Graphene MoS2 Hybrid Research Articles

Design and numerical simulation of a sensitive plasmonic-based nanosensor utilizing MoS2 monolayer and graphene

In this paper, a Kretschmann structure with a graphene-MoS2 hybrid layer has been used to design a sensitive biosensor for the detection of biomolecules. Here, by using a silicon layer, the sensitivity of the nanosensor is increased. Such a result is obtained from strong light-matter interaction between graphene and semiconductor layer. As a result, by changing the active metal and adding an additional silicon layer at a wavelength of 670 nm to access higher sensitivity and lower FWHM for the effective biosensor eventually we reach a sensitivity equal to 192°/RIU. The designed structure is investigated by numerical analysis and using the FDTD method, we numerically extract the optical characteristics of the surface plasmon polariton sensor. The detection range for the proposed structure is obtained with a refractive index of 0.005. Also, the basic parameters of the sensor to achieve the best conditions have been calculated and evaluated. In addition, the overall size of the sensor is 1112 nm × 2000 nm.

Synthesis and characterization of in-situ MoS2-graphene hybrid nanostructured material

Nowadays, it has been challenging to develop novel techniques and synthesis processes for hybrid two-dimensional materials. Hence, this research presents an innovative technique for the fabrication of MoS2-Graphene (MoS2-Gr) hybrid nanostructured materials. The graphene was effectively generated in-situ and incorporated into the interlayer spacing of MoS2, which was synthesized by using a co-precipitation process with diethyl glycol as the solvent, followed by annealing the as-synthesized MoS2 at 800 oC for two hours in an inert atmosphere. The integrated graphene enhanced the width of MoS2 interlayers, exposing a substantial concentration of active edge sites in the hybrid material, according to SEM, XRD, HR-TEM, and other characterizations. This research might lead to the development of viable hybrid structured materials for various applications. In addition, this study outlines a novel advanced approach for creating hybrid 2D nanostructured materials with superior characteristics.

Highly sensitive fiber optic biosensors with graphene-MoS2 heterostructure for hemoglobin detection

Two-dimensional materials, which can be used to modify sensor surfaces to increase sensor sensitivity, have important research in the field of sensors. In this paper, we design a highly sensitive D-shaped photonic crystal fiber sensor with graphene-MoS2 heterostructure for hemoglobin detection. The research utilized the finite element method and involved addition of different layers of graphene and MoS2 to the optical fiber sensing area, and it was determined that the hybrid nano-heterostructures made of monolayer graphene and bilayer MoS2 provided the greatest improvement in sensor performance. The sensor shows excellent detection performance in 1.33∼1.38 refractive index units. Using incident light in the wavelength ranges of 650 nm and 850 nm, the proposed sensor has a maximum wavelength sensitivity of 4700 nm/RIU, a maximum amplitude sensitivity of 327.5 RIU-1, and a resolution of 2.17×10−5 RIU. The range of hemoglobin concentrations detected with this sensor was 0 g/L∼241 g/L, with an average sensitivity of 0.7 nm/(g/L). A fiber biosensor was enhanced with graphene-MoS2 hybrid nanostructures, which exhibit excellent photoelectric properties and detection performance, enabling highly sensitive, highly accurate, and real-time hemoglobin detection. The result shows the significant research value and application prospects in the field of biomedical detection.

Liquid-Phase Exfoliated Graphene-MoS2 Based Saturable Absorber for Q-switched Erbium Doped Fiber Laser

Upon exfoliation from the bulk form, two-dimensional materials have shown ubiquitous properties which are suitable for Q-switched pulsed laser generation. In this research, a successful solution process of graphene-MoS2 nanocomposite saturable absorber through liquid phase exfoliation has been carried out. The method offers a low-cost route for simple and scalable production while providing a promising material quality with on-demand properties and integration flexibility. Stable Q-switched laser operation was realized with graphene-MoS2 hybrid saturable absorber. The pulse duration was measured to be 6 µs with repetition rate of 63.92 kHz corresponding to a peak power and pulse energy of 5.05 mW and 30.87 nJ, respectively.

Hybrid structure based high performance SPR sensor: a numerical approach of structure optimization for DNA hybridization

A MoS2-Graphene hybrid layer Based High Performance Refractive Index SPR Sensor is illustrated in this paper. Intended for the enhancement of sensor angular sensitivity (S), signal to noise ratio (SNR), quality factor (QF), first of all, the impact of gold layer thickness is investigated and optimized to 40 nm, after then the MoS2 and graphene coting layers are optimized to four (4) and three (3) layers, respectively. Further that, at this optimum structure, the minimum reflectance and SPR angle are decorated. It is seen that the angular sensitivity of the optimum assembly, improved to excellent value of 130 deg-RIU−1 with improved angular SNR of 1.37 and QF of 17.02 RIU−1. At the end of this paper, an analysis specifically for numerically DNA hybridization is considered.

Microwave-Assisted Solvothermal Synthesis of Chalcogenide Composite Photocatalyst and Its Photocatalytic CO2 Reduction Activity under Simulated Solar Light

A novel heterostructure consisting of Ru and Cu co-doped ZnS nanopowders (RCZS) into a MoS2-graphene hybrid (MSG) is successfully prepared by the microwave-assisted solvothermal approach. RCZS nanopowders are fabricated on the surface of MSG, which produces a nanoscale interfacial between RCZS and MSG. As the photo-excited electrons of RCZS can easily migrate to MoS2 through graphene by hindering the electron and hole (e– and h+) recombination, the photocatalytic activity could be improved by effective charge transfer. As RCZS are anchored onto the MSG, the photoluminescence intensity of the chalcogenide composite photocatalyst obviously decreases. In addition, a quaternary ruthenium and copper-based chalcogenide RCZS/MSG is able to improve the harvest and utilization of light. With the increase in the concentrations of Ru until 4 mol%, the band gap significantly decreases from 3.52 to 2.73 eV. At the same time, moderate modification by ruthenium can decrease the PL intensity compared to the pristine CZS/MSG sample, which indicates the enhancement of e– and h+ separation by Ru addition. The photocatalytic activity of as-synthesized chalcogenide composite photocatalysts is evaluated by the photocatalytic carbon dioxide reduction. Optimized operation conditions for carbon dioxide reduction have been performed, including the concentration of NaOH solution, the amount of RCZS/MSG photocatalyst, and the content of co-doped ruthenium. The doping of ruthenium would efficiently improve the performance of the photocatalytic activity for carbon dioxide reduction. The optimal conditions, such as the concentration of 2 M NaOH and the 0.5RCZS/MSG dosage of 0.05 g L–1, provide the maximum methane gas yield of 58.6 μmol h−1 g–1.

MoS2–graphene hybrid nanostructures enhanced localized surface plasmon resonance biosensors

We propose a new configuration of a localized surface plasmon resonance (LSPR) biosensor that is based on MoS2–graphene hybrid structures for ultrasensitive detection of molecules. The performance parameters of the proposed biosensor are defined in terms of absorption and sensitivity. Our study show that sensitivity can be greatly increased either by adding a bilayer MoS2/graphene on the Au nanoparticles or by adding the MoS2 layer or the graphene layer on the surface of the Au nanoparticles. The absorption curves for the proposed LSPR biosensor are analyzed and compared with the conventional biosensors without MoS2/graphene. By optimizing the structure of the sensor, we find that the sensitivity as high as 360 nm/RIU can be achieved with 8-layers of MoS2 and 10-layers of graphene. In addition, we show that the sensitivity can be controlled by changing the number of the monolayer of MoS2 and/or graphene. Finally, we show that this sensor can detect successfully impure water after absorption of target single-stranded DeoxyriboNucleic Acid (ssDNA) biomolecules.

Capacitive Deionization of Saline Water by Using MoS2-Graphene Hybrid Electrodes with High Volumetric Adsorption Capacity.

Capacitive deionization (CDI) has received wide attention as an emerging water treatment technology because of its low energy consumption, low cost, and high efficiency. However, the conventional carbon electrode materials for CDI have low densities, which occupy large volumes and are disadvantageous for use in limited space (e.g., in household or on offshore platforms). In order to miniaturize the CDI device, it is quite urgent to develop high volumetric adsorption capacity (VAC) electrode materials. To overcome this issue, we rationally designed and originally developed high VAC MoS2-graphene hybrid electrodes for CDI. It is interesting that MoS2-graphene hybrid electrode has a much higher NaCl VAC of 14.3 mg/cm3 with a gravimetric adsorption capacity of 19.4 mg/g. It has been demonstrated that the adsorption capacity is significantly enhanced because of the rapid ion transport of MoS2 and high electrical conductivity of graphene. In situ Raman spectra and high-angle annular dark-field scanning transmission electron microscopy tests demonstrated a favorable Faradaic reaction, which was crucial to enhancing the NaCl VAC of the MoS2-graphene hybrid electrode. This work opens a new avenue for miniaturizing future CDI devices.

A Numerical Approach to Design the Kretschmann Configuration Based Refractive Index Graphene-MoS2 Hybrid Layers With TiO2-SiO2 Nano for Formalin Detection

In this paper, a Kretschmann configuration based surface plasmon resonance (SPR) sensor is numerically designed using graphene-MoS2 hybrid structure TiO2-SiO2 nano particles for formalin detection. In this design, the observations of SPR angle versus minimum reflectance and SPR frequency (FSPR) versus maximum transmittance (Tmax) are considered. The chitosan is used as probe legend to perform reaction with the formalin (40% formaldehyde) which acts as target legend. In this paper, both graphene and MoS2 are used as biomolecular acknowledgment element (BAE) and TiO2 as well as SiO2 bilayers is used to improve the sensitivity of the sensor. The numerical results show that the variation of FSPR and SPR angles for inappropriate sensing of formalin is quite insignificant which confirms the absence of formalin. On the other hand, these variations for appropriate sensing are considerably significant that confirm the presence of formalin. At the end of this article, the variation of sensitivity of the proposed biosensor is measured in corresponding to the increment of a refractive index with a refractive index step 0.01 refractive index unit (RIU). In inclusion of TiO2-SiO2 bilayers with graphene-MoS2, a maximum sensitivity of 85.375% is numerically calculated.

Design and analysis of graphene–MoS2 hybrid layer based SPR biosensor with TiO2–SiO2 nano film for formalin detection: numerical approach

In this paper, a Surface Plasmon Resonance (SPR) biosensor has been numerically developed that used Graphene–MoS2–Au–TiO2–SiO2 hybrid structure for the detection of formalin. This developed sensor has been sensed the presence the formalin based on attenuated total reflection (ATR) method by observing the change of “surface plasmon resonance angle-the change of minimum reflectance attributor” and “the resonance frequency characteristics (RFC)-maximum transmittance attributor”. Chitosan has been used as probe sensing medium to accelerate particular reaction with the formalin. Here, graphene is used as biomolecular recognition element because of its high adsorption ability and optical characteristics which helps to improve sensor sensitivity, MoS2 used for it has larger band gap, high fluroscence quenching ability, higher optical absorption efficiency, TiO2–SiO2 bilayer as the improvement of sensitivity and Gold (Au) as the sharp SPR curve. Numerical results give the impression that the variation of RFC and SPR angle for improper sensing of formalin is quiet negligible that confirms no formalin is detected whereas for proper sensing these change are considerably countable that confirms the detection of formalin. From the sensor sensitivity analysis, owing to add TiO2–SiO2 bilayer with Graphene–MoS2 Hybrid layer, maximum sensitivity of 85.375% has been numerically resulted. This high sensor performance is for taking advantages of Graphene surface high selectively which detect bio molecular compounds through pi-stacking force, larger work function (5.1 eV) of MoS2 which allows the high sensitive detection of bio targets and Rich plasmon happens at the TiO2–SiO2 interface.

Ultra-sensitive surface plasmon resonance biosensor based on MoS2–graphene hybrid nanostructure with silver metal layer

The optical biosensors based on the plasmonic technology are an important research item in the field of biophotonics. The graphene–molybdenum disulfide (MoS2) based hybrid structures are very effective in designing and fabricating of the sensitive optical biosensors. In this paper, we propose a nanostructure Ag/MoS2/graphene as an optical biosensor with high performance and sensitivity. The proposed configuration for this surface plasmon resonance (SPR) optical biosensor is Kretschmann. Herein, the enhancement of sensitivity for the proposed SPR optical biosensor is investigated in different states. By determining of the numbers of MoS2 layer and the thickness of the metal layer, we increased the sensitivity of the proposed biosensor. The maximum sensitivity ~ 190°/RIU is achieved. For this ultra-sensitive SPR biosensor with maximum sensitivity, the numbers of MoS2 and graphene layer is 2 and the resonance wavelength is determined 680 nm.

One-pot facile methodology to synthesize MoS2-graphene hybrid nanocomposites for supercapacitors with improved electrochemical capacitance

In this study, we use a facile one-pot chemical method to prepare MoS2 and MoS2-graphene hybrid nanostructures. Structural formation is confirmed by transmission electron microscopy and scanning electron microscopy. Furthermore, the refined d-spacing values using transmission electron micrograph for graphene and MoS2 are analyzed. The MoS2 and MoS2-graphene hybrid sheet based electrodes reveal a specific capacitance of 175 and 756 F·g−1, respectively, at 0.5 A·g−1, and the MoS2-graphene supercapacitor retains 88% of the primary capacitance after 10000 cycles. Pure MoS2 exhibits low performance with an electric double-layer capacitive behavior, whereas MoS2-graphene hybrid sheets demonstrate superior storage performance with a pseudo-electric double-layer capacitive behavior. The observed maximum energy density of the MoS2-graphene supercapacitor device is 26.6 Wh·kg−1 at a power density of 125 W·kg−1. The substantially enhanced electrochemical performance of MoS2-graphene hybrid sheets may be ascribed to the synergistic effects of MoS2 and graphene.

Solution-processed Graphene-MoS2 heterostructure for efficient hole extraction in organic solar cells

A major bottleneck exploiting the unique electronic properties of two-dimensional materials like graphene is the lack of mass production methods that are able to produce van der Waals heterostructures. Here, we prepare Graphene-molybdenum disulfide (MoS2) heterostructures via liquid-phase exfoliation followed by hydrothermal reaction, and employ Graphene-MoS2 hybrid thin films as the hole extraction layer in PTB7-Th:PC71BM organic solar cells. We demonstrate a maximum power conversion efficiency of 9.5% whilst retaining more than 93% of the initial efficiency over a storage period of 1000 h, surpassing current reported two-dimensional materials based devices. Our results represent the great potential of two-dimensional heterostructures as hole extraction materials for efficient and stable photovoltaics devices.

Design of an ultrasensitive SPR biosensor based on a graphene-MoS2 hybrid structure with a MgF2 prism.

We propose, to the best of our knowledge, a new configuration of a biosensor based on the graphene-MoS2 hybrid structure by adopting the lower refractive index MgF2 prism in order to improve the sensitivity and the figure of merit (FOM). We can obtain an ultrasensitive sensor with values of sensitivity and FOM as high as 540.8°/RIU and 145/RIU, respectively, by modulating the parameters in the configuration and comparatively choosing a different absentee layer material. The proposed structure is applicable in the realization of an integrated device for the surface plasmon resonance biosensor.

Stable charge retention in graphene-MoS 2 assemblies for resistive switching effect in ultra-thin super-flexible organic memory devices

This study investigated the nonvolatile memory characteristics of devices fabricated with PMMA embedding composite of graphene and molybdenum disulphide, which were employed as charge-trapping centres. X-ray diffraction measurements, Scanning and transmission electron microscope image analysis along with other characterisation techniques were performed for the assessment of the nature of graphene MoS2 hybrid system. Bistable I-V characteristics of the device revealed stable and rewritable memory effect. A significantly high resistance ratio > 104 (Roff/Ron) was observed even after 10 days. The reliability and reproducibility of the devices were tested for 104 cycles. The conduction mechanisms of the fabricated nanocomposite based memory cell were discussed on the basis of experimental data using a charge trapping–detrapping mechanism in the graphene MoS2 hybrid. Owing to the increasing interest in the flexible electronics, bending tests were carried out on the devices fabricated on PET substrates. Bendability test at various bending diameters (40-5 mm) for 100 cycles was carried out to show the mechanical robustness of the device.

Two-dimensional MoS2-graphene hybrid nanosheets for high gravimetric and volumetric lithium storage

Two-dimensional (2D) MoS2-graphene (MoS2-G) hybrid is fabricated simultaneously and scalablely with an efficient electrochemical exfoliation approach from the combined bulk MoS2-graphite wafer. The as-prepared 2D MoS2-G hybrid is tightly covered with each other with lateral sizes of 600 nm to few micrometers and can be directly assembled to flexible films for lithium storage. When used as anode material for lithium ion battery, the resultant MoS2-G hybrid film exhibits both high gravimetric (750 mA h g−1 at 50 mA g−1) and volumetric capacities (1200 mA h cm−3 at 0.1 mA cm−2). Such excellent electrochemical performance should attributed to the unique 2D structure and good conductive graphene network, which not only facilitates the diffusion of lithium ions, but also improves the fast transfer of electrons, satisfying the kinetics requirements for rapid lithium storage.

Preparation of graphene-MoS2 hybrid aerogels as multifunctional sorbents for water remediation

The increasing demand of clean water and effective way to recycle industrial wastewater has offered a new application for carbon-based three-dimensional (3D) porous networks as sorbents due to their superior sorption abilities. Through the surface modification and hybridization with functional materials, the physical and chemical properties of the 3D carbon-based materials can be engineered. In this work, graphene-MoS2 aerogels (GMAs) with bulky shape are synthesized via a one-pot hydrothermal method. The obtained GMAs show quick sorption rate and high sorption capacity towards a wide variety of contaminants. The sorption covers not only organic solvents or organic dyes, but also toxic heavy metals ions such as Hg2+ and Pb2+. More importantly, the sorption capacity towards metal ions can be optimized by simply changing the loading amount of MoS2.

Enhanced electromagnetic wave absorption properties of MoS2-graphene hybrid nanosheets prepared by a hydrothermal method

The MoS2-graphene nanocomposite was directly synthesized via a simple one-step surfactant-free hydrothermal approach, during which the formation of MoS2 nanoflakes and the reduction of graphene oxide happened simultaneously. The morphology and structure of MoS2-graphene nanocomposite were characterized by X-ray diffraction, Raman spectra, scanning electron microscopy and transmission electron microscopy. It was found that the MoS2 nanoflakes were well supported on the surface of graphene sheets to form hetero-layered nanocomposites. The complex permittivity, complex permeability, and electromagnetic wave absorption property of MoS2-graphene nanocomposite were systematically investigated by the coaxial line method. The 10 wt % MoS2-graphene/wax composite with a thickness of 5.5 mm showed a reflection loss below −10 dB in the frequency range of 11.7–14.3 GHz, and the minimum value is −24.2 dB in the frequency of 13.3 GHz. The enhanced electromagnetic wave absorption of MoS2-graphene nanocomposite was attributed to an enhanced dielectric relaxation from a good structural interface between MoS2 nanoflakes and graphene sheets. The MoS2-graphene nanocomposite is a promising candidate as a lightweight and wide-frequency electromagnetic wave absorber.

Modeling of a highly sensitive MoS2-Graphene hybrid based fiber optic SPR biosensor for sensing DNA hybridization

Optical fiber instead of prism is now widely studied in biosensing research. This paper investigates a highly sensitive optical fiber based Ag-MoS2-Graphene hybrid surface plasmon resonance (SPR) biosensor for sensing DNA hybridization. Sensitivity, detection accuracy and quality factor are carefully studied for the performance analysis. Numerical study shows that usingsingle layer of MoS2 in the middle of a Graphene-on-Ag layer, the fiber optic biosensor exhibits high sensitivity of 105.71°/RIU with reasonable detection accuracy and quality factor of 1.626 and 23.23 RIU−1, respectively. This enhanced sensitivity is due to the absorption ability and optical characteristics of graphene biomolecules and high fluorescence quenching ability of MoS2. Numerical investigation also reflects the variation of resonance angle and spectrum of transmitted power for mismatched DNA strands and for complementary DNA strands. These variations are negligible for mismatched DNA strands whereas significantly computable for complementary DNA strands. Thus the proposed sensor effectively differentiates hybridization and single nucleotide polymorphisms (SNP) by examining the level of changes in resonance angle and transmitted power spectrum. Therefore, this fiber optic based Ag-MoS2-Graphene hybrid biosensor might be a promising candidate for the detection of DNA hybridization.

Work Function Tuning in Two-Dimensional MoS2 Field-Effect-Transistors with Graphene and Titanium Source-Drain Contacts

Based on the first principles calculation, we investigate the electronic band structures of graphene-MoS2 and Ti-MoS2 heterojunctions under gate-voltages. By simultaneous control of external electric fields and carrier charging concentrations, we show that the graphene’s Dirac point position inside the MoS2 bandgap is easily modulated with respect to the co-varying Fermi level, while keeping the graphene’s linear band structure around the Dirac point. The easy modulation of graphene bands is not confined to the special cases where the conduction-band-minimum point of MoS2 and the Dirac point of graphene are matched up in reciprocal space, but is generalized to their dislocated cases. This flexibility caused by the strong decoupling between graphene and MoS2 bands enhances the gate-controlled switching performance in MoS2-graphene hybrid stacking-device.