6 Materialchemie
Filtern
Erscheinungsjahr
- 2019 (129) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (129) (entfernen)
Sprache
- Englisch (128)
- Mehrsprachig (1)
Schlagworte
- Mechanochemistry (10)
- XPS (8)
- Nanoparticles (7)
- Cyclization (5)
- In situ (5)
- MALDI-TOF MS (5)
- Polylactide (5)
- XRD (5)
- Broadband dielectric spectroscopy (4)
- NEXAFS (4)
- SAXS (4)
- Catalyst (3)
- Discotic Liquid Crystals (3)
- Epoxy (3)
- Microplastics (3)
- Nanocomposites (3)
- Silicon (3)
- Simulation (3)
- Specific heat spectroscopy (3)
- Synchrotron (3)
- ATR-FTIR spectroscopy (2)
- Boehmite (2)
- Catalysts (2)
- Catechol (2)
- Cocrystal (2)
- Crosslinking (2)
- Double complex salts (2)
- EOS (2)
- EPMA (2)
- Electron microscopy (2)
- Ettringite (2)
- Ferromagnetism (2)
- Flash DSC (2)
- High-pressure (2)
- Interphase (2)
- Laser-induced plasma (2)
- MOF (2)
- Metal phosphonates (2)
- Molecular sieves (2)
- Mueller-Matrix imaging ellipsometry (2)
- Nanomaterial (2)
- Plasma (2)
- Polymers (2)
- Polyurethane (2)
- Single-source precursors (2)
- Small angle scattering (2)
- Small-angle scattering (2)
- Spectroskopic Imaging (2)
- ToF-SIMS (2)
- X-ray Photoelectron Spectroscopy (XPS) (2)
- X-ray diffraction (2)
- XRF (2)
- (ter-)pyridineterminated self-assembled monolayer (1)
- 2,6-diaminopyridine (1)
- 2-oxazoline (1)
- AET (1)
- AISI 304L (1)
- Acoustic levitation (1)
- Acrylamide (1)
- Additives (1)
- Adsorption (1)
- Alkoxysilanes (1)
- Alpha (1)
- Ambient ionization (1)
- Analysis (1)
- Anomalous Small Angle X-ray Scattering (1)
- Antibacterial (1)
- Antibacterial surface coatings (1)
- Antifouling surface coatings (1)
- Antifriction coefficient (1)
- Antimony oxychloride ( Sb4O5Cl2) (1)
- Antiviral activity (1)
- Artificial weathering (1)
- Asymmetrical flow field flow fractionation (AF4) (1)
- Atomic force microscopy (1)
- AuNP (1)
- Automation (1)
- Azobenzene (1)
- BAMline (1)
- BET specific surface area (1)
- BSA (1)
- Bacterial adhesion (1)
- Ball milling (1)
- Battery (1)
- Beta decay (1)
- Biochip (1)
- Biofilm (1)
- Biofunctional Molecules (1)
- Biosensors (1)
- Bloch wall (1)
- Boehmite nanoparticles (1)
- Bone matrix (1)
- Bovine serum albumin (1)
- Brachytherapy (1)
- Brain PET tracers (1)
- Broadband dielectric microscopy (1)
- Bulk temperature (1)
- C-C coupling (1)
- COK-12 (1)
- CXC (1)
- Cancer (1)
- Cancer treatment (1)
- Capillary electrophoresis (CE) (1)
- Categorisation scheme (1)
- Cationic photocuring (1)
- Cationic ring opening polymerization (1)
- Cell size (1)
- Cement admixtures (1)
- Cement hydration (1)
- Ciprofloxacin (1)
- Click chemistry (1)
- Cluster (1)
- Co (1)
- Co-crystal (1)
- Cobalt (1)
- Cobalt and zinc oxides (1)
- Cobalt deposition (1)
- Coherent exchange (1)
- Compressibility (1)
- Computational chemistry (1)
- Conference (1)
- Controlled-shape (1)
- Core-shell nanoparticles (1)
- Corrosion monitoring (1)
- Cristobalite frameworks (1)
- Crosslinking density (1)
- Crystallization (1)
- CuO nanoparticles (1)
- Curie temperature (1)
- Cyclic (1)
- Cycloaliphatic epoxy oligosiloxane (1)
- Cytotoxicity (1)
- DFT (1)
- DNA (1)
- DNA damage (1)
- DPSS-laser (1)
- DSC (1)
- DVS (1)
- Damping factor (1)
- Data (1)
- Decision support (1)
- Degradation (1)
- Density Functional Theory (1)
- Deuterium (1)
- Dielectric properties (1)
- Dielectric spectroscopy (1)
- Diffraction (1)
- Direct/indirect photolysis (1)
- Domain wall (1)
- Dosimetry (1)
- Dynamic heterogeneity (1)
- EC definition of a nanomaterial (1)
- EC nanomaterial definition (1)
- Electrical conductivity (1)
- Electrochemical deposition (ECD) (1)
- Electrochemical sensing (1)
- Electron probe microanalysis (1)
- Electron probe microanalysis (EPMA) (1)
- Energetic Materials (1)
- Energy deposit (1)
- Epoxy conversion degree (1)
- Europium (1)
- Exchange interaction (1)
- Exchange length (1)
- Experimental setup (1)
- Expert system (1)
- Exposed metal sites (1)
- Facilitated activation (1)
- Fast scanning calormetry (1)
- Fe (1)
- Fe-Ni (1)
- Femtosecond laser (1)
- Ferrihydrite (1)
- Fiber Bragg grating (FBG) (1)
- Fluid-flow (1)
- Fluorescence (1)
- Fluoride (1)
- Food (1)
- Friction (1)
- Fully aromatic frameworks (1)
- Functionalized nanographene (1)
- Fundamentals (1)
- Gamma (1)
- Gas separation membranes (1)
- Geant4 (1)
- Geant4-DNA (1)
- Genotoxic and oxidative damage (1)
- Geology (1)
- Glucose (1)
- Goethite (1)
- Gold (1)
- Gold Nanoparticles (1)
- Graphene (1)
- Graphene Oxide (1)
- Grating (1)
- Green rust (1)
- Guest uptake/release (1)
- H-terminated Si3N4 films (1)
- HRMS (1)
- Hazardous substances (1)
- High specific surface area (1)
- High-entropy alloys (1)
- High-resolution synchrotron XRF (1)
- Histology (1)
- Human umbilical cell adhesion (1)
- Hydration (1)
- Hydrogen (1)
- Hydrogen generation (1)
- Hydrogen photoproduction (1)
- Hydrophilic interaction chromatography (1)
- Iinter-laboratory comparison (1)
- Imaging (1)
- Imidazole (1)
- Impact diamonds (1)
- Implant material (1)
- Infrared nano AFM (1)
- Inlet ionization (1)
- Intermodulation (1)
- Intermodulation AFM (1)
- Intermodulation-AFM (1)
- Ion mobility (1)
- Ionic liquid (1)
- Iridium-titanium mixed oxides (1)
- Iron (1)
- Kinetics (1)
- LEE (1)
- LL equation (1)
- LLG (1)
- Lactide (1)
- Landau Lifshitz Gilbert equation (1)
- Landau Lifshitz equation (1)
- Large-pore (1)
- Laser (1)
- Laser-induced X-ray emission (1)
- Laser-induced nanostructures (1)
- Laser-induced periodic surface structures (LIPSS) (1)
- Laser-modified surface (1)
- Laterally-resolved (1)
- Linear polyglycerol (1)
- Liquid crystals (1)
- Liquids (1)
- Localised corrosion (1)
- Lonsdaleite (1)
- Luminescence (1)
- MALDI TOF MS (1)
- MCS (1)
- MOF-74 (1)
- Magnet coupling (1)
- Magnetic Nanoparticles (1)
- Magnetic anisotropy (1)
- Magnetic interacion (1)
- Magnetic moment (1)
- Magnetic properties (1)
- Magnetization dynamics (1)
- Maia detector (1)
- Martensite (1)
- Mass Spectrometry (1)
- Materials (1)
- Matrices (1)
- Melting (1)
- Mesoporous Silica (1)
- Mesoporous thin films (1)
- Metal carbides (1)
- Metal– organic frameworks (1)
- Metal–organic frameworks (1)
- Metrology (1)
- Micellar chromatography (1)
- Microanalysis (1)
- Microdosimetry (1)
- Microencapsulation (1)
- Micromagnetism (1)
- Microwave (1)
- Microwave synthesis (1)
- Mineral tranformation (1)
- Mixed-linkers (1)
- Modelling (1)
- Moisture (1)
- Molecular masses (1)
- Molecular mobility (1)
- Monte-Carlo (1)
- Monte-Carlo simulation (1)
- Multivariate data analysis (1)
- Mussel-inspired adhesives (1)
- Mussel-inspired dendritic polyglycerol (MI-dPG) (1)
- NAP-XPS (1)
- NIR spectroscopy (1)
- NMR spectroscopy (1)
- NP (1)
- NanoSIMS (1)
- Nanocasting (1)
- Nanocomposite (1)
- Nanoconfinement (1)
- Nanomechanical properties (1)
- Nanomechanics (1)
- Nanoparticle (1)
- Nanoparticles with same nominal diameter (1)
- Nanoporous (1)
- Nanorods (1)
- Nanosecond laser (1)
- Nanosecond laser irradiation (1)
- Nanosheets (1)
- Nanostructured material (1)
- Nanostructures (1)
- Near edge X-ray absorption fine structure (1)
- Near-ambient pressure (1)
- Neel wall (1)
- Ni (1)
- Nickel (1)
- Nitrene[2+1]cycloaddition (1)
- Nitrides (1)
- Non-spherical (1)
- Nonclassical crystallization (1)
- Nonporous SiO2 (1)
- OH radicals (1)
- OOMMF (1)
- Object oriented micromagnetic framework (1)
- Optical fibers (1)
- Optical near field (1)
- Optical properties (1)
- Ordered mesoporous silica (1)
- Organic compounds (1)
- Organic micro-pollutant (1)
- Oxidation (1)
- Oxocobaltates (1)
- Oxygen Evolution Catalyst (1)
- Oxygen evolution reaction (OER) (1)
- PXRD (1)
- Paramagnetism (1)
- Particle accretion (1)
- Particle size distribution (1)
- Phase mask (1)
- Phase transition (1)
- Phenolic acid (1)
- Phosphinine (1)
- Phosphorus (1)
- Photo-transformation products (1)
- Photochromism (1)
- Photooxidation (1)
- Photoswitchable monolayers (1)
- Physical and chemical processes (1)
- Plasmon resonance (1)
- Plasmonic nanofocusing spectroscopy (1)
- Platinum (1)
- Polarization spectroscopy (1)
- Polycarbonate (1)
- Polyethylene (1)
- Polyethylene glycol (1)
- Polyethylene glycol (PEG)-grafting antifouling surface (1)
- Polymer (1)
- Polymer blends (1)
- Polymer composites (1)
- Polymer-based nanocomposites (1)
- Polymers of intrinsic microporosity (1)
- Polymorphism (1)
- Polyoxocation (1)
- Polyvinyl alcohol (1)
- Pore size tailoring (1)
- Positron emission tomography (1)
- Post-modification by L-cysteine (1)
- Powder X-ray diffraction (1)
- Powdered activated carbon (1)
- Prediction (1)
- Purine P2Y1 receptors (1)
- Quantitative XPS (1)
- ROPPOC (1)
- Radiation damage (1)
- Radiation protection (1)
- Radiationtherapy (1)
- Radioactive decay (1)
- Radiometabolites (1)
- Raman spectroscopy (1)
- Real-time infrared spectroscopy (1)
- Reference material (1)
- Regulatory identification of nanomaterials (1)
- Rh-Ir alloys (1)
- Ring-expansion polymerization (1)
- Ring-opening polymerization (1)
- Rosin (1)
- SEM (1)
- Salicylate (1)
- Salicylic acid (1)
- Salts (1)
- Sampling (1)
- Sampling techniques (1)
- Scanning electrochemical microscope (SECM) (1)
- Scattering (1)
- Secondary fluorescence correction (1)
- Self-lubricating coating (1)
- Sensing (1)
- Shape-engineered (1)
- Si-Ge (1)
- Silver nanoparticles (1)
- Slags (1)
- Sol-gel processes (1)
- Sonochemical synthesis (1)
- Specific Adsorption of N-2 and Kr (1)
- Spectroscopic ellipsometry (1)
- Spin (1)
- Spontaneous emulsification (1)
- SsNMR (1)
- Stability (1)
- Standardisation (1)
- Steel (1)
- Stereocomplex (1)
- Stimuli-responsive polymers (1)
- Stochastic Landau Lifshitz Gilbert equation (1)
- Stochastic Landau Lifshitz equation (1)
- Streptavidin binding (1)
- Structural anomalies (1)
- Structural defects (1)
- Structural inhomogenities (1)
- Structures under extreme conditions (1)
- Struvite (1)
- Sulfidation (1)
- Superparamagnetism (1)
- Surface (1)
- Surface coating (1)
- Surface functionalization (1)
- Surface modification (1)
- Surface species (1)
- Surface structures (1)
- Sustainability (1)
- Suzuki-Miyaura coupling (1)
- Synchroton x-ray diffraction (1)
- T-SEM (1)
- TTBP-TAZ (1)
- Tattoo inks (1)
- Temeprature scaling (1)
- Temperature effects (1)
- Temperature modulated differential scanning calorimetry (1)
- Thermal degradation (1)
- Thermal extraction-desorption gas chromatography mass spectrometry (1)
- Thermo-responsive polymers (1)
- Thermoplastics (1)
- Thin film analysis (1)
- Thin film systems (1)
- Thin films (1)
- Thin polymer films (1)
- Time-resolved (1)
- Tin(II)octanoate (1)
- Tire particles (1)
- Titanium dioxide (1)
- Topotactic phase transitions (1)
- Toxic metals (1)
- Toxicity (1)
- Trace organic contaminant (1)
- Transformation pathways (1)
- Transmission function (1)
- Two-dimensional hexagonal boron nitride(h-BN) (1)
- Two-dimensional off-line coupling (1)
- UCST polymers (1)
- UV degradation (1)
- Ultrashort laser material interaction (1)
- Ultrashort laser pulses (1)
- Uncertainties (1)
- VAMAS (1)
- Vacuum ionization (1)
- Visible light (1)
- Wastewater (1)
- Water (1)
- Wear (1)
- X-ray Absorption Spectroscopy (1)
- X-ray Photoelectron Spectroscopy (1)
- X-ray absorption Fine Spectroscopy (1)
- X-ray absorption fine structure (1)
- X-ray absorption spectroscopy (1)
- X-ray and electron diffraction (1)
- X-ray photoelectron spectroscopy (1)
- X-ray spectroscopy (1)
- XAFS (1)
- XANES (1)
- XAS (1)
- Zeolitic Imidazolate Frameworks (1)
- Zinc analysis (1)
- Zinc oxide (1)
- beta particle (1)
- clustered nanoparticles (1)
- gamma ray (1)
- low energy electrons (1)
- particle scattering (1)
- radiolysis (1)
- temeprature dependent exchange length (1)
Organisationseinheit der BAM
- 6 Materialchemie (129)
- 6.3 Strukturanalytik (56)
- 6.1 Oberflächen- und Dünnschichtanalyse (29)
- 6.6 Physik und chemische Analytik der Polymere (28)
- 6.2 Material- und Oberflächentechnologien (10)
- 6.5 Synthese und Streuverfahren nanostrukturierter Materialien (10)
- 1 Analytische Chemie; Referenzmaterialien (9)
- 5 Werkstofftechnik (5)
- 6.7 Materialsynthese und Design (4)
- 5.1 Mikrostruktur Design und Degradation (3)
A novel cop olyme r based on supramolecular motif2,6-diaminopyridin e and water-soluble acrylamide, poly[N-(6-ace tamidopyridin-2-yl) acrylamide-co-acrylamide], was synthe-size d via rev ersible addi tion–fragmentation chain transfer (RAFT)polymerization with various monomer compositions. The thermo-respon sive behavior of the copolymers was studied by turbidime-try and dynamic light scattering (DLS). The obtained copolymersshowed an upper critical solution temperature (UCST)-typ e phasetransition behavior in water and electrolyte solution. The phasetransition temperature was found to increase with decreasingam ount of acrylamide in the copolymer and increasing concentra-tion of the solution. Furth ermore, the phase transition temperatureva ried in aqueous solutions of electrolytes according to the naturean d concentration of the electrolyte in accordance with theHoffmeister series. A dramatic solvent isotope effect on thetransition temperature was o bserved in this study, as the transitiontemperature was almost 10–12C higher in D2OthaninH2Oatthesame concentration and acrylamide co mposition. The size of theaggregates below the transition temperature was larger in D2Ocompared to that in H2O that can be explained by deuterium iso-tope effect. The thermoresponsive behavior of the copolymers wasalso investigated in different cell medium and found to be exhibitedUCST-type phase transition behavior in different cell medium.Such behavior of the copo lyme rs can be useful in many a pplica-tions including biomedical, microfluidics, optical materials, and indrug delivery.
The mechanochemical formation of the ionic cocrystals of glucose (Glc) and sodium salts Glc2NaCl·H2O (1) and Glc2NaX (X = Br (2), I (3)) is presented. Products are formed by co-milling Glc with three sodium salts (NaCl, NaBr, NaI). The ionic cocrystals were obtained under both neat grinding and liquid-assisted grinding conditions, the later found to accelerate the reaction kinetics. The crystal structures of the ionic cocrystals (2) and (3) were solved from powder X-ray diffraction data. The structure solution contrasts with the structure of Glc2NaCl·H2O (1) where the electron density at three halide crystallographic sites is modeled as of being the intermediate between water molecule and a chloride ion. The reaction pathways of the three ionic cocrystals were investigated in real time using our tandem approach comprising a combination of in situ synchrotron powder X-ray diffraction and Raman spectroscopy. The results indicate the rapid formation of each cocrystal directly from their respective starting materials without any intermediate moiety formation. The products were further characterized by DTA-TG and elemental analysis.
In this work, a new setup for dispersive XAFS measurements is presented. This reproducible and scanningfree setup yields both time- and laterally-resolved XAFS experiments in a ‘single-shot’. It allows a straightforward adjustment for probing different elements covering many relevant applications in materials science. An incoming energetic broadband beam is diffracted by a Si (111) crystal after passing through the sample and collected by an area sensitive detector. Depending on the energy range of the incoming beam, XANES and/or EXAFS spectra can be recorded with a time resolution down to 1 s. The feasibility of this setup was demonstrated at the BAMline at BESSY II (Berlin, Germany) with reference Fe and Cu foils and the results are hereby presented and discussed. Additionally, an application where time resolution on the second scale is required is briefly evaluated. The presented example concerns studying early stages of zinc(II)2-methylimidazolate (ZIF-8) crystallization. This is particularly important for biomedical applications.
Worldwide there is a variety of regulatory provisions addressing nanomaterials. The identification as nanomaterial in a regulatory context often has the consequence that specific legal rules apply. In identifying nanomaterials, and to find out whether nanomaterial-specific provisions apply, the external size of particles is globally used as a criterion. For legal certainty, its assessment for regulatory purposes should be based on measurements and methods that are robust, fit for the purpose and ready to be accepted by different stakeholders and authorities. This should help to assure the safety of nanomaterials and at the same time facilitate their international trading. Therefore, we propose a categorisation scheme which is driven by the capabilities of common characterisation techniques for particle size measurement. Categorising materials according to this scheme takes into account the particle properties that are most important for a determination of their size. The categorisation is exemplified for the specific particle number based size metric of the European Commission's recommendation on the definition of nanomaterial, but it is applicable to other metrics as well. Matching the performance profiles of the measurement techniques with the material property profiles (i) allows selecting the most appropriate size determination technique for every type of material considered, (ii) enables proper identification of nanomaterials, and (iii) has the potential to be accepted by regulators, industry and consumers alike. Having such a scheme in place would facilitate the regulatory assessment of nanomaterials in regional legislation as well as in international relations between different regulatory regions assuring the safe trade of nanomaterials.
Mesoporous phosphates are a group of nanostructured materials with promising applications, particularly in biomedicine and catalysis. However, their controlled synthesis via conventional template-based routes presents a number of challenges and limitations. Here, we show how to synthesize a mesoporous Magnesium phosphate with a high surface area and a well-defined pore structure through thermal decomposition of a crystalline struvite (MgNH4PO4·6H2O) precursor. In a first step, struvite crystals with various morphologies and sizes, ranging from a few micrometers to several millimeters, had been synthesized from supersaturated aqueous solutions (saturation index (SI) between 0.5 and 4) at ambient pressure and temperature conditions. Afterwards, the crystals were thermally treated at 70–250 °C leading to the release of structurally bound water (H2O) and ammonia (NH3). By combining thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM, TEM), N2 sorption analyses and small- and wide-angle X-ray scattering (SAXS/WAXS) we show that this decomposition process results in a pseudomorphic transformation of the original struvite into an amorphous Mg-phosphate. Of particular importance is the fact that the final material is characterized by a very uniform mesoporous structure with 2–5 nm wide pore channels, a large specific surface area of up to 300 m2 g−1 and a total pore volume of up to 0.28 cm3 g−1. Our struvite decomposition method is well controllable and reproducible and can be easily extended to the synthesis of other mesoporous phosphates. In addition, the so produced mesoporous material is a prime candidate for use in biomedical applications considering that Magnesium phosphate is a widely used, non-toxic substance that has already shown excellent biocompatibility and biodegradability.
The precise analysis of cation diffusion profiles through corrosion scales is an important aspect to evaluate corrosion phenomena under multicomponent chemical load, as during high‐temperature corrosion under deposits and salts. The present study shows a comprehensive analysis of cation diffusion profiles by electron microprobe analysis and microbeam X‐ray absorption near edge structure (µ‐XANES) spectroscopy in mixed oxide/sulfide scales grown on Fe–Cr model alloys after exposing them to 0.5% SO2. The results presented here correspond to depth‐dependent phase identification of oxides and sulfides in the corrosion scales by µ‐XANES and the description of oxidation‐state‐dependent diffusion profiles. Scales grown on low‐ and high‐alloyed materials show both a well‐pronounced diffusion profile with a high concentration of Fe3+ at the gas and a high concentration of Fe2+ at the alloy interface. The distribution of the cations within a close‐packed oxide lattice is strongly influencing the lattice diffusion phenomena due to their different oxidation states and therefore different crystal‐field preference energies. This issue is discussed based on the results obtained by µ‐XANES analysis.
Structural modularity of polymer frameworks is a key advantage of covalent organic polymers, however, only C, N, O, Si and S have found their way into their building blocks so far. Here, we expand the toolbox available to polymer and materials chemists by one additional nonmetal, phosphorus. Starting with a building block that contains a λ⁵‐phosphinine (C₅P) moiety, we evaluate a number of polymerisation protocols, finally obtaining a π‐conjugated, covalent phosphinine‐based framework (CPF‐1) via Suzuki‐Miyaura coupling. CPF‐1 is a weakly porous polymer glass (72.4 m2 g‐1 N2 BET at 77 K) with green fluorescence (λmax 546 nm) and extremely high thermal stability. The polymer catalyzes hydrogen evolution from water under UV and visible light irradiation without the need for additional co‐catalyst at a rate of 33.3 μmol h‐¹ g‐¹. Our results demonstrate for the first time the incorporation of the phosphinine motif into a complex polymer framework. Phosphinine‐based frameworks show promising electronic and optical properties that might spark future interest in their applications in light‐emitting devices and heterogeneous catalysis.
L-Lactide was polymerized in bulk with tin(II)2-ethylhexanoate SnOct2) as catalyst and salicylic acid as cocatalyst. The Lac/Cat ratio, Cocat/Cat ratio, temperature and time were varied. Increasing Cocat/Cat ratios reduced both,polymerization rate and molecular weight. However,under optimized conditions high molar mass (Mw up to 178,000), colorless, cyclic polylactides were formed in a short time. A few polymerizations performed at 160 and 180°C with the combination of SnOct2 and silylated salicylic acid gave similar results. Neat tin II) salicylate was prepared from SnOct2 and used for REPs of L-lactide in bulk, but the results were not better than those obtained from combinations of SnOct2 and salicylic acid. Furthermore, dibutyltin salicylate was synthesized and used as catalyst for polymerizations of L-lactide in bulk at temperatures varying from 102 to 160°C. Cyclic polylactides with Mw’s up to 40,000 were the main reaction products. At 100–102°C a predominance of odd-numbered cycles was found proving a REP mechanism.
Iron (oxyhydr)oxides play an important role in controlling the mobility and toxicity of arsenic (As) in contaminated soils and groundwaters. However, dynamic subsurface geochemical conditions can potentially impact As sequestration since this is highly dependent on the dominant iron mineral phases present and the pathways through which they form. In this study, we investigated the Fe2+-induced transformation of As(V)-bearing ferrihydrite (As-FH) to more crystalline phases under relevant anoxic subsurface conditions. Specifically, we examined the influence of varying Fe2+(aq)/Fe(III)solid¬ ratios on the behavior and speciation of the mineral-bound As species during the mineralogical transformation of As-FH at pH 6.5 for 24 h. At lower Fe2+(aq)/Fe(III)solid¬ ratios (0.5 to 1), goethite, green rust sulfate (GR¬SO4) and lepidocrocite formed within the first 2 hours of the reaction, but only goethite and some unreacted FH remained after 24 h. At Fe2+(aq)/Fe(III)solid¬ ratio = 2, GRSO4 remained stable throughout the 24 h reaction, alongside goethite and unreacted FH. Despite >82% of the As-FH being transformed to goethite GRSO4 in these reactions, no significant As release (>99.9% removal) was observed. However, while As remained mineral-bound, partial oxidation of the initially added As(V) was reduced to As(III), most likely, by the goethite-Fe2+(aq) redox couple. The extent of As(V) reduction increased from ~40% to ~50%, as the Fe2+(aq)/Fe(III)solid¬ ratio increased from 0.5 to 2. Overall, these results provide important insights into transformation pathways of iron (oxyhydr)oxide minerals in As contaminated, anoxic soils and sediments, and also demonstrate the great impact these can have on As oxidation state and, hence, toxicity and mobility in these environments.
Increasing numbers of implant revisions are a current clinical issue. Interactions of the endoprosthesis biomaterial with the body affect implantation time by wear processes, i.e. corrosion and abrasion. Previously, cobalt-chrome implants were shown to cause high levels of cobalt ions being deposited in the bone matrix. To determine a poten- tial functional role of these ions on bone homeostasis, we have developed a non-destructive dual analysis of highly sensitive elemental analysis by synchrotron XRF directly in undecalcified histological bone thin sections (4 μm). In this study, samples from 28 bone samples from hip endoprosthesis carriers (Surface Replacement Arthroplasty, metal-on-metal bearing) with an implant lifetime of 17–1750 days were used. Results were compared to age- matched control specimens. The histological analysis identified areas of bone cell activity and assigned them for XRF measurements. Co-Cr wear particles were identified in the bone marrow. In addition, Co ions were highly enriched in the mineralized bone matrix. The cobalt deposits were not homogeneously distributed, and areas of high signal intensity were identified. Co was distinctly deposited in the newly formed osteoid layer, but also within deeper layers of the bone matrix, whereby the Co concentration increased with higher degrees of bone matrix mineralization. In the current study, we determined cobalt accumulations in the bone matrix and showed for the first time via synchrotron XRF with a high spatial resolution direct on histological slides, that cobalt deposits in the mineralized bone matrix in a mineral-specific way that is dependent upon the implant lifetime.