MoS2 Sheets Research Articles

Toward Urease-free wearable artificial kidney: Widened interlayer spacing MoS2 nanosheets with highly effective adsorption for uremic toxins

The high incidence of kidney disease caused by various factors (such as COVID-19) has triggered an extreme desire for wearable artificial kidney (WAK). Nevertheless, the dialysate regeneration system in WAK presents a very low adsorption capacity of urea, and must rely on the help of urease and zirconium compounds, which make the device too complex and costly, thus limiting their application. In this study, we employ the adsorption activity of defect-rich MoS2 nanosheets with widened interlayer spacing (WDR-MoS2) for the elimination of three crucial uremic toxins (urea, creatinine, and uric acid). The high adsorption performances of WDR-MoS2 are owing to the presence of abundant S atoms between the two MoS2 sheets that can efficiently adsorb uremic toxins through the unique S–N bond. Furthermore, widening the layer spacing of MoS2 is similar to adjusting the aperture of a filter, which can not only speed up the transport of uremic toxins but also prevent the passage of large molecules (such as proteins). Thus, the WDR-MoS2 can neither affect cell viability nor produce hemolysis and coagulation in the blood. Finally, a home-made WDR-MoS2 fixed-bed system without urease and zirconium compounds is used to efficiently remove uremic toxins in the dialysate. WDR-MoS2 is expected to fundamentally solve the materials science challenges in WAK and provide a new design idea for the development of high-performance 2D material-based adsorbents.

Synthesis of Graphene/Silver/Molybdenum Disulphide Composite for Supercapacitor Application

In this study, pristine graphene/silver/molybdenum disulphide (G/Ag/MoS2) and reduced graphene oxide/silver/molybdenum disulphide (rGO/Ag/MoS2) composites materials were prepared via green solvothermal synthesis method and evaluated as supercapacitor electrodes. The morphology and structure of composites were examined by using Scanning Electron Microscopy (SEM), Energy dispersive spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and Raman spectroscopy. SEM and TEM indicate successful reduction of silver nitrate (AgNO3) to spherical Ag nanoparticles (NPs) by sodium citrate. The Ag NPs were observed to be evenly deposited on sheets of rGO and MoS2. From the XPS analysis, the spherical Ag NPs exist in zero-valent state, reflecting successful reduction. Based on cyclic voltammetry (CV) performed under 50 mV/s scan rate, G/Ag/MoS2 ternary composite exhibits the highest specific capacitance of 56.38 F/g which is 31 % and 29 % enhancement in specific capacitance of rGO/Ag/MoS2 ternary composite and Ag/MoS2 binary composite, respectively. It is believed that the presence of graphene may provide conductive pathway and a larger surface area for the distribution of Ag NPs.

Zero-Bias Power-Detector Circuits based on MoS2 Field-Effect Transistors on Wafer-Scale Flexible Substrates.

The design, fabrication, and characterization of wafer-scale, zero-bias power detectors based on 2D MoS2 field-effect transistors (FETs) are demonstrated. The MoS2 FETs are fabricated using a wafer-scale process on 8μm-thick polyimide film, which, in principle, serves as a flexible substrate. The performances of two chemical vapor deposition MoS2 sheets, grown with different processes and showing different thicknesses, are analyzed and compared from the single device fabrication and characterization steps to the circuit level. The power-detector prototypes exploit the nonlinearity of the transistors above the cut-off frequency of the devices. The proposed detectors are designed employing a transistor model based on measurement results. The fabricated circuits operate in the Ku-band between 12 and 18GHz, with a demonstrated voltage responsivity of 45V W-1 at 18GHz in the case of monolayer MoS2 and 104V W-1 at 16GHz in the case of multilayer MoS2 , both achieved without applied DC bias. They are the best-performing power detectors fabricated on flexible substrate reported to date. The measured dynamic range exceeds 30dB, outperforming other semiconductor technologies like silicon complementary metal-oxide-semiconductor circuits and GaAs Schottky diodes.

Construction of 2D MoS2@ZnO heterojunction as superior photocatalyst for highly efficient and selective CO2 conversion into liquid fuel

An advanced photocatalyst heterojunction comprised of 2D sheets of MoS2 and diamond-like shape ZnO nanoparticles was successfully synthesized via a simple calcination route. The structural properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV–visible-NIR absorption spectrophotometer, Photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and Raman analysis. The morphology investigations show the wrapping of MoS2 nanosheets around the agglomerated ZnO nanoparticles forming a hollow-like shaped structure. Moreover, ZnO/MoS2 luminescence revealed a remarkable charge carriers’ separation. The photocatalytic reduction of CO2 was performed under UV-light irradiation of a 150 W Hg lamp in three different solvents. ZnO/MoS2 exhibited high photocatalytic activity towards CO2 photoreduction into CH3OH and minor traces of CH3CHO, and C2H5OH. Methanol was the dominant product with a maximum yield of 170.5 µmol/g. The high photocatalytic activity of ZnO/MoS2 may be attributed to accumulation of electrons on the surface of 2D-MoS2 which granted electrons a great mobility that supported the charge carrier’s separation. In addition, the hollow-like shaped structure may contribute to greater light absorption through photon refractions inside the shell which increases the photocatalytic performance.

Mechanical Behavior of Blisters Spontaneously Formed by Multilayer 2D Materials

AbstractBlisters can form spontaneously when transferring 2D materials on a substrate because of the small molecules trapped at the interface. Though extensive works have revealed a characteristic aspect ratio of these blisters by neglecting the bending effect of the layer, how the bending comes into play as the layer number increases has not been fully understood. Here, by simply measuring the profiles of blisters formed by transferred multilayer graphene and MoS2 sheets, the variable profiles of blisters and the transition of their characteristic shape from a constant aspect ratio to a constant dome curvature are observed. Taking variable profiles of blisters and different characteristics of the interface into consideration, a theoretical model is established, and the mechanism of such transition is further analytically unveiled. In addition, based on this theory, the bending stiffness of sheets and the adhesion energy between sheets and substrates can be obtained simultaneously. This method is simple but robust, providing a new experimental way to explore the mechanical behavior of 2D material structures.

Glycosylated MoS2 Sheets for Capturing and Deactivating E. coli Bacteria: Combined Effects of Multivalent Binding and Sheet Size

AbstractMolybdenum disulfide (MoS2) holds great promise for antibacterial applications owing to its strong photothermal performance and biocompatibility. Most of its antibacterial explorations have sought enhanced antibacterial potency through designing new hybrid inorganic materials, the relationship between its physiochemical properties and antibacterial activities has yet to be explored. This work is the first to investigate the combination effects of different sized and functionalized MoS2 sheets on their antibacterial activities. The bacterial capture abilities of 3 µm mannosylated, galactosylated, and glucosylated sheets, as well as 300 nm mannosylated sheets, all with similar sugar densities, are compared. Only mannosylated MoS2 sheets are found to agglutinate normal Escherichia coli (E. coli) and large mannosylated MoS2 sheets show the strongest E. coli agglutination. Despite slightly weaker photothermal performance under near‐infrared (NIR) laser irradiation, large mannosylated MoS2 sheets exhibit higher antibacterial activity than the smaller sheets. By much stronger specific multivalent binding, large sheets capture E. coli more efficiently and compensate for their reduced photothermal activity. Besides providing a facile approach to eliminate E. coli bacteria, these findings offer valuable guidance for future development of 2D nanomaterial‐based antibacterial agents and filter holder materials, where large‐functionalized sheets can capture and eliminate bacteria powerfully.

Selective Detection of Carbon Monoxide on P-Block Doped Monolayers of MoTe2.

CO and CO2 are among the most commonly monitored gases. However, the currently available semiconductor sensors require heating to ∼400 °C in order to operate effectively. This increases the power demand and shortens their lifespan. Consequently, new material prospects are being investigated. The adoption of novel two-dimensional layered materials is one of the pursued solutions. MoS2 and MoTe2 sheets have already been shown sensitive to NO2 and NH3 even at room temperature. However, their response to other compounds is limited. Hence, this work investigates, by employing density functional theory (DFT) calculations, the doping of Al, Si, P, S, and Cl atoms into the Te vacancy of MoTe2, and its impact on the sensing characteristics for CO and CO2. The computations predict that P doping significantly enhances the molecule-sheet charge transfer (up to +436%) while having only a little effect on the adsorption energy (molecular dynamics show that the molecule can effectively diffuse at 300 K). On the other hand, the doping has a limited impact on the adsorption of CO2. The relative (CO/CO2) response of P-doped MoTe2 is 5.6 compared to the 1.5 predicted for the pristine sheet. Thus, the doping should allow for more selective detection of CO in CO/CO2 mixtures.

Cu2O nanoparticles decorated with MoS2 sheets for electrochemical reduction of CO2 with enhanced efficiency

Cu2O nanoparticles decorated with MoS2 sheets for electrochemical reduction of CO2 with enhanced efficiency

In-situ formation of 2H phase MoS2/cerium-zirconium oxide nanohybrid for potential electrochemical detection of an anticancer drug flutamide

The developing field of sensors is highly motivated and attracted by two-dimensional transition metal dichalcogenides (TMDs) with transition metal oxide integration. Initially, molybdenum disulfide (MoS2), one among the TMDs with cerium-zirconium oxide (CZO), was one-pot synthesized via hydrothermal method for sensing flutamide (FLD). The as-synthesized hybrid nanocomposite was characterized to understand their physical and chemical presence. MoS2-CZO was well assigned with crystalline nature observed from X-ray powder diffraction and X-ray photoelectron spectroscopy. High-resolution transmission electron microscopy confirms the irregularly arranged nanoparticles wrapped with MoS2 sheets. The wide surface area with more electroactive sites has provided higher conductance of the MoS2-CZO/glassy carbon electrode. The limit of detection was 0.005 μM with a linear range of 0.019 μM to 668.5 μM, sensitivity 0.353 μA μM−1 cm−2. The practical feasibility was analyzed with human urine and river water samples, whereas the obtained results showed excellent FLD detection. The fabricated MoS2-CZO with all these distinguished analyses will be an outbreak in the field of electrochemical sensors.

Influence of noncovalent intramolecular and host–guest interactions on imatinib binding to MoS2 sheets: a PXRD/DFT study

The revealed pattern of imatinib drug binding to MoS2 sheets is promising for the combined exploitation of these species for therapeutic purposes.

One-step hydrothermal synthesis of MoS2 nano-flowers CoS2 square composites electrode materials for supercapacitor application

Developing efficient materials for generating and storing renewable energy is now a pressing test for future energy demand. The advent of (2D) two-dimensional materials has attracted much research interest as electrode materials for supercapacitors due to their intriguing mechanical and electrochemical properties. This report used a facile one-step hydrothermal process to synthesize MoS2@CoS2 Composite as electrode materials for supercapacitors with good energy storage performance and explore energy generation and storage applications. The structure and morphology were investigated by X-ray diffraction pattern, field emission scanning electron microscope consisting of square-shaped CoS2 and flower-like MoS2, and characterization; meanwhile, their electrochemical properties were evaluated by CV, GCD, and EIS measurements. The electrochemical performance of symmetric MoS2@CoS2 binary Composite was examined in 1 M H2SO4 in a two-electrode assembly. The as-prepared MoS2@CoS2 electrode exhibited a specific capacitance of 199F/g at a current density of 2A/g, while its counterpart MoS2 electrode exhibited only 127F/g at 2 A/g current density. The MoS2@CoS2 composite attains specific energy and power densities of 27.74 WhKg−1 and 494.46 Wkg−1, respectively, due to the unique morphology of the MoS2-flowery shape and CoS2 square. CoS2 squares effectively prevent the agglomeration and restacking of MoS2 sheets, facilitating smother ion dynamics. Technological demonstration of MoS2@CoS2 cell is presented by illuminating commercially available light-emitting diode for more than 3 min.

Tunable Multi‐Bit Nonvolatile Memory Based on Ferroelectric Field‐Effect Transistors

AbstractFerroelectric field‐effect transistors (FeFETs) with 2D semiconductors as channel materials have been fabricated to achieve miniaturized size, high storage, and low power consumption. The FeFETs are studied based on few‐layer MoS2 sheets on the non‐lead Bi0.85La0.15Fe0.92Mn0.08O3 (BLFMO) ferroelectric films with a large remnant polarization (Pr ≈36 μC cm−2). In FeFETs, the conductivity states of the 2D semiconductor can be tuned by the ferroelectric polarization. It is found that the MoS2‐based FeFETs display a large memory windows exceeding 25 V, a high on/off ratio (>105), remarkable program/erase ratio (≈104), competitive retention, endurance, and high‐speed performance. Moreover, the 2D based FeFETs exhibit switchable multi‐bit data storage by applying different amplitudes of negative gate voltage pulses to enhance the data storage density. On the basis of these characteristics, the 2D‐FeFETs are potentially able to meet the need for scalability, capacity, retention, and endurance of nonvolatile memory.

Improved Interfacial Charge Transfer on Noble Metal‐Free Biomimetic CdS‐Based Tertiary Heterostructure @ 2D MoS2‐CdS‐Cu2O with Enhanced Photocatalytic Water Splitting

AbstractHigh charge separation efficiency with a wide optical absorption window is the prime requirement for the scale up of a stable solar photocatalytic hydrogen generation process. A new noble metal‐free heterostructure of 2D MoS2‐CdS‐Cu2O is designed by depositing cauliflower‐shaped CdS and nanosized Cu2O on exfoliated 2D MoS2. Characterization by XPS, high‐resolution transmission electron microscopy (HRTEM), and UV‐visible spectra confirms the formation of nanosized Cu2O with desired interface formation with MoS2 sheet and CdS thus extending the optical absorption range up to 900 nm. Water splitting activity in the presence of lactic acid is found to be 7.89 and 11.53 mmol g−1 h−1 on MoS2‐CdS and MoS2‐CdS‐Cu2O, respectively, with good repeatability under visible light. Efficient interfacial charge separation is manifested from demised photoluminescence (PL) intensity which supports the suppression of hole‐electron recombination in the tertiary heterostructure. In addition, the formation of dual p‐n junction as indicated from Mott–Schottky analysis further strengthen the faster electron and holes separation objective. Compared to the pure CdS, hydrogen efficiency is 20.96 times higher on a noble metal‐free tertiary catalyst with an apparent quantum efficiency of 8.75%. Hopefully, the 2D material‐based architecture of dual p‐n junction with desired interface engineering will facilitate the catalyst design with increased water splitting activity under solar/visible light.

Single-Layer MoS2-MoO3-x Heterojunction Nanosheets with Simultaneous Photoluminescence and Co-Photocatalytic Features

Single-layer MoS2-MoO3-x heterojunction nanosheets with visible-light-sensitive band gap energy and average lateral dimensions of ~70 nm were synthesized by using a two-step combined exfoliation method. The exfoliation was initiated from pristine MoS2, while some sulfur sites in expanded MoS2 sheets during exfoliating were substituted by ambient non-thermal oxygen, resulting in formation of α-MoO3-x crystalline domains. The morphological features, crystalline structure, phase formation, number of layers, and optical properties of the MoS2-MoO3-x nanosheets were determined by atomic force microscopy; X-ray diffraction; field emission electron microscopy; transmission electron microscopy; and Raman, UV–visible–NIR, diffuse transmittance, and photoluminescence spectroscopies. The produced α-MoO3-x domains displayed a narrower indirect band gap energy (~1.95 eV) than that of stoichiometric MoO3 (~3 eV), and a broad light absorption range from visible to near-infrared region can act as a plasmonic material facilitating the separation of the photoinduced carriers and enhancing the photocatalytic activity of the MoS2 domain, having ~1.75(2.16) eV indirect (direct) band gap energy. In this regard, the MoS2-MoO3-x heterojunction nanosheets showed single-layer-based excitation-dependent luminescence emissions and visible-light-induced photocatalytic features, at the same time. This study can contribute to promising applications of sheet-like nanomaterials for purposes requiring simultaneous photoluminescence and photocatalytic features, such as in-vivo monitoring and targeting.

Hydrothermal Synthesis of 1T-MoS2/Pelagic Clay Composite and Its Application in the Catalytic Reduction of 4-Nitrophenol.

Pelagic clay is an emerging marine resource with strong hydrophilicity, fine particles and a large specific surface area. In this work, a 1T-MoS2/pelagic clay composite was fabricated by hydrothermal synthesis. In the composite, 1T-MoS2 nanosheets are evenly dispersed on the surface of the clay minerals, significantly reducing the agglomeration of MoS2. Compared with pure 1T-MoS2, the 1T-MoS2 nanosheets generated on the surface of pelagic clay have significantly smaller lateral dimensions and thicknesses. Moreover, the specific surface area is much larger than that of the pure 1T-MoS2 nanosheets fabricated by the same method, indicating that the active sites of the MoS2 sheets are fully exposed. In addition, the composite exhibited excellent hydrophilicity, leading to a high dispersibility in aqueous solutions. In this work, the composite was used as a catalyst in the reduction of 4-nitrophenol (4-NP), and the conversion of 4-NP reached up to 96.7%. This result shows that the 1T-MoS2/pelagic clay composite is a promising catalyst in a variety of reactions.

Dual-mode amplified fluorescence oligosensor mediated MOF-MoS2 for ultra-sensitive simultaneous detection of 17β -estradiol and chloramphenicol through catalytic target- recycling activity of exonuclease I

The research outlines a novel ultrasensitive oligosensor which was designed by FRET-based selective simultaneous detection of multiple organic pollutant (chloramphenicol (CP) and 17β-estradiol (17E)) utilizing the MOF-MoS2 nanomaterial with Exo I signal amplification and target recycling strategy. In this oligosensor, the specific oligomers of 17E (ROX-SSO) and CP (TAMRA-SSO) are used as the recognition parts and the ROX and TAMRA as the fluorescent probes. The cubic-MOF incorporated by a few layered MoS2 sheets (MOF-MoS2) is used as oligomer adsorbing material and an efficient fluorescent nanoquencher for reducing the background signal. In this detection approach, the ROX-SSO and TAMRA-SSO probes could be adsorbed on the surface of the MOF-MoS2 through π-stacking and Vander Waals interactions. At the same time, the fluorescence of the ROX and TAMRA could be efficiently quenched due to the energy transfer between fluorophores and MOF-MoS2. In the addition of 17E & CP, the specific oligomers can be preferentially bound with the 17E & CP, and the newly formed ROX-SSO-17E &TAMRA-SSO-CP complex can be released from the MOF-MoS2 surface and the partial recovery of fluorescence signal. Subsequently, the addition of Exo I is to trigger and digest the ROX-SSO-17E &TAMRA-SSO-CP complex, resulted in the remarkable recovery of fluorescence emission. At the same time, the liberated targets mediate a new cycle of digestion, resulting in the ultra-trace detection of targets. Thus, with the aid of the helper MOF-MoS2 the turn-on detection of 17E and CP may be easily accomplished by observing the fluorescence signal of the respective fluorophores from “off” to “on”. Under optimal circumstances, the oligosensor has an excellent accuracy of 17E and CP, with detection limits of 180 and 200 pM, respectively. Furthermore, for the first time, the research successfully utilized this oligosensor to detect 17E and CP in milk, honey and water samples.

Graphene aerogel decorated with MoS2 sheets: an efficient electrochemical sensing platform for caffeic acid in red wine sample

As a typical two-dimensional (2D) transition metal disulfide, molybdenum disulfide (MoS 2 ) shows good electrocatalytic activity, and is considered as a promising sensing material due to its adequate exposed active edges. However, 2D sheet-like structural MoS 2 tends to aggregate, resulting in a decreased specific surface area. In addition, the poor electronic conductivity of MoS 2 limits the electrochemical application. To address these issues, herein, graphene aerogel (GA), with a three-dimensional (3D) nanoarchitecture consisting of a large specific surface area, rapid electron transfer, and excellent electrocatalytic activity, has been employed as a novel framework support for MoS 2 . Through a facile one-step hydrothermal technique, the peeled MoS 2 sheets were incorporated into the GA network. The MoS 2 /GA composite was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The composite combined the excellent electrical conductivity and huge effective surface area of GA with the high catalytic activity of the MoS 2 nanosheets. Due to these advantages, the MoS 2 /GA composite was applied as an electrochemical sensing platform for caffeic acid (CA) detection. The sensor performed good selectivity, wide linear range (1.0 nM-10.0 μM), and low limit of detection (LOD, 0.3 nM). Furthermore, the designed sensor represented good reproducibility and stability, and was successfully applied for detecting CA in red wine samples.

Multi-order phononic frequency comb generation within a MoS2 electromechanical resonator

In this work, we measure and tune simultaneously the vibration of a 1-nm thick MoS2 suspended monolayer with standard electrical excitation and optical techniques. At ambient temperature, we first investigate the strong parametric coupling between two different mechanical modes (ω1 and ω2). We demonstrate a high and quasi-linear tunability of the mode frequencies with the parametric pump voltage. Then, we couple the highly tunable main vibration (ω1) to a parametric pump frequency (ωp) to obtain a high number of sidebands at frequencies ω1 ± m ωp, driving the mechanical mode with a large external electrical force. This oscillating force, applied via the gate voltage, acts as a stress onto the MoS2 sheet. The obtained frequency comb has a large spectral band and contains up to 100 harmonics, with potential applications in quantum information processing and heat or sound transport.

Construction of N-doped C@MoS2 heteroshell with the yolk of Sn nanoparticles as high-performance anodes for sodium-ion batteries

Herein, we demonstrate the reasonable design and preparation of yolk-heteroshell Sn@N-doped C@MoS2 nanospheres as anode materials in sodium-ion battery. Through an effective multi-step strategy, Sn nanoparticles are encapsulated in N-doped C nanocage surrounded by ultra-thin MoS2 nanosheets to form Sn@N-doped C@MoS2 nanospheres. In this novel structure, Sn nanoparticles with high theoretical capacity improve the space utilization inside the heteroshell; the N-doped carbon nanocage as the skeleton not only inhibits the mutual accumulation of Sn and MoS2, but also improves conductivity; the outer MoS2 ultra-thin sheets can consolidate C@MoS2 heteroshell, provide numerous active sites and favor the fast diffusion of Na+/e-. Notably, the combination of carbon nanocage and MoS2 sheets in the yolk-heteroshell structure can effectually buffer the volume expansion of Sn nanoyolks and reinforce C@MoS2 heteroshell while reducing the carbon content. Therefore, the yolk-heteroshell structure plays a crucial role in enhanced reversible capacity and cyclic stability of Sn@N-doped C@MoS2 nanospheres, which activates their sodium storage potential. The yolk-heteroshell Sn@N-doped C@MoS2 nanospheres exhibit high reversible capacity of 488.4 mAh g−1 at 0.1 A g−1 after 300 cycles and long-cycle stability of 350.6 mAh g−1 at 0.5 A g−1 after 500 cycles. Moreover, their full cell delivers a stable reversible discharge capacity of about 80.1 mAh g−1 after 30 cycles at 0.5 C. This work provides a feasible yolk-heteroshell strategy for Sn-based composite nanomaterials.

Mechanical behavior of single layer MoS2 sheets with aligned defects under uniaxial tension

Compared with a single defect or randomly distributed defects, aligned defects are widely found or artificially designed in structures to realize various functions. However, the mechanical behavior of transition metal dichalcogenides with aligned defects is still unclear, which restricts the blooming application in novel flexible nanodevices. Herein, we report the strength and fracture properties of single layer MoS2 (SLMoS2) sheets with aligned defects under uniaxial tension by numerical calculation and theoretical modeling. It is found that the increase of the number of defects and adjacent spacing leads to the decrease of critical strain as well as tensile strength of both pristine and kirigami MoS2 sheets. Three types of crack propagation phenomena are discovered, and an effective theoretical model is employed to uncover the underlying mechanism of crack deflection phenomenon in SLMoS2 sheets with aligned defects. These results provide important insights into mechanical behavior of SLMoS2 sheets and should be helpful for potential applications of the new two-dimensional material.