Thin films of mixed MoOsub.3 and WOsub.3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) ...properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoOsub.3/WOsub.3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoOsub.3. Our combinatorial approach allows the localization of the maximum at 5% accuracy.
Polyoxometalates are clusters of metal-oxide units, comprising a large diversity of nanoscale structures, and have many common building blocks; in fact polyoxometalate clusters are perhaps the ...largest non-biologically derived molecules structurally characterised. Not only can polyoxometalates have gigantic nanoscale molecular structures, but they also a have a vast array of physical properties, many of which can be specifically 'engineered-in'. Here we describe how building block libraries of polyoxometalates can be used to construct systems with important catalytic, electronic, and structural properties. We also show that it is possible to construct complex chemical systems based upon polyoxometalates, manipulating the templating/self templating rules to exhibit emergent processes from the molecular to the macroscopic scale.
Tungsten disulfide polycrystalline microfibers were successfully synthesized by a process involving electrospinning, calcination, and sulfidation steps. We used an aqueous solution of silicotungstic ...acid (H.sub.4SiW.sub.12O.sub.40) and polyvinyl alcohol as precursors for the synthesis of composite fibers by the needle-less electrospinning technique. The obtained green composite fibers (av. diam. 460 nm) were converted by calcination in air to tungsten oxide WO.sub.3 fibers with traces of SiO.sub.2 and a smaller diameter (av. diam. 335 nm). The heat treatment of the WO.sub.3 fibers under flowing H.sub.2/H.sub.2S/N.sub.2 stream led to conversion to tungsten disulfide WS.sub.2 with retention of the fibrous morphology (av. diam. 196 nm). Characterization of the intermediate and final fibers was performed by the XRD, SEM, TEM, HAADF STEM EDS, elemental analyses ICP-OES, and IR spectroscopy methods. Graphical abstract
Modern chemical production processes often emit complex mixtures of gases, including hazardous pollutants such as NOsub.2. Although widely used, gas sensors based on metal oxide semiconductors such ...as WOsub.3 respond to a wide range of interfering gases other than NOsub.2. Consequently, developing WOsub.3 gas sensors with high NOsub.2 selectivity is challenging. In this study, a simple one-step hydrothermal method was used to prepare WOsub.3 nanorods modified with black phosphorus (BP) flakes as sensitive materials for NOsub.2 sensing, and BP-WOsub.3-based micro-electromechanical system gas sensors were fabricated. The characterization of the as-prepared BP-WOsub.3 composite through X-ray diffraction scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the successful formation of the sandwich-like nanostructures. The result of gas-sensing tests with 2–14 ppm NOsub.2 indicated that the sensor response was 1.25–2.21 with response–recovery times of 36 and 36 s, respectively, at 190 °C. In contrast to pure WOsub.3, which exhibited a response of 1.07–2.2 to 0.3–5 ppm Hsub.2S at 160 °C, BP-WOsub.3 showed almost no response to Hsub.2S. Thus, compared with pure WOsub.3, BP-WOsub.3 exhibited significantly improved NOsub.2 selectivity. Overall, the BP-WOsub.3 composite with sandwich-like nanostructures is a promising material for developing highly selective NOsub.2 sensors for practical applications.
In this work, Cusub.2WSsub.4 nanoparticles have been synthesized via a solvothermal decomposition approach using a heterobimetallic single source precursor, WCusub.2Ssub.4(PPhsub.3)sub.3. The single ...source precursor, WCusub.2Ssub.4(PPhsub.3)sub.3, has been characterized using multinuclear NMR spectroscopy, while Cusub.2WSsub.4 nanoparticles have been characterized by powder X-ray diffraction (PXRD) for which Rietveld refinement has been performed to authenticate the lattice structure of the decomposed product, Cusub.2WSsub.4. Furthermore, FESEM and EDAX analyses have been performed to assess the morphology and composition of Cusub.2WSsub.4. An electrochemical study in acidic as well as basic media suggested that Cusub.2WSsub.4 nanoparticles possess efficient bifunctional activity towards electrochemical hydrogen as well as oxygen evolution reactions. Linear sweep voltammetry (LSV) performed in 0.5 N Hsub.2SOsub.4 indicates an onset potential for the HER of 462 mV and a Tafel slope of 140 mV decsup.−1. While LSV performed in 0.1 M KOH indicates an onset potential for the OER of 190 mV and a Tafel Slope of 117 mV decsup.−1.
A novel TiO.sub.2-supported vanadium-substituted tungstophosphoric acid (PW.sub.11V/TiO.sub.2) catalyst was designed and applied for selective catalytic reduction of NO.sub.x by NH.sub.3. Compared ...with the commercial tungstophosphoric acid (PW.sub.12/TiO.sub.2), PW.sub.11V/TiO.sub.2 displayed a nearly 90% activity improvement at 300 °C. In addition, the favorable resistance and stability to SO.sub.2 were also obtained over PW.sub.11V/TiO.sub.2 catalyst. Phase analysis and spectroscopy results indicated the vanadium was successfully incorporated into the molecular structure of PW.sub.12, and the Keggin framework still keep stable over the TiO.sub.2 support. H.sub.2-TPR test proved the incorporation of vanadium promoted the redox ability of PW.sub.11V. The present study provides us an effective way to improve the performance of catalytic removal of NO.sub.x through tungstophosphoric acid catalyst. Graphic After introduction of V species, the obtained PW.sub.11V/TiO.sub.2 catalyst show better NH.sub.3-SCR performance and N.sub.2 selectivity than PW.sub.12/TiO.sub.2 catalyst.
In the present study, we perform a systematic examination of the products formed by mixing and heating of tungsten boride and iridium powders at different ratios in a broad temperature range using ...qualitative and quantitative X-ray analysis and time-of-flight neutron diffraction (TOF-ND), in combination with scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) performed at different accelerating voltages. The well-known and unknown ternary W-Ir-B phases were detected. The Vickers microhardness value for the new ternary Wsub.2Irsub.5Bsub.2 boride was measured. Based on these findings, the ternary Wsub.2Irsub.5Bsub.2 boride can be considered hard.
Similar to translated thermal ablative techniques in clinic, the occurrence of cellular necrosis during tumor photothermal therapy (PTT) would induce inflammatory responses that are detrimental to ...therapeutic outcomes. Inspired by the well-known colorimetric Folin–Ciocalteu assay, monodispersed and renal-clearable tungsten (W)-based polyoxometalate nanoclusters (W-POM NCs, average diameter of around 2.0 nm) were successfully obtained here through a facile redox reaction with natural gallic acid in alkaline aqueous solution. Apart from excellent stability in the form of freeze-dried powder, the as-prepared W-POM NCs occupied considerable biocompatibility toward normal cells/tissues both in vitro and in vivo, since no obvious toxicities were observed by treating female Balb/c mice with concentrated W-POM NCs during the 30 day post-treatment period. More importantly, W-POM NCs exhibited not only considerable near-infrared (NIR) light absorption (coloration effect originated from the existence of electron-trapped W5+) for efficient PTT but also impressive anti-inflammatory ability (eliminating inflammation-related reactive oxygen species by the oxidation of W5+ into W6+ state) to achieve better therapeutic outcomes. Thus, our study pioneers the application of POMs for non-inflammatory PTT with expected safety and efficiency.
Radioresistance is one of the undesirable impediments in hypoxic tumors, which sharply diminishes the therapeutic effectiveness of radiotherapy and eventually results in the failure of their ...treatments. An attractive strategy for attenuating radioresistance is developing an ideal radiosensitization system with appreciable radiosensitization capacity to attenuate tumor hypoxia and reinforce radiotherapy response in hypoxic tumors. Therefore, we describe the development of Gd-containing polyoxometalates-conjugated chitosan (GdW10@CS nanosphere) as a radiosensitization system for simultaneous extrinsic and intrinsic radiosensitization, by generating an overabundance of cytotoxic reactive oxygen species (ROS) using high-energy X-ray stimulation and mediating the hypoxia-inducible factor-1a (HIF-1a) siRNA to down-regulate HIF-1α expression and suppress broken double-stranded DNA self-healing. Most importantly, the GdW10@CS nanospheres have the capacity to promote the exhaustion of intracellular glutathione (reduced GSH) by synergy W6+-triggered GSH oxidation for sufficient ROS generation, thereby facilitating the therapeutic efficiency of radiotherapy. As a result, the as-synthesized GdW10@CS nanosphere can overcome radioresistance of hypoxic tumors through a simultaneous extrinsic and intrinsic strategy to improve radiosensitivity. We have demonstrated GdW10@CS nanospheres with special radiosensitization behavior, which provides a versatile approach to solve the critical radioresistance issue of hypoxic tumors.
Polyoxometalates (POMs) are an emerging class of inorganic metal oxides, which over the last decades demonstrated promising biological activities by the virtue of their great diversity in structures ...and properties. They possess high potential for the inhibition of various tumor types; however, their unspecific interactions with biomolecules and toxicity impede their clinical usage. The current focus of the field of biologically active POMs lies on organically functionalized and POM‐based nanocomposite structures as these hybrids show enhanced anticancer activity and significantly reduced toxicity towards normal cells in comparison to unmodified POMs. Although the antitumor activity of POMs is well documented, their mechanisms of action are still not well understood. In this Review, an overview is given of the cytotoxic effects of POMs with a special focus on POM‐based hybrid and nanocomposite structures. Furthermore, we aim to provide proposed mode of actions and to identify molecular targets. POMs are expected to develop into the next generation of anticancer drugs that selectively target cancer cells while sparing healthy cells.
Next‐generation metallodrugs: This Review aims to critically evaluate the potential of polyoxometalates, especially organically functionalized hybrid and nanocomposite structures, as future clinically applied metallodrugs in the combat against cancer.
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