Bi nanosheets exhibited higher antimicrobial activity against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) at different concentrations of Bi (0.075 and 0.1), showing a tendency to counter the emerging drug resistance against pathogenic bacterial diseases. Consequently, significant inhibition zones were recorded against (MDR) S. aureus ranging from 2.25 to 3.3 mm and 3.25 to 5.05 mm at low and high concentrations of doped-Bi nanosheets and against Gram-negative E. coli ranging from 1 to 1.45 mm at high concentrations. In conclusion, the Bi-doped MoS2 nanocomposite has exhibited significant potential for use in industrial dye degradation applications. Its antibacterial properties can also mitigate health risks associated with the presence of several well-known pathogens in the environment.

Synthesis of biogenic chitosan-functionalized 2D layered MoS2 hybrid nanocomposite and its performance in pharmaceutical applications: In-vitro antibacterial and anticancer activity

A bacterial and viral infection causes life threatening diseases owing to the abuse of antibiotics and the development of antibiotic resistance microbes. Currently, biopolymers have been considered as the most promising materials in the medical field. Herein, the biogenic chitosan-functionalized MoS₂ nanocomposite was prepared by the hydrothermal method with the liquid exfoliation process. The X-ray diffraction (XRD) results of chitosan-MoS₂ hybrid nanocomposite revealed that MoS₂ nanoparticle was found to be 42 nm with a hexagonal crystal structure. FTIR and Raman spectrum revealed that the nitrogen functionalities in the chitosan interacted with MoS₂ to form the nanocomposite. The XPS spectrum of chitosan-MoS₂ nanocomposite confirms that C, N, O, Mo, and S exist in the nanocomposite. Thermal gravimetric analysis (TGA) and Differential thermal analysis (DTA) analysis showed that the chitosan-MoS₂ nanocomposite has higher thermal stability up to 600 °C. In the antibacterial application the chitosan-MoS₂ hybrid nanocomposite shows zones of inhibition against S. aureus as 22, 28, and 32 mm, and against E. coli as 26, 30, and 35 mm. In the anticancer analysis, chitosan-MoS₂ hybrid nanocomposites showed a maximum cell inhibition of 65.45% at 100 μg/mL^-1, resulting in the most significant MCF-7 cell inhibition.

Scalable Solution Processing MoS2 Powders with Liquid Crystalline Graphene Oxide for Flexible Freestanding Films with High Areal Lithium Storage Capacity

Freestanding flexible electrodes with high areal mass loading are required for the development of flexible high-performance lithium-ion batteries (LIBs). Currently they face the challenge of low mass loading due to the limited concentrations attainable in processable dispersions. Here, we report a simple low-temperature hydrothermal route to fabricate flexible layered molybdenum disulfide (MoS₂)/reduced graphene oxide (MSG) films offering high areal capacity and good lithium storage performance. This is achieved using a self-assembly process facilitated by the use of liquid crystalline graphene oxide (LCGO) and commercial MoS₂ powders at a low temperature of 70 °C. The amphiphilic properties of ultralarge LCGO nanosheets facilitates the processability of large-size MoS₂ powders, which is otherwise nondispersible in water. The resultant film with an areal mass of 8.2 mg cm^-2 delivers a high areal capacity of 5.80 mAh cm^-2 (706 mAh g^-1) at 0.1 A g^-1. This simple method can be adapted to similar nondispersible commercial battery materials for films fabrication or production of more complicated constructs via advanced fabrication technologies.

Flower-Like MoS2 for Next-Generation High-Performance Energy Storage Device Applications

Here, a well crystalline 3D flower-like structured MoS2 (~420 nm) has been successfully synthesized on a large scale by a simple hydrothermal technique. The evolution of morphology in the formation process has also been investigated. The crystallinity, purity, and morphology of the sample are characterized by powder X-ray diffraction, Fourier-transform infrared spectroscopy, fieldemission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The FESEM and TEM images reveal that the sample exhibits a uniform 3D flower-like microsphere shape with folded nanosheets, which are stretched out along the edge of the microsphere. The electrochemical performance of the sample has been investigated by cyclic voltammogram, galvanostatic charge-discharge, and electrochemical impedance spectroscopy studies. The results of the electrochemical analysis suggest that the material delivers a maximum specific capacitance (Csp) of 350 F/g at a discharge current density of 0.25 A/g with energy density 17.5 Wh/kg. It also exhibits good capability and excellent cyclic stability (94% capacity retention after 1,000 cycles in 1 A/g) owing to the coupling effect of electrical conductivity with the interesting morphology and larger active surface area. Hence, the sample may be used as a promising electrode material for high-performance energy storage devices.

Nile Blue Functionalized Graphene Aerogel as a Pseudocapacitive Negative Electrode Material across the Full pH Range

The pursuit of new negative electrode materials for redox supercapacitors with a high capacitance, boosted energy, and high rate capability is still a tremendous challenge. Herein, we report a Nile Blue conjugated graphene aerogel (NB-GA) as a negative electrode material with excellent pseudocapacitive performance (with specific capacitance of up to 483 F g^-1 at 1 A g^-1) in all acidic, neutral, and alkaline aqueous electrolytes. The contribution from capacitive charge storage represents 93.4% of the total charge, surpassing the best pseudocapacitors known. To assess the feasibility of NB-GA as a negative electrode material across the full pH range, we fabricated three devices, namely, a symmetric NB-GA||NB-GA device in an acidic (1.0 M H₂SO₄) electrolyte, an NB-GA||MnO₂ device in a pH-neutral (1.0 M Na₂SO₄) electrolyte, and an NB-GA||LDH (LDH = Ni-Co-Fe layered double hydroxide) device in an alkaline (1.0 M KOH) electrolyte. The NB-GA||NB-GA device exhibits a maximum specific energy of 22.1 Wh kg^-1 and a specific power of up to 8.1 kW kg^-1; the NB-GA||MnO₂ device displays a maximum specific energy of 55.5 Wh kg^-1 and a specific power of up to 14.9 kW kg^-1, and the NB-GA||LDH device shows a maximum specific energy of 108.5 Wh kg^-1 and a specific power of up to 25.1 kW kg^-1. All the devices maintain excellent stability over 5000 charge-discharge cycles. The outstanding pseudocapacitive performances of the NB-GA nanocomposites render them a highly promising negative electrode material across the entire pH range.

Transition-Metal-Doped Molybdenum Diselenides with Defects and Abundant Active Sites for Efficient Performances of Enzymatic Biofuel Cell and Supercapacitor Applications

We have demonstrated the synthesis of defect-rich Ni-doped MoSe₂ nanoplates (NiMoSe₂) and their application as an efficient electrocatalyst for enzymatic biofuel cells and electrochemical pseudocapacitors. In this study, a new type of interpretation is proposed that a defective surface facilitates the effective entrapment of enzymes (glucose oxidase (GOD), laccase) for biofuel cells and additional ion diffusion for Faradic charge-discharge reaction. The transmission electron microscopy and UV-vis spectroscopy techniques scrutinized the formation of defects/distortions and the resultant successful entrapment of enzymes. The performed electrochemical characterizations of enzyme-immobilized NiMoSe₂/nickel foam (NF) bioanode (NiMoSe₂/GOD/NF) and biocathode (NiMoSe₂/laccase/NF) exhibited better direct charge conductive behavior at the interface of enzymes and electrode material. Herein, the assembled biofuel cells exhibited an open-circuit voltage ( V_OC = 0.6 V) and a short-circuit current density ( J_SC = 8.629 mA cm^-2) with a maximum power density ( P_max) of 1.2 mW cm^-2. For the electrochemical pseudocapacitor application, the proposed NiMoSe₂/NF exhibited excellent specific capacitance (535.74 F g^-1), with 86.7% rate performance. Finally, this work suggests new insights into both enzymatic biofuel cell and supercapacitor applications.

Boron Doped Graphene Quantum Structure and MoS2 Nanohybrid as Anode Materials for Highly Reversible Lithium Storage

Herein, the boron-doped graphene quantum structure (BGQS), which contains both the advantages of 0-D graphene quantum dot and 2-D reduced graphene oxide, has been fabricated by top-down hydrothermal method and then mixed with molybdenum sulfide (MoS2) to serve as an active electrode material for the enhanced electrochemical performance of lithium ion battery. Results show that 30 wt% of BGQS/MoS2 nanohybrid delivers the superior electrochemical performance in comparison with other BGQS/MoS2 and bare components. A highly reversible capacity of 3,055 mAh g-1 at a current density of 50 mA g-1 is achieved for the initial discharge and a high reversible capacity of 1,041 mAh g-1 is obtained at 100 mA g-1 after 50 cycles. The improved electrochemical performance in BGQS/MoS2 nanohybrid is attributed to the well exfoliated MoS2 structures and the presence of BGQS, which can provide the vitally nano-dimensional contact for the enhanced electrochemical performance. Results obtained in this study clearly demonstrate that BGQS/MoS2 is a promising material for lithium ion battery and can open a pathway to fabricate novel 2-D nanosheeted nanocomposites for highly reversible Li storage application.

Oxidation of 2D-WS2 nanosheets for generation of 2D-WS2/WO3 heterostructure and 2D and nanospherical WO3

Evolution of 2D-WS₂/WO₃ heterostructures as well as 2D and nanospherical WO₃ during the oxidation of WS₂ nanosheets in air.

Graphene/transition metal dichalcogenides hybrid supercapacitor electrode: status, challenges, and perspectives

Supercapacitors, based on fast ion transportation, are among the most promising energy storage solutions that can deliver fast charging-discharging within seconds and exhibit excellent cycling stability. The development of a good electrode material is one of the key factors in enhancing supercapacitor performance. Graphene (G), an allotrope of carbon that consists of a single layer of carbon atoms arranged in a hexagonal lattice, elicits research attention among scientists in the field of energy storage due to its remarkable properties, such as outstanding electrical conductivity, good chemical stability, and excellent mechanical behavior. Furthermore, numerous studies focus on 2D materials that are analogous to graphene as electrode supercapacitors, including transition metal dichalcogenides (TMDs). Recently, scientists and researchers are exploring TMDs because of the distinct features that make 2D TMDs highly attractive for capacitive energy storage. This study provides an overview of the structure, properties, synthesis methods, and electrochemical performance of G/TMD supercapacitors. Furthermore, the combination of G and TMDs to develop a hybrid structure may increase their energy density by introducing an asymmetric supercapacitor system. We will also discuss the future prospect of this system in the energy field.