Oxyhydroxide Nanoparticles Research Articles

Removal of Fe(II) from groundwater via aqueous portlandite carbonation and calcite-solution interactions

Fresh groundwater is sometimes enriched with dissolved ferrous iron (Fe(II)) that restricts its consumption as potable water because it forms colloidal red matter (mainly ferric oxyhydroxides) under oxic conditions at near neutral pH (>6) conditions. As already demonstrated, natural or synthetic calcite material can be used to accelerate the iron oxidation process from Fe(II) to Fe(III), a process that then enhances its precipitation at the calcite-solution interface as confirmed by in situ atomic force microcopy (AFM) observations in this study. The present study mainly reports on a simplified water treatment method to remove ferrous iron (Fe(II)) from water via aqueous carbonation of calcium hydroxide (Ca(OH)2) at ambient temperature (≈20°C) and moderate CO2 pressure (10bar) conditions. In practice, high concentrations of dissolved iron (up to 100mg/L) can be successfully removed using only 4g of Ca(OH)2 per liter of Fe-rich solution (close to 100% of efficiency) and a short treatment time is required (<1h). This method offers various advantages compared with other calcite-based water treatments. For example, other pre-existent dissolved toxic and eutrophic ions such as As, Cu, Cd, Se, P, S, N, etc. can be simultaneously removed from water during the precipitation of calcite and iron oxyhydroxide nanoparticles (<100nm). Additionally, the dissolution of calcium hydroxide prior to the carbonation process increases the pH (12.4), a process that can act as a softening agent in the water being treated. Finally, the resultant red solid-residue containing mainly calcite and iron oxyhydroxide (FeOOH type) nanoparticles could be reused as pigment or mineral filler powder for industrial applications. This integrated method could be used successfully to remove toxic dissolved ions from water while generating solid residues with industrial uses.

Lithium Storage Properties of a Bioinspired 2-Line Ferrihydrite: A Silicon-Doped, Nanometric, and Amorphous Iron Oxyhydroxide.

Inspired by a nanometric iron-based oxide material of bacterial origin, silicon (Si)-doped iron oxyhydroxide nanoparticles or 2-line ferrihydrites (2Fhs) were prepared and their lithium (Li) storage properties were investigated. The structures of the Si-doped 2Fhs strongly depended on the Si molar ratio [x = Si/(Fe + Si)] whose long-range atomic ordering gradually vanished as the Si molar ratio increased, with a structural change from nanocrystalline to amorphous at x = 0.30. The most striking properties were observed for the sample with x = 0.30. Over the voltage range of 1.5-4.0 V at a current rate of 500 mA/g, this material exhibited a relatively high reversible capacity of ∼100 mAh/g, which was four times greater than that of the Si-free 2Fh and indicated a good rate capability and cyclability. The large capacity and good rate and cycle performances are presumably because of the amorphous structure and the strong and stabilizing covalent Si-O bonds, respectively. The minor amount of Si(4+) in the structure of the iron oxyhydroxides is considered to improve the electrochemical properties. Use of more appropriate doping elements and fabrication of more appropriate nanostructures could drastically improve the Li storage properties of the developed bioinspired material.

Synthesis and Characterization of Nanosized Manganese Oxyhydroxide Compounds by Sonochemical Method

Abstract Manganese oxyhydroxide (MnOOH) nanoparticles were synthesized by the reaction of [Mn(Hsal)2] complex and NaOH in the presence of ultrasound irradiation. In this study, the effect of different reaction parameters such as type of solvent, sonication time and type of surfactant on the morphology and the particle size of product were studied. The as-synthesized nanoparticles, with an average size of 10–15 nm, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR) and energy dispersive spectrometry (EDS). To the best of author’s knowledge, it is the first time that [Mn(Hsal)2] complex is used as manganese source for the synthesis of MnOOH nanoparticles.

Hydrothermal synthesis of nanostructured hybrids based on iron oxide and branched PEI polymers. Influence of high pressure on structure and morphology

Homogeneous hybrids in which iron oxide nanoparticles are entrapped within polymer structure are of interest for their potential applications in biomedical field, such as diagnostic, therapeutic and theranostic purposes. For this reason, hybrid nanomaterials based on branched polyethyleneimine (PEI) and iron oxide with different ratios were synthesized in a single step by hydrothermal procedure at high pressure and low temperature. Iron oxide is formed in the presence of branched PEI and the interaction between them takes place in the reaction medium. The influence of synthesis parameters on the hybrid formation, as well as chemical and structural properties was studied by means of FTIR, DSC-TG, HRTEM, electron paramagnetic resonance (EPR), magnetic measurements (SQUID) and 57Fe Mössbauer analyses. It has been shown that synthesis parameters influence thermal stability and morphology of the hybrids. FeO(OH) crystallites of 2–5 nm are formed. Iron oxyhydroxide nanoparticles strongly entrapped in PEI structure are obtained. The low and distributed values of the specific spontaneous magnetisation in samples prepared under the same pressure conditions support the presence of very fine FeO(OH) nanoparticles, which formation and magnetic properties are depending on the mass ratio between iron oxide and PEI.

Selective formation of iron oxide and oxyhydroxide nanoparticles at room temperature: Critical role of concentration of ferric nitrate

Formation of various iron oxides and oxy-hydroxides was monitored during the hydrolysis of ferric nitrate with hydrazine monohydrate under sonication. The hydrolysis of a concentrated solution (0.05 M) of ferric nitrate solution resulted in the formation of γ-Fe2O3 as the major product and that of a lower concentration (0.005 M) formed α-FeOOH as the major product and at intermediate concentrations, γ-FeOOH or a mixture of γ-FeOOH and α-FeOOH was formed. The shape of the particles varied from spherical to acicular to rod shaped as a result of the changes in the phases formed. The as-formed γ-Fe2O3 exhibited a saturation magnetization of 65 emu/g where as the as-prepared α-FeOOH exhibited a very weak magnetic moment of around 4 emu/g.

High-intensity ultrasonication as a way to prepare graphene/amorphous iron oxyhydroxide hybrid electrode with high capacity in lithium battery

The preparation of graphene/iron oxyhydroxide hybrid electrode material with very homogeneous distribution and close contact of graphene and amorphous iron oxyhydroxide nanoparticles has been achieved by using high-intensity ultrasonication. Due to the negative charge of the graphene surface, iron ions are attracted toward the surface of dispersed graphene, according to the zeta potential measurements. The anchoring of the FeO(OH) particles to the graphene layers has been revealed by using mainly TEM, XPS and EPR. TEM observations show that the size of the iron oxide particles is about 4nm. The ultrasonication treatment is the key parameter to achieve small particle size in these graphene/iron oxyhydroxide hybrid materials. The electrochemical behavior of composite graphene/amorphous iron oxyhydroxide prepared by using high-intensity ultrasonication is outstanding in terms of gravimetric capacity and cycling stability, particularly when metallic foam is used as both the substrate and current collector. The XRD-amorphous character of iron oxyhydroxide in the hybrid electrode material and the small particle size contribute to achieve the improved electrochemical performance.

Highlights from the latest articles on vaccine development using nanoparticles.

2014 Designer aluminum salt-based nanoparticles as vaccine adjuvants Evaluation of: Sun B, Ji Z, Liao Y et al. Engineering an effective immune adjuvant by designed control of shape and crystallinity of aluminum oxyhydroxide nanoparticles. ACS Nano. 7(12), 10834–10849 (2013). Aluminum salts, such as aluminum hydroxide, are widely used in vaccines to improve antigen-specific immune responses [1]. Despite their widespread usage, the exact mechanism of their action is still not fully elucidated. Recently, NLPR3 inflammasome, also known as NALP3 or cryopyrin, has been implicated in the immunostimulatory effects observed with aluminum salts [2]. Structural studies using x-ray diffraction and infrared spectroscopy have shown that aluminum hydroxide adjuvant is actually crystalline aluminum oxyhydroxide, as opposed to aluminum hydroxide or Al(OH) 3 . The geometrical shape of the adjuvant in general has also been implicated in its uptake by antigen-presenting cells (APCs). In this study, Sun et al. designed aluminum oxyhydroxide nanoparticles with different morphologies, shapes and hydroxide concentrations and investigated their adjuvant activities [3]. They studied the effect of these parameters on aluminum oxyhydroxide’s ability to trigger the NLPR3 inflammasome and APC uptake, relative to a commercial alum preparation, using in vitro assays and in vivo studies. An aluminum oxyhydroxide library of nanorods, nanoplates and nano polyhedra was synthesized using a hydrothermal method and structures confirmed by transmission electron microscopy, x-ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy analyses. All the nanostructures were able to activate the NLRP3 inflammasome through generation of oxidative stress in THP-1 human monocytes and induce maturation of mouse bone marrow derived dendritic cells and IL-1β cytokine production by them, but the nanorods were more effective than the nanoplates, nanopolyhedra and the commercial alum. The nanorods were hence used in an in vivo immunization study using ovalbumin (OVA) as a model antigen. The OVA-specific immune responses induced by the OVA-adsorbed aluminum oxyhydroxide nanorods tended to be stronger than that induced by OVA-adsorbed on the commercial alum preparation. This study opens the possibility of engineering designer aluminum salt-based adjuvants with a stronger adjuvant activity.

Aggregation of nanoscale iron oxyhydroxides and corresponding effects on metal uptake, retention, and speciation: I. Ionic-strength and pH

The capacity of nanosized particles to adsorb and sequester dissolved metals can be significantly impacted by the mechanism and extent of aggregation the particles have undergone, which in turn can affect the long-term fate and transport of potentially toxic metals in natural aqueous systems. Suspensions of monodisperse nanoscale iron oxyhydroxides were synthesized and subjected to increased pH (pH 8.0, 10.0) or ionic strength (0.1, 1.0M NaNO3) conditions to induce various states of aggregation prior to conducting macroscopic adsorption/desorption experiments with dissolved Cu(II) or Zn(II). The metal adsorption and retention capacities of the nanoparticle aggregates were compared to one another and to non-aggregated control nanoparticles, while the mode(s) of metal sorption to the nanoparticle surfaces were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy analysis.With increasing aggregation by both pH and ionic strength, the proportion of introduced zinc adsorbed to the iron oxyhydroxide nanoparticles progressively decreased from 45% on the monodispersed control particles to as low as 16% on the aggregates, while the proportion of introduced zinc retained upon desorption (obtained by lowering the suspension pH) increased from 7% on the control particles to as much as 17% on the aggregated particles. Copper exhibited a subtler trend of only slightly declining uptake (from 43% to 36%) and retention (from 35% to 30%) with increasing aggregation state. EXAFS analysis was consistent with the macroscopic results, showing relatively little change in Cu speciation between samples analyzed before and after the desorption step but significant increases in Zn–Fe interatomic distances and coordination numbers after desorption. This suggests the presence of both strongly- and weakly-bound zinc ions; the latter are likely affiliated with less stable, more distorted surface sorption sites and are thus more readily desorbed, resulting in the retention of zinc that is bound to more stable, less-distorted sorption sites. For both metals, inner-sphere bidentate sorption appears to dominate the sorption process to the nanoparticle aggregates, with potential structural incorporation into the aggregates themselves.

High-spin ferric ions in Saccharomyces cerevisiae vacuoles are reduced to the ferrous state during adenine-precursor detoxification.

The majority of Fe in Fe-replete yeast cells is located in vacuoles. These acidic organelles store Fe for use under Fe-deficient conditions and they sequester it from other parts of the cell to avoid Fe-associated toxicity. Vacuolar Fe is predominantly in the form of one or more magnetically isolated nonheme high-spin (NHHS) FeIII complexes with polyphosphate-related ligands. Some FeIII oxyhydroxide nanoparticles may also be present in these organelles, perhaps in equilibrium with the NHHS FeIII. Little is known regarding the chemical properties of vacuolar Fe. When grown on adenine-deficient medium (A↓), ADE2Δ strains of yeast such as W303 produce a toxic intermediate in the adenine biosynthetic pathway. This intermediate is conjugated with glutathione and shuttled into the vacuole for detoxification. The iron content of A↓ W303 cells was determined by Mössbauer and EPR spectroscopies. As they transitioned from exponential growth to stationary state, A↓ cells (supplemented with 40 μM FeIII citrate) accumulated two major NHHS FeII species as the vacuolar NHHS FeIII species declined. This is evidence that vacuoles in A↓ cells are more reducing than those in adenine-sufficient cells. A↓ cells suffered less oxidative stress despite the abundance of NHHS FeII complexes; such species typically promote Fenton chemistry. Most Fe in cells grown for 5 days with extra yeast-nitrogen-base, amino acids and bases in minimal medium was HS FeIII with insignificant amounts of nanoparticles. The vacuoles of these cells might be more acidic than normal and can accommodate high concentrations of HS FeIII species. Glucose levels and rapamycin (affecting the TOR system) affected cellular Fe content. This study illustrates the sensitivity of cellular Fe to changes in metabolism, redox state and pH. Such effects broaden our understanding of how Fe and overall cellular metabolism are integrated.

Zn(II) and Cu(II) adsorption and retention onto iron oxyhydroxide nanoparticles: effects of particle aggregation and salinity.

BackgroundIron oxyhydroxides are commonly found in natural aqueous systems as nanoscale particles, where they can act as effective sorbents for dissolved metals due to their natural surface reactivity, small size and high surface area. These properties make nanoscale iron oxyhydroxides a relevant option for the remediation of water supplies contaminated with dissolved metals. However, natural geochemical processes, such as changes in ionic strength, pH, and temperature, can cause these particles to aggregate, thus affecting their sorption capabilities and remediation potential. Other environmental parameters such as increasing salinity may also impact metal retention, e.g. when particles are transported from freshwater to seawater.ResultsAfter using synthetic iron oxyhydroxide nanoparticles and nanoparticle aggregates in batch Zn(II) adsorption experiments, the addition of increasing concentrations of chloride (from 0.1 M to 0.6 M) appears to initially reduce Zn(II) retention, likely due to the desorption of outer-sphere zinc surface complexes and subsequent formation of aqueous Zn-Cl complexes, before then promoting Zn(II) retention, possibly through the formation of ternary surface complexes (supported by EXAFS spectroscopy) which stabilize zinc on the surface of the nanoparticles/aggregates. In batch Cu(II) adsorption experiments, Cu(II) retention reaches a maximum at 0.4 M chloride. Copper-chloride surface complexes are not indicated by EXAFS spectroscopy, but there is an increase in the formation of stable aqueous copper-chloride complexes as chloride concentration rises (with CuCl+ becoming dominant in solution at ~0.5 M chloride) that would potentially inhibit further sorption or encourage desorption. Instead, the presence of bidentate edge-sharing and monodentate corner-sharing complexes is supported by EXAFS spectroscopy. Increasing chloride concentration has more of an impact on zinc retention than the mechanism of nanoparticle aggregation, whereas aggregation condition is a stronger determinant of copper retention.ConclusionsBased on these model uptake/retention studies, iron oxyhydroxide nanoparticles show potential as a strategy to remediate zinc-contaminated waters that migrate towards the ocean. Copper retention, in contrast, appears to be optimized at an intermediate salinity consistent with brackish water, and therefore may release considerable fractions of retained copper at higher (e.g. seawater) salinity levels.

Mössbauer, EPR, and modeling study of iron trafficking and regulation in Δccc1 and CCC1-up Saccharomyces cerevisiae.

Strains lacking and overexpressing the vacuolar iron (Fe) importer CCC1 were characterized using Mössbauer and EPR spectroscopies. Vacuolar Fe import is impeded in Δccc1 cells and enhanced in CCC1-up cells, causing vacuolar Fe in these strains to decline and accumulate, respectively, relative to WT cells. Cytosolic Fe levels should behave oppositely. The Fe content of Δccc1 cells grown under low-Fe conditions was similar to that in WT cells. Most Fe was mitochondrial with some nonheme high spin (NHHS) FeII present. Δccc1 cells grown with increasing Fe concentration in the medium contained less total Fe, less vacuolar HS FeIII, and more NHHS FeII than in comparable WT cells. As the Fe concentration in the growth medium increased, the concentration of HS FeIII in Δccc1 cells increased to just 60% of WT levels, while NHHS FeII increased to twice WT levels, suggesting that the NHHS FeII was cytosolic. Δccc1 cells suffered more oxidative damage than WT cells, suggesting that the accumulated NHHS FeII promoted Fenton chemistry. The Fe concentration in CCC1-up cells was higher than in WT cells; the extra Fe was present as NHHS FeII and FeIII and as FeIII oxyhydroxide nanoparticles. These cells contained less mitochondrial Fe and exhibited less ROS damage than Δccc1 cells. CCC1-up cells were adenine-deficient on minimal medium; supplementing with adenine caused a decline of NHHS FeII suggesting that some of the NHHS FeII that accumulated in these cells was associated with adenine deficiency rather than the overexpression of CCC1. A mathematical model was developed that simulated changes in Fe distributions. Simulations suggested that only a modest proportion of the observed NHHS FeII in both strains was the cytosolic form of Fe that is sensed by the Fe import regulatory system. The remainder is probably generated by the reduction of the vacuolar NHHS FeIII species.

Influence of iron content, surface area and charge distribution in the arsenic removal by activated carbons

Abstract Due to the high number of toxicological issues, the presence of asenic (V) in water supplies is a major problem of public concern. Adsorption by iron modified activated carbons stands as an interesting alternative for the removal of arsenic (V) from aqueous solutions. However, the question of which of the activated carbon properties have impact during arsenic (V) uptake has arisen. The influence of textural and chemical features of several activated carbons (AC), un-modified and modified with iron oxyhydroxide nanoparticles, for the removal of arsenic (V) from aqueous solution was studied. The surface area ( S BET ), micropore volume, surface charge and iron content of 28 ACs were determined. Results showed that the S BET of materials range from 388 to 1747 m 2 /g, the point of zero charge (PH PZC ) from 3 to 11 and the iron content range from negligible to around 2%. A detailed data analysis demonstrated that the most important parameter of AC when removing arsenic (V) from water is the pH PZC (52.5% of contribution); however, the presence of iron is indispensable for enhancing the adsorption capacity (by 36.5%). An empirical model indicated that in order to effectively remove arsenic from water a basic AC with an iron content of about 1% is desirable. Arsenic (V) adsorption isotherms under normal conditions demonstrated that the materials studied have a great potential for water polishing. Finally it is suggested that the arsenate uptake by iron-modified AC is conducted by two simultaneous mechanisms: ligand interchange with iron oxyhydroxide particles and electrostatic attraction on basic AC.

Kinetics of crystal growth of nanogoethite in aqueous solutions containing nitrate and sulfate anions

Iron oxyhydroxide nanoparticles, relatively abundant and highly reactive components of most natural ecosystems, are known to grow via the oriented attachment (OA)-based crystal growth pathway. Here, we conducted experiments in highly alkaline solutions containing sulfate and nitrate anions to test the differential impact of these anions on the various steps in this growth pathway. Nanogoethite (α-FeOOH) was prepared by reacting ferric sulfate or ferric nitrate with potassium hydroxide, and aging at room temperature, 50, 60 and 70 °C. X-ray diffraction (XRD) was used to confirm the synthesis of goethite and Rietveld analyses were used to determine the particle sizes in samples with different aging times. Particle morphology and microstructure of some samples were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images confirmed growth of goethite nanorods via OA. OA growth kinetics were modeled using a previously reported kinetic equation. An Arrhenius plot indicated the activation energy for OA-based crystal growth in the sulfate system was 45.2 kJ mol−1, higher than in the nitrate system (23.1 kJ mol−1). The magnitude of the activation energy suggests that the rate-limiting step for OA growth is diffusion of nanoparticles in solution, a first step necessary for particle–particle attachment. We attribute the larger effect of sulfate compared to nitrate on the activation energy to greater structuring of water by sulfate. The kinetic pre-exponential factor for the sulfate system is much higher than that for the nitrate system, and results in faster growth kinetics at high temperature. Sulfate may accelerate the dehydration of the interface, a subsequent step required for OA-based growth, possibly through increasing the rate of water exchange at the nanoparticle surfaces. These findings motivate conduction of new experiments to further probe the kinetics of individual steps in OA-based crystal growth, suggest routes to inhibit or promote OA relative to atom-by-atom growth pathways, and provide clues to how variation in solution chemistry could impact mineral growth in natural systems.

The Lack of Synchronization between Iron Uptake and Cell Growth Leads to Iron Overload in Saccharomyces cerevisiae during Post-exponential Growth Modes

Fermenting cells growing exponentially on rich (YPAD) medium underwent a transition to a slow-growing state as glucose levels declined and their metabolism shifted to respiration. During exponential growth, Fe import and cell-growth rates were matched, affording an approximately invariant cellular Fe concentration. During the transition period, the high-affinity Fe import rate declined slower than the cell-growth rate declined, causing Fe to accumulate, initially as Fe(III) oxyhydroxide nanoparticles but eventually as mitochondrial and vacuolar Fe. Once the cells had reached slow-growth mode, Fe import and cell-growth rates were again matched, and the cellular Fe concentration was again approximately invariant. Fermenting cells grown on minimal medium (MM) grew more slowly during the exponential phase and underwent a transition to a true stationary state as glucose levels declined. The Fe concentration of MM cells that just entered the stationary state was similar to that of YPAD cells, but MM cells continued to accumulate Fe in the stationary state. Fe initially accumulated as nanoparticles and high-spin Fe(II) species, but vacuolar Fe(III) also eventually accumulated. Surprisingly, Fe-packed 5-day-old MM cells suffered no more reactive oxygen species (ROS) damage than younger cells, suggesting that the Fe concentration alone does not accurately predict the extent of ROS damage. The mode and rate of growth at the time of harvesting dramatically affected cellular Fe content. A mathematical model of Fe metabolism in a growing cell was developed. The model included the import of Fe via a regulated high-affinity pathway and an unregulated low-affinity pathway. The import of Fe from the cytosol to vacuoles and mitochondria and nanoparticle formation were also included. The model captured essential trafficking behavior, demonstrating that cells regulate Fe import in accordance with their overall growth rate and that they misregulate Fe import when nanoparticles accumulate. The lack of regulation of Fe in yeast is perhaps unique compared to the tight regulation of other cellular metabolites. This phenomenon likely derives from the unique chemistry associated with Fe nanoparticle formation.

Engineering an effective immune adjuvant by designed control of shape and crystallinity of aluminum oxyhydroxide nanoparticles.

Adjuvants based on aluminum salts (Alum) are commonly used in vaccines to boost the immune response against infectious agents. However, the detailed mechanism of how Alum enhances adaptive immunity and exerts its adjuvant immune effect remains unclear. Other than being comprised of micrometer-sized aggregates that include nanoscale particulates, Alum lacks specific physicochemical properties to explain activation of the innate immune system, including the mechanism by which aluminum-based adjuvants engage the NLRP3 inflammasome and IL-1β production. This is putatively one of the major mechanisms required for an adjuvant effect. Because we know that long aspect ratio nanomaterials trigger the NLRP3 inflammasome, we synthesized a library of aluminum oxyhydroxide (AlOOH) nanorods to determine whether control of the material shape and crystalline properties could be used to quantitatively assess NLRP3 inflammasome activation and linkage of the cellular response to the material's adjuvant activities in vivo. Using comparison to commercial Alum, we demonstrate that the crystallinity and surface hydroxyl group display of AlOOH nanoparticles quantitatively impact the activation of the NLRP3 inflammasome in human THP-1 myeloid cells or murine bone marrow-derived dendritic cells (BMDCs). Moreover, these in vitro effects were correlated with the immunopotentiation capabilities of the AlOOH nanorods in a murine OVA immunization model. These results demonstrate that shape, crystallinity, and hydroxyl content play an important role in NLRP3 inflammasome activation and are therefore useful for quantitative boosting of antigen-specific immune responses. These results show that the engineered design of aluminum-based adjuvants in combination with dendritic cell property-activity analysis can be used to design more potent aluminum-based adjuvants.

Mössbauer Study and Modeling of Iron Import and Trafficking in Human Jurkat Cells

The Fe content of Jurkat cells grown on transferrin-bound iron (TBI) and Fe(III) citrate (FC) was characterized using Mössbauer, electron paramagnetic resonance, and UV-vis spectroscopies, as well as electron and inductively coupled plasma mass spectrometry. Isolated mitochondria were similarly characterized. Fe-limited cells contained ~100 μM essential Fe, mainly as mitochondrial Fe and nonmitochondrial non-heme high-spin Fe(II). Cells replete with Fe also contained ferritin-bound Fe and Fe(III) oxyhydroxide nanoparticles. Only 400 ± 100 Fe ions were loaded per ferritin complex, regardless of the growth medium Fe concentration. Ferritin regulation thus appears to be more complex than is commonly assumed. The magnetic and structural properties of Jurkat nanoparticles differed from those of yeast mitochondria. They were smaller and may be located in the cytosol. The extent of nanoparticle formation scaled nonlinearly with the concentration of Fe in the medium. Nanoparticle formation was not strongly correlated with reactive oxygen species (ROS) damage. Cells could utilize nanoparticle Fe, converting such aggregates into essential Fe forms. Cells grown on galactose rather than glucose respired faster, grew slower, exhibited more ROS damage, and generally contained more nanoparticles. Cells grown with TBI rather than FC contained less Fe overall, more ferritin, and fewer nanoparticles. Cells in which the level of transferrin receptor expression was increased contained more ferritin Fe. Frataxin-deficient cells contained more nanoparticles than comparable wild-type cells. Data were analyzed by a chemically based mathematical model. Although simple, it captured essential features of Fe import, trafficking, and regulation. TBI import was highly regulated, but FC import was not. Nanoparticle formation was not regulated, but the rate was third-order in cytosolic Fe.

Desulfurization of Model Diesel Fuel on Activated Carbon Modified with Iron Oxyhydroxide Nanoparticles: Effect of tert-Butylbenzene and Naphthalene Concentrations

Commercially activated carbon Filtrasorb 400 (F400) was modified with iron oxyhydroxide nanoparticles and tested, in a continuous process, as a diesel fuel desulfurization medium. Model diesel fuel (MDF) was prepared as a mixture of decane and hexadecane, with 20 ppm of sulfur from dibenzothiophenes (dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT)), and different concentrations of tert-butylbenzene and naphthalene. The calculated selectivities and adsorption capacities for DBT and DMDBT were analyzed at different concentration of aromatics. The results indicate that, while the concentration of naphthalene greatly affects the adsorption capacity of both DBT and DMDBT, the concentration of tert-butylbenzene only affects DMDBT uptake. At low concentration of aromatics, iron-containing carbon performs better than unmodified carbon and further oxidized species were identified on the surface of the iron-modified activated carbon. This indicates that iron is acting as an acidic center, attracting basic DBT and DMDBT, and is acting as an oxidant for the adsorbed species. With an increase in the content of aromatics in MDF, the difference in the desulfurization performance between the studied materials diminishes. After thermal regeneration of the iron-containing sample, 95% of the pore volume is recovered and only a 10% loss in the DBT and DMDBT adsorption capacity is observed.

Magnetic properties of ferritin and akaganeite nanoparticles in aqueous suspension

We have studied the magnetically induced optical birefringence Δn of horse spleen ferritin (HSF) and aqueous suspensions of several different-sized iron oxyhydroxide nanoparticles coated with different polysaccharides mimicking ferritin. The structure and dimensions of the akaganeite mineral core were characterized by XRD and TEM, respectively. The stability of the suspensions in the measurement temperature range from 278 to 358 K was confirmed by UV–Vis absorption spectroscopy. The values of optical polarizability anisotropy Δα, magnetic susceptibility anisotropy Δχ, and permanent magnetic dipole moment μ m of the akaganeite nanoparticles have been estimated on the basis of the temperature dependence of the Cotton–Mouton (C–M) constant. The magnetic birefringence of Fe-sucrose has been described tentatively by different types of Langevin function allowing another estimation of Δχ and μ m. The obtained permanent magnetic dipole moment μ m of the studied akaganeite nanoparticles proves small and comparable to that of HSF. The value of μ m is found to increase with decreasing nanoparticle diameter. Observed in a range spanning more than five orders of magnitude, the linear relation between the C–M constant and the iron concentration provides a basis for possible analytical application of the C–M effect in biomedicine. The established relation between the C–M constant and the nanoparticle diameter confirms that the dominant contribution to the measured magnetic birefringence comes from the magnetic susceptibility anisotropy Δχ. A comparison of the C–M constants of the studied akaganeite nanoparticles with the data obtained for HSF provides evidence that the ferritin core behaves as a non-Euclidian solid.

Synthesis and characterization of mesoporous Ni–Co oxy-hydroxides for pseudocapacitor application

Mesoporous binary nickel–cobalt (Ni–Co) oxy-hydroxides have been obtained through the microwave-assisted hydrothermal annealing (MAHA) method. The porosity control of the nanostructured Ni–Co oxy-hydroxide nanoparticles is achieved through adding the pluronic triblock copolymer F127 as the surfactant. The structural and electrochemical properties of porous Ni–Co oxy-hydroxide nanostructures are characterized by means of X-ray diffraction (XRD), Brumauer–Emmett–Teller (BET) analysis, transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cyclic voltammetry (CV). The electrochemical measurement demonstrates that the Ni–Co oxy-hydroxides calcined at 200°C are able to deliver a specific capacitance of 636Fg−1 in 1M NaOH, suggesting their high potential as a novel electrode material of pseudocapacitors with good electrochemical reversibility. In the asymmetric supercapacitor test, the positive electrode is Ni–Co oxy-hydroxide and negative electrode is activated carbon. The specific energy and power, measured at 2Ag−1, for this asymmetric combination are equal to ca. 17Whkg−1 and 1.6kWkg−1, respectively.

Structural properties of nickel hydroxide/oxyhydroxide and oxide nanoparticles obtained by microwave-assisted oxidation technique

Abstract Nickel hydroxide (β-Ni(OH) 2 ) and nickel oxyhydroxide (β-NiOOH) nanoparticles assigned as P and PO, respectively, were successfully synthesized through a microwave-assisted oxidation technique using sodium hydroxide as the precipitating agent and sodium hypochlorite as the oxidizing agent. NiO nanoparticles were then obtained by thermal decomposition of nickel oxyhydroxide (PO) compound. The effect of the parameters such as concentration of the precipitating agent and calcination temperature on the structural characteristics of the products was investigated. The as-prepared materials were well characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetry (TGA), and scanning electron microscopy (SEM) analytical techniques. XRD and SEM results indicated that the crystallinity and particle size of the products depend on NaOH concentration and calcination temperature.