•TX100 strongly enhanced the adsorption and photodegradation of NOF in Bi2WO6 dispersions under visible light irradiation (400–750nm).•Cu2+ (10mM) significantly suppressed the photocatalytic ...degradation of NOF.•FT-IR demonstrated that the NOF adsorbed on Bi2WO6 was completely degraded.•Three possible photocatalytic degradation pathways of NOF were proposed, according to the HPLC/MS/MS analysis.
Photocatalytic degradation is an alternative method to remove pharmaceutical compounds in water, however it is hard to achieve efficient rate because of the poor solubility of pharmaceutical compounds in water. This study investigated the photodegradation of norfloxacin in a nonionic surfactant Triton-X100 (TX100)/Bi2WO6 dispersion under visible light irradiation (400–750nm). It was found that the degradation of poorly soluble NOF can be strongly enhanced with the addition of TX100. TX100 was adsorbed strongly on Bi2WO6 surface and accelerated NOF photodegradation at the critical micelle concentration (CMC=0.25mM). Higher TX100 concentration (>0.25mM) lowered the degradation rate. In the presence of TX100, the degradation rate reached the maximum value when the pH value was 8.06. FTIR analyses demonstrated that the adsorbed NOF on the catalyst was completely degraded after 2h irradiation. According to the intermediates identified by HPLC/MS/MS, three possible degradation pathways were proposed to include addition of hydroxyl radical to quinolone ring, elimination of piperazynilic ring in fluoroquinolone molecules, and replacement of F atoms on the aromatic ring by hydroxyl radicals.
Nanolayered coatings are proposed for use in microelectronic devices where the size/performance ratio is becoming increasingly important, with the aim to achieve existing quality requirements while ...reducing the size of the devices and improving their ability to perform stably over multiple cycles. Si-SiOsub.2-W structures have been proposed as a potential material for the fabrication of microelectronic devices. However, before such materials can be implemented in devices, their properties need to be carefully studied. In this study, Si-SiOsub.2-W nanolayered structures were fabricated and subjected to numerous thermal treatment cycles at 150 °C. A total of 33 heating cycles were applied, resulting in a cumulative exposure of 264 h. The changes in chemical bonds and microstructure were monitored using Fourier Transform Infrared spectrometry (FTIR) and scanning electron microscopy (SEM). The FTIR signal at 960 cmsup.−1, indicating the presence of W deposited on SiOsub.2, was selected to characterize the thermal stability during the heating cycles. The estimated signal intensity variation closely resembled the normal inhomogeneity of the nanolayers. The increase in slope intensity was estimated to be 1.7 × 10sup.−5.
Magic-angle twisted bilayer graphene (TBG), with rotational misalignment close to 1.1 degrees, features isolated flat electronic bands that host a rich phase diagram of correlated insulating, ...superconducting, ferromagnetic and topological phases1-6. Correlated insulators and superconductivity have been previously observed only for angles within 0.1 degree of the magic angle and occur in adjacent or overlapping electron-density ranges; nevertheless, the origins of these states and the relation between them remain unclear, owing to their sensitivity to microscopic details. Beyond twist angle and strain, the dependence of the TBG phase diagram on the alignment4,6 and thickness ofthe insulating hexagonal boron nitride (hBN)7,8 used to encapsulate the graphene sheets indicates the importance of the microscopic dielectric environment. Here we show that adding an insulating tungsten diselenide (WSe2) monolayer between the hBN and the TBG stabilizes superconductivity at twist angles much smaller than the magic angle. For the smallest twist angle of 0.79 degrees, superconductivity is still observed despite the TBG exhibiting metallic behaviour across the whole range of electron densities. Finite-magnetic-field measurements further reveal weak antilocalization signatures as well as breaking of fourfold spin-valley symmetry, consistent with spin-orbit coupling induced in the TBG via its proximity to WSe2. Our results constrain theoretical explanations for the emergence of superconductivity in TBG and open up avenues towards engineering quantum phases in moiré systems.
Monolayer tungsten disulphide (WS.sub.2) is a direct band gap semiconductor which holds promise for a wide range of optoelectronic applications. The large-area growth of WS.sub.2 has previously been ...successfully achieved using a W(CO).sub.6 precursor, however, this is flammable and a potent source of carbon monoxide (CO) upon decomposition. To address this issue, we have developed a process for the wafer-scale growth of monolayer WS.sub.2 from a tungsten hexachloride (WCl.sub.6) precursor in a commercial cold-wall CVD reactor. In comparison to W(CO).sub.6, WCl.sub.6 is less toxic and less reactive and so lends itself better to the large-scale CVD growth of 2D layers. We demonstrate that a post-growth H.sub.2S anneal can lead to a dramatic improvement in the optical quality of our films as confirmed by photoluminescence (PL) and Raman measurements. Optimised films exhibit PL exciton emission peaks with full width at half maximum of 51 ± 2 meV, comparable to other state-of-the-art methods. We demonstrate that our WS.sub.2 films can be readily transferred from the sapphire growth substrate to a Si/SiO.sub.2 target substrate with no detectable degradation in quality using a polystyrene support layer. Our approach represents a promising step towards the industrial-scale fabrication of p-n junctions, photodetectors and transistors based on monolayer WS.sub.2.
Inhibitions of amyloid β (Aβ) aggregation and Aβ-haem peroxidase-like activity have received much attention because these two symptoms can be the primary targets of therapeutic strategies for ...Alzheimer's disease (AD). Recently, our group found that polyoxometalate (POM) with a Wells-Dawson structure can efficiently inhibit Aβ aggregation. However, the interaction between POMs and Aβ is robust, but still needs to improve Aβ binding affinity. More importantly, it is unclear whether POMs can cross the blood-brain barrier and decrease Aβ-haem peroxidase-like activity. Here we show that our designed series of transition metal-functionalized POM derivatives with a defined histidine-chelated binding site have much better Aβ inhibition and peroxidase-like activity inhibition effects than the parent POM. More intriguingly, we show that these compounds can cross the blood-brain barrier and are metabolized after 48 h. Our work provides insights into the design, synthesis and screening of inorganic metal compounds as multifunctional therapeutic agents against AD.
We have developed a simple and efficient strategy to fabricate WS2 nanosheets with low toxicity and good water solubility via a liquid exfoliation method by using H2SO4 intercalation and ...ultrasonication. The as-prepared WS2 nanosheets were employed not only as an NIR absorbing agent for photothermal therapy (PTT) but also as a photosensitizer (PS) carrier for photodynamic therapy (PDT) due to their sheet like structure that offers large surface area to load PS molecules. Moreover, singlet-oxygen generation of the PSs-WS2 complex could be finely controlled by NIR irradiation that could manipulate the PSs release behavior from WS2 nanosheets. The synergistic anti-tumor effect of WS2 nanosheets mediated PDT-PTT was also evaluated carefully and the results clearly showed that the efficacy of combined PDT-PTT treatment of cancer cells is significantly higher than those of PDT-only and PTT-only treatment, indicating enhanced efficiency of the combined therapeutic system. In addition, the WS2 could be used as a computed tomography (CT) contrast agent for bio-imaging since W atoms have strong X-ray attenuation ability, making them a multifunctional theranostic platform for simultaneous imaging-guided diagnosis and therapy.
Antibodies are recognition molecules that can bind to diverse targets ranging from pathogens to small analytes with high binding affinity and specificity, making them widely employed for sensing and ...therapy. However, antibodies have limitations of low stability, long production time, short shelf life, and high cost. Here, we report a facile approach for the design of luminescent artificial antibodies with nonbiological polymeric recognition phases for the sensitive detection, rapid identification, and effective inactivation of pathogenic bacteria. Transition-metal dichalcogenide (TMD) nanosheets with a neutral dextran phase at the interfaces selectively recognized S. aureus, whereas the nanosheets bearing a carboxymethylated dextran phase selectively recognized E. coli O157:H7 with high binding affinity. The bacterial binding sites recognized by the artificial antibodies were thoroughly identified by experiments and molecular dynamics simulations, revealing the significance of their multivalent interactions with the bacterial membrane components for selective recognition. The luminescent WS2 artificial antibodies could rapidly detect the bacteria at a single copy from human serum without any purification and amplification. Moreover, the MoSe2 artificial antibodies selectively killed the pathogenic bacteria in the wounds of infected mice under light irradiation, leading to effective wound healing. This work demonstrates the potential of TMD artificial antibodies as an alternative to antibodies for sensing and therapy.
A van der Waals heterostructure built from atomically thin semiconducting transition metal dichalcogenides (TMDs) enables the formation of excitons from electrons and holes in distinct layers, ...producing interlayer excitons with large binding energy and a long lifetime. By employing heterostructures of monolayer TMDs, we realize optical and electrical generation of long-lived neutral and charged interlayer excitons. We demonstrate that neutral interlayer excitons can propagate across the entire sample and that their propagation can be controlled by excitation power and gate electrodes. We also use devices with ohmic contacts to facilitate the drift motion of charged interlayer excitons. The electrical generation and control of excitons provide a route for achieving quantum manipulation of bosonic composite particles with complete electrical tunability.
Synergistic directing roles of six lacunary fragments resulted in an unprecedented Zr24-cluster substituted poly(polyoxotungstate) Na10K22Zr24O22(OH)10(H2O)2(W2O10H)2(GeW9O34)4(GeW8O31)2·85H2O ...(Na10K22·1·85H2O), which contains the largest Zr24O22(OH)10(H2O)2 (Zr24) cluster in all the Zr-based poly(polyoxometalate)s to date. The most remarkable feature is that the centrosymmetric Zr24-cluster-based hexamer contains two symmetry-related Zr12O11(OH)5(H2O)(W2O10H)(GeW9O34)2(GeW8O31)(16-) trimers via six μ3-oxo bridges and was simultaneously trapped by three types of different segments of B-α-GeW9O34, B-α-GeW8O31, and W2O10. The other interesting characteristic is that there are two pairs of intriguing triangular atom alignments: one is composed of the Zr(2,4,6,8,11) and W21 atoms and the other contains the Ge(1-3), Zr(3,5,7,9,10,12) and W26 atoms, and the Zr5 atom is inside the triangle; a linking mode is unobserved. The oxygenation reactions of thioethers by H2O2 were evaluated when Na10K22·1·85H2O served as a catalyst. Results show that it is an effective catalyst for oxygenation of thioethers by H2O2. The unique redox property of oxygen-enriched polyoxotungstate fragments and Lewis acidity of the Zr cluster imbedded in Na10K22·1·85H2O provide a sufficient driving force for the catalytic conversion from thioethers to sulfoxides/sulfones.
Developing highly efficient Au/TiOsub.2/WOsub.3 heterostructures with applications in heterogeneous photocatalysis (photocatalytic degradation) and surface-enhanced Raman spectroscopy (dye detection) ...is currently of paramount significance. Au/TiOsub.2/WOsub.3 heterostructures were obtained via heat or time-assisted synthesis routes developed by slightly modifying the Turkevich-Frens synthesis methods and were investigated by TEM, SEM, XRD, Raman spectroscopy, XPS, photoluminescence, and UV-vis DRS techniques. Structural features, such as WOsub.3 crystalline phases, TiOsub.2 surface defects, as well as the WOsub.3 (220) to TiOsub.2-A (101) ratio, were the key parameters needed to obtain heterostructures with enhanced photocatalytic activity for removing oxalic acid, phenol, methyl orange, and aspirin. Photodegradation efficiencies of 95.9 and 96.9% for oxalic acid; above 96% (except one composite) for phenol; 90.1 and 97.9% for methyl orange; and 81.6 and 82.1% for aspirin were obtained. By employing the SERS technique, the detection limit of crystal violet dye, depending on the heterostructure, was found to be between 10sup.−7-10sup.−8 M. The most promising composite was Au/TiOsub.2/WOsub.3-HW-TA it yielded conversion rates of 82.1, 95.9 and 96.8% for aspirin, oxalic acid, and phenol, respectively, and its detection limit for crystal violet was 10sup.−8 M. Au/TiOsub.2/WOsub.3-NWH-HA achieved 90.1, 96.6 and 99.0% degradation efficiency for methyl orange, oxalic acid, and phenol, respectively, whereas its limit of detection was 10sup.−7 M. The Au/TiOsub.2/WOsub.3 heterojunctions exhibited excellent stability as SERS substrates, yielding strong-intensity Raman signals of the pollutant molecules even after a long period of time.
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