Phosphate Species Research Articles

Characterization of chemical reactions of silver diammine fluoride and hydroxyapatite under remineralization conditions.

Silver Diammine Fluoride (SDF) is a clinically used topical agent to arrest dental caries. However, the kinetics of its chemical interactions with hydroxyapatite (HA), the principal inorganic component of dental enamel, are not known. The aim was to characterize the step-wise chemical interactions between SDF and HA powder during the clinically important process of remineralization. Two grams of HA powder were immersed in 10 ml acetic acid pH = 4.0 for 2 h to mimic carious demineralization. The powder was then washed and dried for 24 h and mixed with 1.5 ml SDF (Riva Star) for 1 min. The treated powder was then air-dried for 3 min, and 0.2 g was removed and stored in individual tubes each containing 10 ml remineralizing solution. Powder was taken from each tube at various times of exposure to remineralization solution (0 min, 10 min, 2 h, 4 h, 8 h, 24 h, and 10 days), and characterized using Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) spectroscopy. 19F MAS-NMR spectra showed that calcium fluoride (CaF2) started to form almost immediately after HA was in contact with SDF. After 24 h, the peak shifted to -104.5 ppm suggesting that fluoride substituted hydroxyapatite (FSHA) was formed with time at the expense of CaF2. The 31P MAS-NMR spectra showed a single peak at 2.7 ppm at all time points showing that the only phosphate species present was crystalline apatite. The 35Cl MAS-NMR spectra showed formation of silver chloride (AgCl) at 24 h. It was observed that after the scan, the whitish HA powder changed to black color. In conclusion, this time sequence study showed that under remineralization conditions, SDF initially reacted with HA to form CaF2 which is then transformed to FSHA over time. In the presence of chloride, AgCl is formed which is subsequently photo-reduced to black metallic silver.

Crucial Chemical Revelations in 45S5 Bioactive Glass via Sequential Precursor Integration Order.

Among the wet chemical nanoparticle fabrication techniques, the sol-gel process happens through hydrolysis and subsequent polycondensation reactions. The bioactive glass known as the 45S5 SiO2-Na2O-CaO-P2O5 quaternary system has intricate chemistry, yet its advantages benefit the biomedical field on an enormous scale. The order in which the ethanol and TEOS inclusions are exchanged was investigated in this work because it has a direct impact on the early hydrolysis process. Another strategy involves adding phosphate species to the sol before gelation, modifying the network chemistry, and interpreting the findings. Adding phosphate species before gelation in the biomaterial (E-Si-P) resulted in the formation of hydroxyapatite and other calcium silicate phases at 800 °C. Swapping ethanol and TEOS biomaterials (E-Si and Si-E) resulted in the sodium-calcium silicate phase only. Si-E with strong Si-O-Si siloxane rings demonstrated superior mechanical stability, hemocompatibility, and bioactivity. This compact Si-O-Si decreased the surface area of Si-E. XPS spectra revealed that E-Si-P has the lowest Na 1s binding energy (BE) and the highest BE for Si 2p. More Si-O-/Si-OH groups formed by E-Si make the network weak and decrease the surface area and protein adsorption. These differences significantly influenced the morphology, surface properties, mechanical studies, and compatibility test. This study has further unraveled the protocol to design a biomaterial with mechanical stability and load-bearing ability. In addition, the appropriate protocol to yield the desired property-rich biomaterial with preserved bioactivity, mechanical stability, cytocompatibility, as well and surface porosity has been elaborated in detail.

APOE genotype dictates lipidomic signatures in primary human hepatocytes

Apolipoprotein E (APOE) genetic variants are most notably known for their divergent impact on the risk of developing Alzheimer’s disease. While APOE genotype has been consistently shown to modulate lipid metabolism in a variety of cellular contexts, the effect of APOE alleles on the lipidome in hepatocytes is unknown. In this study, we investigated the contribution of APOE alleles to lipidomic profiles of donor-derived primary human hepatocytes from 77 subjects. Lipidomic data obtained by liquid chromatography-mass spectrometry were analyzed across ε2/ε3, ε3/ε3, and ε3/ε4 genotypes to reveal how APOE modulates lipid relative levels over age and between groups. Hepatic APOE concentration, measured by ELISA, was assessed for correlation with lipid abundance in subjects grouped as per APOE genotype and sex. APOE genotype-specific differential lipidomic signatures associated with age for multiple lipid classes but did not differ between sexes. Compared to ε2/ε3, ε3/ε4 hepatocytes had higher abundance of acylcarnitines (AC) and acylphosphatidylglycerol (AcylPG) as a class, as well as higher medium and long-chain ACs, AcylPG, phosphatidylglycerol (PG), bis(monoacylglycerol)phosphate (BMP), monoacylglycerol (MG) and diacylglycerol (DG) species. The ε3/ε4 hepatocytes also exhibited a higher abundance of medium and long-chain ACs compared to the ε3/ε3 hepatocytes. Only in the ε3/ε4 hepatocytes, APOE concentration was lower and showed a negative correlation with BMP levels, specifically in females. APOE genotype dictates a differential lipidome in primary human hepatocytes. The lipids involved suggest mitochondrial dysfunction with accompanying alterations in neutral lipid storage, reflective of a general disturbance of free fatty acid metabolism in human hepatocytes with the ε4 allele.

CLN3 deficiency leads to neurological and metabolic perturbations during early development.

Juvenile neuronal ceroid lipofuscinosis (or Batten disease) is an autosomal recessive, rare neurodegenerative disorder that affects mainly children above the age of 5 yr and is most commonly caused by mutations in the highly conserved CLN3 gene. Here, we generated cln3 morphants and stable mutant lines in zebrafish. Although neither morphant nor mutant cln3 larvae showed any obvious developmental or morphological defects, behavioral phenotyping of the mutant larvae revealed hyposensitivity to abrupt light changes and hypersensitivity to pro-convulsive drugs. Importantly, in-depth metabolomics and lipidomics analyses revealed significant accumulation of several glycerophosphodiesters (GPDs) and cholesteryl esters, and a global decrease in bis(monoacylglycero)phosphate species, two of which (GPDs and bis(monoacylglycero)phosphates) were previously proposed as potential biomarkers for CLN3 disease based on independent studies in other organisms. We could also demonstrate GPD accumulation in human-induced pluripotent stem cell-derived cerebral organoids carrying a pathogenic variant for CLN3 Our models revealed that GPDs accumulate at very early stages of life in the absence of functional CLN3 and highlight glycerophosphoinositol and BMP as promising biomarker candidates for pre-symptomatic CLN3 disease.

Osteocalcin: Promoter or Inhibitor of Hydroxyapatite Growth?

Osteocalcin is the most abundant noncollagenous bone protein and the functions in bone remineralization as well as in inhibition of bone growth have remained unclear. In this contribution, we explain the dual role of osteocalcin in the nucleation of new calcium phosphate during bone remodeling and in the inhibition of hydroxyapatite crystal growth at the molecular scale. The mechanism was derived using pH-resolved all-atom models for the protein, phosphate species, and hydroxyapatite, along with molecular dynamics simulations and experimental and clinical observations. Osteocalcin binds to (hkl) hydroxyapatite surfaces through multiple residues, identified in this work, and the fingerprint of binding residues varies as a function of the (hkl) crystal facet and pH value. On balance, the affinity of osteocalcin to hydroxyapatite slows down crystal growth. The unique tricalcium γ-carboxylglutamic acid (Gla) domain hereby rarely adsorbs to hydroxyapatite surfaces and faces instead toward the solution. The Gla domain enables prenucleation of calcium phosphate for new bone formation at a slightly acidic pH of 5. The growth of prenucleation clusters of calcium phosphate continues upon increase in pH value from 5 to 7 and is much less favorable, or not observed, on the native osteocalcin structure at and above neutral pH values of 7. The results provide mechanistic insight into the early stages of bone remodeling from the molecular scale, help inform mutations of osteocalcin to modify binding to apatites, support drug design, and guide toward potential cures for osteoporosis and hyperosteogeny.

Growth and phosphate uptake of microalgae under different phosphate conditions

Microalgae could utilize the nutrients in the environment and therefore are widely used in wastewater treatment. The variety and complexity of phosphates in the water column and different types of wastewater can affect the growth of microalgae, which further affects the treatment efficiency of phosphorus- containing wastewater. In this study, phosphate uptake and microalgal growth were investigated under different phosphate conditions. The results showed that the increase of phosphate concentration could promote the growth of microalgae. Phosphate species affected the phosphate uptake and transformation process. Orthophosphate and polyphosphate were first adsorbed on the surface of microalgae and then transported inside the cell. Polyphosphates produce desorption in the early stages of uptake. The adsorbed polyphosphates were released back into the culture medium and were taken up and utilized again in the later stages of incubation. Polyphosphates were taken up and utilized by microalgae for a longer period of time than orthophosphates. It was also found that orthophosphate was more readily utilized by microalgae compared to polyphosphate. An increase in phosphate concentration promotes the growth of microalgae.

Probing the Effect of Environments on the Stability of Ni2P Nanoparticle Electrocatalysts

Ni2P has been shown to be an effective catalyst for the hydrogen evolution reaction (HER), making it a promising replacement for Pt which is the current state of the art HER catalyst.1,2 H2 is a clean-energy critical fuel and chemical highlighted by the US Department of Energy’s “Hydrogen Shot,” which seeks to reduce “the cost of carbon-neutral hydrogen by 80% to $1 per 1 kg in 1 decade, highlighting the key role of hydrogen in implementing carbon-neutral solutions.”3 Ni2P is also a good or promising catalyst for other reactions, such as alcohol oxidation, hydrodesulfurization,4,5 nitrate reduction, and oxygen evolution reaction.6 However, Ni2P and other TMPs are susceptible to oxidation, which can lead to catalyst degradation and loss in certain conditions.7,8 Stability is an important part of catalysis, especially for achieving the goals of the Hydrogen Shot. Therefore, it is important to understand complex degradation mechanisms in order to better understand structure-activity relationships in these materials. In the present work, in situ Ni K-edge X-ray absorption spectroscopy (XAS) and ex situ P Kα and Kβ X-ray emission spectroscopy (XES) couple together to understand the degradation of Ni2P and show the effects of electrolyte pH, ligands, and air on Ni2P nanoparticles.5 nm Ni2P nanoparticles were synthesized by heating NiCl2 and tris(diethylamino)phosphine in oleylamine. The nanoparticles were drop cast onto carbon fiber paper electrodes and Si wafers or Au-coated wafers for P Kα and Kβ XES. Oleylamine ligands are removed by thermal annealing. Electrochemical experiments were conducted with a three-electrode cell using carbon fiber paper or Au-coated wafers deposited with Ni2P nanoparticles as working electrode, Ag/AgCl calibrated to the H2 redox couple as reference electrode, and graphite rod as counter electrode. P Kα and Kβ XES experiments were conducted inside a N2 glovebox to prevent unintentional air oxidation. Transmission-mode Ni K-edge XAS was conducted on a benchtop spectrometer.Upon exposure to air, as-synthesized Ni2P nanoparticles were studied via P Kα and Kβ XES. Results showed that the phosphide species converted to phosphate with analysis of intermediates well fit by a simple two-phase mixture. Phosphide:phosphate ratios were quantified using linear combination analysis, providing a powerful tool to analyze P speciation on various samples in an inert environment and with minimal loss of material, both advantages of this system over 31P magic angle spinning solid state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. Continued work looks at analyzing the effects of the ligand environment on the stability of nanoparticles in electrolytes spanning from acidic to basic pH. We hypothesize that ligands will significantly stabilize the nanoparticles against corrosion and that without ligands Ni2P readily converts to a nickel phosphate species upon exposure to electrolyte.References(1) Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2013, 135 (25), 9267–9270. https://doi.org/10.1021/ja403440e.(2) Liu, P.; Rodriguez, J. A. Catalysts for Hydrogen Evolution from the [NiFe] Hydrogenase to the Ni2P(001) Surface: The Importance of Ensemble Effect. J. Am. Chem. Soc. 2005, 127 (42), 14871–14878. https://doi.org/10.1021/ja0540019.(3) Bullock, M.; More, K. Basic Energy Sciences Roundtable: Foundational Science for Carbon-Neutral Hydrogen Technologies (Report); DOESC Office of Basic Energy Sciences, 2022. https://doi.org/10.2172/1834317.(4) Layan Savithra, G. H.; Muthuswamy, E.; Bowker, R. H.; Carrillo, B. A.; Bussell, M. E.; Brock, S. L. Rational Design of Nickel Phosphide Hydrodesulfurization Catalysts: Controlling Particle Size and Preventing Sintering. Chem. Mater. 2013, 25 (6), 825–833. https://doi.org/10.1021/cm302680j.(5) Rodriguez, J. A.; Kim, J.-Y.; Hanson, J. C.; Sawhill, S. J.; Bussell, M. E. Physical and Chemical Properties of MoP, Ni2P, and MoNiP Hydrodesulfurization Catalysts: Time-Resolved X-Ray Diffraction, Density Functional, and Hydrodesulfurization Activity Studies. J. Phys. Chem. B 2003, 107 (26), 6276–6285. https://doi.org/10.1021/jp022639q.(6) Menezes, P. W.; Indra, A.; Das, C.; Walter, C.; Göbel, C.; Gutkin, V.; Schmeiβer, D.; Driess, M. Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting. ACS Catal. 2017, 7 (1), 103–109. https://doi.org/10.1021/acscatal.6b02666.(7) Ha, D.-H.; Han, B.; Risch, M.; Giordano, L.; Yao, K. P. C.; Karayaylali, P.; Shao-Horn, Y. Activity and Stability of Cobalt Phosphides for Hydrogen Evolution upon Water Splitting. Nano Energy 2016, 29, 37–45. https://doi.org/10.1016/j.nanoen.2016.04.034.(8) Parra-Puerto, A.; Ng, K. L.; Fahy, K.; Goode, A. E.; Ryan, M. P.; Kucernak, A. Supported Transition Metal Phosphides: Activity Survey for HER, ORR, OER, and Corrosion Resistance in Acid and Alkaline Electrolytes. ACS Catal. 2019, 11515–11529. https://doi.org/10.1021/acscatal.9b03359.

Theoretical and Experimental Studies of Molecular Interactions between Engineered Graphene and Phosphate Ions for Graphene-Based Phosphate Sensing.

Fundamental understanding of the interactions of nanoscale materials with molecules of interest is essential for the development of electronic devices, such as sensors. In particular, structures and molecular interaction properties of engineered graphenes are still largely unexplored, despite these materials' great potential to be used as molecular sensors. As an example of end user application, the detection of phosphorus in the form of phosphate in a soil environment is important for soil fertility and plant growth. However, due to the lack of an affordable technology, it is currently hard to measure the amount of phosphate directly in the soil; therefore, suitable sensor technologies need to be developed for phosphate sensors. In this work, pristine graphene and several modified graphene materials (oxygenated graphene, graphene with vacancies, and curved graphene) were studied as candidates for phosphate sensor materials using density functional theory (DFT) calculations. Our calculations showed that both pristine graphene and functionalized graphene were able to adsorb phosphate species strongly. In addition, these graphene nanomaterials showed selectivity of adsorption of phosphate with respect to nitrate, with stronger adsorption energies for phosphate. Furthermore, our calculations showed significant changes in electrical conductivities of pristine graphene and functionalized graphenes after phosphate species adsorption, in particular, on graphene with oxygen (hydroxyl and epoxide) functional groups. Experimental measurements of electrical resistivity of graphene before and after adsorption of dihydrogen phosphate showed an increase in resistivity upon adsorption of phosphate, consistent with the theoretical predictions. Our results recommend graphene and functionalized graphene-based nanomaterials as good candidates for the development of phosphate sensors.

Enhancement of optical and radiation shielding properties in calcium–magnesium silicate bioactive glasses through Na2O and P2O5 additives

The present study investigates the influence of Na2O/MgO and P2O5/SiO2 substitutions on the structure and protective properties of bioactive glasses composed of 32CaO–19MgO–0.5P2O5–0.5CaF2–48SiO2 (mole %). The glass samples are prepared using the conventional melt-quenching method. Optical analyses, including refractive index (n), molar refraction (Rm), and cationic polarizability (αm), are calculated and discussed to examine structural modifications. Raman spectroscopy is employed for detailed structural analysis. The effects of compositional changes on the protective parameters are thoroughly investigated by theoretically determining mass attenuation using the newly developed Phy-X/PSD software and XCOM programs, which are then experimentally confirmed at three selected radioactive isotope energies. Experimental measurements of mass attenuation coefficient follow the sequence: MACG1 > MACG2 > MACG3 > MACG4. Raman spectroscopy results indicate that the glass network primarily consists of silicate and phosphate species as the main structural units. An increase in the molar ratio of Na2O and P2O5 improves the radiation shielding effectiveness of the samples. Among them, sample G5, with the lowest SiO2 and MgO content, exhibits the best shielding characteristics due to its high density and molar fraction of Na2O and P2O5. A correlation between microhardness and protective effectiveness is also established. The obtained results support the potential use of these glasses as dual agents for both radiation shielding and medical devices simultaneously.

Destabilization mechanism of acid aluminum phosphate solution: Effects of P/Al ratio, concentration and boron doping

The poor long-term stability of acid aluminum phosphate (AAP) solutions limits their industrial application. To understand its destabilization mechanism, the effects of phosphorus to aluminum ratio, concentration, and boron doping on the stability of the AAP solution are investigated. The destabilization mechanism involves polymerizing the aluminum phosphate species to form insoluble aluminum phosphate compounds. The solution concentration controls the polymerization kinetics, and reducing the concentration can improve the stability of the AAP solution. Boron introduction improves solution stability by reducing the number of active sites on the aluminum phosphate species available for polymerization and by increasing solution viscosity to restrict the movement of the aluminum phosphate species.

APOE genotype‐specific lipidomic signatures in primary human hepatocytes

AbstractBackgroundApolipoprotein E (APOE) is primarily responsible for cholesterol homeostasis in the periphery and in the brain through independently regulated pathways, as it does not cross the blood‐brain barrier (BBB). Carriers of the APOE ε4 allele have a 3‐ to 15‐fold higher risk of developing Alzheimer’s disease (AD). Recently, we demonstrated that hepatic APOE4 was associated with alterations in AD‐relevant brain functions, suggesting clinical significance of plasma APOE, 90% of which is derived from the liver. How APOE genotype affects the hepatic lipidome is yet unknown. In this study, we assessed APOE genotype‐specific lipidomic profiles of primary human hepatocytes and their association with hepatic APOE.MethodWe conducted a lipidomic analysis of primary human hepatocytes isolated from 77 subjects by use of Ultra Performance Liquid Chromatography‐Tandem Mass Spectrometry. Lipid class levels over age across ε2/ε3, ε3/ε3 and ε3/ε4 genotypes were assessed using Pearson correlation analysis and between‐group comparisons for lipid class and species levels, controlled for demographic variables, were performed using one‐way ANOVA with Tukey HSD correction for multiple comparisons. We assessed hepatic APOE levels by ELISA in order to compare APOE expression between APOE genotypes and investigate correlations with lipid levels.ResultWe found APOE allele‐specific lipidomic patterns over age and between groups. APOE genotype differentially modulated the relationship between age and lipid levels across multiple lipid classes. The ε4 carriers had higher acylcarnitines (AC) and acylphosphatidylglycerol (AcylPG) as a class, as well as higher medium and long‐chain ACs, AcylPG, bis(monoacylglycerol)phosphate (BMP), monoacylglycerol and diacylglycerol species compared to ε2 carriers. Hepatocyte APOE levels decreased with age in the whole cohort, but correlated with monoacylglycerols (MG) and phosphatidylcholine (PC) only in ε4 carriers. We observed no differences in APOE hepatocyte levels specific to genotype or sex of the donor.ConclusionAPOE genotype dictates a differential lipidome in primary human hepatocytes but has no effect on APOE levels. The lipids involved suggest mitochondrial dysfunction with accompanying alterations in neutral lipid storage, reflective of a general disturbance of free fatty acid metabolism in human hepatocytes with the ε4 allele.

Ultrahigh-porosity Ranunculus-like MgO adsorbent coupled with predictive deep belief networks: A transformative method for phosphorus treatment

Phosphorus is a nonrenewable material with a finite supply on Earth; however, due to the rapid growth of the manufacturing industry, phosphorus contamination has become a global concern. Therefore, this study highlights the remarkable potential of ranunculus-like MgO (MO4–MO6) as superior adsorbents for phosphate removal and recovery. Furthermore, MO6 stands out with an impressive adsorption capacity of 596.88 mg/g and a high efficacy across a wide pH range (2–10) under varying coexisting ion concentrations. MO6 outperforms the top current adsorbents for phosphate removal. The process follows Pseudo-second-order and Langmuir models, indicating chemical interactions between the phosphate species and homogeneous MO6 monolayer. MO6 maintains 80 % removal and 96 % recovery after five cycles and adheres to the WHO and EUWFD regulations for residual elements in water. FT-IR and XPS analyses further reveal the underlying mechanisms, including ion exchange, electrostatic, and acid-base interactions. Ten machine learning (ML) models were applied to simultaneously predict multi-criteria (sorption capacity, removal efficiency, final pH, and Mg leakage) affected by 15 diverse environmental conditions. Traditional ML models and deep neural networks have poor accuracy, particularly for removal efficiency. However, a breakthrough was achieved by the developed deep belief network (DBN) with unparalleled performance (MAE = 1.3289, RMSE = 5.2552, R2 = 0.9926) across all output features, surpassing all current studies using thousands of data points for only one output factor. These captivating MO6 and DBN models also have immense potential for effectively applying in the real water test with error < 5 %, opening immense horizons for transformative methods, particularly in phosphate removal and recovery.

Insight into the Change in Local pH near the Electrode Surface Using Phosphate Species as the Probe.

The difference between solution pH and local pH near an electrode surface greatly determines the electrocatalytic performance. However, there is still a lack of a facile and universal method for the local pH detection of various electrode reactions, leaving the origin of local pH changes unclear. Herein, by using phosphate species in phosphate buffer solution (PBS) as the pH probe, we demonstrate a universal local pH detection strategy through in situ Raman spectroscopy for various electrode reactions. Oxygen evolution is chosen as the example to detect the potential-dependent local pH change. Then the strategy extends to nitrate reduction, nitrobenzene reduction, and benzylamine oxidation. By comparing the local pH changes in different reactions, we reveal that the local pH change is strongly dependent on the reaction current, the ability of the system to replenish the local H+/OH-, and the number of H+/OH- per electron transfer of the electrode reaction.

Low-temperature hydroformylation of ethylene by phosphorous stabilized Rh sites in a one-pot synthesized Rh-(O)-P-MFI zeolite

Zeolites containing Rh single sites stabilized by phosphorous were prepared through a one-pot synthesis method and are shown to have superior activity and selectivity for ethylene hydroformylation at low temperature (50 °C). Catalytic activity is ascribed to confined Rh2O3 clusters in the zeolite which evolve under reaction conditions into single Rh3+ sites. These Rh3+ sites are effectively stabilized in a Rh-(O)-P structure by using tetraethylphosphonium hydroxide as a template, which generates in situ phosphate species after H2 activation. In contrast to Rh2O3, confined Rh0 clusters appear less active in propanal production and ultimately transform into Rh(I)(CO)2 under similar reaction conditions. As a result, we show that it is possible to reduce the temperature of ethylene hydroformylation with a solid catalyst down to 50 °C, with good activity and high selectivity, by controlling the electronic and morphological properties of Rh species and the reaction conditions.

Influence of Artificially Altered Engine Oil on Tribofilm Formation and Wear Behaviour of Grey Cast Cylinder Liners

This work investigates the influence of altered engine oil on the tribological performance, focusing in particular on wear and interconnected tribofilm formation. For this purpose, Zinc dialkyldithiophosphate (ZDDP) additivated engine oils of different degradation levels, produced in an artificial oil alteration process, were used in tribometer tests with a nitride steel piston ring against a grey cast iron cylinder liner model contact. Parameters were chosen to simulate the boundary and mixed lubrication regime typical for the top dead centre conditions of an internal combustion engine of a passenger car. Wear of the cylinder liner specimens was continuously monitored during the tribometer tests by the radio-isotope concentration (RIC) method, and tribofilms were posteriorly investigated by X-ray photoelectron spectroscopy (XPS). The results clearly show that the steady-state wear rates for experiments with altered lubricants were significantly lower than for the experiments with fresh lubricants. XPS analysis on the formed tribofilms revealed a decrease in sulphide and an increase in sulphate states for altered oils evaluated at 120 °C oil temperature, correlating with a decrease in steady-state wear rate. This finding emphasizes the role of sulphate species in the tribofilm formation process and its anti-wear capabilities, in contrast to the sulphide species and the (poly-)phosphate species, as outlined in most of the ZDDP literature. Moreover, the RIC signal that represents the amount of wear in the engine oil showed a decrease over time for specific altered lubricants and test conditions. These “negative” trends in the wear signal are remarkable and have been identified as an incorporation of wear particles from the lubricant into the tribofilm. This finding is supported by XPS results that detected an iron-oxide layer with a remarkably similar quantity within the tribofilm on the surface. Based on these findings, an assessment of the minimum film formation rate and particle incorporation rate was achieved, which is an important basis for adequate tribofilm formation and wear models.

Aiming to a smart agriculture through the electrochemical impedance of a chitosan-molybdate membrane as a function of available phosphate species

Aiming to a smart agriculture through the electrochemical impedance of a chitosan-molybdate membrane as a function of available phosphate species

Sustainable removal of nutrients (n and p) in a wastewater treatment plant, with eggshell (biocalcium)

Biological treatments have become insufficient to treat municipal wastewater with greater toxicity and excess nitrogen and phosphate species, thus affecting the organisms that consume the water. In this work, a process was implemented for the removal of nutrients through three stages: stage A, complete aeration (24 h, 43 months); stage B, decreased aeration (12 h, 17 months); and stage C, decreased aeration with biocalcium (12 h, 19 months). The addition of biocalcium from eggshell promoted the formation of flocks, which resulted in the removal of nitrites (61 %), nitrates (84 %), total nitrogen (57 %), total phosphorus (8.3 %), sedimentable solids (50 %), total suspended solids (69 %), BOD5 (76 %), helminth eggs (50 %) and fecal coliforms (54 %). The statistical analyses in the three stages indicated that there is a strong correlation between the concentration of fats and oils and the removal of sedimentable solids and total suspended solids, since these parameters were correlated by 97 and 89 %, respectively. Sedimentable solids were correlated with total suspended solids by 94 %, while nitrates and total nitrogen were correlated 92 %, which favors the removal of nutrients in wastewater. The increase in the concentration of nitrogen in the sludge in stage C generated a C:N ratio of 7.98. This ratio shows that the sludge is feasible for use as a mediator of soils and a biofertilizer because of the high contents of calcium, phosphorus and nitrogen. In addition, biocalcium promoted the precipitation of hydroxyapatite, struvite, calcite and quartz. In general, the three stages of the treatment contributed to the stabilization of the wastewater treatment plant (WWTP) in an efficient, economical, and safe way.

Mechanism of NH3-SCR over P/CeO2 Catalysts Investigated by Operando Spectroscopies.

This study reports a comprehensive investigation into the active sites and reaction mechanism for the selective catalytic reduction of NO by NH3 (NH3-SCR) over phosphate-loaded ceria (P/CeO2). Catalyst characterization and density functional theory calculations reveal that H3PO4 and H2P2O6 species are the dominant phosphate species on the P/CeO2 catalysts under the experimental conditions. The reduction/oxidation half-cycles (RHC/OHC) were investigated using in situ X-ray absorption near-edge structure for Ce L3-edge, ultraviolet-visible, and infrared (IR) spectroscopies together with online analysis of outlet products (operando spectroscopy). The Ce4+(OH-) species, possibly adjacent to the phosphate species, are reduced by NO + NH3 to produce N2, H2O, and Ce3+ species (RHC). The Ce3+ species is reoxidized by aqueous O2 (OHC). The results from IR spectroscopy suggest that the RHC initiates with the reaction between NO and Ce4+(OH-) to yield Ce3+ and gaseous HONO, which then react with NH3 to produce N2 and H2O via NH4NO2 intermediates.

Transduction of Amine-Phosphate Supramolecular Interactions and Biosensing of Acetylcholine through PEDOT-Polyamine Organic Electrochemical Transistors.

Organic electrochemical transistors (OECTs) are important devices for the development of flexible and wearable sensors due to their flexibility, low power consumption, sensitivity, selectivity, ease of fabrication, and compatibility with other flexible materials. These features enable the creation of comfortable, versatile, and efficient portable devices that can monitor and detect a wide range of parameters for various applications. Herein, we present OECTs based on PEDOT-polyamine thin films for the selective monitoring of phosphate-containing compounds. Our findings reveal that supramolecular single phosphate-amino interaction induces higher changes in the OECT response compared to ATP-amino interactions, even at submillimolar concentrations. The steric character of binding anions plays a crucial role in OECT sensing, resulting in a smaller shift in maximum transconductance voltage and threshold voltage for bulkier binding species. The OECT response reflects not only the polymer/solution interface but also events within the conducting polymer film, where ion transport and concentration are affected by the ion size. Additionally, the investigation of enzyme immobilization reveals the influence of phosphate species on the assembly behavior of acetylcholinesterase (AchE) on PEDOT-PAH OECTs, with increasing phosphate concentrations leading to reduced enzyme anchoring. These findings contribute to the understanding of the mechanisms of OECT sensing and highlight the importance of careful design and optimization of the biosensor interface construction for diverse sensing applications.

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.