Calcium manganese oxides as oxygen evolution catalysts: O2 formation pathways indicated by 18O-labelling studies

Oxygen evolution catalysed by calcium manganese and manganese-only oxides was studied in (18)O-enriched water. Using membrane-inlet mass spectrometry, we monitored the formation of the different O(2) isotopologues (16)O(2), (16)O(18)O and (18)O(2) in such reactions simultaneously with good time resolution. From the analysis of the data, we conclude that entirely different pathways of dioxygen formation catalysis exist for reactions involving hydrogen peroxide (H(2)O(2)), hydrogen persulfate (HSO(5)(-)) or single-electron oxidants such as Ce(IV) and [Ru(III) (bipy)(3)](3+) . Like the studied oxide catalysts, the active sites of manganese catalase and the oxygen-evolving complex (OEC) of photosystem II (PSII) consist of μ-oxido manganese or μ-oxido calcium manganese sites. The studied processes show very similar (18)O-labelling behaviour to the natural enzymes and are therefore interesting model systems for in vivo oxygen formation by manganese metalloenzymes such as PSII.     

Performance of a Halo Ion Trap Mass Analyzer with Exit Slits for Axial Ejection

The halo ion trap (IT) was modified to allow for axial ion ejection through slits machined in the ceramic electrode plates rather than ejecting ions radially to a center hole in the plates. This was done to preserve a more uniform electric field for ion analysis. An in-depth evaluation of the higher-order electric field components in the trap was also performed to improve resolution. The linear, cubic and quintic (5th order) electric field components for each electrode ring inside the IT were calculated using SIMION (SIMION version 8, Scientific Instrument Services, Ringoes, NJ, USA) simulations. The preferred electric fields with higher-order components were implemented experimentally by first calculating the potential on each electrode ring of the halo IT and then soldering appropriate capacitors between rings without changing the original trapping plate design. The performance of the halo IT was evaluated for 1% to 7% cubic electric field (A ₄/A ₂) component. A best resolution of 280 (m/Δm) for the 51-Da fragment ion of benzene was observed with 5% cubic electric field component. Confirming results were obtained using toluene, dichloromethane, and heptane as test analytes.     

Bulk and shear mechanical loss of titania-doped tantala

We report on the mechanical loss from bulk and shear stresses in thin film, ion beam deposited, titania-doped tantala. The numerical values of these mechanical losses are necessary to fully calculate the Brownian thermal noise in precision optical cavities, including interferometric gravitational wave detectors like LIGO. We found the values from measuring the normal mode mechanical quality factors, Q's, in the frequency range of about 2000-10,000 Hz, of silica disks coated with titania-doped tantala coupled with calculating the elastic energy in shear and bulk stresses in the coating using a finite element model. We fit the results to both a frequency independent and frequency dependent model and find ${?}_{\mathrm{shear}}=(8.3\pm 1.1)\times {10}^{?4}$, ${?}_{\mathrm{bulk}}=(6.6\pm 3.8)\times {10}^{?4}$ with a frequency independent model and ${?}_{\mathrm{shear}}\left(f\right)=(5.0\pm 0.7)\times {10}^{?4}+(5.4\pm 1.1)\times {10}^{?8}f$, ${?}_{\mathrm{bulk}}\left(f\right)=(11\pm 2.8)\times {10}^{?4}?(8.7\pm 4.7)\times {10}^{?8}f$ with a frequency dependent (linear) model. The ratio of these values suggest that modest improvement in the coating thermal noise may be possible in future gravitational wave detector optics made with titania-doped tantala as the high index coating material by optimizing the coating design to take advantage of the two different mechanical loss angles.     

Development of a Gas-Tight Syringe Headspace GC-FID Method for the Detection of Ethanol,and a Description of the Legal and Practical Framework for Its Analysis,in Samples of English and Welsh Motorists’ Blood and Urine

Ethanol is the most commonly used recreational drug worldwide. This study describes the development and validation of a headspace gas chromatography flame ionisation detection (HS-GC-FID) method using dual columns and detectors for simultaneous separation and quantitation. The use of a dual-column, dual-detector HS-GC-FID to quantitate ethanol is a common analytical technique in forensic toxicology; however, most analytical systems utilise pressure-balance injection rather than a simplified gas-tight syringe, as per this technique. This study is the first to develop and validate a technique that meets the specifications of the United Kingdom’s requirements for road traffic toxicology testing using a Shimadzu GC-2014 gas-tight syringe. The calibration ranged from 10 to 400 mg/100 mL, with a target minimum linearity of r2 > 0.999, using tertiary butanol as the internal standard marker. The method has an expanded uncertainty at 99.73% confidence of 3.64% at 80 mg/100 mL, which is the blood alcohol limit for drink driving in England and Wales. In addition, at 200 mg%—the limit at which a custodial sentence may be imposed on the defendant—the expanded uncertainty was 1.95%. For both the 80 mg% and 200 mg% concentrations, no bias was present in the analytical method. This method displays sufficient separation for other alcohols, such as methanol, isopropanol, acetaldehyde, and acetone. The validation of this technique complies with the recommended laboratory guidelines set out by United Kingdom and Ireland Association of Forensic Toxicologists (UKIAFT), the recently issued Laboratory 51 guidelines by the United Kingdom Accreditation Service (UKAS), and the criteria set out by the California Code of Regulations (CCR), 17 CCR § 1220.1.     

Measurement of Nanometer Distances in Solution via 13C NMR Spectroscopy—Shrinking of Macrocycles with Increasing Temperature

For a molecular system, size and shape are of elementary importance for its function and properties. Therefore, the determination of distances within a molecule is essential. However, the commonly used methods are only suitable for distances smaller than 4 Å or larger than 15 Å. Here, we show that by incorporating a molecular spring, we can measure distances in macrocycles in the range of 10 Å using ¹³C NMR spectroscopy. The accuracy of the method also allows to determine the temperature dependence of the distances. In one case, we find a contraction of the length by almost 10 % upon heating. This shrinking due to heating can be considered as inverse thermoelasticity at the molecular level and is a previously completely overlooked phenomenon that can be used in the future as a tool to change the length and, thus, the function of a system.     

Atypical “Masked” Frustrated Lewis Pair Character in a Geminal-Linked Phosphine-Borane

We report the synthesis and reactivity of the geminal-linked fluorene-derived P/B frustrated Lewis pair (FLP) ⁱPr₂P(C₁₃H₈)BCy₂ ( 1 ). Compound 1 displays anomalous behavior towards small molecules, acting as a “masked” FLP. This behavior stems from significant polarization of the B−C(fluorene) bond in 1 , as identified by density functional theory (DFT) computations. We exploit this B−C bond polarity through reactions with PhPCl₂, H₃N ⋅ BH₃, and ⁱPrNH₂, demonstrating P−Cl and N−H bond activation, respectively.     

On phosphorus chemical shift anisotropy in metal (IV) phosphates and phosphonates: A 31P NMR experimental study

The phosphorus chemical shift anisotropies, ³¹PΔcs, and asymmetry parameters η were measured by the ³¹P{¹H} NMR experiments in static and low-frequency spinning samples of the zirconium phosphates and phosphonates and also in the mixed Zr (IV)/Sn (IV) phosphate/phosphonate material. The data obtained have shown a 111 connectivity in the HPO₄ and PO₃ groups, which does not change at modification and intercalation of the materials. The ³¹PΔcs values of the phosphonate groups (43–49 ppm) significantly surpass the values characterizing the HPO₄ groups (23–37 ppm). The ³¹P Δcs values obtained for the metal (IV) phosphates were discussed in terms of P-O distances. The ³¹P chemical shift anisotropy parameters can help at elucidation of local structures in phosphate and phosphonate materials.     

Compartmentalized Polyampholyte Microgels by Depletion Flocculation and Coacervation of Nanogels in Emulsion Droplets

In pH-responsive drug carriers, the distribution of charges has been proven to affect delivery efficiency but is difficult to control and verify. Herein, we fabricate polyampholyte nanogel-in-microgel colloids (NiM−C) and show that the arrangement of the nanogels (NG) can easily be manipulated by adapting synthesis conditions. Positively and negatively charged pH-responsive NG are synthesized by precipitation polymerization and labelled with different fluorescent dyes. The obtained NG are integrated into microgel (MG) networks by subsequent inverse emulsion polymerization in droplet-based microfluidics. By confocal laser scanning microscopy (CLSM), we verify that depending on NG concentration, pH value and ionic strength, NiM−C with different NG arrangements are obtained, including Janus-like phase-separation of NG, statistical distribution of NG, and core–shell arrangements. Our approach is a major step towards uptake and release of oppositely charged (drug) molecules.     

Sustainable Design of Structural and Functional Polymers for a Circular Economy

To achieve a sustainable circular economy, polymer production must start transitioning to recycled and biobased feedstock and accomplish CO₂ emission neutrality. This is not only true for structural polymers, such as in packaging or engineering applications, but also for functional polymers in liquid formulations, such as adhesives, lubricants, thickeners or dispersants. At their end of life, polymers must be either collected and recycled via a technical pathway, or be biodegradable if they are not collectable. Advances in polymer chemistry and applications, aided by computational material science, open the way to addressing these issues comprehensively by designing for recyclability and biodegradability. This Review explores how scientific progress, together with emerging regulatory frameworks, societal expectations and economic boundary conditions, paint pathways for the transformation towards a circular economy of polymers.     

Effect of photoinitiator on the molar mass distribution obtained from a pulsed laser polymerization

The choice of the photoinitiator is not usually regarded as being as important consideration in attempting to determine the value of the propagation rate coefficient k_p from a pulsed laser-initiated polymerization (PLP). It is shown that in fact the choice of the photoinitiator can profoundly influence the success of such experiments. Specially, for a number of monomers it was found that the successful determination of k_p is essentially impossible when 1,1-azodicyclohexanecarbonitrile is employed as a photoinitiator. The likely reason for this phenomenon is discussed from which it would seem appropriate to be wary in using any azo compound as a PLP photoinitiator. From PLP experiments with a non-azo photoinitiator, ambient pressure k_p has been determined for bulk polymerization of methyl methacrylate over an extended temperature range.