Vanadium-based polyoxometalate as new material for sodium-ion battery anodes

Affordable energy storage is crucial for a variety of technologies. One option is sodium-ion batteries (NIBs) for which, however, suitable anode materials are still a problem. We report on the application of a promising new class of materials, polyoxometalates (POMs), as an anode in NIBs. Specifically, Na6[V10O28]·16H2O is being synthesized and characterized. Galvanostatic tests reveal a reversible capacity of approximately 276 mA h g−1 with an average discharge potential of 0.4 V vs. Na/Na+, as well as a high cycling stability. The underlying mechanism is rationalized to be an insertion of Na+ in between the [V10O28]6− anions rather than an intercalation into a crystal structure; the accompanying reduction of V+V to V+IV is confirmed by X-ray Photoelectron Spectroscopy. Finally, a working full-cell set-up is presented with the POM as the anode, substantiating the claim that Na6[V10O28]·16H2O is a promising option for future high-performing sodium-ion batteries

Water splitting with polyoxometalate-treated photoanodes: Enhancing performance through sensitizer design

Visible light driven water oxidation has been demonstrated at near-neutral pH using photoanodes based on nanoporous films of TiO2, polyoxometalate (POM) water oxidation catalyst [{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2]10- (1), and both known photosensitizer [Ru(bpy)2(H4dpbpy)]2+ (P2) and the novel crown ether functionalized dye [Ru(5-crownphen)2(H2dpbpy)] (H22). Both triads, containing catalyst 1, and catalyst-free dyads, produce O2 with high faradaic efficiencies (80 to 94%), but presence of catalyst enhances quantum yield by up to 190% (maximum 0.39%). New sensitizer H22 absorbs light more strongly than P2, and increases O2 quantum yields by up to 270%. TiO2-2 based photoelectrodes are also more stable to desorption of active species than TiO2-P2: losses of catalyst 1 are halved when pH > TiO2 point-of-zero charge (pzc), and losses of sensitizer reduced below the pzc (no catalyst is lost when pH < pzc). For the triads, quantum yields of O2 are higher at pH 5.8 than at pH 7.2, opposing the trend observed for 1 under homogeneous conditions. This is ascribed to lower stability of the dye oxidized states at higher pH, and less efficient electron transfer to TiO2, and is also consistent with the 4th 1-to-dye electron transfer limiting performance rather than catalyst TOFmax. Transient absorption reveals that TiO2-2-1 has similar 1st electron transfer dynamics to TiO2-P2-1, with rapid (ps timescale) formation of long-lived TiO2(e-)-2-1(h+) charge separated states, and demonstrates that metallation of the crown ether groups (Na+/Mg2+) has little or no effect on electron transfer from 1 to 2. The most widely relevant findings of this study are therefore: (i) increased dye extinction coefficients and binding stability significantly improve performance in dye-sensitized water splitting systems; (ii) binding of POMs to electrode surfaces can be stabilized through use of recognition groups; (iii) the optimal homogeneous and TiO2-bound operating pHs of a catalyst may not be the same; and (iv) dye-sensitized TiO2 can oxidize water without a catalyst

Enhancing the dissolution of phenylbutazone using Syloid® based mesoporous silicas for oral equine applications

Three mesoporous silica excipients (Syloid® silicas AL-1 FP, XDP 3050 and XDP 3150) were formulated with a model drug known for its poor aqueous solubility, namely phenylbutazone, in an attempt to enhance the extent and rate of drug dissolution. Although other forms of mesoporous silica have been investigated in previous studies, the effect of inclusion with these specific Syloid® silica based excipients and more interestingly, with phenylbutazone, is unknown. This work reports a significant enhancement for both the extent, and rate, of drug release for all three forms of Syloid® silica at a 1:1 drug:silica ratio over a period of 30 minutes. An explanation for this increase was determined to be conversion to the amorphous form and an enhanced drug loading ability within the pores. Differences between the release profiles of the three silicas was concluded to be a consequence of the physicochemical differences between the three forms. Overall, this study confirms that Syloid® silica based excipients can be used to enhance dissolution, and potentially therefore bioavailability, for compounds with poor aqueous solubility, such as phenylbutazone. In addition, it has been confirmed that drug release can be carefully tailored based on the choice of Syloid® silica and desired release profile

Mechanical and structural characterization of tibial prosthetic interfaces before and after aging under simulated service conditions

Prosthesis interface is one of the most important components to promote individual's health and comfort, as it establishes direct contact with the skin and transfers loads generated during gait. The aim of this study was to mechanically characterize, three commercial interfaces (block copolymer, silicone gel and silicone elestomer), under static and dynamic conditions, before and after undergoing a process of chemical aging in synthetic sweat for periods up to 90 days. Static mechanical compression tests were performed on the materials, as well as fatigue tests to assess their static and dynamic mechanical behaviors, respectively. For the second, a sinusoidal load was applied with an appropriate range of deformation for each material. Several analytical techniques were also used to characterize the materials, namely Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and morphology characterization by Scanning Electron Microscopy (SEM). All the tested materials have strong viscoelastic behavior, showing a linear response for small deformations, followed by a nonlinear behavior for higher deformation. The block copolymer and the silicone gel are affected by aging in synthetic sweat in a similar way, with a significant increase of their rigidity after 30 days, followed by a progressive reduction. The silicone elastomer displays a continuous increase of rigidity along the 90 days of storage, being the most sensitive to aging affects. It also exhibits the lowest stiffness value, being suitable for uses that require maximum comfort. All materials demonstrate chemical and structural stability under service simulated conditions. (C) 2014 Elsevier Ltd. All rights reserved

ASSESSING THE PERFORMANCE OF NEWLY DEVELOPED SILICA NANOPARTICLES AGAINST LEAD AND PHOSPHATE ION REMOVAL FROM CONTAMINATED SOLUTIONS USING ADSORPTION ISOTHERM

This study investigates the removal of Lead and Phosphate ion from aqueous solution using new silica nanoparticles doped with europium (H1) which was characterized using Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Fourier-transform Infrared Spectroscopy (FTIR). The aim of this research is to develop a novel adsorbent material that can efficiently remove contaminated ions from wastewater or aqueous solutions. The adsorption of lead and phosphate ion onto the silica nanoparticles is investigated, and the efficiency of this removal is evaluated. Equilibrium data analysis reveals linear fitting with Langmuir isotherm with 24.76 mg/g Lead ion uptake, while for phosphate the uptake capacity is around 55.62 mg/g at 298.15 K. Overall, this research provides valuable insights into the development of silica nanoparticles doped with europium as a potential adsorbent for the removal of lead and phosphate ion from solution. The findings contribute to the advancement of water purification and environmental remediation technologie

Synthesis and Structure of Hexatungstochromate(III), [H3CrIIIW6O24]6–

The hexatungstochromate(III) [H3CrIIIW6O24]6- (1) was synthesized in aqueous, basic medium by simple reaction of chromium(III) nitrate nonahydrate and sodium tungstate dihydrate in a 1:6 ratio. Polyanion 1 represents the first Anderson-Evans type heteropolytungstate with a trivalent hetero element. The sodium salt of 1 with the formula Na6[H3CrIIIW6O24]·22H2O (1a) was fully characterized in the solid state by single crystal XRD, FT-IR spectroscopy, and thermogravimetric analysis

MOLYBDENUM VERSUS TUNGSTEN BASED POLYOXOMETALATES FOR HIGHLY EFFECTIVE METHYLENE BLUE REMOVAL

[SiW12O40]4-(SiW12) and [Mo8O26]4- (Mo8) were synthesized and characterized by Fourier Transform Infrared spectroscopy (FTIR). The prepared polyoxometalates were studied as potential adsorbents for the removal of methylene blue (MB) from an aqueous solution. Various operational parameters—contact time, adsorbent dose, initial dye concentration, pH, and temperature— were meticulously assessed by UV/Vis spectrophotometry to study its impact on the adsorption efficacy. An inverse relationship was observed between the percentage dye removal and the initial dye concentration, highlighting the complexes\u27 superior adsorption capabilities under lower dye loads. The studied complexes displayed significantly better efficiency under acidic conditions. Both SiW12 and Mo8 exhibited high percentages of removal for methylene blue within only 10 min for MO8 and 5 min for SiW12. These results not only underline the proficiency of SiW12 and Mo8 as adsorbents, but also position them as promising candidates for fast and effective water purification strategies in the face of escalating environmental pollution challenges

The association of waterpipe tobacco smoking with later initiation of cigarette smoking: A systematic review and meta-analysis exploring the gateway theory

Introduction There is a concern that waterpipe tobacco smoking (WTS) can lead to the later initiation of cigarette smoking, a concept referred to as the â € gateway theory'. The objective of the study was to systematically review the literature for the association of WTS with later initiation of cigarette smoking. Methods We searched Medline, Embase and ISI Web of Science in April 2018 without using any language or date restrictions. We selected eligible studies, abstracted data and assessed the risk of bias using a duplicate and independent approach. We meta-analysed the ORs across eligible studies using the inverse variance method and the random-effects model. We assessed the certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation methodology. Results We included eight papers reporting on six eligible prospective cohort studies with a total of 21 224 participants, belonging to the adolescent and young adult age categories. The pooled adjusted OR for the association between ever waterpipe user (compared with never waterpipe user) at baseline, with â € cigarette smoking initiation' (ever cigarette use) was 2.54 (95% CI 1.60 to 4.02) at 6 months to 3 years follow-up (moderate certainty evidence). The pooled adjusted OR for the association between ever waterpipe user (compared with never waterpipe user) at baseline, with â € current cigarette smoking' (past 30-day cigarette use) was 2.04 (95% CI 1.32 to 3.15) at 1-2 years follow-up (moderate certainty evidence). The pooled adjusted OR for the association between past 30-day waterpipe user (compared with never waterpipe user) at baseline, with current cigarette smoking (past 30-day cigarette use) 2.46 (95% CI 1.73 to 3.49) at 6 months to 1 year follow-up (high certainty evidence). Conclusion Our findings indicate that WTS is associated with more than doubling of the odds of later initiation of cigarette smoking, supporting the gateway theory. Strengthening WTS policies is a priority and further research is needed on the development and evaluation of appropriate clinical and public health interventions. © 2020 BMJ Publishing Group. All rights reserved

Photocatalytic and Kinetic Study on the Degradation of Three Food Pesticides Using Vanadium-Substituted Polyoxotungstates

Mono-, di-, and tri-vanadium-substituted Keggin-type heteropolyoxoanions [SiW12O40]4− and [PW12O40]4− were evaluated as photocatalysts for the photodegradation of three hazardous food pesticides: atrazine, chlorpyrifos, and dieldrin. Kinetic experiments were performed under UV irradiation at 254 nm. The degradation of each pesticide was assessed by investigating its disappearance with time using high-performance liquid chromatography equipped with an ultra-violet spectrophotometer detector. The photocatalytic degradation of the three pesticides exhibited first-order kinetics. It was found that the introduction of vanadium addenda atoms into the Keggin-type polyoxometalates decrease the degradation rate for the photocatalytic transformation of each pesticide as well as the degradation percentage. This effect was significantly related to the number of vanadium metal ions substituting the tungsten addenda atoms. As a general trend, the photocatalytic efficiency of {XVW11} was better than that of {XV3W9}. Accordingly, a marked drop was noticed in the photocatalytic degradation of atrazine, where 90% was decomposed in the presence of [α-SiW12O40]4− at a rate of 1 mg/L min, whereas the degradation percentage decreased to 55% in the presence of [α-SiVW11O40]5− at a decreased rate of 0.7 mg/L min. Hence, the negative effect on the degradation percentage was evident for the Si-based POMs, which drops from 90 to 38%, 83 to 32%, and 60 to 23% for atrazine, chlorpyrifos, and dieldrin, respectively. Similar effect was observed for the P-based POMs under the studied conditions. © 2019, University of Tehran

Crystallization and preliminary X-ray crystallographic analysis of latent isoform PPO4 mushroom (<i>Agaricus bisporus)</i>tyrosinase

Tyrosinase exhibits catalytic activity for theortho-hydroxylation of monophenols to diphenols as well as their subsequent oxidation to quinones. Owing to polymerization of these quinones, brown-coloured high-molecular-weight compounds called melanins are generated. The latent precursor form of polyphenol oxidase 4, one of the six tyrosinase isoforms fromAgaricus bisporus, was purified to homogeneity and crystallized. The obtained crystals belonged to space groupC121 (two molecules per asymmetric unit) and diffracted to 2.78 Å resolution. The protein only formed crystals under low-salt conditions using the 6-tungstotellurate(VI) salt Na6[TeW6O24]·22H2O as a co-crystallization agent.</jats:p