Solid-state 31P Research Articles

Fire and salvage logging increased recalcitrant soil organic matter and reduced soil functionality in Mediterranean pine forests.

Postfire management actions are used to mitigate damage caused by wildfires. Salvage logging, often employed to restore ecosystem functions in burnt stands, plays an essential role in reducing economic losses and the burn severity of future wildfires. However, its ecological implications for soil functionality still need to be understood, especially in the Mediterranean basin, which is prone to erosion and desertification. This study aimed to investigate the effects of fire on (i) soil organic matter (SOM) quality and composition using differential scanning calorimetry-thermogravimetry (DSC-TG) and solid-state nuclear magnetic resonance (13C CPMAS NMR) and (ii) phosphorus (P) forms using solid-state 31P NMR spectroscopy in a wildfire that affected 3200 ha in southeastern Spain in July 2017. One year after the fire, we monitored four Pinus halepensis Mill. stand categories based on soil burn severity (SBS): unburnt, low SBS, high SBS and high SBS areas with salvage logging (n=36, nine plots per SBS level). We collected soil samples and analysed soil pH, SOM content and SOM quality, along with biological activity indicators (carbon biomass, basal respiration, β-glucosidase, phosphatase activities) and P forms. We ran ANOVA statistical tests to identify significant differences in soil properties among SBS levels. We also established general linear regressions of thermo-recalcitrance values and aromaticity with biological soil quality indices to compare both techniques for detecting changes in SOM quality and composition. The results indicated that fire increased soil pH (up to 0.3), particularly in the plots with higher SBS levels. SOM decreased significantly with increasing SBS level (down to < 5 % at the high SBS level), with a shift from labile compounds (carbohydrates) to more recalcitrant ones (aromatics). Organic P forms were depleted, while orthophosphate levels rose, increasing the risk of irreversible fixation. This study also highlights that DSC-TG is a cost-effective technique for assessing SOM quality changes. Understanding these effects is essential for developing policies to conserve and restore fire-affected areas and to promote practices that enhance soil functionality and resilience.

Chemical Bonds Formed in Solid Wood by Reaction with Maleic Anhydride and Sodium Hypophosphite

The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not been studied yet. To resolve this, the reaction was studied with solid-state 13C cross-polarization magic-angle-spinning (CP-MAS) and 31P MAS nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to reveal the formation of bonds between wood components, MA and SHP during the treatments to explain the formation of cross-linking and the possible fixation of phosphorus in wood. XPS, solid state 13C and 31P MAS NMR revealed the maleation of wood in the absence of SHP, whilst its presence led to forming a succinic adduct observed through the C-P bond formation, as evidenced by the loss of the maleate C=C bonds at around 130 ppm and the upfield shift of the peak at 165–175 ppm, which was also significantly smoothed, as well as the increase in a peak at 26 ppm due to the reaction between the maleate group and SHP; however, the C-P-C bond could not be unambiguously rationalized from the obtained data. On the other hand, a resonance line at 16 ppm in 31P MAS NMR and the peaks in the XPS P 2p spectrum suggested the formation of a cross-linked structure at low concentrations of SHP, which was more likely to be phosphonate (C-P-O) than organophosphinic acid (C-P-C). The results herein provide a greater fundamental understanding of the mechanisms involved in the reaction of wood, MA and SHP, providing further scope for improved treatment systems in the future.

Mechanochemical Polyoxometalate Super-Reduction with Lithium Metal.

In this first systematic investigation of mechanochemical polyoxometalate (POM) reduction, (TBA)3[PMo12O40] was reacted with n equiv of lithium metal (n = 1-24) to generate PMo12/n products which were shown to be mixtures of electron-rich PMo12Lix species. FTIR analysis revealed the lengthening/weakening of terminal Mo═O bonds with increasing levels of reduction, while EXAFS spectra indicated the onset of Mo-Mo bond formation at n ∼ 8 and a significant structural change at n > 12. Successive MoVI reductions were monitored by XANES and XPS, and at n = 24, results were consistent with the formation of at least one MoIV-MoIV bonded {MoIV3} triad together with MoV. Upon dissolution, the PMo12Lix species present in the solid PMo12/n products undergo electron exchange and single-peak 31P NMR spectra were observed for n = 1-12. For n ≥ 16, changes in solid state and solution 31P NMR spectra coincided with the emergence of features in the UV-vis spectra associated with MoV-MoV and {MoIV3} bonding in an ε-Keggin structure. Bonding between {Li(NCMe)}+ and 2-electron-reduced PMo12 in (TBA)4[PMo12O40{Li(NCMe)}] suggests that super-reduction gives rise to more extensive Li-O bonding that ultimately causes lithium-oxide-promoted TBA cation decomposition and POM degradation, which might explain the appearance of XPS peaks for Mo2C at n ≥ 16. This work has revealed some of the complex, unexplored chemistry of super-reduced POMs and establishes a new, solvent-free approach in the search for a better fundamental understanding of the electronic properties and reactivity of electron-rich nanoscale metal oxides.

Polyphosphonate covalent organic frameworks

Herein, we report polyphosphonate covalent organic frameworks (COFs) constructed via P-O-P linkages. The materials are synthesized via a single-step condensation reaction of the charge-assisted hydrogen-bonded organic framework, which is constructed from phenylphosphonic acid and 5,10,15,20‐tetrakis[p‐phenylphosphonic acid]porphyrin and is formed by simply heating its hydrogen-bonded precursor without using chemical reagents. Above 210 °C, it becomes an amorphous microporous polymeric structure due to the oligomerization of P-O-P bonds, which could be shown by constant-time solid-state double-quantum 31P nuclear magnetic resonance experiments. The polyphosphonate COF exhibits good water and water vapor stability during the gas sorption measurements, and electrochemical stability in 0.5 M Na2SO4 electrolyte in water. The reported family of COFs fills a significant gap in the literature by providing stable microporous COFs suitable for use in water and electrolytes. Additionally, we provide a sustainable synthesis route for the COF synthesis. The narrow pores of the COF effectively capture CO2.

A sol-gel templating route for the synthesis of hierarchical porous calcium phosphate glasses containing zinc

Hierarchical porous phosphate-based glasses (PPG) have great potential in biomedicine. Micropores (pore size <2 nm) increase the surface area, mesopores (pore size 2–50 nm) facilitate the absorption and diffusion of therapeutic ions and molecules making them ideal controlled delivery systems, while macropores (pore size >50 nm) facilitate the movement and diffusion of cells and fluids. In addition, the bioresorbability of PPG allows for their complete solubility in body fluid, alongside simultaneous formation of new tissue. Making PPG via the traditional melt-quenching (MQ) synthesis method used for phosphate-based glasses (PG), is not straightforward. Hence, we present here a route for preparing such glasses using a combination of sol-gel (SG) and templating methods. Hierarchical PPG in the P2O5–CaO–Na2O system with the addition of 1, 3 and 5 mol % of Zn2+ were prepared with pore dimensions ranging from the micro-to the macro scales using Pluronic 123 (P123) as a surfactant. The presence of micropores (0.30–0.46 nm), mesopores (1.75–9.35nm) and macropores (163–207 nm) was assessed via synchrotron-based Small-Angle X-ray Scattering (SAXS), with the presence of the latter two confirmed by Scanning Electron Microscopy (SEM). Structural characterisation performed using 31P solid state magic angle spinning nuclear magnetic resonance (MAS NMR) and Fourier Transform Infrared (FTIR) spectroscopies shows the presence of Q2, Q1 and Q0 phosphate species with a predominance of Q1 species in all compositions. Dissolution studies in deionised (DI) water confirm that controlled release of phosphates, Ca2+, Na+ and Zn2+ is achieved over a period of 7 days. In particular, the release of Zn2+ is proportional to its loading, making its delivery particularly easy to control.

On the Structure and Role of Avian Eggshells: A 31P, 1H, and 13C Solid-State NMR Study.

The eggshell is a composite and highly ordered structure formed by biomineralization. Besides other functions, it has a vital and intricate role in the protection of an embryo from various potentially harsh environmental conditions. Solid-state nuclear magnetic resonance (SSNMR) has been used for detailed structural investigations of the chicken, tinamou, and flamingo eggshell materials. 31P NMR spectra reveal that hydroxyapatite and β-tricalcium phosphate in the ratio 3:2 represent major constituents of phosphate species in the eggshells. All three eggshells exhibit similar spectra, except for the line widths, which implies different structural order of phosphate species in the chicken, tinamou, and flamingo eggshells. 1H NMR spectra for these materials are comparable, differentiating overlapped peaks in three spectral regions at around 7, 4-5, and 1-2 ppm. These spectral regions have been attributed to protons from NH or CaHCO3, water, and possibly isolated monomeric water molecules or hydroxyl groups in calcium-deficient hydroxyapatite. 1H-13C CP MAS NMR revealed the presence of organic matter in the form of lipids and proteins. Two overlapped resonances in the carbonyl region at around 173 and 169 ppm are assigned to the carbonyls of the peptide bonds and the bicarbonate unit in calcite, respectively. Fourier-transform infrared spectroscopy (FTIR) spectra confirmed the presence of structural units detected in the NMR spectra.

Probing Chemical Equilibrium in Frozen Sodium Phosphate Buffer Solution by 31P Solid-State NMR.

Phosphate buffers are crucial for cryopreservative stability in pharmaceuticals, food processing, biomedical sciences, and biology. However, their freeze concentrates lack quantitative characterization, especially regarding the physicochemical properties of phosphate salt species in equilibrium at subzero temperatures. This study employs 31P solid-state NMR (ssNMR) to analyze frozen sodium phosphate (NaP) solutions, providing insights into phase composition, ionic strength, and pH. For the first time, we have directly quantified phosphate species in frozen NaP buffer, including crystallized disodium phosphate dodecahydrate (Na2HPO4·12H2O) content and the concentrations of H2PO4- and HPO42- in the freeze concentrate. This enabled the calculation of the pH as well as the ionic strength in the freeze concentrate. Trehalose effectively mitigated pH shifts in buffer solutions by preventing the selective crystallization of salt, a spectroscopic phenomenon not previously observed experimentally.

Phospholipid Membrane Interactions of Model Ac-WL-X-LL-OH Peptides Investigated by Solid-State Nuclear Magnetic Resonance.

The role of aromatic amino acids in peripheral protein membrane binding has been reported to involve cation-π interactions with choline lipids. In this study, we have investigated the interactions of the model pentapeptide Ac-WL-X-LL-OH (where X = L, Y, F, or W) with the phospholipid membrane using solid-state NMR. The effect of guest residue X on the peptide-lipid interactome was complementary to the seminal report on the interfacial hydrophobicity scale by Wimley and White. We found that the phospholipids retained a lamellar phase in the presence of each of the peptides with an aromatic X residue, whereas the Leu peptide perturbed the bilayer to an extent where an additional isotropic phase was observed. The solid-state NMR 13C and 31P data provide additional information on the influence of these short peptides on the membrane that has not been previously reported. The magnitude of membrane perturbation was in the order of guest residue X = L > Y~F > W, which is consistent with the relative amino acid interfacial affinity reported by Wimley and White. Further work is, however, required to uncover the behavior of the peptide and localization in the membrane domain due to ambiguity of the 13C NMR data. We have launched efforts in this regard for the objective of better understanding the role of aromatic amino acids in peripheral membrane protein binding.

Phosphaarsenes - Combining Phospha- and Arsa-Wittig-Reagents.

Dipnictenes of the type RPn=PnR (Pn=P, As, Sb, Bi) can be viewed as dimers of the corresponding pnictinidenes R-Pn. Phosphanylidene- and arsanylidenephosphoranes (R-Pn(PMe3); Pn=P, As) have been shown to be versatile synthetic surrogates for the delivery of pnictinidene fragments. We now report that thermal treatment of 1 : 1 mixtures of R-P(PMe3) and R'-As(PMe3) gives access to arsaphosphenes of the type RP=AsR'. Three examples are presented and the properties and reactivity of Mes*P=AsDipTer (1) (Mes*=2,4,6-tBu3-C6H2; DipTer=2,6-(2,6-iPr2C6H3)2-C6H3) were studied in detail. Solid state 31P NMR spectroscopy revealed a large 31P NMR chemical shift anisotropy with a span of ca. 920 ppm for 1 while computational methods were employed to investigate this pronounced magnetic deshielding of the P atom in 1. In the presence of the carbene IMe4 (IMe4=:C(MeNCMe)2) 1 is shown to be split into the corresponding NHC adducts Mes*P(IMe4) and DipTerAs(IMe4), which is additionally shown for diarsenes.

Phosphorus release and realignment in anaerobic digestion of thermal hydrolysis pretreatment sludge – Masking effects from high ammonium

Waste activated sludge (WAS) is a significant phosphorus (P) repository, and there is a growing interest in P recovery from WAS. Typically, the commercial technology for treating WAS involves thermal hydrolysis pretreatment (THP) coupled with anaerobic digestion (AD). However, there is ongoing debate regarding the transformation and distribution of P throughout this process. To address this, a long-term THP-AD process was operated in this study to comprehensively investigate P transformation and distribution. The results revealed that a substantial biodegradation of dissolved organic nitrogen (DON) raised the pH of the digestate to 8.3 during the AD process. This increased pH facilitated the dissolution of Al, leading to a reduction of 6.92 mg/L of NaOH-P. Simultaneously, sulfate reduction contributed to a decrease of 11.04 mg/L of Bipy-P in the solid. However, the reduction of Bipy-P and NaOH-P in the solid did not result in an improved P release to the supernatant. Conversely, a decrease of 23.60 mg/L P in the aqueous phase was observed after anaerobic digestion. The disappeared P was primarily precipitated with Mg and Ca, driven by the increased pH, and it contributed to the increase of HCl-P in the solid from 107.80 to 144.52 mg/L. These findings were further confirmed by results obtained from scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and solid-state 31P nuclear magnetic resonance (NMR) spectroscopy. This study provides valuable insights into the mechanisms of P transformation during THP-AD process that is nearly opposite from conventional AD system.

Exploring Deactivation Reasons of Biomass-Based Phosphorus-Doped Carbon as a Metal-Free Catalyst in the Catalytic Dehydroaromatization of n-Heptane.

Catalytic dehydroaromatization of n-alkanes into high-value aromatics has garnered extensive interest from both academia and industry. Our group has previously reported that phosphorus-doped carbon materials exhibit high selectivity for C-H bond activation in the dehydroaromatization of n-hexane. In this study, using n-heptane as a probe, we synthesized biomass-based phosphorus-doped carbon catalysts to investigate the impact of hydrogen heat treatment and carbon deposition on catalyst structure. Despite achieving an initial conversion of n-heptane at approximately 99.6%, with a toluene selectivity of 87.9%, the catalyst activity fell quickly. Moreover, longer hydrogen treatment time and higher hydrogen concentrations were found to accelerate catalyst deactivation. Thermogravimetric analysis (TGA) and N2 adsorption measurements (BET) indicated that a small amount of coke deposition was not the primary cause of catalyst deactivation. Temperature-programmed desorption of ammonia gas (NH3-TPD) revealed a significant decrease in acid-active functional groups. X-ray photoelectron spectroscopy (XPS) and solid-state 31P NMR spectroscopy confirmed the reduction of active central phosphorus species. These results suggest that catalyst deactivation primarily arises from the decrease in acidity and the partial reduction of phosphorus-containing groups, leading to a substantial loss of active sites. This work contributes new perspectives to understanding the properties and design improvements of metal-free carbon catalysts.

Small organic molecules containing amorphous calcium phosphate: synthesis, characterization and transformation.

As the primary solid phase, amorphous calcium phosphate (ACP) is a pivotal precursor in cellular biomineralization. The intrinsic interplay between ACP and Howard factor underscores the significance of understanding their association for advancing biomimetic ACP development. While organic compounds play established roles in biomineralization, this study presents the synthesis of ACP with naturally occurring organic compounds (ascorbate, glutamate, and itaconate) ubiquitously found in mitochondria and vital for bone remodeling and healing. The developed ACP with organic compounds was meticulously characterized using XRD, FTIR, and solid-state 13C and 31P NMR. The morphological analysis revealed the characteristic spherical morphology with particle size close to 20nm of all synthesized ACP variants. Notably, the type of organic compound strongly influences true density, specific surface area, particle size, and transformation. The in vitro analysis was performed with MC3T3-E1 cells, indicating the highest cell viability with ACP_ASC (ascorbate), followed by ACP_ITA (itaconate). The lowest cell viability was observed with 10 %w/v of ACP_GLU (glutamate); however, 1 %w/v of ACP_GLU was cytocompatible. Further, the effect of small organic molecules on the transformation of ACP to low crystalline apatite (Ap) was examined in Milli-Q® water, PBS, and α-MEM.

In-depth characterization of phosphate intercalated Mg Al Layered double hydroxides and study of the PO4 release properties.

Slow-release fertilizers (SRFs) form the core of innovative strategies in sustainable agriculture. Layered Double Hydroxides (LDH), known for their high capacity to sequester plant nutrients, especially phosphate, are emerging as promising candidates for SRF synthesis. The phosphate release properties of MgAl LDH (with a targeted Mg/Al ratio of 2.0) intercalated with HPO42- anions were assessed in various aqueous environments. A comprehensive analysis, including in-depth chemical and structural characterizations (ICP-OES, XRD, PDF, 27Al NMR, 31P NMR, FTIR, SEM) of the as-prepared phase unveiled a more intricate composition than anticipated for a pure or ideal Mg2Al-HPO4 LDH, encompassing an excess of intercalated phosphate in conjunction with K+. Beyond the intercalated phosphate, solid state 31P NMR speciation identified multiple HxPO4(-3+x) environments, indicating a portion of the phosphate reacting with intralayer Mg2+ to form K-struvite. Additionally, some phosphates were adsorbed onto the surface of amorphous aluminum hydroxide, a side phase formed during MgAl coprecipitation. The phosphate release demonstrated rapid kinetics, occurring within 6 days. Moreover, the released phosphate increased significantly when reducing the Solid/Liquid (S/L) ratio (58%) and further increasing in the presence of carbonate ions (90%). The released phosphate varied from 12% to 90% under different release conditions, transitioning from water to a 3.33 mM NaHCO3 aqueous solution at a low S/L ratio (from 20 mg LDH per mL to 0.02 mg LDH per mL). The simultaneous release of K+, Mg2+, Al3+ indicated the complete dissolution of the K-struvite and partial dissolution of phosphate intercalated MgAl LDH. These results enhanced our understanding of the mechanism governing phosphate release from MgAl LDH, paving the way for potential phosphate recovery by LDH or for the development of LDH-based SRFs.

Quantitative 31P magnetic resonance imaging on pathologic rat bones by ZTE at 7T

BackgroundOsteoporosis is characterized by low bone mineral density (BMD), which predisposes individuals to frequent fragility fractures. Quantitative BMD measurements can potentially help distinguish bone pathologies and allow clinicians to provide disease-relieving therapies. Our group has developed non-invasive and non-ionizing magnetic resonance imaging (MRI) techniques to measure bone mineral density quantitatively. Dual-energy X-ray Absorptiometry (DXA) is a clinically approved non-invasive modality to diagnose osteoporosis but has associated disadvantages and limitations. PurposeEvaluate the clinical feasibility of phosphorus (31P) MRI as a non-invasive and non-ionizing medical diagnostic tool to compute bone mineral density to help differentiate between different metabolic bone diseases. Materials and methodsFifteen ex-vivo rat bones in three groups [control, ovariectomized (osteoporosis), and vitamin-D deficient (osteomalacia - hypo-mineralized) were scanned to compute BMD. A double-tuned (1H/31P) transmit-receive single RF coil was custom-designed and in-house-built with a better filling factor and strong radiofrequency (B1) field to acquire solid-state 31P MR images from rat femurs with an optimum signal-to-noise ratio (SNR). Micro-computed tomography (μCT) and gold-standard gravimetric analyses were performed to compare and validate MRI-derived bone mineral densities. ResultsThree-dimensional 31P MR images of rat bones were obtained with a zero-echo-time (ZTE) sequence with 468 μm spatial resolution and 12–17 SNR on a Bruker 7 T Biospec having multinuclear capability. BMD was measured quantitatively on cortical and trabecular bones with a known standard reference. A strong positive correlation (R = 0.99) and a slope close to 1 in phantom measurements indicate that the densities measured by 31P ZTE MRI are close to the physical densities in computing quantitative BMD. The 31P NMR properties (resonance linewidth of 4 kHz and T1 of 67 s) of ex-vivo rat bones were measured, and 31P ZTE imaging parameters were optimized. The BMD results obtained from MRI are in good agreement with μCT and gravimetry results. ConclusionQuantitative measurements of BMD on ex-vivo rat femurs were successfully conducted on a 7 T preclinical scanner. This study suggests that quantitative measurements of BMD are feasible on humans in clinical MRI with suitable hardware, RF coils, and pulse sequences with optimized parameters within an acceptable scan time since human femurs are approximately ten times larger than rat femurs. As MRI provides quantitative in-vivo data, various systemic musculoskeletal conditions can be diagnosed potentially in humans.

Deconvolution of Charge-Transfer, Mass Transfer, and Ohmic Resistances of Phosphonic Acid-Sulfonic Acid Ionomer Binders in Electrochemical Hydrogen Pumps

Ion-pair high-temperature polymer electrolyte membranes (HT-PEMs) paired with phosphonic acid ionomer electrode binders have substantially improved the performance of HT-PEM electrochemical hydrogen pumps (EHPs)1, 2 and fuel cells3. Recently, blending poly(pentafluorstyrene-co-tetrafluorostyrene phosphonic acid) (PTFSPA) with NafionTM improved ionomer conductivity under anhydrous conditions in the temperature range of 100 °C to 250 °C. Using the said polymer blend as an electrode binder resulted in a 2 W.cm-2 peak power density of fuel cells4 at 240 °C (a HT-PEM fuel cell record). However, much is still unknown about how phosphonic acid ionomers blended with perfluorosulfonic acid (PFSA) materials affect electrode kinetics and gas transport in porous electrodes. In this work, we studied the ionic conductivity, electrode kinetics, and gas transport resistance of 3 types of phosphonic acid ionomers, poly(vinyl phosphonic acid), poly(vinyl benzyl phosphonic acid) by themselves and when blended with Aquivion®. These studies were performed in the context of an EHP platform – both membrane electrode assemblies (MEAs) and interdigitated electrode arrays (IDAs) decorated with nanoscale platinum electrocatalysts with thin film ionomer electrolytes. For all phosphoric acid ionomer types, the addition of Aquivion® promoted ionic conductivity, hydrogen oxidation/evolution reaction kinetics (HOR/HER), and hydrogen gas permeability. Solid-state 31P NMR revealed that the addition of Aquivion® significantly reduced phosphate ester formation in phosphoric acid ionomers and this played a vital role in enhancing ionomer blend conductivity. Using the best blend variant, PTFSPA-Aquivion®, a remarkable EHP performance of 5.1 A.cm-2 at 0.4 V at T = 200 °C was attained. Density functional theory (DFT) simulations identified that phosphonic acids with electron-withdrawing moieties reduced the propensity of the phosphonic acid to adsorb to platinum electrocatalyst surfaces. All phosphonic acid ionomers are anticipated to have a greater affinity for adsorption on platinum when compared to sulphonic acid ionomers (PFSAs). The relative adsorption affiliation of the various phosphoric acid ionomers from DFT is consistent with an explanation that stronger anion-specific adsorption has a detrimental impact and is commensurate with experimentally obtained MEA charge-transfer kinetics. A machine learning-aided compositional model5 revealed that the addition of Aquivion® reduced activation and concentration overpotentials in EHP MEAs and improved exchange current density and diffusivity in EHP IDAs. Future work involves employing the EHPs in a real-world application for separating and compressing hydrogen from the natural gas mixture.References Venugopalan, G.; Bhattacharya, D.; Andrews, E.; Briceno-Mena, L.; Romagnoli, J.; Flake, J.; Arges, C. G., Electrochemical Pumping for Challenging Hydrogen Separations. ACS Energy Letters 2022, 7 (4), 1322-1329.Venugopalan, G.; Bhattacharya, D.; Kole, S.; Ysidron, C.; Angelopoulou, P. P.; Sakellariou, G.; Arges, C. G., Correlating high temperature thin film ionomer electrode binder properties to hydrogen pump polarization. Materials Advances 2021, 2 (13), 4228-4234.Atanasov, V.; Lee, A. S.; Park, E. J.; Maurya, S.; Baca, E. D.; Fujimoto, C.; Hibbs, M.; Matanovic, I.; Kerres, J.; Kim, Y. S., Synergistically integrated phosphonated poly(pentafluorostyrene) for fuel cells. Nat Mater 2021, 20 (3), 370-377.Lim, K. H.; Lee, A. S.; Atanasov, V.; Kerres, J.; Park, E. J.; Adhikari, S.; Maurya, S.; Manriquez, L. D.; Jung, J.; Fujimoto, C.; Matanovic, I.; Jankovic, J.; Hu, Z.; Jia, H.; Kim, Y. S., Protonated phosphonic acid electrodes for high power heavy-duty vehicle fuel cells. Nature Energy 2022, 7 (3), 248-259.Briceno-Mena, L. A.; Venugopalan, G.; Romagnoli, J. A.; Arges, C. G., Machine learning for guiding high-temperature PEM fuel cells with greater power density. Patterns 2021, 2 (2), 100187. Figure 1

Arrangement of lipid vesicles and bicelle-like structures formed in the presence of Aβ(25–35) peptide

Our complementary experimental data and molecular dynamics (MD) simulations results reveal the structure of previously observed lipid bicelle-like structures (BLSs) formed in the presence of amyloid-beta peptide Aβ(25–35) below the main phase transition temperature (Tm) of saturated phosphatidylcholine lipids and small unilamellar vesicles (SUVs) above this temperature. First, we show by using solid-state 31P nuclear magnetic resonance (NMR) spectroscopy that our BLSs being in the lipid gel phase demonstrate magnetic alignment along the magnetic field of NMR spectrometer and undergo a transition to SUVs in the lipid fluid phase when heated through the Tm. Secondly, thanks to the BLS alignment we present their lipid structure. Lipids are found located not only in the flat bilayered part but also around its perimeter, which is corroborated by the results of coarse-grained (CG) MD simulations. Finally, peptides appear to mix randomly with lipids in SUVs while assuming predominantly unordered secondary structures revealed by circular dichroism (CD), Raman spectroscopy, and all-atom MD simulations. Importantly, the former is changing little when the system undergoes morphological transitions between BLSs and SUVs. Our structural results then offer a platform for studying and understanding mechanisms of morphological transformations caused by the disruptive effect of amyloid-beta peptides on the lipid bilayer.

Insights into Glyphosate Adsorption in Aqueous Solutions Using Zn-Al Layered Double Oxide

AbstractContamination of surface and groundwater with glyphosate, used widely on crops to control weeds, can cause severe environmental damage. Processes for glyphosate removal from water bodies have been developed, but few are effective and all are expensive. This objective of the present study was to investigate the use of a layered double oxide as a potentially effective and inexpensive material to remove glyphosate from water. Equilibrium, kinetics, and adsorption mechanisms were evaluated, in addition to the effects of competing anions and temperature on glyphosate adsorption. Up to 95% of glyphosate was removed from a synthetic solution in 50 min by Zn2Al-LDO (layered double oxide in Zn/Al ratio of 2:1) at pH 10. The adsorption isotherms were type L and the Langmuir model best fitted the experimental data, with a qmax value of 191.96 μg mg–1 at 25°C. The XRD pattern did not support the hypothesis of intercalation of glyphosate anions, whereas Fourier-transform infrared and solid-state 13C and 31P magic angle spinning nuclear magnetic resonance confirmed the adsorption of glyphosate anions on the Zn2Al-LDO surface, through carboxylate and phosphonate moiety interactions with end-on and side-on modes. The degree of removal of glyphosate increased with increasing temperature and decreased with increasing concentration of competing anions, with carbonate anions having the most prominent effect on the inhibition of glyphosate adsorption. The adsorption kinetics fitted a pseudo-first order law. Moreover, the intraparticle diffusion model suggested that the adsorption process depends on the formation and thickness of the film at the solution/solid interface.

31P Nuclear Magnetic Resonance Spectroscopy as a Probe of Thorium-Phosphorus Bond Covalency: Correlating Phosphorus Chemical Shift to Metal-Phosphorus Bond Order.

We report the use of solution and solid-state 31P Nuclear Magnetic Resonance (NMR) spectroscopy combined with Density Functional Theory calculations to benchmark the covalency of actinide-phosphorus bonds, thus introducing 31P NMR spectroscopy to the investigation of molecular f-element chemical bond covalency. The 31P NMR data for [Th(PH2)(TrenTIPS)] (1, TrenTIPS = {N(CH2CH2NSiPri3)3}3-), [Th(PH)(TrenTIPS)][Na(12C4)2] (2, 12C4 = 12-crown-4 ether), [{Th(TrenTIPS)}2(μ-PH)] (3), and [{Th(TrenTIPS)}2(μ-P)][Na(12C4)2] (4) demonstrate a chemical shift anisotropy (CSA) ordering of (μ-P)3- > (═PH)2- > (μ-PH)2- > (-PH2)1- and for 4 the largest CSA for any bridging phosphido unit. The B3LYP functional with 50% Hartree-Fock mixing produced spin-orbit δiso values that closely match the experimental data, providing experimentally benchmarked quantification of the nature and extent of covalency in the Th-P linkages in 1-4 via Natural Bond Orbital and Natural Localized Molecular Orbital analyses. Shielding analysis revealed that the 31P δiso values are essentially only due to the nature of the Th-P bonds in 1-4, with largely invariant diamagnetic but variable paramagnetic and spin-orbit shieldings that reflect the Th-P bond multiplicities and s-orbital mediated transmission of spin-orbit effects from Th to P. This study has permitted correlation of Th-P δiso values to Mayer bond orders, revealing qualitative correlations generally, but which should be examined with respect to specific ancillary ligand families rather than generally to be quantitative, reflecting that 31P δiso values are a very sensitive reporter due to phosphorus being a soft donor that responds to the rest of the ligand field much more than stronger, harder donors like nitrogen.

Inducing differences in modification degree and binding mode of organophosphonic acid grafted titania by changing pH and hydrocarbon chain length

Organically modified metal oxide surfaces are of interest in many applications since they combine the advantages of metal oxide supports (structural properties, chemical and mechanical stability) and organic functionalities (for specific surface interactions). Although surface modification with organophosphonic acids (PAs) with an alkyl or aminoalkyl functional group on TiO2 has been investigated previously, knowledge of the synthesis-properties correlation (e.g. the binding mode of the PAs) is still lacking, especially for functional group-surface interactions. These are however important as they can influence functional group availability in applications such as (metal) sorption. In this work, the dependence of modification degree and phosphorus chemical environment on pH and chain length (C1 to C6) was investigated with TGA, ICP-OES, nitrogen/argon sorption, XPS, and solid-state 31P NMR and DFT calculations. The TGA and the ICP-OES results showed a clear impact of pH on surface modification degrees, with a different response for modification with alkyl- and aminoalkylphosphonic acids, featuring a more rapid decrease in modification degrees from pH 2 upwards for the alkylphosphonic acids compared to the aminoalkylphosphonic acids. Moreover, a clear correlation can be found between the aminoalkyl chain length and the NH2/NH3+ ratio. In addition, a positive correlation between the modification degree and the protonation degree of the amine group is observed for aminomethylphosphonic acid (AMPA) and 2-aminoethylphosphonic acid (2AEPA) modified samples, while this is absent for longer alkyl chains. This is supported by DFT calculations that indicate that the most stable binding modes of AMPA and 2AEPA grafted on the anatase (101) surface include hydrogen bonds between NH3+ and the surface oxygen atoms, in contrast, the most stable binding modes for 3-aminopropylphosphonic acid (3APPA), 4-aminobutylphosphonic acid (4ABPA), and 6-aminohexylphosphonic acid (6AHPA) grafted on the anatase (101) surface involve a Lewis acid-base interaction between NH2 and a surface Ti site.

The effect of ZnO on the structural and radiation shielding properties in borophosphate glasses

In this work, the influence of ZnO content in the structural and radiation shielding parameters of zinc borophosphate glass were studied. The glass batch was prepared by using the melt-quenching technique. The structural analyses have been carried out using XRD, Raman spectroscopy, 11B and 31P solid state MAS NMR. Density and glass transition temperature (Tg) were measurements and band gap were determined. XRD confirms the non-crystalline nature of the prepared samples. Changes in the structural characteristics with composition are associated with a replacement of BO4 by BO3 units and the replacement of PO4 phosphorous units by PO4−1 and PO4−2 units, leading to an increase of the average number of non-bridging oxygen (NBO). Density values revealed an increase of up to 43% and Tg shows reduction followed by stability with the replacement of P2O5 by ZnO. Band gap energies were measured as a function of ZnO content. Photon interaction parameters of the zinc borophosphate glasses have been investigated by the mass attenuation coefficient (MAC), half value layer (HVL), and mean free path (MFP). For radiation in the X-ray range (40 KeV), the MAC value for glass is 887% higher than for concrete and the HVL decreases almost four times, from 20 to 6 mm thickness, with the increase of ZnO content. The rise in ZnO content also improves all radiation attenuation parameters and the results reported here show that zinc borophosphate glasses present better results than ordinary concrete and is comparable to lead-based glasses. These characteristics make this glass system an excellent choice as a high-energy ionizing radiation attenuator.