2D WS2 Nanosheets Research Articles

A Photoelectrochemical Sensor for the Sensitive Detection of Cysteine Based on Cadmium Sulfide/Tungsten Disulfide Nanocomposites.

In this work, a CdS-nanoparticle-decorated WS2 nanosheet heterojunction was successfully prepared and first used to modify ITO electrodes for the construction of a novel photoelectrochemical sensor (CdS/WS2/ITO). The thin-film electrode was fabricated by combining electrophoretic deposition with successive ion layer adsorption and reaction techniques. The results indicated that the synthesized heterojunction nanomaterials displayed excellent photoelectrochemical performance which was much better than that of pristine CdS nanoparticles and 2D WS2 nanosheets. Owing to the formation of the surface heterojunction and the effective interfacial electric field, the enhanced separation of photogenerated electron-hole pairs led to a remarkable improvement in the photoelectrochemical activity of CdS/WS2/ITO. This heterojunction architecture can protect CdS against photocorrosion, resulting in a stable photocurrent. Based on the specific recognition between cysteine and CdS/WS2/ITO, through the specificity of Cd-S bonds, a visible-light-driven photoelectrochemical sensor was fabricated for cysteine detection. The novel photoelectrochemical biosensor exhibited outstanding analytical capabilities in detecting cysteine, with an extremely low detection limit of 5.29 nM and excellent selectivity. Hence, CdS-WS2 heterostructure nanocomposites are promising candidates as novel advanced photosensitive materials in the field of photoelectrochemical biosensing.

Electrophoretic assisted fabrication of additive-free WS2 nanosheet anodes for high energy density lithium-ion batteries.

2D WS2 nanosheets (NSs) are gaining popularity in the domain of Li-ion batteries (LIBs) due to their unique structures, which can enable reversible insertion and extraction of alkali metal ions. While synthesis methods have mostly relied on the exfoliation of bulk materials or direct growth on substrates, here we report an alternative approach involving colloidal hot-injection synthesis of 2D WS2 in 2H and 1T' crystal phases followed by their electrophoretic deposition (EPD) on the current collector. The produced 2D WS2 NSs' films do not require any additional additives during deposition, which boosts the energy density of the additive-free LIBs produced. The 1T' and 2H NSs exhibit long-term stable cyclic performance at C/5 for 600 cycles. At a high cycling rate (1C), the 2H NSs outperform the 1T' NSs, delivering a 1st cycle reversible capacity of 513 mA h g-1 with capacity retention of 73% after 100 cycles (compared to 205 mA h g-1, and 84 mA h g-1 respectively for NS-1T'). Post-cycling investigation confirms that there is no leaching or cracking of the active material on the surface of anodes after 100 cycles at C/5, which enables mechanical stability, and impressive battery performance of the WS2 NS electrodes.

Probe ultrasonication synthesis of Eu2O3-doped 2D WS2 nanosheets for highly selective and sensitive quantification of human catecholamines by fluorescent quenching and shifting

Tungsten disulfide (WS2) nanosheets have been intensively investigated in many fields due to their high crystallinity, outstanding electrochemical properties, and structural integrity. A cutting-edge bottom-up approach with the assistance of probe ultrasonication and annealing was used to synthesize 2D WS2 nanosheets. These nanosheets were modified by probe ultrasonication-assisted doping of Eu2O3 to obtain the reddish-orange color fluorescence with a 68.32% relative quantum yield. This as-synthesized material was used to develop a quenching and shifting associated turn-off turn-on combined type bio-sensor for the detection of human catecholamines. It showed a perfect and wide linear range of 50–800 µM for norepinephrine, epinephrine, and dopamine while the reported detection limits were 0.36 µM, 0.91 µM, and 0.15 µM, respectively. It showed a great recovery of 95% for the human urine sample analysis with spiked analytes. In addition, this could be used as a drug quality assurance option for neurotransmitter drugs.

Confined oxidation of 2D WS2 nanosheets forming WO3/WS2 nanocomposites for room temperature NO2 gas sensing application

In this article, we synthesized WO3/WS2 nanocomposites by facile hydrothermal synthesis followed by thermal annealing treatment and analysed its gas sensing properties. The thermal annealing process was carried out in different temperatures from 400 ℃ to 600 ℃ to form WO3/WS2 nanocomposite. During the thermal annealing process, the hydrothermally synthesized pure WS2 nanosheets undergo partial oxidation constructing WO3 on the surface developing active heterojunctions leading to increment in the sensing performance. The fabricated WO3/WS2 samples showed superior sensitivity and selectivity towards NO2 gas molecules. The pristine WS2 nanosheets showed a response of 26% towards 10 ppm of NO2 gas with a response and recovery time of 13 s /18 s, whereas WO3/WS2 nanocomposite prepared by annealing at 600 ℃ showed a maximum response of around 123% with a short response time of 11 s and recovery time of 163 s. The DFT calculations were performed to understand the gas sensing performance and interfacial charge transfer between the WO3/WS2 nanocomposite and gas molecules. Therefore, this study demonstrates that the indigenous heterojunctions contribute extensively to improving the gas detection capabilities of WO3/WS2 nanocomposites at room temperature.

Synthesis of highly efficient novel two-step spatial 2D photocatalyst material WS2/ZnIn2S4 for degradation/reduction of various toxic pollutants

In this article, we report the synthesis, characterization of novel biofriendly 2D/2D heterostructure WS2/ZnIn2S4 material in which 2D WS2 nanosheets are uniformly distributed spatially onto the spherically arranged 2D leaves of ZnIn2S4. We then studied the in-depth photocatalytic degradation activity of this novel nanocomposite and its pristine component materials on cationic dye: malachite green, anionic dye: congo red and reduction of heavy metal: chromium(VI) and the degradation efficiency of composite material was also tested on rhodamine-B, methylene blue, methyl orange dyes and acetaminophen/paracetamol drug. Form factor, structure factor and shape factor analysis has been carried out using X-ray diffractometry (XRD). Bond vibrations, functional groups and phonon vibration mode analysis has been done based on Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. Morphological and compositional analysis has been done using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDAX) and X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM). Surface area and pore size/distribution was characterized using Brunauer–Emmett–Teller (BET) method and Barrett-Joyner-Halenda Model. Degradation pathways and intermediate products are proposed using the high-performance liquid chromatography (HPLC). Photocatalytic activity of the nanocomposite WS2/ZnIn2S4 is compared with pristine ZnIn2S4 and pristine WS2, which shows more than 50% enhancement in both efficiency and rate of degradation/reduction for all the pollutants. A scavenger study was carried out to get insight of primary and secondary reactive oxygen species (ROS) taking part in degradation. Exciton lifetime, surface charge and stability, and flat band positions were studied based on time-correlated single photon counting (TCSPC) also known as time-resolved photoluminescence (TRPL), zeta potential, and Mott-Schottky respectively. Rate kinetics study was performed to analyze the physical and chemical behaviour of the nanocomposite with pollutants in consideration. Results show ∼100%, ∼90%, and ∼95% degradation efficiency by the heterostructure for malachite green (MG), congo red (CR), and reduction of heavy metal chromium (Cr(VI)) respectively within 5 min, which is a huge improvement as compared to pristine WS2 and pristine ZnIn2S4, both of which show the efficiencies of only ∼25% to∼75% in all the cases.

Synergetic electrochemical performance of tungsten oxide/tungsten disulfide/MWCNTs for high-performance aqueous asymmetric supercapattery devices

In this work, a binary WO3/WS2 nanocomposite is synthesized by a single-step sulfurization of WO3 through chemical vapor deposition (CVD) process. Then the synthesized composite was blended with MWCNTs to produce a WO3/WS2/MWCNTs ternary composite for a high-performance supercapacitor. X-ray diffraction, Raman, and X-ray photoelectron spectroscopy were used to investigate comprehensively structural characteristics and chemical bonding of the synthesized nanocomposite. FESEM reveals that agglomeration of 1D MWCNTs, and 2D WS2 nanosheets with WO3 nanoparticles enhance the surface area as well as conductivity of electrode material which in turn leads to superior electrochemical properties of the ternary nanocomposite. The electrochemical measurements suggest that the WO3/WS2/MWCNTs composite is the best-optimized electrode with a specific capacitance of 517 C/g. By employing the optimized electrode as positive and activated carbon (AC) treated as a negative electrode an asymmetric supercapattery (ASC) device was assembled. The ASC device displays a high energy density of 86 Wh/kg and power density of 11828 W/kg with only 5 % degradation in initial capacitance after 5000 continuous cycles. In conclusion, composting is a promising approach to boost the overall performance of supercapacitors.

Piezocatalytic 2D WS2 Nanosheets for Ultrasound‐Triggered and Mitochondria‐Targeted Piezodynamic Cancer Therapy Synergized with Energy Metabolism‐Targeted Chemotherapy (Adv. Mater. 18/2023)

Piezodynamic Cancer Therapy In article number 2300437, Tae Il Lee, Min Suk Shim, and co-workers develop piezocatalytic 2D WS2 nanosheets incorporated with mitochondria-targeting moieties and glycolysis inhibitors. The piezoelectric 2D WS2 nanosheets efficiently generate reactive oxygen species by piezoelectric polarization under ultrasound irradiation. The WS2 nanosheets enable the selective and effective treatment of tumors via ultrasound-triggered and mitochondria-targeted piezodynamic therapy synergized with energy metabolism-targeted chemotherapy.

Piezocatalytic 2D WS2 Nanosheets for Ultrasound-Triggered and Mitochondria-Targeted Piezodynamic Cancer Therapy Synergized with Energy Metabolism-Targeted Chemotherapy.

Piezoelectric nanomaterials that can generate reactive oxygen species (ROS) by piezoelectric polarization under an external mechanical force have emerged as an effective platform for cancer therapy. In this study, piezoelectric 2D WS2 nanosheets are functionalized with mitochondria-targeting triphenylphosphonium (TPP) for ultrasound (US)-triggered, mitochondria-targeted piezodynamic cancer therapy. In addition, a glycolysis inhibitor (FX11) that can inhibit cellular energy metabolism is loaded into TPP- and poly(ethylene glycol) (PEG)-conjugated WS2 nanosheet (TPEG-WS2 ) to potentiate its therapeutic efficacy. Upon US irradiation, the sono-excited electrons and holes generated in the WS2 are efficiently separated by piezoelectric polarization, which subsequently promotes the production of ROS. FX11-loadedTPEG-WS2 (FX11@TPEG-WS2 )selectively accumulates in the mitochondria of human breast cancer cells. In addition, FX11@TPEG-WS2 effectively inhibits theproduction of adenosine triphosphate . Thus, FX11@TPEG-WS2 exhibits outstanding anticancer effects under US irradiation. An in vivo study using tumor-xenograft mice demonstrates that FX11@TPEG-WS2 effectively accumulated in the tumors. Itstumor accumulation is visualized using in vivo computed tomography . Notably, FX11@TPEG-WS2 with US irradiation remarkably suppresses the tumor growth of mice without systemic toxicity. This study demonstrates that the combination of piezodynamic therapy and energy metabolism-targeted chemotherapy using mitochondria-targeting 2D WS2 is a novel strategy for the selective and effective treatment of tumors.

Fabrication of gold nanodots decorated on 2D tungsten sulfide (Au-WS2) photoanode for simultaneous oxidation of phenol and arsenic (III) from industrial wastewater

Two dimensional (2D) photoelectrocatalysts with a tunable band gap and a large surface area have emerged in recent years for advanced oxidation processes that remove toxic compounds from wastewater. In this study, ultra-thin 2D tungsten sulfide (2D WS2) photoelectrocatalysts have been fabricated using organosulfur sources, and the resulting 2D WS2 has high chemical stability and visible light band edges. Additionally, citrate stabilized Au nanodots were successfully incorporated into the 2D WS2 nanosheets in order to reduces the charge carrier recombination. The morphology, composition, chemical state, and optical properties of the Au-WS2 photoanodes have been systematically investigated. An Au-WS2 photoanode is successfully assembled in a photoelectrochemical cell (PEC) for removing phenol and oxidizing toxic As(III) into non-toxic As(V) under visible light. The studies show that the Au-WS2 photoanode had an oxidation efficiency of 99% for phenol and 95% for As(III) under visible light illumination. Furthermore, X-ray photoelectron spectroscopy (XPS) and theoretical analyses were used to investigate the oxidation pathways of phenol and As(III). A reachability study was carried out to demonstrate that mixed synthetic wastewater containing phenol and arsenite could be used for extended periods in a practical manner. In this study, Au-WS2 photoanodes were demonstrated to be highly effective in enhancing environmental remediation using advanced oxidation methods.

Novel organophosphonate-decorated WS2 nanosheets towards flame retardancy and mechanical enhancement of epoxy resin

By noncovalently surface-modifying 2D WS2 nanosheets (WC) with in situ generated iron ethylenediamine tetramethylene phosphonate (FeP), novel organophosphonate-decorated nanosheets (WC@FeP) were designed and prepared. Combining the physical barrier effects of WC nanosheets with the catalytic charring activity of FeP, WC@FeP improved the flame retardancy of the epoxy resin (EP), including heat inhibition and smoke suppression. Compared with those of neat EP, the EP composites containing 8 wt% of the WC@FeP (EP/8WC@FeP) passed a UL94 V-0 rating with a LOI value increased from 22.5 to 29.5 vol%. Furthermore, the peak heat release rate (PHRR), total heat release rate (THR), and total smoke release (TSP) of EP/8WC@FeP were remarkably reduced by 58.2%, 25.1%, and 44.5%, respectively. In addition, thanks to the large aspect ratio of the decorated nanosheets with flexible-but-tough nature, WC@FeP effectively enhanced the mechanical properties of the composites, in which the tensile strength and modulus of EP/8WC@FeP were enhanced by 23% and 24%, respectively, without sacrificing the toughness. Taking advantage of these features, the surface organo-decoration of 2D nanosheets broadens their applications in polymeric materials.

Facile and novel preparation of 2D-MoS2/carbon nanodots composite with high adsorption efficiency and capacity for dye removal

Here, hydrophobic bulk molybdenum disulfide (MoS2) was efficiently exfoliated into two dimensional (2D) nanosheets assisted with amphiphilic carbon nanodots (CNDs) in pure water. The optimized concentration of obtained 2D-MoS2 is as high as 0.41 mg/mL, which is higher than that of reported literatures. The average lateral size and layer number of 2D-MoS2 is 142.6 (±2.3) nm and 4, respectively. The characterizations and simulation demonstrated that CNDs can be instantly adsorbed on the surface of 2D-MoS2 and form 2D-MoS2/CNDs composite. Thus, after standing for 1000 h, the concentration of 2D-MoS2 still accounts for 90 % of the initial concentration with the help of CNDs. Further, this technique can also be used to prepare graphene and 2D-WS2 nanosheets. 2D-MoS2/CNDs composite as adsorbent showed excellent adsorption capacity (1136.9 mg/g) and ultrafast adsorption rate (1 min) for methylene blue removal, which benefits from abundant adsorption sites and high dispersion. This work not only develops a facile and universal technique for green preparation of 2D nanomaterials in one pot, but also provides a promising adsorbent for removing organic pollutants from aqueous solution.

Ultrahigh photocatalytic hydrogen evolution performance of coupled 1D CdS/1T-phase dominated 2D WS2 nanoheterojunctions

Solar-powered photocatalytic hydrogen production from water using semiconductors provides an eco-friendly and promising approach for converting solar energy into hydrogen fuel. Bulk semiconductors generally suffer from certain limitations, such as poor visible-light utilization, rapid recombination of charge carriers, and low catalytic capability. The key challenge is to develop visible-light-driven heterojunction photocatalysts that are stable and highly active during the water splitting process. Here, we demonstrate the integration of one-dimensional (1D) CdS nanorods with two-dimensional (2D) 1T-phase dominated WS2 nanosheets for constructing mixed-dimensional heterojunctions for the photocatalytic hydrogen evolution reaction (HER). The resulting 1D CdS/2D WS2 nanoheterojunction exhibited an ultrahigh hydrogen-evolution activity of ∼70 mmol·g−1·h−1 that was visible to the naked eye, as well as long-term stability under visible light illumination. The results reveal that the synergy of hybrid nanoarchitectures and intimate interfacial contact between the 1D CdS nanorods and 1T-phase dominated 2D WS2 nanosheets facilitates charge carrier transport, which is beneficial for achieving superior hydrogen evolution.

Cataluminescence on 2D WS2 nanosheets surface for H2S sensing

In the present work, two-dimensional (2D) transition metal dichalcogenides (TMDs) WS2 nanosheets, which was synthesized through simple ultrasonic-assisted liquid exfoliation, was used for constructing H2S CTL gas sensor for the first time. With respect to other H2S CTL gas sensors based on metal oxides and metal-free materials, this sensor based on WS2 nanosheets is outstanding in H2S sensing with excellent properties at relative low temperature of 187 ℃. Furthermore, both of the response and recovery time are as fast as 0.2 s with linear range of 0.26–6.38 µg mL−1 (R2 =0.9933) and detection limit of 0.06 µg·mL−1 (S/N = 3). The characterization results showed that as-prepared WS2 nanosheets had larger surface, richer edges and more sulfur defects by comparing with bulk WS2, which are beneficial for catalytic performance improving. Importantly, the possible mechanism is proposed. In detail, some amount of WO3 were in-situ generated forming WS2/WO3 hybrids, and WO3 could keep exchange balance with WS2 during H2S sensing attributed to repeatable S-O bonding exchange. This is crucial for the repeatability of the sensor. This work provides a new view for CTL gas sensing mechanism and may open a new avenue of applying TMDs in H2S CTL sensors.

The first report on formation of Al-W-Cu grain boundary phase and its influence on mechanical behavior of 2D-WS2 reinforced Al-4Cu alloy matrix composites

Nanostructured two-dimensional (2D) WS2 reinforced Al-4Cu alloy matrix composites were prepared via spark plasma sintering (SPS) at 550 and 570 °C. The microstructure and interface characteristics of the composites were investigated. In situ formation of Al-W-Cu ternary phase at the grain boundaries of the Al-rich matrix phase was observed on sintering. High-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) with quantitative mapping confirmed that the structure of ternary Al-W-Cu (Al12W0.6Cu0.4) belongs to bcc phase (space group: Im3̅ (204), similar to that of binary bcc-Al12W phase. Such bcc intermetallic phase was absent in pure Al-matrix under identical sintering conditions. The ternary intermetallic phase along with the retained 2D-WS2 contributed to about 41% increase in the hardness of the alloy composite. Nanoindentation hardness and Young’s modulus of the Al-W-Cu ternary intermetallic were found to be around 4.6 GPa and 104 GPa, respectively. The formation mechanism of Al-W-Cu intermetallic phase from 2D-WS2 nanosheets and Al-4Cu matrix was elucidated with Calphad (Calculation of Phase Diagrams)-based Gibbs energy analysis.

A high performance self-powered photodetector based on a 1D Te-2D WS2 mixed-dimensional heterostructure.

One-dimensional (1D)–two-dimensional (2D) van der Waals (vdWs) mixed-dimensional heterostructures with advantages of an atomically sharp interface, high quality and good compatibility have attracted tremendous attention in recent years. Herein, a mixed-dimensional vertical heterostructure is constructed by transferring mechanically exfoliated 2D WS2 nanosheets on epitaxially grown 1D tellurium (Te) microwires. According to the theoretical type-II band alignment, the device exhibits a photovoltaic effect and serves as an excellent self-powered photodetector with a maximum open-circuit voltage (Voc) up to ∼0.2 V. Upon 635 nm light illumination, the photoresponsivity, external quantum efficiency and detectivity of the self-powered photodetector (SPPD) are calculated to be 471 mA W−1, 91% and 1.24 × 1012 Jones, respectively. Moreover, the dark current of the SPPD is highly suppressed to the sub-pA level due to the large lateral built-in electric field, which leads to a high Ilight/Idark ratio of 104 with a rise time of 25 ms and decay time of 14.7 ms. The abovementioned properties can be further enhanced under a negative bias of −2 V. In brief, the 1D Te–2D WS2 mixed-dimensional heterostructures have great application potential in high performance photodetectors and photovoltaics.

Vertically-Oriented WS2 Nanosheets with a Few Layers and Its Raman Enhancements.

Vertically-oriented two-dimensional (2D) tungsten disulfide (WS2) nanosheets were successfully grown on a Si substrate at a temperature range between and 550 °C via the direct chemical reaction between WCl6 and S in the gas phase. The growth process was carefully optimized by adjusting temperature, the locations of reactants and substrate, and carrier gas flow. Additionally, vertically-oriented 2D WS2 nanosheets with a few layers were tested as a surface-enhanced Raman scattering substrate for detecting rhodamine 6G (R6G) molecules where enhancement occurs from chemical enhancement by charge transfer transition from semiconductor). Raman spectra of R6G molecules adsorbed on vertically-oriented 2D WS2 nanosheets exhibited strong Raman enhancement effects up to 9.2 times greater than that on the exfoliated WS2 monolayer flake sample. From our results, we suggest that the WS2 nanosheets can be an effective surface-enhanced Raman scattering substrate for detecting target molecules.

Hierarchically flower-like WS2 microcrystals for capture and recovery of Au (III), Ag (I) and Pd (II)

In the past few years, two-dimensional (2D) nanomaterials have emerged great potential for the removal of valuable metals and the capture of polluted-heavy metals. Herein, hierarchically flower-like microcrystals with 2D WS2 nanosheets (F-WS2 MCs) were prepared by one-pot hydrothermal synthesis strategy and its adsorption performances for precious metals were systematically assessed. The excellent adsorption efficiencies of ∼86.8%, ∼27.6%, and ∼94.1% towards Ag (I), Pd (II), and Au (III) respectively were achieved within 120 min, and the adsorption curves were in good agreement with a pseudo-second-order kinetic model showing a fast uptake rate at the optimum pH values (1.30 for Au (III), 1.43 for Ag (I), and 3.20 for Pd (II)). The adsorption isotherm followed well in the Langmuir model with the maximum removal capacities (qmax) of 186.2 mg g−1 for Ag (I), 67.29 mg g−1 for Pd (II), and 1340.6 mg g−1 for Au (III), respectively. Furthermore, for recycling purposes, the relevant desorption solution was investigated with different ratios of monobasic acid and thiourea, suggesting the best desorption efficiency of 93.03%, 88.08%, and 85.34% for Ag (I), Pd (II), and Au (III), respectively. By characterizing the crystalline phase, and micromorphology element mapping of F-WS2 MCs before and after adsorption, the strong affinity and significant adsorption–reduction were indicated to dominate the adsorption process. Therefore, this work broadens the application range of WS2 microcrystals, providing an alternative material for capturing precious metals and wastewater treatment applications.

Self‐Assembling of Conductive Interlayer‐Expanded WS2 Nanosheets into 3D Hollow Hierarchical Microflower Bud Hybrids for Fast and Stable Sodium Storage

AbstractTransition‐metal dichalcogenides have emerged as promising anodes of sodium ion batteries (SIBs). Their practical SIB application calls for an easy‐to‐handle synthetic technique capable of fabricating favorable properties with high conductivity and stable structure. Here, a solvothermal strategy is reported for bottom‐up self‐assembling of nanoflowers' building block, i.e., conductive interlayer‐expanded 2D WS2 nanosheets thanks to in situ interlayer modification by nitrogen‐doped carbon matrix, into 3D hollow microflower bud‐like hybrids (H‐WS2@NC). The 3D nano/microhierarchical hollow structures are constructed by conductive interlayer‐expanded WS2 nanosheets' building blocks, providing abundant channels facilitating mass transport/electrons transfer, robust protection layer to avoid the direct contact between WS2 nanosheets and electrolyte, sufficient inner space for accommodating volume variation, and decreased ions diffusion energy barrier for accelerating electrochemical kinetics, as revealed by density functional theory calculations. As such, the 3D H‐WS2@NC hybrids exhibit quite attractive sodium storage performance with high reversible capacity, superior rate capability, and impressively long cycling life. The 3D H‐WS2@NC is further verified as anode of sodium‐ion full cell pairing with Na3V2(PO4)3/rGO cathode, delivering a stable reversible capacity of 296 mAh g−1 at 0.5 A g−1 with high energy density of 128 Wh kg−1total at a power density of 386 W kg−1total.

Mixed matrix membranes composed of WS2 nanosheets and fluorinated poly(2,6-dimethyl-1,4-phenylene oxide) via Suzuki reaction for improved CO2 separation

A method of introducing trifluoromethyl group (-CF3) to the polymer backbone by Suzuki reaction was developed to prepare fluorinated polymers for gas separation. The CO2 permeability increased 119% after the -CF3 group was substituted. Tungsten disulfide (WS2), a graphene-like two-dimensional material, was used for first time as an inorganic filler to prepare composite MMMs to separate CO2, N2 and CH4. The introduction of WS2 nanosheets increases more transport channels for gas molecules, which lead to the permeability and selectivity of MMMs obviously improved in comparison with the pristine FPPO membrane. The CO2/N2 selectivity and CO2/CH4 selectivity of 10 wt% WS2-FPPO MMMs reached a maximum about 29.6 and 39.4, respectively, with a CO2 permeability of 472 Barrer at 10 psig and 291 K. The best performance of MMMs for CO2/N2 and CO2/CH4 surpasses the Robeson's upper bound line. The MMMs showed strong stability in long-term observation. The results indicated a new direction for CO2 separation by introducing -CF3 group to polymer and using 2D WS2 nanosheets as nanofiller.

Fluorescent 2D WS2 Nanosheets Bearing Chemical Affinity Elements for the Recognition of Glycated Hemoglobin.

It is required to exfoliate and functionalize 2D transition metal dichalcogenides (TMDs) in an aqueous solution for biological and medical applications. Herein, the approach for the simultaneous exfoliation and functionalization of 2D WS2 nanosheets using boronic acid-modified poly(vinyl alcohol) (B-PVA) in an aqueous solution is reported, and the B-PVA-functionalized WS2 nanosheets (B-PVA-WS2 ) are exploited as a fluorescent biosensor for the detection of glycated hemoglobin, HbA1c. The synthetic B-PVA polymer facilitates the exfoliation and functionalization of WS2 nanosheets from the bulk counterpart in the aqueous solution via a pulsed sonication process, resulting in fluorescent B-PVA-WS2 nanohybrids with a specific recognition of HbA1c. The fluorescence of the B-PVA-WS2 is quenched in the presence of HbA1c, whereas PVA-functionalized WS2 (PVA-WS2 ), not bearing boronic acid as a recognition moiety, shows no fluorescence changes upon the addition of the target. The B-PVA-WS2 is able to selectively detect HbA1c at the concentration as low as 3.3 × 10-8 m based on its specific fluorescence quenching.