Molybdenum Disulfide Nanosheets Research Articles

Boosting the energy storage performance of aqueous NH4+ symmetric supercapacitor based on the nanostructured molybdenum disulfide nanosheets

Nanostructured molybdenum disulfide (MoS2-2H phase) is a well-known metal dichalcogenide and promising material for electrochemical energy storage due to its unique properties, including structural stability, tuneable bandgap, and dangling-bond free basal surface. However, electrochemical devices based on MoS2 suffer from a short lifespan, low power density, and safety. Herein, we proposed 2H-MoS2 nanosheets as a capacitive energy storage material for aqueous ammonium-ion supercapacitors (AASCs) to address the above-mentioned issues. MoS2 nanosheets were grown on carbon cloth (MoS2@CC) with a wet-chemical method as binder-free capacitive electrodes, and a symmetric supercapacitor (SSC) was assembled to evaluate its energy storage performance. According to our simulation results with density functional theory (DFT), the ammonium sulfate (NH4)2SO4 aqueous solution was selected as the ammonium-ion electrolyte. The MoS2@CC electrode exhibits outstanding NH4+ ion storage by achieving a high capacitance of 1,010 Fg−1 at 1 Ag−1 and ultra-high rate performance (60% at 50-folded high current density) with 98% capacitance retention after 10,000 cycles. The pseudocapacitive charge storage process governs the NH4+ intercalation/deintercalation mechanism through the bounding/breaking of H with S atoms. A symmetric AASC was fabricated using the MoS2@CC and an aqueous (NH4)2SO4 electrolyte to assess the practical performance. The assembled AASC can operate at a wide potential window (0.0–1.5 V) and demonstrates high charge storage performance (237 Fg−1 at 1 Ag−1 and 133 Fg−1 at 50 Ag−1) with extremely stable rate and cycling performance of ∼ 99% up to 50,000 cycles. This study would give an effective and a succinct technique for creating metal dichalcogenide with porous structure for advanced NH4+ storage.

MoS2 nanosheets based label-free colorimetric aptasensor for Escherichia coli O157: H7 detection

The aggregation behavior of large-scale two-dimensional molybdenum disulfide (MoS2) nanosheets prepared by sonication-assisted exfoliation in environmental friendly 45% ethanol/water mixture under different conditions (e.g., salt concentration, cation valence and nanosheets size) had been examined to make them more appropriate for biological sensing application. Adjustment of sonication time and centrifuging speed could be utilized to select MoS2 nanosheets with various concentrations and sizes. Higher concentrations of salt and cations with higher valence were more effective to aggregate MoS2 nanosheets and settle them than their counterparts, which could be attributed to the perturbation of attractive van der Waals forces and repulsive Coulombic interactions. Moreover, the ethanol in mixture was capable of assisting MoS2 nanosheets to resist this aggregation initiated by salt but it would disturb the stability of aptamer functionalized MoS2 nanosheets in salt solution. The interplay of Escherichia coli O157: H7 (E. coli O157:H7) aptamer functionalized MoS2 nanosheets and salt was then inspired to develop a high sensitive detection method of E. coli O157:H7. The introduction of target bacteria induced MoS2 nanosheets to be exposed to cations, and promoted the aggregation and sedimentation behavior of MoS2 nanosheets. The change in extinction of MoS2 nanosheets had a linear relationship with E. coli O157:H7 concentration in a range of 500–5000 CFU/mL with a detection limit of 116 CFU/mL. This proposed colorimetric sensor expands the application scope of MoS2 nanosheets and shows its promising potential as an alternative tool for bacteria detection in food and water quality monitoring.

Vertically molybdenum disulfide nanosheets on carbon cloth using CVD by controlling growth atmosphere for electrocatalysis

Molybdenum disulfide (MoS2) has been deemed as one of the promising noble-metal-free electrocatalysts for hydrogen evolution reaction (HER), but it suffers from the inert basal plane and low electronic conductivity. Regulating the morphology of MoS2 during the synthesis on conductive substrates is a synergistic strategy for enhancing the HER performance. In this work, vertical MoS2 nanosheets were fabricated on carbon cloth (CC) using an atmospheric pressure chemical vapor deposition method. The growth process could be effectively tuned through introducing hydrogen gas during vapor deposition process, resulting in nanosheets with increased edge density. The mechanism for edge-enriching through controlling the growth atmosphere is systematically studied. The as-prepared MoS2 exhibits excellent HER activity due to the combination of optimized microstructures and coupling with CC. Our findings provide new insights to design advanced MoS2-based electrocatalysts for HER.

Efficient and scalable encapsulation process of highly conductive 1T-MoS2 nanosheets on Ni-rich LiNi0.83Co0.11Mn0.06O2 cathode materials for high-performance lithium-ion batteries

Ni-rich LiNi1-x-yCoxMnyO2 (NCM) is an attractive cathode material that can meet the growing global demand of the Lithium-ion battery market owing to its high energy density and low cost. However, it still suffers from cyclic and thermal instability due to several issues, such as structural deterioration and excessive cathode electrolyte interface (CEI) layer formation arising from side reactions occurring at the NCM particle surface. In this study, molybdenum disulfide (MoS2) nanosheets with a metallic 1T phase are synthesized by chemical exfoliation, functionalized with polyethyleneimine (PEI), and uniformly coated on the surface of Ni-rich NCM particles through electrostatic interactions. As a result, the ceMoS2-PEI layer effectively alleviates the electrochemical performance degradation of NCM caused by irreversible phase transitions, microcrack formation, transition metal dissolution, and thick CEI layer formation by suppressing side reactions due to direct contact with the organic electrolyte or hydrofluoric acid on the surface of NCM. In addition, the ceMoS2-PEI layer provides a sufficient transport pathway for charge transfer and Li+ ion diffusion, thereby mitigating electrode polarization and impedance increase. Consequently, NCM/ceMoS2-PEI electrodes exhibit a high discharge capacity of 150.6 mAh g−1 at 5C and outstanding capacity retention of 96.9 % after 100 cycles at 1C. Moreover, further cycle tests in harsh environments, such as high mass loading and operating temperature, demonstrate that the ceMoS2-PEI layer coating more effectively improves the structural and thermal stability of the Ni-rich NCM in harsh environments.

Development and in vitro evaluation of donepezil hydrochloride-loaded thermo-responsive polymer grafted molybdenum disulfide nanosheets: Modeling using response surface methodology

Nanocarriers are utilized to deliver bioactive substances in the treatment of neurodegenerative diseases such as Alzheimer's. In this work, we prepared donepezil hydrochloride-loaded molybdenum disulfide modified thermo-responsive polymer as the thermo-responsive nanocarrier. Then, glycine was grafted to the surface of the polymer to improve the targeting and sustained release. The morphology, crystallinity, chemical bonding, and thermal behavior of nanoadsorbent were fully characterized by field emission scanning electron microscopes, energy dispersive X-ray, X-ray diffraction, Fourier-transform infrared spectroscopy, and thermo-gravimetric measurement. Response surface methodology with the central composite design was applied to optimize the sorption key factors such as pH solution (A: 5–9), contact time (B: 10–30 min), and temperature (C: 30–50 °C). Non-linear isotherm modeling confirmed that the sorption of the drug follows the Ferundlich model based on higher correlation coefficient values (R2 =0.9923) and lower errors values (root means square errors: 0.16 and Chi-square: 0.10), suggesting a heterogeneous multilayer surface sorption. The non-linear sorption kinetic modeling revealed that the pseudo-second-order kinetic model well-fitted the sorption data of the drug on the nanoadsorbent surface based on higher R2 values (R2 =0.9876) and lower errors values (root means square errors: 0.05 and Chi-square: 0.02). The in vitro drug release experiment of donepezil hydrochloride shown that about 99.74 % of drug release was found to be occurred at pH= 7.4 (T = 45 °C) within 6 h, whereas about 66.32 % of drug release occurred at pH= 7.4 (T = 37 °C). The release of donepezil hydrochloride from as prepared drug delivery system has shown a sustained release profile, which was fitted to Korsmeyer-Peppas kinetics.

All-optical plasma modulation by the plasma channel induced in the molybdenum disulfide dispersion solution

The molybdenum disulfide (MoS2) nanosheet is successfully synthesized using a hydrothermal Li-intercalation exfoliation method. We experimentally show that the MoS2 dispersion solution can be used for optical modulation and all-optical switching based on the plasma channel induced by control pulses. The modulated signal light has a good transmission property in free space. The spatial modulation of the signal laser can be easily adjusted through the power of control lasers and the suspension concentration. The influence of suspension concentration and type on the free-space propagation of modulated signal light is also investigated. Results reveal a potential application of MoS2 as an all-optical modulator for diversified photoelectric applications.

Ultrathin thin-film composite membrane integrated with MoS2 conjugated with thiol ligands for isopropanol dehydration by pervaporation

In recent years, transition metal dichalcogenides (TMDs) have garnered much significant attention for their potential in fabricating high-performance membranes and applications in water treatment. In the present study, molybdenum disulfide (MoS2) nanosheets were modified using organic thiols to synthesize amino, hydroxyl, and carboxyl-functionalized MoS2. These modified nanosheets were subsequently integrated into polyamide matrix to develop thin-film nanocomposite (TFN) membranes for dehydration of isopropanol-water mixtures through pervaporation. A comprehensive examination of the impact of incorporating functionalized MoS2 on the physical and chemical properties and separation performance of the resulting TFN membranes was carried out. Embedding MoS2 created a bumpy structure with protuberances on the membrane surface. Amine groups from the modified MoS2 played a crucial role in crosslinking with trimesoyl chloride during interfacial polymerization, contributing to an enhanced crosslinking degree in the membrane. Compared with the pristine membrane, hydroxyl and carboxyl-modified MoS2, the TFN membrane incorporated with amine-modified MoS2 exhibited the highest separation performance with total flux of 1438 g m−2 h−1 and water content in permeate of 99.37 wt% for separating 70 wt% isopropanol aqueous solution. Remarkably, the TFN membrane exhibited a robust performance under high operating temperatures and high feed water concentrations, demonstrating its resilience in challenging conditions. Furthermore, the membrane exhibited stable long-term operational performance, highlighting its potential for pervaporation dehydration applications in the industry. The insights gained from this study contribute to the ongoing development of advanced membrane technologies based on TMDs.

Selective Photothermal Therapy Based on Lipopolysaccharide Aptamer Functionalized MoS2 Nanosheet‐Coated Gold Nanorods for Multidrug‐Resistant Pseudomonas aeruginosa Infection (Adv. Healthcare Mater. 15/2023)

Targeted Photothermal Therapy Combined with the outstanding photothermal conversion efficiency of gold nanorods (AuNRs), superior biocompatibility of molybdenum disulfide (MoS2) nanosheets, and strong specificity of lipopolysaccharides aptamer (LPS apt), composite nanorods (MoS2-AuNRs-apt) exhibit excellent therapeutic effects for multidrug-resistant pseudomonas aeruginosa and excess M1 macrophage in vitro, as well as infectious wounds in vivo. This work is found in article 2202794 by Yongyu Rui, Lei Zheng, and co-workers.

A 3D-printed orthopedic implant with dual-effect synergy based on MoS2 and hydroxyapatite nanoparticles for tumor therapy and bone regeneration

Treatments for malignant bone tumors are urgently needed to be developed due to the dilemma of precise resection of tumor tissue and subsequent bone defects. Although polyether-ether-ketone (PEEK) has widely attracted attention in the orthopedic field, its bioinertness and poor osteogenic properties significantly restrict its applications in bone tumor treatment. To tackle the daunting issue, we use a hydrothermal technique to fabricate novel PEEK scaffolds modified with molybdenum disulfide (MoS2) nanosheets and hydroxyapatite (HA) nanoparticles. Our dual-effect synergistic PEEK scaffolds exhibit perfect photothermal therapeutic (PTT) property dependent on molybdous ion (Mo2+) concentration and laser power density, superior to conventional PEEK scaffolds. Under near-infrared (NIR) irradiation, the viability of MG63 osteosarcoma cells is significantly reduced by modified PEEK scaffolds, indicating a tumor-killing potential in vitro. Furthermore, the incorporation of HA nanoparticles on the surface of PEEK bolsters proliferation and adherence of MC3T3-E1 cells, boosting mineralization for further bone defect repair. The results of micro-computed tomography (micro-CT) and histological analysis of 4-week treated rat femora demonstrate the preeminent photothermal and osteogenesis capacity of 3D-printed modified scaffolds in vivo. In conclusion, the dual-effect synergistic orthopedic implant with photothermal anticancer property and osteogenic induction activity strikes a balance between tumor treatment and bone development promotion, offering a promising future therapeutic option.

Photo-assisted Zn-air battery-driven self-powered aptasensor based on the 2D/2D Schottky heterojunction of cadmium-doped molybdenum disulfide and Ti3C2Tx nanosheets for the sensitive detection of penicillin G

A novel photocatalyzed Zn-air battery-driven (ZAB)-based aptasensor has been manufactured using the two dimensional (2D)/2D Schottky heterojunction as photocathode and Zn plate as photoanode. It was then employed to sensitively and selectively detect penicillin G (PG) in the complex environment. The 2D/2D Schottky heterojunction was established by the in situ growth of cadmium-doped molybdenum disulfide nanosheets (Cd–MoS2 NSs) around Ti3C2Tx NSs (denoted as Cd–MoS2@Ti3C2Tx) by using phosphomolybdic acid (PMo12) as precursor, thioacetamide as sulfur source, and Cd(NO3)2 as a doping agent through the hydrothermal method. The gained Cd–MoS2@Ti3C2Tx heterojunction possessed contact interface, hierarchical structure, and plenty of sulfur and oxygen vacancies, thus showing the enhanced separation ability of photocarriers and electron transfer. Due to the enhanced UV–vis light adsorption ability, high photoelectric conversion efficiency, and exposed catalytic active sites, the constructed photocatalyzed ZAB displayed a boosted output voltage of 1.43 V under UV–vis light irradiation. The developed ZAB-driven self-powered aptasensor demonstrated an ultralow detection limit of 0.06 fg mL−1 within a PG concentration ranged from 1.0 fg mL−1 to 0.1 ng mL−1, as deduced from the power density-current curves, along with high specificity, good stability and promising reproducibility, as well as excellent regeneration ability and wide applicability. The present work provided an alternative analysis method for the sensitive analysis of antibiotics based on the portable photocatalyzed ZAB-driven self-powered aptasensor.

Selective Activation of Cells by Piezoelectric Molybdenum Disulfide Nanosheets with Focused Ultrasound.

An accurate method for neural stimulation within the brain could be very useful for treating brain circuit dysfunctions and neurological disorders. With the aim of developing such a method, this study investigated the use of piezoelectric molybdenum disulfide nanosheets (MoS2 NS) to remotely convert ultrasound energy into localized electrical stimulation in vitro and in vivo. The application of ultrasound to cells surrounding MoS2 NS required only a single pulse of 2 MHz ultrasound (400 kPa, 1,000,000 cycles, and 500 ms pulse duration) to elicit significant responses in 37.9 ± 7.4% of cells in terms of fluxes of calcium ions without detectable cellular damage. The proportion of responsive cells was mainly influenced by the acoustic pressure, number of ultrasound cycles, and concentration of MoS2 NS. Tests using appropriate blockers revealed that voltage-gated membrane channels were activated. In vivo data suggested that, with ultrasound stimulation, neurons closest to the MoS2 NS were 3-fold more likely to present c-Fos expression than cells far from the NS. The successful activation of neurons surrounding MoS2 NS suggests that this represents a method with high spatial precision for selectively modulating one or several targeted brain circuits.

Chemically Engineered Sulfur Vacancies on Few-Layered Molybdenum Disulfide Nanosheets for Remarkable Surface-Enhanced Raman Scattering Activity

In recent years, molybdenum disulfide nanosheets (MoS2 NSs) with sulfur surface defects have been used for surface-enhanced Raman scattering (SERS). However, methods to generate sulfur defects on the MoS2 NS surface are sophisticated and expensive. In this study, we present a relatively straightforward approach to quickly creating sulfur defects on MoS2 NSs by chemical treatment with NaBH4. Few-layered MoS2 NSs (FL-MoS2 NSs) were formed by exfoliating bulk-MoS2 in isopropanol. By oxidation–reduction reactions of FL-MoS2 NSs mixed with a suitable concentration of NaBH4, the resulting MoS2 NSs with abundant sulfur defects (SV-FL-MoS2 NSs) can be obtained. Spectroscopic and electron microscopic methods are used to demonstrate sulfur defects in SV-FL-MoS2 NSs. Rhodamine (R6G) and rhodamine-B (RhB) were used as Raman analytes to evaluate the SERS efficiency of SV-FL-MoS2 NSs. The developed SERS substrate provided detection limits of 1 × 10–8 M for both R6G and RhB, with enhancement factors of 2.21 × 106 and 4.02 × 106, respectively. Our measurements of SV-FL-MoS2 NSs’ energy band gap and R6G/RhB confirmed that charge transfer (CT) and tight molecular contacts are responsible for their excellent SERS sensitivity. With the development of new, low-cost semiconductor-based SERS materials, this discovery could impact materials science and biosensing platforms.

The Dynamic Interaction of Surfactants with Colloidal Molybdenum Disulfide Nanosheets Calls for Thermodynamic Stabilization by Solvents.

Top-down liquid-phase exfoliation (LPE) and bottom-up hot-injection synthesis are scalable methods to produce colloids of two-dimensional (2D) van der Waals (vdW) solids. Generally thought off as two entirely different fields, we show that similar stabilization mechanisms apply to colloids of molybdenum disulfide (MoS2) produced by both methods. By screening the colloidal stability of MoS2 produced in a hot-injection synthesis in a wide range of solvents, we observe that colloidal stability can be understood based on solution thermodynamics, wherein matching the solubility parameter of solvent and nanomaterial maximizes colloidal stability. Identical to MoS2 produced through LPE, optimal solvents to disperse MoS2 produced from the bottom-up have similar solubility parameters of ≈22 MPa1/2 and include aromatic solvents with polar functionalities, such as o-dichlorobenzene, and polar aprotic solvents, such as N,N-dimethylformamide. We further complemented our findings by nuclear magnetic resonance (NMR) spectrscopy, highlighting that organic surfactants, such as oleylamine and oleic acid, have a minimal affinity toward the nanocrystal surface and engage in a highly dynamic adsorption/desorption equilibrium. We thus conclude that hot injection yields MoS2 colloids with comparable surfaces as those produced by LPE. These similarities might offer the prospect of using established procedures developed for LPE nanomaterials to postprocess colloidally synthesized dispersions of 2D colloids as processable inks.

Interactions of molybdenum disulfide nanosheets with wheat plants under changing environments: More than meets the eye?

Molybdenum disulfide (MoS2) nanosheets are being increasingly employed in various applications. It is therefore imperative to assess their potential environmental implications in a changing world, particularly in the context of global warming. Here, we assessed the effects of MoS2 nanosheets on wheat Triticum aestivum L. under today's typical climatic conditions (22 °C) and future climatic conditions (30 °C), respectively. The results showed that MoS2 nanosheets (10 and 100 Mo mg/L) did not significantly affect wheat plant growth, root morphological traits, and chlorophyll fluorescence, regardless of dose and temperature. However, the metabolic processes were significantly altered in T. aestivum upon exposure to individual MoS2 nanosheets and to a combination of MoS2 nanosheets and future global warming. As a non-specific protective strategy, the wheat plants that were under stress conditions maintained the stability of cell membranes and thus relieved cell injury by accumulating more glycerophospholipids. Warming additionally influenced the nitrogen and carbon pool reallocation in wheat root. MoS2 nanosheets mainly depleted a range of antioxidant metabolites involved in phenylpropanoid biosynthesis and taurine and hypotaurine metabolism, while warming activated vitamin B6 cofactors related to vitamin B6 metabolism. Metabolites involved in glutathione metabolism were uniquely upregulated while most metabolites associated with nucleotide metabolisms were uniquely downregulated in combination-treated wheat. Overall, wheat plants regulated a wide range of growth-related processes, including carbohydrate, amino acids, lipid, vitamins, and nucleotide metabolism, to maintain optimal metabolite pool sizes and eventually global metabolic homeostasis upon different stress conditions. Our findings provide novel insights into MoS2 nanosheets-mediated crop responses under global warming.

Fabrication of La‐Doped MoS2 Nanosheets with Tuned Bandgap for Dye Degradation and Antimicrobial Activities, Experimental and Computational Investigations

AbstractThe development of efficient catalysts with a large number of active sites, tunable bandgap, and large surface area has been very challenging. In addition, a significant bottleneck in the application of catalysts for water treatment is their dissolution under extreme conditions, such as highly acidic or highly alkaline conditions that lead to poor application of the reported materials in real‐world applications. In this study, the lanthanum (La)‐doped molybdenum disulfide (MoS2) nanosheets are reported for efficient breakdown of toxic pollutants from wastewater under a wide pH range from strongly alkaline to strongly acidic solutions. The La‐MoS2 nanosheets (NSs) are prepared by a facile hydrothermal approach using a two‐step methodology. A redshift is observed upon La doping, indicating that the bandgap is lowered after La doping in MoS2. The changes in bandgap and electronic structure are further investigated using the density functional theory (DFT), which reveal that doping of La introduces new states within the bandgap region, allowing for further induced energy transitions. The La‐MoS2, having a doping concentration of 2%, exhibits the highest catalytic activity against methylene blue (MB) in neutral, acidic, and alkaline solutions, as well as substantial inhibitory activity for bacterial strains such as Escherichia coli (E. coli). In summary, the modified catalyst provides a pathway to design highly efficient catalysts for all pH range water treatment as well as good activity against microbes.

Abstract 820: Photo-activatable ON-OFF microparticles for on-demand pulsatile drug delivery in a breast cancer model

Abstract The ability to treat tumors with high efficacy in a local microenvironment, while mitigating the side effects of systemic toxicity is an area of active investigation. Towards this goal, designing a minimally-invasive local therapeutic modality, with a controlled, pulsatile drug release mechanism is an attractive proposition. In this study, a near-infrared (NIR) photo-activatable microparticle was developed for localized, pulsatile delivery of encapsulated anticancer drugs into the tumor with simultaneous thermal ablation, with controlled ON-OFF thermal cycles using NIR laser irradiation. The microparticles were fabricated using a poly(caprolactone) (PCL) matrix, containing 2D molybdenum disulfide (MoS2) nanosheets as the NIR-responsive photothermal agent, and doxorubicin or violacein, as hydrophilic and hydrophobic model anticancer drugs, respectively. Cubic microparticles of 200 µm size were fabricated by casting a polymer-MoS2-drug film on PDMS mold with loading efficiency of 2 μg MoS2 per particle, and 0.2-8 μg of drug per particle. A cytotoxicity assay was performed to test the efficacy of the loaded microparticles in reducing the viability of 4T1 murine-derived cell culture, using the ON-OFF laser switch mechanism. In order to select a suitable laser power and duration of treatment for in vivo studies, a Machine Learning algorithm based on a Random Forest classifier was trained, to arrive at the optimal treatment conditions: 0.4-0.5 W/cm2 of laser power at 808 nm, for 3 cumulative minutes of laser irradiation, to reach the target temperature of 50 °C, which activates PCL melting and subsequent drug release. The effect of pulsatile treatment was studied in vivo in a murine-derived 4T1 subcutaneous mouse model of breast cancer, using this photo-activatable ON-OFF switch mechanism, for up to 3 cycles of laser irradiation. As control groups, tumor only (no treatment), laser only (no drug or microparticle), drug only (no laser or microparticle), microparticles only (no drug or laser), and microparticles with laser (no drug) were studied. The cohorts receiving the photo-activated 3-cyclic treatment for both drugs showed increased median survival up to 40 days post tumor induction, compared to a median survival of 16 days for the control groups. Although one laser cycle was enough to trigger drug release, there was a significant shrinkage in the tumor volume noticed with 3 cycles, with eventual scarring and shedding of the tissue with no evidence of residual tumor at the primary site. While this cyclic drug release modality is very effective at treating the primary site, subsequent histopathology revealed that the aggressive tumor in some animals had metastasized to the liver and other organs. More work is ongoing to design better targeted approaches to deliver the drug-loaded microparticles to the site of metastatic tumors, to increase the survival prospects of this disease. Citation Format: Maria Kanelli, Neelkanth M. Bardhan, Morteza Sarmadi, Shahad Alsaiari, William Rothwell, Apurva Pardeshi, Angela M. Belcher, Ana Jaklenec, Robert S. Langer. Photo-activatable ON-OFF microparticles for on-demand pulsatile drug delivery in a breast cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 820.

Long-term exposure of molybdenum disulfide nanosheets leads to hepatic lipid accumulation and atherogenesis in apolipoprotein E deficient mice

Before their large-scale applications, it is necessary to understand the biological effects of nanomaterials. Although two-dimensional nanomaterials (2D NMs) molybdenum disulfide nanosheets (MoS2 NSs) are promising in biomedical fields, the current knowledge regarding their toxicities is inadequate. Using apolipoprotein E deficient (ApoE−/−) mice as a long-term exposure model, this study demonstrated that intravenous (i.v.) injection of MoS2 NSs most accumulated in the liver and caused in situ hepatic damage. Histopathological examination indicated severe infiltration of inflammatory cells and irregular central veins in the MoS2 NSs-treated mouse liver. Meanwhile, the overwhelming expressions of inflammatory cytokines, dyslipidemia, and dysregulated hepatic lipid metabolism implied the potential vascular toxicity of MoS2 NSs. Indeed, our result supported that MoS2 NSs exposure is highly associated with atherosclerotic progression. This study provided the first line of evidence on the vascular toxicity of MoS2 NSs, which remind scientists to pay attention to the rational use of MoS2 NSs, especially in the biomedical fields.

Boosting flame retardancy of thermoplastic polyurethane: Synergistic effect of nickel phosphide nanoparticles and molybdenum disulfide nanosheets

AbstractFor the first time, a novel nanohybrid based on nickel phosphide (Ni2P) nanoparticles and molybdenum disulfide (MoS2) nanosheets was facilely synthesized for enhancing flame retardancy and smoke suppression of thermoplastic polyurethane (TPU). The synergistic effect on flame retardancy is proposed. TPU composite with 2 wt% Ni2P/MoS2 hybrid exhibits the best overall flame retardancy, while TPU composites with the same amount of individual Ni2P nanoparticles and MoS2 nanosheets are average in performance. Specifically, the 41.2% reduction of peak heat release rate (PHRR) is achieved for TPU/Ni2P/MoS2 composite, which is only 16.8% and 26.4% for TPU/Ni2P and TPU/MoS2 composites, respectively. In addition, a more intact protective char layer of TPU/Ni2P/MoS2 composite can be observed. These results clearly suggest the synergistic effect between Ni2P nanoparticles and MoS2 nanosheets. It is hypothesized that physical barrier effect and chemical catalytic ability of Ni2P/MoS2 hybrid contribute to the dramatic reduction of heat release and smoke production. The strategy proposed here is a simple yet efficient approach to fabricate high‐performance MoS2‐based flame retardants.

Precision electroforming of nickel nanocomposite mould for defects-free demoulding in polymer micro replication: Surface properties, performance validation and mould release mechanism

Microinjection moulding and micro/nano hot embossing are two promising manufacturing processes for the mass production of polymer workpieces with micro/nano structures. However, adhesion and friction between polymer workpieces and mould tools can cause structural distortion and surface damage. Besides, the nickel mould's lifetime is limited by its low hardness and wear resistance. To address these issues, we proposed a new methodology to codeposit micro/nanomaterials into nickel mould for microhardness enhancement and effective mould release. In this study, polytetrafluoroethylene (PTFE) microparticles, tungsten disulfide (WS2) and molybdenum disulfide (MoS2) nanosheets were incorporated into nickel mould by electroforming. Cobalt was added as a secondary phase to improve the microhardness and wear resistance of the composite mould. The result indicated that WS2 nanosheets achieved the most significant performance enhancement among three micro/nanomaterials, represented as the microhardness improved from 191 HV for pure nickel to 564 HV for nickel/WS2 nanocomposites, along with the coefficient of friction (COF) against the polymethyl methacrylate (PMMA) pin reducing from 0.72 to 0.10 in the initial stage of the sliding. With the incorporation of micro/nanomaterials, the wettability altered from hydrophilic for pure nickel to hydrophobic for the composite moulds. The study shows that the addition of cobalt improved the microhardness of the composite moulds but meanwhile induced more adhesive wear during the pin-on-disc test. Finally, a nickel/WS2 nanocomposite mould is successfully fabricated via electroforming with feature sizes from 70 to 180 μm and its lubricating properties are validated by micro hot embossing PMMA microfluidic chips with good surface quality and structural integrity.

Enhanced non-layer-dependent piezo-response in sailboat-like vertical molybdenum disulfide nanosheets for piezo-catalytic hydrogen evolution and dye degradation: Effect of microstructure and phase composition

The piezo-response of two-dimensional molybdenum disulfide(MoS2) only exists at the edge of odd-number layers. It’s crucial to design reasonable micro/nano-structures and construct tight interfaces to weaken layer-dependence, enhance energy harvesting, charge transfer and active sites exposure to improve piezoelectricity. The novel sailboat-like-vertical-MoS2-nanosheets(SVMS), in which abundant vertical MoS2 nanosheets(∼20 nm, 1–5 layers) are uniformly distributed on horizontal substrate of MoS2, with abundant vertical interfaces and controllable phase composition are prepared by facile method. The larger geometric-asymmetry enhances mechanical energy capture. Experiment and theory revealed the enhanced in-/out-of-plane polarization, higher piezo-response in multi-directions and abundant active edge sites of SVMS, thereby eliminating the layer-dependence and generating higher piezo-potential. Cooperating with the Mo-S bonds at vertical interfaces, free electrons-holes are efficiently separated and migrated. The piezo-degradation of Rhodamine B(RhB) and hydrogen evolution rate under ultrasonic/stirring are 0.16 min−1 and 1598 μmolg−1h−1 for SVMS(2H) with the highest piezo-response (under ultrasonic wave, stirring and water flow), which are over 1.6 and 3.1 times than few-layer MoS2 nanosheets. 94% RhB(500 mL) is degraded under water-flow(60 min). The mechanism was proposed. Overall, the design of SVMS with enhanced piezoelectricity was studied and modulated by regulating microstructure and phase composition, which has excellent application potential in fields of environment, energy and novel materials.