Phosphate Species Research Articles

Insights of nanostructure and nanomechanical properties of the tribofilm derived from CoAl-hexametaphosphate layered double hydroxide on sliding steel surfaces

This study successfully synthesizes CoAl-hexametaphosphate layered double hydroxide (HMP-LDH) via anion exchange. The application of HMP-LDH leads to substantial wear and friction reduction of 88% and 25%, respectively, outperforming the PAO-4 base oil. In-depth characterizations of tribofilms formed on wear scars and tracks were conducted using various techniques, including Raman, X-ray photoelectron spectroscopy, scanning transmission electron microscopy - energy dispersive X-ray spectroscopy, and cryo-electron energy loss spectroscopy. It was found that the predominant composition of the tribofilm consists of mixed oxide and phosphate species. Notably, metallic cobalt is observed near the tribofilm-steel interface. Nanoindentation and nanoscratch were performed on the HMP tribofilm. The relationship between the nanostructure and nanomechanical properties and their influence on friction and wear have been revealed.

Infrared and Raman Diagnostic Modeling of Phosphate Adsorption on Ceria Nanoparticles.

Cerium dioxide (CeO2; ceria) nanoparticles (CeNPs) are promising nanozymes that show a variety of biological activity. Effective nanozymes need to retain their activity in the face of surface speciation in biological environments, and characterizing surface speciation is therefore critical to understanding and controlling the therapeutic capabilities of CeNPs. In particular, adsorbed phosphates can impact the enzymatic activity exploited to convert phosphate prodrugs into therapeutics in vivo and also define the early stages of the phosphate-scavenging processes that lead to the transformation of active CeO2 into inactive CePO4. In this work, we utilize ab initio lattice-dynamics calculations to study the interaction of phosphates with the three major surfaces of ceria and to predict the infrared (IR) and Raman spectral signatures of adsorbed phosphate species. We find that phosphates adsorb strongly to CeO2 surfaces in a range of stable binding configurations, of which 5-fold coordinated P species in a trigonal bipyramidal coordination may represent a stable intermediate in the early stages of phosphate scavenging. We find that the phosphate species show characteristic spectral fingerprints between 500 and 1500 cm-1, whereas the bare CeO2 surfaces show no active modes above 600 cm-1, and the 5-fold coordinated P species in particular show potential diagnostic P-O stretching modes between 650 and 700 cm-1 in both IR and Raman spectra. This comprehensive exploration of different binding modes for phosphates on CeO2 and the set of reference spectra provides an important step toward the experimental characterization of phosphate speciation and, ultimately, control of its impact on the performance of ceria nanozymes.

Surface Adsorption of Amorphous Phosphate on RuNi-Doped Molybdate for the Hydrogen Evolution Reaction.

Developing highly active and cost-effective electrocatalysts is critical for enhancing the intrinsic performance of electrocatalytic water splitting. Oxoanion-based compounds, such as phosphates and molybdates, have emerged as promising electrocatalysts owing to their advantageous properties of nontoxicity, low price, and strong water adsorption ability. However, their relatively inferior activity has impeded extensive investigation into electrochemical applications. Herein, an amorphous phosphate-adsorbed and RuNi-doped molybdate (RuNiMo-P) composite is synthesized on nickel foam (NF) support by using a simple two-step method. Significantly, an acidic solution of phosphomolybdic acid (PMo12), containing a low concentration of Ru, can etch the NF, contributing to the in situ growth of the RuNi-doped molybdate precursor. Subsequent phosphating ensures the surface formation of the amorphous phosphate layer due to abundant oxygen in the precursor. The strong structural interaction between RuNi-doped molybdate and amorphous phosphate in RuNiMo-P prompts an enhanced hydrogen evolution reaction (HER) performance, delivering an overpotential of 38 mV at a current density of -10 mA cm-2, a Tafel slope of 53 mV dec-1, and good stability in an alkaline medium. Characterizations after HER reveal that RuNi doping, partial dissolution of phosphate and molybdate species, and newly formed NiOOH nanosheets can expose active sites, facilitate charge transfer, and modify electronic structures, thereby improving the HER performance effectively.

Unveiling the Oxygen Evolution Mechanism with FeNi (Hydr)oxide under Neutral Conditions.

Large-scale solar-driven water splitting is a way to store energy, but it requires the development of practical and durable oxygen evolution reaction (OER) catalysts. The present paper aims to investigate the mechanism of the OER, local pH, high-valent metal ions, limitations, conversions, and details during the OER in the presence of FeNi foam using in situ surface-enhanced Raman spectroscopy. This research also explores the use of in situ surface-enhanced Raman spectroscopy for detecting species on foam surfaces during the OER. The acidic media around the electrode not only limit the process but also affect the phosphate ion protonation and overall catalysis effectiveness. The study proposes that FeNi hydroxides serve as true catalysts for OER under neutral conditions, rather than FeNi phosphates. However, phosphate species remain crucial for proton transfer and water molecule adsorption. Changes observed in pH at the open-circuit potential suggest new insights concerning the coordination of Ni(II) to phosphate ions under certain conditions. By extrapolating the Tafel plot, the overpotential for the onset of OER was determined to be 470 mV. Furthermore, the overpotentials for current densities of 1 and 5 mA/cm2 were 590 and 790 mV, respectively. These findings offer valuable insights into the advancement of the OER catalysts and our understanding of the underlying mechanism for efficient water splitting; both are crucial elements for the purpose of energy storage.

The role of reactive phosphate species in the abatement of micropollutants by activated peroxymonosulfate in the treatment of phosphate-rich wastewater.

This study investigated the mechanisms of forming reactive species to degrade micropollutants through the activation of peroxymonosulfate (PMS) by phosphate, a prevalent ion in wastewater. Considering the density functional theory results, the formation of hydrogen bonds between phosphate and PMS molecules might be the crucial step in the overall reactions, which prefers producing ⋅OH and reactive phosphate species (RPS, namely H2PO4⋅, HPO4⋅-, and PO4⋅2-) to yielding SO4⋅-. Besides, in the phosphate (5mM)/PMS system at pH=8, HPO4⋅- was modeled to be the dominant radical with a steady-state concentration of 3.6×10-12M, which was 666 and 773 times higher than those of ⋅OH and SO4⋅-. The contributions of 1O2, ⋅OH, SO4⋅-, and RPS to the micropollutant decomposition in phosphate/PMS were studied, and RPS were found to be selective for micropollutants with electron-donating moieties (such as phenolic and aniline groups). Additionally, the degradation pathways of bisphenol A, diclofenac, ibuprofen, and atrazine in phosphate/PMS were proposed according to the detected transformation products. Cytotoxicity analysis was carried out to evaluate the potential environmental impacts resulting from the degradation of micropollutants by phosphate/PMS. This study confirmed the significance of RPS for micropollutant degradation during PMS-based treatment in phosphate-rich scenarios.

Kinetics of the precipitation reaction between aluminium and contaminant orthophosphate ions

ABSTRACT The removal of phosphorous from wastewater in metal-orthophosphate systems typically occurs by simultaneous adsorption on poorly soluble metal hydroxides and by precipitation reactions between metal ions and orthophosphates in solution. To understand the individual contribution of these mechanisms to the removal of phosphorus, the main aim of this study was to determine the kinetics of consumption of contaminant orthophosphates by the precipitation reaction with aluminium ions in a solution free of insoluble aluminium hydroxide. To define the amount of aluminium and phosphorous compounds to be dissolved in water to have this desired reacting condition at a given pH, the solubilities of KH2PO4(s), Al(OH)3(s) and AlPO4(s) were examined at 25 °C in the pH range ∼2.6 to 7.9. pH-solubility diagrams for these ionic solids were made by solving a system of nonlinear algebraic equations involving dissolution, dissociation and hydrolysis reactions at equilibrium. The kinetics of the reaction between aluminium and orthophosphate ions at a reacting condition free of solids except for the product AlPO4(s) was investigated in a well-stirred batch reactor at pH ∼3.1 and 3.5 at 25 °C. A detailed kinetic model involving ten species, seven reversible reactions of hydrolysis of soluble aluminium and orthophosphate species and one reversible precipitation reaction between aluminium and phosphate ions revealed a rate constant for the latter reaction of 5.968 × 1010 L mol−1 s−1 (p = 0.191). XRD, TGA/DTGA and EDX analyses of the filtered and dried reacting mixture confirmed that the only solid product of the precipitation reaction was hydrated AlPO4(s).

Unexpected Cu and Zn speciation patterns in the broiler feed-animal-excreta system revealed by XAS spectroscopy

Trace minerals such as copper (Cu) and zinc (Zn) are animal nutrition supplements necessary for livestock health and breeding performance, yet they also have environmental impacts via animal excretion. Here we investigated changes in Cu and Zn speciation from the feed additive to the broiler excreta stages. The aim of this study was to assess whether different Cu and Zn feed additives induce different Cu and Zn speciation patterns, and to determine the extent to which this speciation is preserved throughout the feed-animal-excreta system. Synchrotron-based X-ray absorption spectroscopy (XAS) was used for this investigation. The principal findings were: (i) in feed, Cu and Zn speciation changed rapidly from the feed additive signature (Cu and Zn oxides or Cu and Zn sulfates) to Cu and Zn organic complexes (Cu phytate and Zn phytate). (ii) in the digestive tract, we showed that Cu and Zn phytate were major Cu and Zn species; Cu sulfide and Zn amorphous phosphate species were detected but remained minor species. (iii) in fresh excreta, Cu sulfide and Zn amorphous phosphate were major species. These results should help to: (i) enhance the design of future research studies comparing different feed additive performances; (ii) assess Cu and Zn bioavailability in the digestive tract; (iii) gain further insight into the fate of Cu and Zn in cultivated soils when poultry manure is used as fertilizer.

Phosphate Coordination in a Water-Oxidizing Cobalt Oxide Electrocatalyst Revealed by X-ray Absorption Spectroscopy at the Phosphorus K-Edge

In the research on water splitting at neutral pH, phosphorus-containing transition metal oxyhydroxides are often employed for catalyzing the oxygen evolution reaction (OER). We investigated a cobalt–phosphate catalyst (CoCat) representing this material class. We found that CoCat films prepared with potassium phosphate release phosphorus in phosphate-free electrolytes within hours, contrasting orders of magnitude’s faster K+ release. For P speciation and binding mode characterization, we performed technically challenging X-ray absorption spectroscopy experiments at the P K-edge and analyzed the resulting XANES and EXAFS spectra. The CoCat-internal phosphorus is present in the form of phosphate ions. Most phosphate species are likely linked to cobalt ions in Co–O–PO3 motifs, where the connecting oxygen could be a terminal or bridging ligand in Co-oxide fragments (P–Co distance, ~3.1 Å), with additional ionic bonds to K+ ions (P–K distance, ~3.3 Å). The phosphate coordination bond is stronger than the ionic K+-binding, explaining the strongly diverging ion release rates of phosphate and K+. Our results support a structural role of phosphate in the CoCat, with these ions binding at the margins of Co-oxide fragments, thereby limiting the long-range material ordering. The relations of catalyst-internal phosphate ions to cobalt’s redox-state changes, proton transfer, and catalytic activity are discussed.

Hybrid planktonic-biofilm cultivation of a Nordic mixed-species photosynthetic consortium: A pilot study on carbon capture and nutrient removal

Mixed-species photosynthetic consortia have several advantages over conventional microalgal monocultures, including better carbon capture, more efficient wastewater treatment, and resilience to environmental stressors. In this study, a constructed photosynthetic consortium was investigated using a hybrid cultivation approach (combined planktonic and biofilm growth) in a pilot-scale raceway pond. A blend of locally-sourced waste streams was used as growth medium; biogas digestate and aquaculture effluent. The consortium performed well in terms of carbon capture, with 80.1% and 78.6% removal of inorganic and organic carbon species, respectively, over a 42-day cultivation period. Removal of phosphate and nitrogen species was suboptimal; 46.8% of phosphate had been consumed by the end of cultivation, but just 27.9% of total nitrogen had been removed. Despite inefficient total nitrogen removal, nitrite and ammonia were almost completely depleted after 15 days. Light microscopy was employed to monitor biofilm formation and changes in biodiversity over time, which helped to elucidate the processes responsible for nutrient and carbon flux, as well as biofilm formation and interspecies associations. Understanding how different mechanisms and biological functions can be encouraged or inhibited in mixed-species consortia is imperative for tailoring consortia to industrially-relevant applications, such as carbon capture, nutrient removal, or production of biomass or specific metabolites. The present study demonstrates not only the importance of cultivating dynamic, biodiverse, and adaptable consortia instead of fragile monocultures, but also the utility in real-time monitoring of such systems, so that environmental parameters can be adjusted for optimal performance.

Optimizing Household Waste and Cow Dung Proportions for Quality Vermicompost Production

Aim: To standardize the ratio of household waste and cow dung for quality vermicompost based on physical properties.
 Study Design: Completely Randomized Design (Factorial).
 Place and Duration of Study: Vermicompost Production Unit, RPCAU, Pusa during April 2018 to June 2018.
 Methodology: Household waste was combined with cow dung in three different proportions (35:65, 50:50 and 65:35 ratio of household waste and cow dung, respectively) along with rock phosphate and suitable species of earthworms @ 2 kg per ton of material at suitable temperature and moisture (370C and 65% w/w respectively) under shade. Various physical parameters were analyzed at 30, 60 and 90 days after setting the windrows.
 Results: Vermicompost prepared from household waste and cow dung in (50:50) ratio recorded lowest moisture content 16.0% and highest water holding capacity (20.7%) at the end of vermicomposting process (90 days) and 94% of material passed through 4.0 mm IS sieve.
 Conclusion: Vermicompost prepared from household waste and cow dung in equal proportion (50:50) emerged out as better quality vermicompost based on the observed physical characteristics.

Optimization of chromatographic buffer conditions for the simultaneous analysis of phosphatidylinositol and phosphatidylinositol phosphate species in canola.

The phosphatidylinositols and phosphatidylinositol phosphates are a set of closely related lipids known to influence various cellular functions. Irregular distributions of these molecules have been correlated with the development and progression of multiple diseases, including Alzheimer's, bipolar disorder, and various cancers. As a result, there is continued interest regarding the speciation of these compounds, with specific consideration on how their distribution may differ between healthy and diseased tissue. The comprehensive analysis of these compounds is challenging due to their varied and unique chemical characteristics, and current generalized lipidomics methods have proven unsuitable for phosphatidylinositol analysis and remain incapable of phosphatidylinositol phosphate analysis. Here we improved upon current methods by enabling the sensitive and simultaneous analysis of phosphatidylinositol and phosphatidylinositol phosphate species, whilst enhancing their characterization through chromatographic resolution between isomeric species. A 1mM ammonium bicarbonate and ammonia buffer was determined optimal for this goal, enabling the identification of 148 phosphatidylinositide species, including 23 lyso-phosphatidylinositols, 51 phosphatidylinositols, 59 oxidized-phosphatidylinositols, and 15 phosphatidylinositol phosphates. As a result of this analysis, four distinct canola cultivars were differentiated based exclusively on their unique phosphatidylinositide-lipidome, indicating analyses of this type may be of use when considering the development and progression of the disease through lipidomic profiles.

Choice of Electrolyte Impacts the Selectivity of Proton-Coupled Electrochemical Reactions on Hydrogen Titanate

Proton-coupled electron transfer (PCET) reactions involving transition metal oxides are prevalent in aqueous electrochemical systems used for energy storage and conversion. Here, we elucidate the role of electrolyte on PCET mechanisms in transition metal oxides in aqueous acidic electrolytes using layered hydrogen titanate (H2Ti3O7) as an example. We identify three processes by which electrolyte protons interact with hydrogen titanate at the electrochemical interface: (1) adsorption at the surface and/or insertion into the bulk, (2) adsorption as part of the hydrogen evolution reaction (HER) at the surface, and (3) dissolution of the hydrogen titanate. We utilize a combined experimental and computational (ReaxFF) approach to probe how the competition for protons and electrons among these processes influences electrochemical properties, including the energy storage, Coulombic efficiency (CE), rate capability, and lifetime. In an acidic buffered electrolyte (1 M H3PO4), the CE increases from an average of 48% to 71% and the specific capacity increases from 83 to 90 mAh g–1 as compared to a strong acid electrolyte (1 M H2SO4). We propose that H3PO4 mitigates the HER and hydrogen titanate dissolution, thereby increasing the operating potential window for proton adsorption/insertion for charge storage in hydrogen titanate. Material characterization and computational results indicate that adsorption of phosphate species onto the surface of hydrogen titanate may decrease its dissolution upon reduction, thereby improving electrode performance. We offer a preliminary solution to improve energy storage performance via electrolyte tuning by decreasing the prevalence of the HER and electrode dissolution.

Photosystems under high light stress: throwing light on mechanism and adaptation.

High light stress decreases the photosynthetic rate in plants due to photooxidative damage to photosynthetic apparatus, photoinhibition of PSII, and/or damage to PSI. The dissipation of excess energy by nonphotochemical quenching and degradation of the D1 protein of PSII and its repair cycle help against photooxidative damage. Light stress also activates stress-responsive nuclear genes through the accumulation of phosphonucleotide-3'-phosphoadenosine-5'-phosphate, methylerythritol cyclodiphosphate, and reactive oxygen species which comprise the chloroplast retrograde signaling pathway. Additionally, hormones, such as abscisic acid, cytokinin, brassinosteroids, and gibberellins, play a role in acclimation to light fluctuations. Several alternate electron flow mechanisms, which offset the excess of electrons, include activation of plastid or plastoquinol terminal oxidase, cytochrome b 6/f complex, cyclic electron flow through PSI, Mehler ascorbate peroxidase pathway or water-water cycle, mitochondrial alternative oxidase pathway, and photorespiration. In this review, we provided insights into high light stress-mediated damage to photosynthetic apparatus and strategies to mitigate the damage by decreasing antennae size, enhancing NPQ through the introduction of mutants, expression of algal proteins to improve photosynthetic rates and engineering ATP synthase.

A novel electric spark precipitation and electrospinning strategy to prepare cerium hydroxide nanocomposite for phosphate uptake from aqueous solutions

Phosphorus is a main cause of eutrophication in water bodies, the use of adsorbents to reduce phosphate concentration in water is considered an effective way to combat eutrophication. Herein, a new and effective strategy for phosphorus removal with a PAN based cerium hydroxide nanocomposite (CHP) is shown, we combined electrospinning and spark ablation techniques, where an electrospun fiber membrane polyacrylonitrile (PAN) was used as a carrier, spark ablation produced clean nano-cerium aerosol embedded in it as the active ingredient, and a combined hydrothermal method to develop PAN based cerium hydroxide nanocomposite (CHP), the crystal size of ceria nanoparticles was 120–210 nm. CHP can capture phosphate selectively with a maximum adsorption capacity of 86.7 mg·P/g, which is higher than that for most cerium-based adsorbents and is easily separated from the liquid with high efficiency and economy. The adsorption mechanism showed that CeO2 plays an important role in phosphorus adsorption through oxidation, reduction, and ligand exchange. Compared to mesoporous structures, fibrous structures are more favorable for reducing the aggregation of nanoparticles (NPs) and adsorption of large phosphate species. The spark ablation method immobilized active cerium dioxide NPs very stably on the fiber with high efficiency and limited environmental impact. In conclusion, our results have promising applications for lake eutrophication treatment.

Ascendancy of Cr2O3 on morphology, spectroscopic and dielectric properties of GeO2–Li2O–P2O5–MgO glasses

The dielectric, physical, and optical properties of 5GeO2–30Li2O–55P2O5–(10-x)MgO–xCr2O3 (x varies from 0 to 0.9 mol%) glasses were investigated. The specimens were synthesized using melt quenching and heat treatment techniques. The non-crystalline behavior of the specimens was analyzed by X-ray diffraction. The physical parameters of these glasses were also determined. These parameters indicate the compact nature of the glasses. The optical absorption spectra of the specimens show bands corresponding to Cr3+ ions. The optical band gap (Eg) and Urbach energy (ΔE) of glasses were evaluated. Fourier-transform infrared and Raman spectra showed typical bands related to the phosphate species and supported the structural changes in the glasses. The emission and electron spin resonance (ESR) spectra confirmed the presence of chromium ions (Cr3+ state) in the glasses. An increase in the intensity of the ESR resonance signals and emission bands suggested an increase in the number of chromium ions. The dielectric parameters of the samples are also determined.

Effects of carbonate species and chloride ions on calcium phosphate nucleation of biological apatite

Apatite is the principal inorganic component of biological hard tissues such as bone and teeth, and thus is essential to the existence of vertebrate life. Because carbonate species and chloride ions are ubiquitous in the fluids of vertebrate life forms, and these species are known to compete with phosphate species, it is critical to understand the influence of these anions on the nucleation of biological apatite. In this study, the important roles of carbonate and chloride ions in mediating inorganic calcium phosphate (CaP) phase nucleation are revealed both theoretically and experimentally. Theoretical investigations suggest that the Ca-O coordination number is an important descriptor for the nucleation of CaP and the interface interaction of the CaP-additive. Positive surface charges on the outermost Ca2+ ions of CaP clusters could attract carbonate species and Cl− ions, promoting the formation of CaP phase. In the presence of carbonate species and Cl− ions, the crystallization of hydroxyapatite (HA) from its precursor brushite (DCPD) has been observed in our experimental studies. The Cl− ion-doped B-type HA is proposed to be the most likely biological apatite based on equilibrium oxygen isotope fractionation and vibrational spectroscopic analysis. The insight gained here may help rationalize the control of biomineralization, and will guide the synthesis of anion-doped biological functional apatite materials.

A novel method of iron oxalate production through the valorization of red mud

Bauxite residues known as “Red Mud” (RM) are the principal waste of caustic digestion of bauxite from the Bayer Process, whose costs of disposal are expensive and cover 5 % of the total costs of extraction and processing for aluminum production. Nevertheless, this material can be considered an important source of high-value elements, such as rare earths (REEs) and metals, Fe, Ti, Al and others. In this work, the focus has been on the recovery of iron in the form of the compound Fe(II) oxalate. Four types of acids have been used (HCl, H2SO4, H3PO4, H2C2O4) for iron extraction from RM coming from Montenegro. Hydrochloric acid shows a higher iron extraction capacity, reaching an iron extraction yield in solution of 22.6 %. Sulfuric and phosphoric acid, instead, interacted with RM leading to the formation of sulfonate and phosphate species, inhibiting the leaching ability of individual species. Oxalic acid showed the least amount of iron ions extracted but formed a stable ionic complex in solution, Fe2(C2O4)3∙2 H2O. Starting from this complex it was possible to recover the corresponding salt by a reduction and precipitation process. Through a pre-treatment with HCl and a subsequent treatment with oxalic acid, it was possible to obtain a better yield of iron oxalate. Starting from the laboratory scale, a CHEMCAD plant was conceptualized with a yield higher than 16 % per pass (repeatable 3 times with a global iron yield>50 %) and obtaining iron(II) oxalate dihydrate with purity up to 96%wt. In a holistic view of the problem, the proposed process can operate in parallel with other procedures proposed in the literature for the recovery of other valuable substances from red mud. Data Availability StatementNot applicable.

Introducing the 3R Program in Teaching Laboratories to Promote Sustainability Science through Miniaturization Studies on the Spectrophotometric Determination of Organic Carbon and Phosphorus in Soil

The general assembly meeting of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 2015 adopted the 17 Sustainable Development Goals (SDGs) aimed at achieving a better and more sustainable world by 2030. Incorporating sustainable values through a series of pedagogical strategies into university curricula to help future professionals enhance their understanding of sustainability and how they relate to it is one of the crucial steps to help achieve Sustainable Development Goals (SDGs) through education. Inspired by the principles of Green Analytical Chemistry (GAC) and the “3R” (reduce, recycle, and reuse) approach, a laboratory experiment has been developed to illustrate the basic concept of reaction miniaturization step by step. This article presents a novel experimental design consisting of 7 sessions, which includes all elements of the 3R approach. Herein, students miniaturize the conventional calorimetric determination of soil organic carbon (OC) and soil available phosphorus (P) utilizing recycled microtips and microcentrifuge tubes. Students apply their critical thinking abilities to compute and compare the waste generated, the analysis cost, and the time required for each test using the conventional approach (CA) and miniature approach (MA). They further assess the greenness of both approaches using the open-source Analytical GREEnness (AGREE) software. While students carry out these experiments, they acquire laboratory skills and reinforce their understanding of sustainability, Beer–Lambert law, how OC relates to the bioavailability of anionic nutrients such as PO43– phosphate species, and how such relationships can statistically vary based on the methods applied. Learning outcomes were assessed to evaluate the experimental design.

Self-Induced and Progressive Photo-Oxidation of Organophosphonic Acid Grafted Titanium Dioxide.

While synthesis-properties-performance correlations are being studied for organophosphonic acid grafted TiO2 , their stability and the impact of the exposure conditions on possible changes in the interfacial surface chemistry remain unexplored. Here, the impact of different ageing conditions on the evolution of the surface properties of propyl- and 3-aminopropylphosphonic acid grafted mesoporous TiO2 over a period of 2 years is reported, using solid-state 31 P and 13 C NMR, ToF-SIMS and EPR as main techniques. In humid conditions under ambient light exposure, PA grafted TiO2 surfaces initiate and facilitate photo-induced oxidative reactions, resulting in the formation of phosphate species and degradation of the grafted organic group with a loss of carbon content ranging from 40 to 60 wt %. By revealing its mechanism, solutions were provided to prevent degradation. This work provides valuable insights for the broad community in choosing optimal exposure/storage conditions that extend the lifetime and improve the materials' performance, positively impacting sustainability.

Selective excitation with recoupling pulse schemes uncover properties of disordered mineral phases in bone-like apatite grown with bone proteins

Bone construction has been under intensive scrutiny for many years using numerous techniques. Solid-state NMR spectroscopy helped unravel key characteristics of the mineral structure in bone owing to its capability of analyzing crystalline and disordered phases at high-resolution. This has invoked new questions regarding the roles of persistent disordered phases in structural integrity and mechanical function of mature bone as well as regarding regulation of early events in formation of apatite by bone proteins which interact intimately with the different mineral phases to exert biological control.Here, spectral editing tethered to standard NMR techniques is employed to analyze bone-like apatite minerals prepared synthetically in the presence and absence of two non-collagenous bone proteins, osteocalcin and osteonectin. A 1H spectral editing block allows excitation of species from the crystalline and disordered phases selectively, facilitating analysis of phosphate or carbon species in each phase by magnetization transfer via cross polarization. Further characterization of phosphate proximities using SEDRA dipolar recoupling, cross-phase magnetization transfer using DARR and T1/T2 relaxation times demonstrate that the mineral phases formed in the presence of bone proteins are more complex than bimodal. They reveal disparities in the physical properties of the mineral layers, indicate the layers in which the proteins reside and highlight the effect that each protein imparts across the mineral layers.