X-ray Absorption Near-edge Structure Spectroscopy Research Articles

Deep understanding of LiCoO2 electrode degradation for optimized recycling strategies

Empowered by a synergistic combination approach of Scanning Transmission X-ray Microscopy (STXM) imaging and X-ray Absorption Near Edge Structure (XANES) spectroscopy, a quantitative analysis on the composition and spatial distribution of the cathode in a failed 18650 LiCoO2 (LCO) battery was conducted. Distinct compositional differences between the central and peripheral cathode regions in the failed LCO battery were discerned by utilizing bulk XANES in Total Electron Yield (TEY) and Fluorescence Yield (FY) modes. The central region shows more severe degradation in terms of LCO reduction and excess cathode-electrolyte interface (CEI) buildup. Meanwhile, the STXM technique precisely imaged a specific region of interest in the center of the cathode, covering C, O, and F K-edges, and Co L2,3-edge, to deeply investigate the degradation. Quantitative chemical mapping with spatially resolved XANES spectroscopy, facilitate an in-depth understating of the interfacial reactions on battery electrodes and battery failure fundamentals.

Manganese exposure from spring and well waters in the Shenandoah Valley: interplay of aquifer lithology, soil composition, and redox conditions

Manganese (Mn) is of particular concern in groundwater, as low-level chronic exposure to aqueous Mn concentrations in drinking water can result in a variety of health and neurodevelopmental effects. Much of the global population relies on drinking water sourced from karst aquifers. Thus, we seek to assess the relative risk of Mn contamination in karst by investigating the Shenandoah Valley, VA region, as it is underlain by both karst and non-karst aquifers and much of the population relies on water wells and spring water. Water and soil samples were collected throughout the Shenandoah Valley, to supplement pre-existing well water and spring data from the National Water Information System and the Virginia Household Water Quality Program, totaling 1815 wells and 119 springs. Soils were analyzed using X-ray fluorescence and Mn K-Edge X-ray absorption near-edge structure spectroscopy. Factors such as soil type, soil geochemistry, and aquifer lithology were linked with each location to determine if correlations exist with aqueous Mn concentrations. Analyzing the distribution of Mn in drinking water sources suggests that water wells and springs within karst aquifers are preferable with respect to chronic Mn exposure, with < 4.9% of wells and springs in dolostone and limestone aquifers exceeding 100 ppb Mn, while sandstone and shale aquifers have a heightened risk, with > 20% of wells exceeding 100 ppb Mn. The geochemistry of associated soils and spatial relationships to various hydrologic and geologic features indicates that water interactions with aquifer lithology and soils contribute to aqueous Mn concentrations. Relationships between aqueous Mn in spring waters and Mn in soils indicate that increasing aqueous Mn is correlated with decreasing soil Mn(IV). These results point to redox conditions exerting a dominant control on Mn in this region.

Protaetia brevitarsis larvae produce frass that can be used as an additive to immobilize Cd and improve fertility in alkaline soils

Bioconversion of agricultural waste by Protaetia brevitarsis larvae (PBL) holds significant promise for producing high-quality frass organic amendments. However, the effects and mechanisms of PBL frass on Cd immobilization in an alkaline environment remain poorly understood. In this study, three types of frass, namely maize straw frass (MF), rice straw frass (RF), and sawdust frass (SF), were produced by feeding PBL. The Cd immobilization efficiencies of three frass in alkaline solutions and soils were investigated through batch sorption and incubation experiments, and spectroscopic techniques were employed to elucidate the sorption mechanisms of Cd onto different frass at the molecular level. The results showed that MF proved to be an efficient sorbent for Cd in alkaline solutions (176.67–227.27 mg g−1). X-ray absorption near-edge structure (XANES) spectroscopy indicated that Cd immobilization in frass is primarily attributed to the association with organic matter (OM-Cd, 78–90%). And MF had more oxygen-containing functional groups than the other frass. In weakly alkaline soils, MF application (0.5–1.5%) significantly decreased Cd bioavailability (5.65–18.48%) and concurrently improved soil nutrients (2.21–56.79%). Redundancy analysis (RDA) unveiled that pH, CEC, and available P were important factors controlling Cd fractions. Path analysis demonstrated that MF application affected Cd bioavailability directly and indirectly by influencing soil chemical properties and nutrients. In summary, MF, the product of PBL-mediated conversion maize straw, demonstrated promise as an effective organic amendment for Cd immobilization and fertility improvement in alkaline soils.

Realization of Organocerium-Based Fullerene Molecular Materials Showing Mott Insulator-Type Behavior.

Electron-rich organocerium complexes (C5Me4H)3Ce and [(C5Me5)2Ce(ortho-oxa)], with redox potentials E1/2 = -0.82 V and E1/2 = -0.86 V versus Fc/Fc+, respectively, were reacted with fullerene (C60) in different stoichiometries to obtain molecular materials. Structurally characterized cocrystals: [(C5Me4H)3Ce]2·C60 (1) and [(C5Me5)2Ce(ortho-oxa)]3·C60 (2) of C60 with cerium-based, molecular rare earth precursors are reported for the first time. The extent of charge transfer in 1 and 2 was evaluated using a series of physical measurements: FT-IR, Raman, solid-state UV-vis-NIR spectroscopy, X-ray absorption near-edge structure (XANES) spectroscopy, and magnetic susceptibility measurements. The physical measurements indicate that 1 and 2 comprise the cerium(III) oxidation state, with formally neutral C60 as a cocrystal in both cases. Pressure-dependent periodic density functional theory calculations were performed to study the electronic structure of 1. Inclusion of a Hubbard-U parameter removes Ce f states from the Fermi level, opens up a band gap, and stabilizes FM/AFM magnetic solutions that are isoenergetic because of the large distances between the Ce(III) cations. The electronic structure of this strongly correlated Mott insulator-type system is reminiscent of the well-studied Ce2O3.

Mapping the redox state of the young Solar System using ytterbium valence state

We have determined the valence state of Ytterbium (Yb) in a collection of meteorites covering 4–5 orders of magnitude in oxygen fugacity (fO2) by X-ray absorption near-edge structure (XANES) spectroscopy at the Yb L2 edge. In the studied meteorite minerals, Yb abundance was between 1 and 30 ppm. The data were obtained from merrillite grains (theoretical formula Ca18Na2Mg2(PO4)14) from two equilibrated ordinary chondrites (one H6 and one LL6), on oldhamite grains (theoretical formula CaS) from three EH enstatite chondrites (from EH3 to EH5) and four EL enstatite chondrites (from EL3 to EL6), on one merrilite grain and one stanfieldite grain (theoretical formula Ca4(Mg,Fe,Mn)5(PO4)6) from a pallasite, on merrillite grains from a eucrite, and in a phosphorous-bearing phase from an ungrouped primitive achondrite (NWA 11119). The obtained Yb XANES spectra were compared to those measured in terrestrial apatites (containing 17–79 ppm Yb) and in synthetic materials (metallic Yb, YbS, Yb2S3, Yb2O3). In terrestrial apatites, as well as in ordinary chondrites, in the eucrite, in the pallasite, and in the ungrouped achondrite NWA 11119, Yb is present as Yb3+ only. In enstatite chondrites, about half of the Yb in CaS is in the Yb2+ form and the fraction of Yb2+ may be slightly higher in EH compared to EL. It appears that Yb redox state can be used to build a redox scale for the most reduced objects of the Solar System as shown by this slight difference between EH and EL. However, the absence of a strong difference in Yb redox state between EH and EL chondrites suggests that the observed difference in Yb abundance anomalies in oldhamites found between EH and EL is not due to oxygen fugacity prevailing during parent-body equilibration but rather to fractionation related to volatility.

Magnetic properties of nano(iron oxide)-decorated graphene oxide

Graphene oxide (GO) decorated with magnetic iron oxide nanoparticles is of great interest due to its potential applications in nanomedicine, electromagnetic insulation, and electro-catalysis. Herein, we studied the effect of the preparation conditions by hydrothermal synthesis on the phase composition of graphene oxide decorated with iron oxide nanoparticles. GO samples using two different amounts of a 2Fe3+/Fe2+ solution were prepared under a pH = 11, whereas hydrazine treatment was done to half the batch. Electron microscopy images show that Fe-oxide nanoparticles with an average size of 5–10 nm appeared decorating graphene platelets. Graphene oxide decorated rolls form in hydrazine-treated samples. Infrared spectra suggest a mixture of iron oxide phases with increased goethite upon hydrazine treatment. X-ray diffraction and X-ray Absorption Near Edge Structure spectroscopy (XANES) in the Fe K-edge determined the relative amount of the resulting iron oxide phases. Mixtures of magnetite, maghemite, hematite, and goethite were observed depending on the sample preparation conditions. The effect of phase composition on the magnetic properties was also studied. The saturation magnetization varied from 3.5 to ca. 50 Am2/kg at 300 K; it is proportional to the magnetite/maghemite content and reduces as the amount of goethite increases. The coercive field in the samples increases up to 1.6–2.4 mT at 300 K. The saturation magnetization has a slower decay with temperature when compared to a reference sample of magnetite nanoparticles, which suggests a magnetoelectric coupling due to the nanoparticle distribution onto the conductive graphene sheet.

Elucidating the Complex Oxidation Behavior of Aqueous H3PO3 on Pt Electrodes via In Situ Tender X-ray Absorption Near-Edge Structure Spectroscopy at the P K-Edge.

In situ tender X-ray absorption near-edge structure (XANES) spectroscopy at the P K-edge was utilized to investigate the oxidation mechanism of aqueous H3PO3 on Pt electrodes under various conditions relevant to high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) applications. XANES and electrochemical analysis were conducted under different tender X-ray irradiation doses, revealing that intense radiation induces the oxidation of aqueous H3PO3 via H2O yielding H3PO4 and H2. A broadly applicable experimental procedure was successfully developed to suppress these undesirable radiation-induced effects, enabling a more accurate determination of the aqueous H3PO3 oxidation mechanism. In situ XANES studies of aqueous 5 mol dm-3 H3PO3 on electrodes with varying Pt availability and surface roughness reveal that Pt catalyzes the oxidation of aqueous H3PO3 to H3PO4. This oxidation is enhanced upon applying a positive potential to the Pt electrode or raising the electrolyte temperature, the latter being corroborated by complementary ion-exchange chromatography measurements. Notably, all of these oxidation processes involve reactions with H2O, as further supported by XANES measurements of aqueous H3PO3 of different concentrations, showing a more pronounced oxidation in electrolytes with a higher H2O content. The significant role of water in the oxidation of H3PO3 to H3PO4 supports the reaction mechanisms proposed for various chemical processes observed in this work and provides valuable insights into potential strategies to mitigate Pt catalyst poisoning by H3PO3 during HT-PEMFC operation.

Phosphorus fractions and speciation in an alkaline, manured soil amended with alum, gypsum, and Epsom salt.

Snowmelt runoff is a dominant pathway of phosphorus (P) losses from agricultural lands in cold climatic regions. Soil amendments effectively reduce P losses from soils by converting P to less soluble forms; however, changes in P speciation in cold climatic regions with fall-applied amendments have not been investigated. This study evaluated P composition in soils from a manured field with fall-amended alum (Al2(SO4)3·18H2O), gypsum (CaSO4·2H2O), or Epsom salt (MgSO4·7H2O) using three complementary methods: sequential P fractionation, scanning electron microscopy with energy-dispersive X-rays (SEM-EDX) spectroscopy, and P K-edge X-ray absorption near-edge structure spectroscopy (XANES). Plots were established in an annual crop field in southern Manitoba, Canada, with unamended and amended (2.5 Mg ha-1) treatments having four replicates in 2020 fall. Soil samples (0-10cm) taken from each plot soon after spring snowmelt in 2021 were subjected to P fractionation. A composite soil sample for each treatment was analyzed using SEM-EDX and XANES. Alum- and Epsom salt-treated soils had significantly greater residual P fraction with a higher proportion of apatite-like P and a correspondingly lower proportion of P sorbed to calcite (CaCO3) than unamended and gypsum-amended soils. Backscattered electron imaging of SEM-EDX revealed that alum- and Epsom salt-amended treatments had P-enriched microsites frequently associated with aluminum (Al), iron (Fe), magnesium (Mg), and calcium (Ca), which was not observed in other treatments. Induced precipitation of apatite-like species may have been responsible for reduced P loss to snowmelt previously reported with fall application of amendments.

Behavior of Tantalum in a Fe-Dominated Synthetic Fayalitic Slag System—Phase Analysis and Incorporation

Pyrometallurgical processes produce slags that may contain valuable elements because of their high oxygen affinity. However, the concentration is extremely low, which causes losses. In fact, these elements, for example, tantalum and rare earth elements, are less than 1% recycled. To return such technologically important elements to the material cycle, pyrometallurgically is used to enrich them in the simplest possible compounds within the slag, which have favorable properties for recovery (morphology, crystal size, magnetic properties), allowing further mechanical separation. The purpose of modification of the slag system is to obtain engineered artificial minerals” (EnAM), a process in which targeted minerals with high element concentration are formed. In this article, this approach is investigated using tantalum-rich fayalitic slag, since this slag is commonly found in the industry for the pyrometallurgical treatment of waste electric and electronic equipment. Synthetic fayalitic slags in reducing environment under different cooling rates were produced with Ta addition. The characterization of the produced samples was carried out using powder X-ray diffraction (PXRD) and electron probe microanalysis (EPMA). Additionally, the speciation of Fe and Ta was accessible through X-ray absorption near-edge structure (XANES) spectroscopy. EPMA also provided a semiquantitative assessment of the Ta distribution in these individual compounds. In these slags, tantalum accumulated in perovskite-like oxidic and silicate compounds as well as in magnetic iron oxides. The enrichment factor is highest in tantalite/perovskite-type oxides (FexTayO6, CaxFeyTazO3) with up to 60 wt.% Ta and ‘tantalomagnetite’ (FeII(FeIII(2−5/3xTax)O4) with a maximum of ~30 wt.% Ta (only fast cooling). This is followed by a perovskite-like silicon containing oxide (XYO3) with 12–15 wt.% Ta (only slow cooling), and a hedenbergite-like compound (XYZ2O6) with a varying content of 0.3–7 wt.%. The Ta concentration in pure Fe, Fe(1-x)O, hercynitic spinel and hematite is negligible. Despite the very low phase fraction, the most promising EnAM compound is nevertheless perovskite-like tantalum oxide, as the highest enrichment factor was obtained. Tantalum-rich magnetite-like oxides also could be promising.

Combinatorial characterization of metastable luminous silver cations

Thermodynamically metastable glasses that can contain metastable species are important functional materials. X-ray absorption near-edge structure (XANES) spectroscopy is an effective technique for determining the valence states of cations, especially for the doping element in phosphors. Herein, we first confirm the valence change of silver cations from monovalent to trivalent in aluminophosphate glasses by X-ray irradiation using a combination of Ag L3-edge XANES, electron spin resonance, and simulated XANES spectra based on first-principles calculations. The absorption edge of the experimental and simulated XANES spectra demonstrate the spectral features of Ag(III), confirming that AgO exists as Ag(I)Ag(III)O2. A part of Ag(I) changes to Ag(III) by X-ray irradiation, and the generation of Ag(III) is saturated after high irradiation doses, in good agreement with conventional radiophotoluminescence (RPL) behaviour. The structural modelling based on a combination of quantum beam analysis suggests that the local coordination of Ag cations is similar to that of Ag(III), which is confirmed by density functional theory calculations. This demonstration of Ag(III) in glass overturns the conventional understanding of the RPL mechanism of silver cations, redefining the science of silver-related materials.

Impact of Synthesis Parameters upon the Electronic Structure in PVD-Deposited CdxZn1-xO Composite Thin Films: An XPS-XANES Investigation.

The impact of different synthesis parameters, such as thickness, postsynthesis annealing temperature, and oxygen gas flow rate, upon the electronic structure is discussed in detail in the present experimental investigation. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) spectroscopy techniques are used to evaluate the surface electronic properties along with the presence and stability of the CdO2 surface oxide in CdxZn1-xO (x = 0.4) composite thin films. The thin films were synthesized with varying thicknesses using a Cd0.4Zn0.6O (CZO) ceramic and Cd0.4Zn0.6 (CZ) metallic targets and oxygen gas flow rates during magnetron sputtering. The Zn L3,2 edge and O K edge XANES spectra are affected by the oxygen gas flow rate. For the zero rate, an increase in intensity is observed in the Zn L3,2 edge, and notable changes occur in the overall spectral features of the O K edge. In the films synthesized in the presence of oxygen, highly probable O 2p → antibonding Zn 3d electronic transitions decrease the probability of the Zn 2p1/2 → antibonding Zn 3d electronic transition by filling the vacant antibonding Zn 3d states, leading to the reduction in overall intensity in the Zn L3,2 edge. Scanning electron microscopy reveals grain growth with increasing annealing temperature. The annealing induces orbital hybridization, generating new electronic states with higher transition probabilities and intensity enhancement in both Zn L3,2 and O K edges. The presence of the CdO2 surface phase is confirmed by analyzing the Cd 3d5/2 and O 1s XPS core levels. The CdO2 surface phase is observed in the films synthesized using the CZO target for all thicknesses, while the CZ target is only observed for higher thicknesses. Further postsynthesis annealing treatment results in the disappearance of the CdO2 phase. The CdO2 surface phase can be controlled by varying the film thickness and postsynthesis annealing temperature.

Arsenic(III) sorption on organo-ferrihydrite coprecipitates: Insights from maize and rape straw-derived DOM

The mobility of arsenic (As) specie in agricultural soils is significantly impacted by the interaction between ferrihydrite (Fh) and dissolved organic material (DOM) from returning crop straw. However, additional research is necessary to provide molecular evidence for the interaction of toxic and mobile As (As(III)) specie and crop straw-based organo- Fh coprecipitates (OFCs). This study investigated the As(III) sorption behaviours of OFCs synthesized with maize or rape derived-DOM under various environmental conditions and the primary molecular sorption mechanisms using As K-edge X-ray absorption near edge structure (XANES) spectroscopy. According to our findings, pure Fh adsorbed more As(III) relative to the other two OFCs, and the presence of natural organic matter in the OFCs induced more As(III) adsorption at pH 5.0. Findings from this study indicated a maximum As(III) sorption on Ma (53.71 mg g⁻1) and Ra OFC (52.46 mg g⁻1) at pH 5.0, with a sharp decrease as the pH increased from 5.0 to 8.0. Additionally, As K-edge XANES spectroscopy indicated that ∼30% of adsorbed As(III) on the OFCs undergoes transformation to As(V) at pH 7–8. Functional groups from the DOM, such as O–H, COOH, and CO, contributed to As(III) desorption and its oxidation to As(V), whereas ionic strength analysis revealed inner complexation as the dominant As(III) sorption mechanism on the OFCs. Overall, the results indicate that the interaction of natural organic matter (NOM) with As(III) at higher pH promotes As(III) mobility, which is crucial when evaluating As migration and bioavailability in alkaline agricultural soils.

Controllable sulfur redox multi-pathway reactions regulated by metal-free electrocatalysts anchored with LiS3* radicals

Regulating sulfur redox kinetics is an effective strategy for addressing the critical issues in lithium-sulfur batteries and improving their comprehensive performance. However, the sluggish and complex sulfur reduction reaction (SRR) kinetics can seriously deteriorate the electrochemical performance of lithium-sulfur batteries, hindering a clear comprehension of the electrocatalytic mechanism and presenting challenges for targeted design. Hence, it is crucial to elucidate the SRR mechanism and further refine the catalytic principle. In this study, the SRR mechanism and the pivotal role of radicals are comprehensively explored using ultrathin nitrogen-oxygen co-doped carbon nanosheets (UN/O-CNS) as an electrocatalytic model, combining density functional theory calculations with experimental techniques, such as X-ray absorption near-edge structure spectroscopy. The abundant N-O active sites of UN/O-CNS can synergistically anchor LiS3* radicals, facilitating efficient multi-pathway sulfur conversion. Additionally, UN/O-CNS can capture and catalyze polysulfides while also bi-directionally catalyzing Li2S. The S@UN/O-CNS cells ultimately demonstrate ultra-long cycling performance and high load capacity. The successful operation in pouch cells validates the practical effectiveness of UN/O-CNS. Overall, this study offers novel insights into the complexity and potential pathways of sulfur redox reaction, providing new perspectives for exploring the catalytic mechanism of cost-effective metal-free electrocatalysts.

X-ray absorption spectroscopy and theoretical investigations of the effect of extended ligands in potassium organic matter interaction.

Potassium (K) is an essential nutrient for plant growth, and despite its abundance in soil, most of the K is structurally bound in minerals, limiting its bioavailability and making this soil K reservoir largely inaccessible to plants. Microbial biochemical weathering has been shown to be a promising pathway to sustainably increase plant available K. However, the mechanisms underpinning microbial K uptake, transformation, storage, and sharing are poorly resolved. To better understand the controls on microbial K transformations, we performed K K-edge x-ray absorption near-edge structure (XANES) spectroscopy on K-organic salts, including acetate, citrate, nitrate, oxalate, and tartrate, which are frequently observed as low molecular weight organic acids secreted by soil microbes, as well as humic acid, which acts as a proxy for higher molecular weight organic acids. The organic salts display feature-rich K XANES spectra, each demonstrating numerous unique features spanning ∼13eV range across the absorption edge. In contrast, the spectra for humic acid have one broad, wide feature across the same energy range. We used a combination of time-dependent density functional theory and the Bethe-Salpeter equation based approach within the OCEAN code to simulate the experimental spectra for K-nitrate (KNO3) and K-citrate [K3(C6H5O7)·H2O] to identify the electronic transitions that give rise to some of the outlying and unique spectral features in the organic salts. KNO3 has both the lowest and highest lying energy features, and K3(C6H5O7)·H2O is produced by several soil microbes and is effective at mineral weathering. Our results analyze the K-organic salt bonding in detail to elucidate why the spectral shapes differ and indicate that the K K-edge XANES spectra are associated with the entire ligand despite similar first-shell bonding environments around the K center. The improved understanding of K bonding environments with organic ligands and their use for interpretation of the K-XANES spectra provides an important toolkit to understand how K is transformed by microbial processes and made bioavailable for plant uptake.

Mechanisms of Uptake and Translocation of Thallium in Brassica Vegetables: An X-ray Fluorescence Microspectroscopic Investigation.

Most nonoccupational human exposure to thallium (Tl) occurs via consumption of contaminated food crops. Brassica cultivars are common crops that can accumulate more than 500 μg Tl g-1. Knowledge of Tl uptake and translocation mechanisms in Brassica cultivars is fundamental to developing methods to inhibit Tl uptake or conversely for potential use in phytoremediation of polluted soils. Brassica cultivars (25 in total) were subjected to Tl dosing to screen for Tl accumulation. Seven high Tl-accumulating varieties were selected for follow-up Tl dosing experiments. The highest Tl accumulating Brassica cultivars were analyzed by synchrotron-based micro-X-ray fluorescence to investigate the Tl distribution and synchrotron-based X-ray absorption near-edge structure spectroscopy (XANES) to unravel Tl chemical speciation. The cultivars exhibited different Tl tolerance and accumulation patterns with some reaching up to 8300 μg Tl g-1. The translocation factors for all the cultivars were >1 with Brassica oleracea var. acephala (kale) having the highest translocation factor of 167. In this cultivar, Tl is preferentially localized in the venules toward the apex and along the foliar margins and in minute hot spots in the leaf blade. This study revealed through scanning electron microscopy and X-ray fluorescence analysis that highly Tl-enriched crystals occur in the stoma openings of the leaves. The finding is further validated by XANES spectra that show that Tl(I) dominates in the aqueous as well as in the solid form. The high accumulation of Tl in these Brassica crops has important implications for food safety and results of this study help to understand the mechanisms of Tl uptake and translocation in these crops.

Understanding phosphorus mobilization mechanisms in acidic soil amended with calcium-silicon-magnesium-potassium fertilizer

Calcium-silicon-magnesium-potassium fertilizer (CSMP) is usually used as an amendment to counteract soil acidification caused by historical excessive nitrogen (N) applications. However, the impact of CSMP addition on phosphorus (P) mobilization in acidic soils and the related mechanisms are not fully understood. Specifically, a knowledge gap exists with regards to changes in soil extracellular enzymes that contribute to P release. Such a knowledge gap was investigated by an incubation study with four treatments: i) initial soil (Control), ii) urea (60 mg kg−1) addition (U); iii) CSMP (1%) addition (CSMP) and iv) urea (60 mg kg−1) and CSMP (1%) additions (U + CSMP). Phosphorus mobilization induced by different processes was distinguished by biologically based P extraction. The Langmuir equation, K edge X-ray absorption near-edge structure spectroscopy, and ecoenzyme vector analysis according to the extracellular enzyme activity stoichiometry were deployed to investigate soil P sorption intensity, precipitation species, and microbial-driven turnover of organophosphorus. Results showed that CaCl2 extractable P (or citric acid extractable P) content increased by 63.4% (or 39.2%) in the soil with CSMP addition, compared with the study control. The accelerated mobilization of aluminum (Al)/iron (Fe)-bound P after CSMP addition, indicated by the reduction of the sum of FePO4·2H2O and AlPO4 proportion, contributed to this increase. The decrease of P sorption capacity can also be responsible for it. The CSMP addition increased enzyme extractable P in the soil nearly 7-fold and mitigated the limitations of carbon (C) and P for soil microorganisms (indicated by the enzyme stoichiometry and ecoenzyme vector analysis), suggesting that microbial turnover processes also contribute to P mobilization in amended acidic soil. These findings indicate that the P mobilization in CSMP amended acidic soil not only attributed to both decreasing P sorption capacity and dissolving phosphate precipitation, but also to the increase of the microbial turnover of the organophosphorus pool.

Characterization of Bisphosphonate Hydrate Crystals by Phosphorus K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy.

X-ray absorption near-edge structure (XANES) spectroscopy is a new method for the characterization of active pharmaceutical ingredients. XANES spectra show unique features depending on the electronic states of the X-ray absorbing elements and provide information about the chemical environment that affects the electronic states. In this study, six bisphosphonate hydrate crystals were used to investigate, for the first time, how the phosphorus K-edge XANES spectra are affected by the interatomic interactions and charged states of phosphonate moieties. Phosphorus K-edge XANES spectra showed several differences among the bisphosphonates. In particular, the chlorine atoms covalently bonded near the phosphonate and the number of electric charges of the phosphonate moieties seemed to have large effects on peak shape in XANES spectra. Unique shapes of the XANES spectra demonstrated that differences in interactions at the oxygen atoms of the phosphonate moieties could change the shapes of the XANES spectrum peaks to the extent that each material was distinguished based on the spectra. Since slight differences in interatomic interactions and charged states lead to variations in the spectra, XANES spectroscopy could be widely applied as the fingerprint method to evaluate active pharmaceutical ingredients.

Soil phosphorus cycling across a 100-year deforestation chronosequence in the Amazon rainforest.

Deforestation of tropical rainforests is a major land use change that alters terrestrial biogeochemical cycling at local to global scales. Deforestation and subsequent reforestation are likely to impact soil phosphorus (P) cycling, which in P-limited ecosystems such as the Amazon basin has implications for long-term productivity. We used a 100-year replicated observational chronosequence of primary forest conversion to pasture, as well as a 13-year-old secondary forest, to test land use change and duration effects on soil P dynamics in the Amazon basin. By combining sequential extraction and P K-edge X-ray absorption near edge structure (XANES) spectroscopy with soil phosphatase activity assays, we assessed pools and process rates of P cycling in surface soils (0-10 cm depth). Deforestation caused increases in total P (135-398 mg kg-1 ), total organic P (Po ) (19-168 mg kg-1 ), and total inorganic P (Pi ) (30-113 mg kg-1 ) fractions in surface soils with pasture age, with concomitant increases in Pi fractions corroborated by sequential fractionation and XANES spectroscopy. Soil non-labile Po (10-148 mg kg-1 ) increased disproportionately compared to labile Po (from 4-5 to 7-13 mg kg-1 ). Soil phosphomonoesterase and phosphodiesterase binding affinity (Km ) decreased while the specificity constant (Ka ) increased by 83%-159% in 39-100y pastures. Soil P pools and process rates reverted to magnitudes similar to primary forests within 13 years of pasture abandonment. However, the relatively short but representative pre-abandonment pasture duration of our secondary forest may not have entailed significant deforestation effects on soil P cycling, highlighting the need to consider both pasture duration and reforestation age in evaluations of Amazon land use legacies. Although the space-for-time substitution design can entail variation in the initial soil P pools due to atmospheric P deposition, soil properties, and/or primary forest growth, the trend of P pools and process rates with pasture age still provides valuable insights.

Designing M13 Bacteriophage and Fe-Nanonest Self-Assembly System for Universal and Facile Preparation of Metal Single Atoms as Stable Mimicking Enzymes.

Metal single-atom catalysts (MSACs) possess multiple advantages in chemical synthesis; their efficient fabrication routes, however, remain a challenge to date. Here, an interdisciplinary design using M13 bacteriophage virus as a biotemplate to carry Fe nanoclusters, which we figuratively call "Fe-nanonests", is proposed to enable facile and versatile synthesis of MSACs. The feasibility and generality of this self-assembly method was demonstrated by the observation of six different metal single atoms (MSAs) including Ag, Pt, Pd, Zn, Cu, and Ni. With Pd as a representative, key factors dominating the fabrication were determined. The Pd single atoms exhibited excellent horseradish peroxidase (HRP)-like activity, which was further improved by 50% via genetic editing of the M13 pVIII protein terminals. Excellent stability was also observed in the quantification of acid phosphatase, a cancer predictor. X-ray absorption near-edge structure spectroscopy has been applied to the analysis of Pd single atoms as well, and the Pd-N4 coordination explained the mechanism of high HRP-like catalytic activity. The MSAs synthesized by the M13 phage and Fe-nanonest self-assembly method show promising prospects in non-cold-chain medical detection applications.

X-ray absorption near-edge, terahertz and Raman spectroscopies evidence growth-orientation dependent cation order, phase transitions and spin–phonon coupling in half-metallic Ca2FeMoO6 thin films

The disorder due to anti-site cation distribution is intrinsic to the double perovskites wherein the crystal orientations of the substrate template are predicted to offer different degrees of cation order in thin film form. To demonstrate this effect, epitaxial thin films of half-metallic double perovskite Ca2FeMoO6 (CFMO) were prepared on (100) and (111) oriented LaAlO3 substrates in vacuum and nitrogen atmospheres. The findings using X-ray absorption near-edge structure, Terahertz (THz) and Raman spectroscopies, in combination with magnetization show that (111) epitaxial template effectively restricts the Fe–Mo anti-site cation disorder. A resultantly enhanced cation order in (111) films induces dramatic transformations in its properties as follows: (i) significantly enhanced ferromagnetic exchange interactions and saturation magnetization, (ii) a significant increase in the Curie temperatures, (iii) a metallic behavior down to much lower temperature (∼75 K) compared to that down to 200 K for (100) film, (iv) an enhanced spin–phonon coupling. The complex THz optical conductivity spectra evaluated in the framework of Drude and Drude–Smith phenomenological models and the temperature-dependent Raman data fitted to the Balkanski model corroborate well to indicate an enhanced cation order in (111) films. While this study establishes a dominant role of crystallographic orientation in the much-desired control of cation order in double perovskites, a demonstration of the same in room temperature half-metallic CFMO system could reinforce its technological utility both as active and passive components in emergent spintronic functionalities.