MoS2 Nanoflowers Research Articles

Rationally assembled nano-microarchitecture of MoS2 nanoflower tightly anchored on polypyrrole microtube towards constructing fire-safe EP composite

As for organic flame retardants, the high dosages (up to 20 wt%) are usually required to achieve favorable flame retardancy, which often causes serious aggregation in epoxy resin (EP). Thus, the applications of flame retarded EP composites are restricted by the jeopardized mechanical property. Therefore, a nano-microarchitecture of MoS2 nanoflowers in-situ grown on polypyrrole microtube (P-Mo) is rationally constructed as flame retardant for EP. The peak heat release rate and total heat release are significantly reduced by 47.4% and 22.2%, when adding 3.0 wt% P-Mo, demonstrating the hindered heat release. Besides, the peak smoke production rate and peak CO yield show reductions of 46.8% and 62.9% separately, which proves the hindered toxicants emission. Thermogravimetric analysis/infrared spectrometry results also show the attenuated releases of toxic CO and NO. These results jointly demonstrate that using P-Mo can efficiently suppress the fire hazard of EP, ascribed to the physical barrier, chemical catalyzing and charring promotion actions. Surprisingly, the storage modulus value is enhanced by 20.9%, when only using 1.0 wt% P-Mo.

Piezoelectric Nanozyme for Dual-Driven Catalytic Eradication of Bacterial Biofilms.

Catalytic nanomedicine can in situ catalytically generate bactericidal species under external stimuli to defend against bacterial infections. However, bacterial biofilms seriously impede the catalytic efficacy of traditional nanocatalysts. In this work, MoSe2 nanoflowers (NFs) as piezoelectric nanozymes were constructed for dual-driven catalytic eradication of multi-drug-resistant bacterial biofilms. In the biofilm microenvironment, the piezoelectricity of MoSe2 NFs was cascaded with their enzyme-mimic activity, including glutathione oxidase-mimic and peroxidase-mimic activity. As a result, the oxidative stress in the biofilms was sharply elevated under ultrasound irradiation, achieving a 4.0 log10 reduction of bacterial cells. The in vivo studies reveal that the MoSe2 NFs efficiently relieve the methicillin-resistant Staphylococcus aureus bacterial burden in mice under the control of ultrasound at a low power density. Moreover, because of the surface coating of antioxidant poly(ethyleneimine), the dual-driven catalysis of MoSe2 NFs was retarded in normal tissues to minimize the off-target damage and favor the wound healing process. Therefore, the cascade of piezoelectricity and enzyme-mimic activity in MoSe2 NFs reveals a dual-driven strategy for improving the performance of catalytic nanomaterials in the eradication of bacterial biofilms.

Porous three-dimensional network of MoSe2 microspheres bridged by ZnO nanoparticles with excellent absorption bandwidth toward electromagnetic waves

The design of a three-dimensional (3D) porous structure and rough surface morphology has proven to be a practical strategy for preparing highly efficient electromagnetic wave (EW) absorbents. In this study, ZnO nanoparticles were synthesized via a hydrothermal method, and MoSe2 nanoflowers were introduced and adhered to each other to form ZnSe@MoSe2 microspheres. The microspheres exhibit a 3D porous structure and rough surface morphology, allowing the EWs to effectively penetrate the material and forcing the EWs to undergo multiple reflections and scattering. Additionally, the excellent EW-absorbing performance of the composite results from the synergistic effect of multiple components. The maximum effective absorption bandwidth was 8.6 GHz, which was observed at a thickness of 2.2 mm and covered the entire Ku-band. The minimum reflection loss was − 44 dB, which was obtained at a thickness of 1.9 mm. This study provides significant insights into the design and preparation of highly efficient EW absorbents.

Photocatalytic and Antimicrobial Performance Evaluation of Reusable MoS2 Nanoflowers under Visible Light

2D semiconductor material, Molybdenum Disulfide (MoS2), with unique properties similar to that of graphene, is considered as a potential candidate for photocatalytic and antimicrobial applications. In the current work, MoS2 was prepared by a simple hydrothermal method using sodium molybdate and thiourea as precursors. The calculated band gap values of MoS2 grown at 200 °C and 180 °C were 2.1 eV and 1.98 eV, respectively. Flower like morphology was observed from FESEM analysis. Multi layered structure of MoS2 was confirmed from the difference the peak value obtained for A1g and E1 2g vibrational modes observed from Raman spectra. The reusability of the synthesized MoS2 was analyzed against MB dye degradation. The pristine MoS2 removed ∼98% of the dye molecules from the water under the minimum wattage (20 W) of visible light in 180 min. The catalyst retained good stability even after the third degradation, confirming the reusability of MoS2. The disk diffusion method was used to evaluate the antimicrobial activity of the grown MoS2 nanostructures. The gram-positive and gram-negative bacteria used in present study were Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli and Bacillus serius. Investigation of the antibacterial activity of MoS2 against these four different pathogens was carried out in detail and the resistance function was measured.

Correction: Liu et al. Functionalized MoS2 Nanoflowers with Excellent Near-Infrared Photothermal Activities for Scavenging of Antibiotic Resistant Bacteria. Nanomaterials 2021, 11, 2829

In the original publication [...].

MoS2 nanoflowers decorated with single Fe atoms catalytically boost the activation properties of peroxymonosulfate

Reductive iron species have been widely used in advanced oxidation technologies (AOPs) and have shown great potential for the catalytic degradation of various organic pollutants. However, preparing reductive iron-based catalysts that can effectively degrade organic pollutants over a wide pH range remains challenging. Herein, we constructed xFe-MoS2 nanoflowers by introducing atomically dispersed Fe into MoS2 nanosheets, which were demonstrated to catalytically boost the activation of PMS toward the Rhodamine B (RhB) degradation. At an initial concentration of 20 mg L−1, the catalyst xFe-MoS2 could complete the fading and removal of RhB in as fast as three minutes. The 4%Fe-MoS2 showed excellent catalytic performance for RhB degradation over a broad pH range (3.0–11.0), with maximal activity at pH 3.0. MoS2 showed a remarkable synergistic effect in improving the adsorption of RhB and Fe2+/Fe3+ cycling on the catalyst surface, which significantly accelerated the removal efficiency of RhB. Sulfate radicals (SO4•−) and superoxide radicals (O2•−) were identified as the predominant active species during the RhB degradation process. Furthermore, the 4%Fe-MoS2 exhibited great stability and sustainable reactivity. This study provides theoretical analysis and practical exploration of the development and utilization of MoS2 decorated with Fe single atoms for removing pollutants by activating PMS.

A combined experimental and theoretical study on the structural, optical and electronic properties of hetero interface-functionalized MoS2 /Co3O4 nanocomposite

Co3O4 decorated MoS2 nanoflower (MoS2/Co3O4) has been successfully synthesized by a simple hydrothermal method. A combined experimental and theoretical investigation was performed to comprehend the effect of Co3O4 on the structural, optical, and electronic properties of MoS2 nanoflowers. A number of characterization techniques have been used to study the surface morphologies, structural properties, chemical constitution, and optical properties of the nanocomposites including, FE-SEM, TEM, XRD, XPS, and UV–VIS spectroscopy. Flower-like structures of MoS2 and MoS2/Co3O4 have been observed from the FE-SEM and TEM images. The Rietveld refinement of the X-ray diffraction (XRD) pattern was used to estimate the various structural parameters of the nanoflowers which also confirms the phase purity of the MoS2 nanoflower. X-ray photoelectron spectroscopy (XPS) results revealed strong electronic interaction between Mo–S and Co–O in the nanocomposites. The optical bandgap of the as-prepared samples was estimated using diffusive reflectance spectra and was found to be varied between 1.44 eV to 1.27 eV nanostructure due to the incorporation of Co3O4 nanoparticle. To fully understand and validate the structural, optical, and electrical characteristics of the samples, density functional theory (DFT) calculations were carried out. DFT results revealed that the Mo-4d and Co-3d orbital-orbital interactions occur due to the incorporation of Co3O4 into MoS2, leading to a decrease in the band gap. Moreover, a charge redistribution occurred between MoS2 and Co3O4 interface, creating more active sites for electro and opto-catalytic reactions. Among the results, the red shift of the optical absorbance spectra is the most obvious one enabling our synthesized nanocomposite to absorb in the near-infrared range. This study will offer a new insight into the fabrication of transition oxide-based hetero-interface influenced MoS2 functional devices for diverse applications.

A sequential delivery system based on MoS2 nanoflower doped chitosan/oxidized dextran hydrogels for colon cancer treatment

A sequential delivery system based on MoS2 nanoflower (MoS2 NF) doped chitosan (CS)/oxidized dextran (OD) hydrogels is developed for the treatment of colon cancer. 5-Fluorouracil (5-FU) is combined with polyethylenimine (PEI) decorated MoS2 NF via electrostatic attraction and hydrogen bonding, and the obtained 5-FU/PEI/MoS2 is encapsulated by 1-tetradecanol (TD), a commonly used phase transition material. The resultant TD/5-FU/PEI/MoS2 (TFPM) is then co-encapsulated with methotrexate (MTX) in the CS/OD hydrogels generated via Schiff base reaction and electrostatic attraction. Because the electrostatic attraction between CS and OD is pH-sensitive, MTX and TD/5-FU/PEI/MoS2 can be easily released from the hydrogels at pH 7.4. MoS2 is an outstanding photothermal agent, and the generated hyperthermia under near infrared (NIR) irradiation can lead to the melting of TD and the consequent release of 5-FU encapsulated. More importantly, the generated hyperthermia under NIR irradiation can realize the chemo-photothermal synergistic tumor therapy. Finally, the practicability of the developed sequential delivery system is demonstrated by cytotoxicity test.

Functionalized MoS2: circular economy SERS substrate for label-free detection of bilirubin in clinical diagnosis.

A one-pot hydrothermal synthesis of Fe-doped MoS2 nanoflowers (Fe-MoS2 NFs) has been developed as a surface-enhanced Raman spectroscopy (SERS) substrate. The Fe-MoS2 NFs display high reproducibility, stability, and recyclability, which is beneficial for the development of the sustainable ecological environment. The SERS substrate provides a high enhancement factor of 105, which can be ascribed to the inducing defects by doping Fe that can improve the charge transfer between probe molecules and MoS2. TheFe-MoS2 NFshave beenused to detect bilirubin in serum. The Fe-MoS2 NF SERS substrate exhibits a linear detection range from 10-3 to 10-9M with a low limit of detection (LOD) of 10-8M. Thesubstrate displays an excellent selectivity to bilirubin in the presence of other potentiallyinterfering molecules (dextrose and phosphate). These results providea novel concept to synthesize ultra-sensitive SERS substrates and open up a wide range of possibilities for new applications of MoS2 in clinical diagnosis.

Photocatalytic Activity of MoS2 Nanoflower-Modified CaTiO3 Composites for Degradation of RhB under Visible Light

Nanoflower-like MoS2 deposited on the surface of rectangular CaTiO3(CTO) was designed and synthesized via a simple template-free strategy. Through SEM, TEM, and other characterization methods, the MoS2 nanoflowers were confirmed to be well deposited on the surface of CTO. LED was used as the visible light source, and rhodamine B (RhB) in an aqueous solution was used as the model pollutant to assess the photodegradation activity of the samples. The results showed that the MoS2/CaTiO3(MCTO) composite significantly improved the photocatalytic degradation of rhodamine B (RhB) in water, compared with a single CTO, and with the MCTO-2 composite photocatalysts, 97% degradation of RhB was achieved in 180 min, and its photocatalytic activity was about 5.17 times higher than that of the bare CTO. The main reasons for enhancing photocatalytic performance are the strong interaction between the nanoflower-like MoS2 and rectangular CTO, which can lead to the effective separation of electron transfer and photoexcited electron-hole pairs in MCTO composites. This work provides a new notion for researching an effective method of recycling catalytic materials.

Enhancing hydrogen evolution reaction (HER) performance by loading MoS2 nanoflowers into three-dimensional graphene aerogel skeleton

We successfully loaded different quantities of MoS2 nanoflowers (MoS2-NF) into three-dimensional graphene aerogel skeleton (GA) by hydrothermal and freeze-drying process. The prepared MoS2 nanoflowers/graphene hybrid aerogels (denoted as MoS2-NF/GA) exhibit a gradually decreasing initial overpotential and Tafel slope with increasing of MoS2-NF, indicating a gradually improvement of HER performance. The enhancement may be explained by the benefit from excellent conductivity of GA to the acceleration of electrons transferring and the increased MoS2 active sites ascribed from the highly dispersed distribution of MoS2-NF in the GA. This study provides a method for loading controllably nanomaterials into three-dimensional graphene aerogel skeleton and a strategy for enhancing HER performance of MoS2-NF.

Simultaneous removal of Cr(VI) and phenol in a dual-chamber photocatalytic microbial fuel with NiCo2O4/MoS2/GF photocathode

Efficient treatment and resource utilization of sewage are of great value for global sustainability. In this study, a composite photocathode was prepared by loading NiCo2O4 nanosheets and MoS2 nanoflowers to a graphite felt (GF)-based electrode through a two-step hydrothermal and calcination method. A photocatalytic microbial fuel cell (PMFC) was constructed using the NiCo2O4/MoS2/GF photocathode and carbon felt (CF) anode in a dual-chamber H-type battery. Cr(VI) and phenol were employed as target pollutants in the cathode chamber. The photoelectric performance of the NiCo2O4/MoS2/GF photocathode and the removal efficiency of the battery system were studied systematically. When a mixed solution of Cr(VI) and phenol was used, the removal rates of Cr(VI) and phenol after 24 h of light exposure were 8.13 % and 12.65 % higher than those when Cr(VI) or phenol was used alone, respectively. At the same time, the output power density of the battery in the mixed pollutants was 362.7 mW/m3, which was 45.78 % higher than that in the single Cr(VI) solution (248.8 mW/m3). The excellent performance of the PMFC was attributed to three reasons: (1) NiCo2O4 and MoS2 were simultaneously excited as two narrow-bandgap semiconductors, and the utilization rate of light energy was increased; (2) The Z-scheme heterojunction between NiCo2O4 and MoS2 improved the separation efficiency of the photoelectric carriers and retained the high valence band of NiCo2O4 and low conduction band of MoS2 to the greatest extent, which is crucial for the PMFC to achieve electronic export and double contaminant removal; and (3) the NiCo2O4 nanosheet and MoS2 nanoflower structures enhanced the contact between the catalysts and the pollutants.

Omnidirectionally irradiated three-dimensional molybdenum disulfide decorated hydrothermal pinecone evaporator for solar-thermal evaporation and photocatalytic degradation of wastewaters

Although most solar steam generation devices are effective in desalinating seawater and purifying wastewaters with heavy metal ions, they are ineffective in degrading organic pollutants from wastewaters. Herein, we design novel solar-driven water purification devices by decoration of three-dimensional pinecones with MoS2 nanoflowers via a one-step hydrothermal synthesis for generating clean water. The vertically arrayed channels in the central rachis and the unique helically arranged scales of the hydrothermal pinecone can not only transfer bulk water upward to the evaporation surface, but also absorb more solar light from different incident angles for solar-thermal evaporation and photodegradation of wastewaters under omnidirectional irradiations. The decorated MoS2 nanoflowers can not only enhance the solar-thermal energy conversion efficiency, but also decompose organic pollutants in the bulk water by their photocatalytic degradation effects. The resultant hydrothermal pinecone with in situ decorated MoS2 (HPM) evaporator exhibits a high evaporation rate of 1.85 kg m−2 h−1 under 1-sun irradiation with a high energy efficiency of 96 %. During the solar-driven water purification processes, the powdery HPM can also photodegrade organic pollutants of methylene blue and rhodamine B with high removal efficiencies of 96 % and 95 %, respectively. For practical demonstration, by floating in the methylene blue solution under 1-sun irradiation, the bulky HPM can generate clean water by simultaneous solar-thermal evaporation and photocatalytic degradation. The integration of solar steam generation and photocatalytic degradation mechanisms makes the HPM evaporator highly promising for practical high-yield purification of wastewaters.

Co0.75Mo3S3.75/CoS2@2D-MoS2 nanosheets on carbon cloth: A progressive binder-free electrocatalyst for hydrogen evolution reaction

The development of ultrathin non-noble metal dichalcogenide electrocatalysts with tunable physical properties such as phase transformations, defect engineering, and activating plane edges is essential in order to enhance their electrocatalytic performance for water splitting applications. In this present work, we account to report a facile approach to cationic modulations through a single-step hydrothermal approach for the fabrication of a two-dimensional (2D) self-assembled ultrathin Co0.75Mo3S3.75/CoS2 (Co–Mo–S) @MoS2 nanoflowers directly grown on carbon fibre cloth. The systematic physicochemical relationship of cobalt ion modulations into MoS2 nanoflowers (Co/Mo/S) enabled the formation of flower-like Co–Mo–S@MoS2 ultrathin nanosheets with enhanced active sites, resulting in enhanced electrocatalytic contribution for hydrogen evolution reaction. The synthesised catalyst exhibited an ultralow overpotential value of 43 mV (RHE) at 20 mA/cm2, very small Tafel value of ∼36.6 mV/dec, and long durability/stability of 51 h of electrolysis. As a whole, these presented results demonstrate a rational construction of 2D ion modulated MoS2 ultrathin nanosheet electrodes that are beneficial for sustainable energy storage devices, which could be potentially extended to other dimensional MoS2 based materials.

Influence of polycrystalline MoS2 nanoflowers on mouse breast cancer cell proliferation via molten salt sintering

In this paper, polycrystalline molybdenum disulfide (MoS2) nanoflowers were prepared by mixing ammonium molybdate tetrahydrate [(NH4)6Mo7O24·4H2O] and potassium thiocyanate (KSCN) at 300 °C for 2 h via molten salt sintering method. Under scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM), MoS2 showed popcorn-like shape, which surface distribution defects were easy to be further modified. MoS2 as a nano-enzyme was used to inhibit the proliferation of mouse breast cancer cells (4 T1), which had 69.8 % inhibitory effect on 4 T1 cell proliferation. Electron spin resonance (ESR) analysis showed that MoS2 could produce a large number of stable hydroxyl radicals (–OH). The disulfide bond in MoS2 was highly sensitive to reactive oxygen species (ROS). High ROS level leads to the death of cancer cells under oxidative stress and inhibits the proliferation of 4 T1. This work demonstrates that MoS2 is a potential anticancer drug or carrier for cancer treatment.

Environmental gas sensing studies using flower-like MoS2 hybrid structure

Molybdenum disulfide (MoS2) is one of the most potent transition metal dichalcogenide (TMDc) material for gas sensing applications due to its various advantageous properties. It exhibits modest electron mobilities, reduced dimensionality, and favorable mechanical properties. The deposition of metal nanoparticles on nanostructured MoS2 leads to the modification in their sensing properties. By keeping in view, present work reports the fabrication of stable MoS2 nanoflowers (MNF) and their hybrids (Au-MoS2 nanoflowers). The hydrothermal approach was used to synthesize MNF nanostructures and in order to form the hybrid Au-MoS2 nanoflower (AuMNF) Au nanoparticle were deposited over MNF by an inert gas evaporation method. X-ray Diffraction and micro–Raman spectroscopy were used to study MNF and AuMNF hybrid structures. XRD found MoS2 1 T-2H mixed-phase. The peak shift and broadening in E1g, J3, and E3g modes for AuMNF hybrids was observed compared to MNF. The flower-like morphology of the pristine and hybrid nanostructures was confirmed via the Scanning electron microscopy (SEM) technique and transmission electron microscopy (TEM). Furthermore, the fabricated samples MNF and AuMNF hybrids were investigated for environmental gas sensing. According to the results of the gas sensing tests, the AuMNF hybrid provides the best sensing response. The gas sensing measurements revealed that the best sensing response is found from the AuMNF hybrid. This hybrid shows a response of 21.2 % in the presence of CO, which is 5.5 times higher than the response of pure MoS2. These findings contribute to a better interpretation of how the resistance of MoS2 nanostructures reacts towards CO gas exposure. These findings contribute to a better interpretation of how the resistance of MoS2 nanostructures reacts towards CO gas exposure.

Surface engineering of nanoflower-like MoS2 decorated porous Si3N4 ceramics for electromagnetic wave absorption

MoS2 nanoflower decorated porous Si3N4 ceramics were prepared by a combination of vacuum infiltration and hydrothermal reaction. Excellent electromagnetic wave absorption performance was achieved by constructing MoS2-Si3N4 heterostructures.

MoS2 nanoflower-decorated lignin nanoparticles for superior lubricant properties.

Lignin has been, for a long time, treated as a low-value waste product. To change this scenario, high-value applications have been recently pursued, e.g., the preparation of hybrid materials with inorganic components. Although hybrid inorganic-based materials can benefit from the reactive lignin phenolic groups at the interface, often responsible for optimizing specific properties, this is still an underexplored field. Here, we present a novel and green material based on the combination of hydroxymethylated lignin nanoparticles (HLNPs) with molybdenum disulfide (MoS2) nanoflowers grown via a hydrothermal route. By bringing together the lubricant performance of MoS2 and the structural stability of biomass-based nanoparticles, a MoS2-HLNPs hybrid is presented as a bio-derived additive for superior tribological performances. While FT-IR analysis confirmed the structural stability of lignin after the hydrothermal growth of MoS2, TEM and SEM micrographs revealed a homogeneous distribution of MoS2 nanoflowers (average size of 400 nm) on the HLNPs (average size of 100 nm). Regarding the tribological tests, considering a pure oil as reference, only HLNPs as bio-derived additives led to a reduction in the wear volume of 18%. However, the hybrid of MoS2-HLNPs led to a considerably higher reduction (71%), pointing out its superior performance. These results open a new window of opportunity for a versatile and yet underexplored field that can pave the way for a new class of biobased lubricants.

MoS2/Au/Ag Nanostructures for Ratiometric Surface-Enhanced Raman Scattering Determination of Pesticide Residues

Surface-enhanced Raman scattering (SERS) is a promising method for rapid and sensitive detection of pesticide residues. Herein, a three-dimensional MoS2/Au/Ag nanostructure was developed by employing composite systems containing semiconductors, noble metal nanoparticles, and internal standard. The MoS2 nanoflowers provide abundant anchors for the loading of plasmonic nanoparticles so as to generate intense electromagnetic “hot spots,” and the Au-MBN/Ag nanostructures can increase the accuracy of SERS detection with the calibration ability of the internal standard molecules (4-mercaptobenzonitrile, 4-MBN). Therefore, the MoS2/Au/Ag nanostructures integrate the advantages of high-enhancement SERS substrates and high-accuracy ratiometric Raman detection. Moreover, the nanostructures were fabricated via a facile procedure and showed high sensitivity, accuracy, and reproducibility in SERS detection. The nanostructures also showed good linear fitting between the ratios of Raman intensity and logarithmic concentrations of analytes in ratiometric SERS analysis. In addition, thiabendazole (TBZ) in apple juice was successfully detected by using the as-prepared SERS substrates with a limit of detection down to 0.1 ppm in practical applications. To conclude, the MoS2/Au/Ag nanostructures showed excellent SERS activity in ratiometric analysis and the substrate is expected to have great potential for the quantitative detection of low-concentration pesticide residues.

Low-frequency vibration induced piezoelectric boost to photocatalytic hydrogen evolution through 2D-2D-stacked MoS2-carbon nitride

MoS2-carbon nitride heterostructures which are highly sensitive to low-frequency vibration are demonstrated to be the catalysts for piezo-photocatalytic hydrogen evolution reaction (HER). The configuration of MoS2 nanostructure on carbon nitride plays a crucial role in the piezo-photocatalytic HER activity of MoS2-carbon nitride heterostructure. With the cocatalyst of Pt NPs on the carbon nitride portion, 2D-2D stacked MoS2-carbon nitride catalyst exhibits considerably higher HER rate compared to the pristine carbon nitride and MoS2 nanoflower (NF)-carbon nitride catalysts under illumination coupling with the mechanical energy of vortex-induced shearing force. Experimental and calculation results indicate that the MoS2 nanosheets mainly perform as the piezopotential generator to induce an electric field in the carbon nitride counterpart. With the configuration of 2D-2D stacking, the light harvesting of carbon nitride in the heterostructure remains the same as the pristine one. Nevertheless, the recombination of photogenerated electron-hole pairs in the carbon nitride portion of the MoS2-carbon nitride heterostructure is inhibited due to the electric field induced by MoS2 nanosheet under low-frequency vortex vibration, resulting in the significantly boosted HER rate obtained from the 2D-2D stacked MoS2-carbon nitride heterostructure.