MoS2 Nanoflowers Research Articles

Approaching the Theoretical Sodium Storage Capacity and Ultrahigh Rate of Layer‐Expanded MoS2 by Interfacial Engineering on N‐Doped Graphene

AbstractMolybdenum disulfide (MoS2) holds great potential for sodium storage due to its high theoretical capacity of 670 mAh g−1. However, its theoretical capacity is hardly realized because of low conductivity, sluggish electrochemical kinetics, and unsatisfied structural stability. Herein, a polyaniline‐mediated interfacial engineering strategy for the growth of interlayer‐expanded MoS2 nanoflowers on N‐doped graphene “land” (E‐MoS2/NG) using Mo7O246− anions adsorbed on positively charged polyaniline as the “seeds” is reported. The strong interfacial interaction between MoS2 and graphene through MoN bonds as well as ultrathin interlayer‐expanded MoS2 can significantly improve the electrochemical kinetics and structural stability. As a result, E‐MoS2/NG with a high MoS2 content of 90 wt% shows a high capacity (620 mAh g−1 at 0.1 A g−1), an ultrahigh rate capability (201 mAh g−1 at 50 A g−1), and outstanding cycle performance (390 mAh g−1 after 1000 cycles at 1 A g−1). Importantly, MoS2 in the composite approaches its theoretical capacity of 670 mAh g−1. Furthermore, the assembled E‐MoS2/NG//activated carbon sodium ion capacitor delivers high energy densities of 150 and 82 Wh kg−1 at 35 and 14 421 W kg−1, respectively, and a capacity retention of 78.1% after 1500 cycles at 10 A g−1, demonstrating great potential for practical application.

In-situ surface-enhanced Raman scattering based on MTi20 nanoflowers: Monitoring and degradation of contaminants

Real-time and in-situ monitoring of chemical reactions has attracted great attention in many fields. In this work, we in-situ monitored the photodegradation reaction process of methylene blue (MB) by Surface enhanced Raman scattering (SERS) technique. An effective and versatile SERS platform assembled from MoS2 nanoflowers (NFs) and TiO2 nanoparticles (NPs) was prepared successfully. The optimized MoS2/TiO2 substrate (MTi20) exhibits not only an ultra-high SERS response but also the excellent catalytic degradation performance to the contaminant MB, which provided a new material for real-time and in-situ monitoring the photodegradation process. Experiments prove that the detection limit is as low as 10-13 M, and degradation rate is as high as 97.2% in 180 s, respectively. And the activity of the substrate kept in the air for 90 days is almost unchanged. Furthermore, as a practical SERS substrate, MTi20 can also detect trace amounts of other harmful substances including malachite green (MG), bisphenol A (BPA) and endosulfan. Thus, this study come up with a new orientation at the real-time and in-situ monitoring of photocatalytic reaction and may be applied in environmental monitoring and food security fields in the future.

MoS2 nanoflower incorporated with Au/Pt nanoparticles for highly efficient hydrogen evolution reaction

Hydrogen evolution reaction (HER) by effective catalysts has been extensively investigated as a promising way to produce H2 as a clean and sustainable energy source. Previous studies have identified Pt as one of the most efficient catalysts due to the fast kinetics and the moderate hydrogen binding energy, while the high-cost of Pt restrains the practical applications. In this research, we present a hydrothermal method to fabricate the hybrid of nanoscale noble metals incorporated in the earth-abundant material MoS2. The results indicate that incorporation of a small amount of Au and Pt strongly enhances the HER performance compared with pure MoS2, which attributes to the enhanced electrical charge transfer, increased active sites, and reduced resistance. Especially, the electrocatalytic performance of the as-synthesized 5% weight loading Pt-MoS2 is comparable with the commercial 10% Pt/C catalyst, with a low overpotential of 103 mV vs. RHE at the current density of 10 mA cm−2 and Tafel slope of 56 mV dec–1. The sample also exhibits excellent durability, and the low amount of noble metal usage could reduce the cost to a large extent, making it more practical to be applied in hydrogen generation. The strategy to control the particle size with the various morphologies of the supporting material MoS2 may also be useful to develop other noble metal–based catalysts.

Improved performance of sulfonated poly ether ether ketone/three-dimensional hierarchical molybdenum disulfide nanoflower composite proton exchange membrane for fuel cells

As one of the most essential components of fuel cells, the commercialized Nafion-based proton exchange membranes(PEMs) suffer from several drawbacks like high cost and methanol permeability. The aim of this work is to fabricate a high performance PEM with combined low cost and methanol permeability together with high proton conductivity. Three-dimensional hierarchical molybdenum disulfide (MoS2) nanoflower is synthesized via a facile one-pot hydrothermal method, and then was embedd into sulfonated poly ether ether ketone (SPEEK) matrix to prepare composite PEM. The three-dimensional hierarchical architectures of MoS2 nanoflower can not only avoid the aggregation of MoS2 nanosheets but also provide abundant surface area and active sites, which are of benefit to fully take advantage of the intrinsic water absorption and methanol diffusion resistance ability of MoS2 nanosheets. The formed hydrogen bond network with water passway contributes to the improvement in proton conduction of composite membrane. As a consequence, composite membrane with 1 wt% MoS2 nanoflower loading content achieves optimized proton conductivity (0.123 S cm−1, 80 °C) and methanol permeability (21.5 × 10–7 cm2 s−1, 70 °C), which is 59.7% higher and 79.1% lower than that of SPEEK control membrane. Owing to increased proton conductivity and decreased methanol permeability, the maximum power density of the SPEEK/MoS2-1 composite membrane is 82.7 mW cm−2 at 70 °C, which is nearly 64.7% higher than that of pure SPEEK membrane (only 50.2 mW cm−2). Furthermore, the durability test confirms that the SPEEK/MoS2 composite membrane still possesses satisfactory stability even after continuous operation at 70 °C for 100 h.

Synthesis and electrorheological properties of silica-coated MoS2 nanocomposites with hierarchical and core-shell structure

The silicon oxide coated flower-like sheet layered MOS2 is synthesized by a simple two-step method, in which a modified hydrothermal method was firstly used to synthesize 3D radically oriented MoS2 nanoflowers initially and increase the surface area and enhance the active site to enable the SiO2 to grow on MoS2 uniformly by using a modified hydrolysis method. Field emission scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), transmission electron microscope (TEM), X-ray powder diffractometer (XRD), Fourier infrared spectrometer (FI-IR), X-ray photoelectron spectroscopy (XPS) etc., were used to characterize the morphology, structure, and chemical composition state of the monodispersed and characterized core/shell nanoparticles. At the same time, a high-voltage vol rotary rheometer was used to test the ER performance and dielectric performance of the prepared MoS2/SiO2-based suspension. The comprehensive analysis of rheological, dielectric, and conductive properties shows that MoS2/SiO2-based electrorheological fluid is a very promising electrorheological fluid material.

Effects of anionic substitution in molybdenum oxysulfide supported on reduced graphene oxide sheets for the hydrogen evolution reaction and supercapacitor application

An easy facile technique to incorporate anionic substitution in MoS2 nano-flowers supported on reduced graphene oxide leading to enhanced hydrogen evolution and supercapacitor performance.

Cellulose acetate-MoS2 nanopetal hybrid: A highly sensitive and selective electrochemical aptasensor of Troponin I for the early diagnosis of Acute Myocardial Infarction

In this work, a novel aptamer-based CA-MoS2 hybrid biosensor was developed for diagnosis of Acute Myocardial Infraction (AMI). Specifically, a novel petal-like MoS2 nanoflower was used as the active material on the Screen-Printed Electrode (SPE) for AMI biomarker determination. The aptamer-based CA-MoS2–24 hybrid was able to attain a low limit of detection (LOD) and sensitivity to 10 fM at a linear range from 10 fM to 1 nM with good reproducibility based on an electrochemical impedance spectroscopy and a ~4 folds higher selectivity of troponin I compared to the signal from other biomolecules in human serum, retaining a 91% stability after 6 weeks. This novel CA-MoS2 aptamer-based biosensor with a 2.3% RSD value has the potential to revolutionize medical diagnosis by conducting multiple biomolecule detection on a single sensing platform.

Near-infrared light-triggered nitric oxide release combined with low-temperature photothermal therapy for synergetic antibacterial and antifungal

In recent years, nitric oxide (NO) has been widely studied as a non-drug resistant antimicrobial agent, but the issue of low NO loading capacity as well as premature leakage during transportation limit its further application. Herein, we have developed a BNN6-loading molybdenum disulfide (MoS2) nanoflowers denoted PEG-MoS2-BNN6 with near-infrared light-triggered NO release and hyperthermia properties to realize the antibacterial and antifungal capability. The PEG-MoS2-BNN6 was synthesized by grafting polyethylene glycol (PEG) to MoS2 nanoflowers and the NO donor BNN6 was subsequently loaded via hydrophobic interaction. The incorporation of PEG can effectively improve the biocompatibility of MoS2. Moreover, BNN6 achieves a high payload thanks to the layered nanoflower structure of PEG-MoS2. Under the 808 ​nm laser irradiation for 10 ​min, the obtained PEG-MoS2-BNN6 could not only generate heat locally for low-temperature photothermal therapy (PTT) but also activate the decomposition of BNN6 to release NO. Notably, the simultaneously generated NO and gentle hyperthermia could trigger great antimicrobial effects against both S. aureus and Candida albicans, which effectively solved the limitations of monotherapy. Overall, this nanoplatform with low-temperature PTT/NO synergistic effects provides a new strategy to solve bacterial and fungal infections, which is promising in biomedical application in the future.

Piezo-Photocatalytic Reduction of Au(I) by Defect-Rich MoS2 Nanoflowers for Efficient Gold Recovery from a Thiosulfate Solution

To achieve a more efficient gold recovery from a thiosulfate solution, piezo-photocatalytic reduction of Au(I) with defect-rich MoS2 nanoflowers (DR-MoS2 NFs) as a catalyst was proposed in this wor...

Grinding-assisted heterogeneous nucleation of BiOAc on MoS2 nanoflowers to heterojunction with good visible-light photocatalytic performance

Bismuth oxide subacetate (CH3COO(BiO); BiOAc) with a large band gap energy (Eg) was first applied as an ultraviolet-light-driven photocatalyst in our group. MoS2 nanoflowers have been used to improve the visible-light photocatalytic activity of bismuth-based semiconductors with wide Eg because of their good visible-light response. Herein, the grinding-assisted solid-state reaction method was used to prepare a MoS2/BiOAc composite to improve the visible-light photoreactivity of BiOAc. As compared with commonly used wet chemical and hydrothermal routes, the grinding-assisted synthesis facilitated heterogeneous nucleation, which was beneficial to achieving close contact and subsequent charge transfer and separation at the interfaces, resulting in enhanced photocatalytic activity for malachite green, methylene blue, and antibiotic tetracycline degradation under visible-light irradiation. Notably, the dispersion in the mixing solution of ethanol and water (v/v=1) of MoS2 nanosheets induced self-assembly into flower-like nanostructures, thus enhancing the photocatalytic activity of MoS2/BiOAc. A possible mechanism for visible-light photocatalysis of MoS2/BiOAc was proposed.

Enhanced electrochemical sensor based on gold nanoparticles and MoS2 nanoflowers decorated ionic liquid-functionalized graphene for sensitive detection of bisphenol A in environmental water

In this study, a novel electrochemical sensor was constructed based on gold nanoparticles-MoS2 nanoflowers/ionic liquid functionalized graphene (AuNPs/MoS2-NFs/IL-graphene) nanocomposites for low level detection of bisphenol (BPA). The prepared nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The prepared nanocomposites were also explored the effect of pH and scan rate to the results. The electrochemical performance of the sensor was then evaluated by cyclic voltammetry and differential pulse voltammetry, and it was showed that the sensor had prominent electrochemistry activity towards the BPA. Under the optimized experimental conditions, a large linear relationship in the range of 0.05–4.0 μM was detected between the peak current and the concentration of BPA, and the detection limit was 0.028 μM. The results showed that the sensor had high sensitivity, great selectivity, and excellent stability. Finally, the developed electrochemical sensor was successfully applied toward the determination of BPA in lake water samples and the satisfactory recoveries ranged from 95.7% to 105.4%. Thus, this sensor provided a promising candidate for BPA detection in the environmental water.

Hollow multi-nanochannel carbon nanofiber/MoS2 nanoflower composites as binder-free lithium-ion battery anodes with high capacity and ultralong-cycle life at large current density

The electrode materials with high pseudocapacitance can enhance the rate capability and cycling stability of lithium-ion storage devices. Herein, we fabricated MoS2 nanoflowers with ultra-large interlayer spacing on N-doped hollow multi- nanochannel carbon nanofibers (F2-MoS2/NHMCFs) as freestanding binder-free anodes for lithium-ion batteries (LIBs). The ultra-large interlayer spacing (0.78∼1.11 nm) of MoS2 nanoflowers can not only reduce the internal resistance, but also increase accessible active surface area, which ensures the fast Li+ intercalation and deintercalation. The NHMCFs with hollow and multi-nanochannel structure can accommodate the large internal strain and volume change during lithiation/delithiation process, it is beneficial to improving the cycling stability of LIBs. Benefiting from the above combined structure merits, the F2-MoS2/NHMCFs electrodes deliver a high rate capability 832 mA h g−1 at 10 A g−1 and ultralong cycling stability with 99.29 and 91.60 % capacity retention at 10 A g−1 after 1000 and 2000 cycles, respectively. It is one of the largest capacities and best cycling stability at 10 A g−1 ever reported to date, indicating the freestanding F2-MoS2/NHMCFs electrodes have potential applications in high power density LIBs.

Highly sensitive and selective acute myocardial infarction detection using aptamer‐tethered MoS 2 nanoflower and screen‐printed electrodes

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Cardiac troponin I (cTn1) is a commonly used biomarker for the diagnosis of AMI. Although there are various detection methods for the rapid detection of cTn1 such as optical, electrochemical, and acoustic techniques, electrochemical aptasensing techniques are commonly used because of their ease of handling, portability, and compactness. In this study, an electrochemical cTn1 biosensor, MoS2 nanoflowers on screen-printed electrodes assisted by aptamer, was synthesized using hydrothermal technique. Field emission scanning electron microscopy revealed distinct 2D nanosheets and jagged flower-like 3D MoS2 nanoflower structure, with X-ray diffraction analysis revealing well-stacked MoS2 layers. Voltammetry aptasensing of cTn1 ranges from 10fM to 1nM, with a detection limit at 10fM and a sensitivity of 0.10nAµM-1 cm-2 . This is a ∼fivefold improvement in selectivity compared with the other proteins and human serum. This novel aptasensor retained 90% of its biosensing activity after 6 weeks with a 4.3% RSD and is a promising high-performance biosensor for detecting cTn1.

Investigation of photocatalytic and antimicrobial activities of BaWO4–MoS2 nanoflowers

Abstract In this work, we have synthesized BaWO4–MoS2 nanocomposites by the simple co-precipitation method and investigated their photocatalytic activities with Rhodamine-B as a test contaminant. The BaWO4/MoS2 photocatalyst was characterized by X-ray diffraction (XRD), Energy dispersive X-ray analysis (EDAX), Fourier Transform Infra-Red spectroscopy (FT-IR), and Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller (B.E.T) techniques. The optical properties were investigated using the UV-Vis-DRS spectroscopy and a clear red shift has been observed in the bandgap energy of the synthesized BaWO4– MoS2. The nanocomposites exhibit a flower-like morphology with the required elemental composition of Ba, W, O, Mo and S. The photocatalytic activity of the BaWO4–MoS2 nanocomposites (75 mg) for dye (20 μM) removal is 95% upon a solar light exposure in 80 min. The photocatalytic reactions were found to obey the pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. The repeatability of photocatalytic activity was also studied. Studies on antimicrobial activity reveal that the nanoparticles possess inhibition activity against staphylococcus aureus, pseudomonas aeruginosa and Candida albicans.

MoO2 coated few layers of MoS2 and FeS2 nanoflower decorated S-doped graphene interoverlapped network for high-energy asymmetric supercapacitor

Herein, the ultra-thin layer MoS2 coverd MoO2 nanocrystal arraying on sulfur-doped graphene framework (MoS2-MoO2/3DSG) is obtained via a simple hydrothermal procedure accompanied with high temperature annealing. Sodium thiosulfate and ethanethiol are used as sulfur sources to form three-dimensional sulfur doped graphene (3DSG) in the hydrothermal process. Importantly, MoO2 nano-particles are uniformly loaded on MoS2 nanosheets and 3DSG via in-situ collaborative technology. As a result, the stable conductive network take full use of the characteristics of high specific capacitance of MoO2 nanoparticles, convenient ion transport channel of two-dimensional MoS2 nanoflakes and efficient charge transfer and cross-linked 3DSG to improve the electrochemical activity and enhance the dynamics of electrons / ions, which is up to 1150.37 F g−1 specific capacitance and maintains 94.6% of the original capacitance after 10,000 cycles. Also, FeS2 nanoflowers in situ loading on 3DSG (FeS2/3DSG) with enhanced the overall performance of the device are fabricated. The asymmetric supercapacitor with the positive electrode of MoS2-MoO2/3DSG and the negative electrode of FeS2/3DSG can work efficiently and stably under the voltage of 1.7 V, and provide energy density of 87.38 Wh kg−1 at the power density of 683.94 Wkg−1, displaying an outstanding application prospect for energy storage.

MoSe2 nanoflowers as efficient electrode materials for supercapacitors

Herein, we report a facile hydrothermal synthesis of MoSe2 nanoflowers composed of several MoSe2 nanosheets for electrochemical energy storage. As an electrode material of supercapacitor, MoSe2 nanoflower exhibits high specific capacitance (95 Fg−1) and excellent cycling stability (90% after 10,000 cycles) due to their porous morphology, indicating their applicability as a potential electrode material for energy storage devices.

Three-Dimensional Porous Graphene Supported MoS2 Nanoflower Prepared by a Facile Solvothermal Method with Excellent Rate Performance and Sodium-Ion Storage.

Sodium-ion batteries (SIBs), as a supplement of lithium-ion batteries (LIBs), are attracting intensive research interest due to their low cost and abundance. Molybdenum disulfide (MoS2) is regarded as a suitable candidates for SIBs electrode materials, which suffer from prominent volume expansion and poor conductivity. In this study, three-dimensional porous graphene composites loaded with MoS2 were prepared via a facile two-step method. The MoS2 nanoflower particles were uniformly dispersed within the layered graphene matrix, and a three-dimensional porous graphene supported MoS2 nanoflower battery (MoS2/3DG) was demonstrated to have superior performance to that of the pristine pure MoS2 nanoflower battery. At a current density of 100 mA/g, the MoS2/3DG delivered a reversible capacity of 420 mAh/g. What is more, it yielded a reversible specific capacity of 310 mAh/g at 2 A/g, showing an excellent rate of 73.8%. The excellent performance of the novel MoS2/3DG composite are attributed to the promoted infiltration of electrolytes and the hindered volume expansion for the porous structure, good conductivity, and robust mechanical properties of graphene.

Re-usable self-poled piezoelectric/piezocatalytic films with exceptional energy harvesting and water remediation capability.

The need for sustainable technologies to address environmental pollution and energy crisis is paramount. Here we present a novel multifunctional nanocomposite, free standing film by combining piezoelectric molybdenum sulphide (MoS2) nanoflower with poly vinylidene fluoride (PVDF) polymer, which can harness otherwise wasted mechanical energy for useful energy generation and/or water purification. The unique MoS2 nanoflower morphology is exploited to render the whole nanocomposite piezo active. A number of features are demonstrated to establish potential practical usage. Firstly, the nanocomposite is piezoelectric and piezocatalytic simultaneously without requiring any poling step (i.e. self-poled). Secondly, the self-poled piezoelectricity is exploited to make a nanogenerator. The nanogenerator produced >80 V under human finger tapping with a remarkable power density, reaching 47.14 mW cm−3. The nanocomposite film is made by simple solution casting, and the corresponding nanogenerator powers up 25 commercial LEDs by finger tapping. Last but not the least, the developed films show efficient, fast and stable piezocatalytic dye degradation efficiency (>90% within 20 min) against four different toxic and carcinogenic dyes under dark condition. Reusability of at least 10 times is also demonstrated without any loss of catalytic activity. Overall, our nanocomposite has clear potential for use as self-powered sensor and energy harvester, and in water remediation systems. It should potentially also be deployable as a surface mounted film/coating in process engineering, industrial effluent management and healthcare devices systems.

Evaluating the Effect of Varying the Metal Precursor in the Colloidal Synthesis of MoSe2 Nanomaterials and Their Application as Electrodes in the Hydrogen Evolution Reaction.

Herein we report on the use of different metal precursors in the synthesis of MoSe2 nanomaterials in order to control their morphology. The use of Mo(CO)6 as the metal precursor resulted in the formation of wrinkled few-layer nanosheets, while the use of H2MoO4 as the metal precursor resulted in the formation of nanoflowers. To investigate the effect of the morphologies on their performance as catalysts in the hydrogen evolution reaction, electrochemical characterization was done using linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrical impedance spectroscopy (EIS). The MoSe2 nanoflowers were found to have superior electrochemical performance towards the hydrogen evolution reaction with a lower Tafel slope, on-set potential, and overpotential at 10 mA/cm2 compared to the wrinkled few-layer nanosheets. This was found to be due to the higher effective electrochemical surface area of the nanoflowers compared to the nanosheets which suggests a higher number of exposed edge sites in the nanoflowers.

Cu2O/MoS2 composites: a novel photocatalyst for photocatalytic degradation of organic dyes under visible light

The novel nanocomposite Cu2O/MoS2-12 was synthesized by a simple two-step method. Cu2O nanospheres grow on the surface of MoS2 nanoflowers and have high photocatalytic activity. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) X-ray photoelectron spectroscopy (XPS), ultraviolet-visible light (UV-vis) photoluminescence (PL) spectroscopy, UV-vis diffuse reflection (UV-DRS), and electrochemical impedance (EIS) were used to study the structure and properties of the samples. The photocatalytic properties of the materials were evaluated by degrading methyl orange (MO) under visible light. The results show that CM-12 can completely degrade MO in 30 min, and the pseudo-first-order kinetic constant of degradation is 8.76 times that of pure Cu2O, which can be attributed to the composite material that can greatly reduce the recombination rate of photogenerated electrons and holes, and it has good stability. After repeated use for 5 times, the degradation rate can still reach 40%. Through experiments and theoretical results, a possible photocatalytic mechanism is proposed. To the best of our knowledge, this work was the first example of combining MoS2 with Cu2O and applying it to photocatalytic degradation of organic pollutants. It was beneficial for developing new photocatalysts and improving the catalytic performance of conventional photocatalysts.