Goethite Nanoparticles Research Articles

Investigating the Uptake and Some Subcellular Effects of Manufactured Goethite Nanoparticles on Lumbriculus variegatus

Investigating the Uptake and Some Subcellular Effects of Manufactured Goethite Nanoparticles on Lumbriculus variegatus The aims of this work were: 1) to investigate whether the freshwater oligochaete Lumbriculus variegatus incorporates manufactured goethite nanoparticles (NPs) after an acute exposure; 2) to evaluate the influence of a solution of humic acids (HA) on the uptake of NPs; 3) to investigate the effects of these NPs on several biomarkers related to the generation of reactive oxygen species (ROS). NPs were analyzed by transmission electron microscopy. To evaluate the uptake, animals were exposed to 10 mg NPs L-1 for 48 h and then depurated for different periods (0;4;16, and 24 h). Iron concentrations were measured by atomic absorption spectrophotometry. Biomarker parameters were determined in oligochaetes exposed to a suspension containing 10 mg NPs L-1 for 48 h without depuration. Oligochaetes depurated for 4 h presented higher levels of Fe in their whole body tissues than control organisms. However, values returned to control levels when the oligochaetes were depurated for periods longer than 16 h, suggesting that organisms may transitorily incorporate the NPs in their digestive tract and/or superficially adsorbed them but they could not absorb the NPs. Exposures for periods longer than 48 h did not increase the Fe body burden. The presence of a 20 mg L-1 of humic acid solution prevented the NPs uptake. Several biomarker parameters related to the generation of reactive oxygen species were assessed. The activity of the enzyme superoxide dismutase and levels of total glutathione were higher in animals exposed to the NPs for 48 h than in controls. However, the catalase activity and the determination of the total scavenger capacity (TOSC assay) were not modified.The release of manufactured nanomaterials to the aquatic environment may elicit some subcellular responses even when the NPs are not absorbed by the organisms.

Gamma-irradiation synthesis of iron oxide nanoparticles in the presence of PEO, PVP or CTAB

Black hydrogels were synthesized using γ-irradiation of poly(ethylene oxide) (PEO)/iron(III) chloride precursor solutions. The magnetic properties of such hydrogels were improved by adding 2-propanol as a hydroxyl scavenger and/or NaBH4 as a strong chemical reducing agent; however, the rigidity and compactness of thus synthesized PEO hydrogels deteriorated. The magnetic suspension containing pure magnetite nanoparticles was obtained using γ-irradiation of an Fe(III)/PEO deoxygenated aqueous solution in the presence of 2-propanol and NaBH4. The γ-irradiation of an iron(III) chloride aqueous precursor solution in the presence of PVP produced a magnetic suspension due to the formation of a small amount of δ-FeOOH (feroxyhyte). The γ-irradiation of Fe(III)/CTAB (cetyltrimethylammonium bromide) aqueous solutions favored the formation of goethite. γ-irradiation in the presence of 2-propanol increased the yield of rod-like goethite nanoparticles. A small amount of δ-FeOOH found in the Fe(III)/PVP and Fe(III)/CTAB suspensions suggests the formation of Fe(OH)2upon γ-irradiation, which then under atmospheric conditions rapidly oxidized into δ-FeOOH.

Impact of environmental conditions on aggregation kinetics of hematite and goethite nanoparticles

Hematite and goethite nanoparticles were used as model minerals to investigate their aggregation kinetics under soil environmental conditions in the present study. The hydrodynamic diameters of hematite and goethite nanoparticles were 34.4 and 66.3 nm, respectively. The positive surface charges and zeta potential values for goethite were higher than for hematite. The effective diameter for goethite was much larger than for hematite due to anisotropic sticking of needle-shaped goethite during aggregation. Moreover, the critical coagulation concentration (CCC) values of nanoparticles in solutions of NaNO3, NaCl, NaF, and Na2SO4 were 79.2, 75.0, 7.8, and 0.5 mM for hematite and they were 54.7, 62.6, 5.5, and 0.2 mM for goethite, respectively. The disparity of anions in inducing hematite or goethite aggregation lay in the differences in interfacial interactions. NO3 − and Cl− could decrease the zeta potential and enhance aggregation mainly through increasing ionic strength and compressing electric double layers of hematite and goethite nanoparticles. F− and SO4 2− highly destabilized the suspensions of nanoparticles mainly through specific adsorption and then neutralizing the positive surface charges of nanoparticles. Specific adsorption of cations could increase positive surface charges and stabilize hematite and goethite nanoparticles. The Hamaker constants of hematite and goethite nanoparticles were calculated to be 2.87 × 10−20 and 2.29 × 10−20 J−1, respectively. The predicted CCC values based on DLVO theory were consistent well with the experimentally determined CCC values in NaNO3, NaCl, NaF, and Na2SO4 systems, which demonstrated that DLVO theory could successfully predict the aggregation kinetics even when specific adsorption of ions occurred.

Optimization of lead removal from aqueous solution using goethite/chitosan nanocomposite by response surface methodology

Abstract This work investigates goethite/chitosan nanocomposites for their use in lead removal from aqueous solutions. Goethite nanoparticles were synthesized and characterized by FTIR, DLS, and SEM. Goethite nanoparticles were identified as nanospheres with the average diameter of 10–60 nm. The optimum conditions were determined using response surface methodology (RSM) based on three-variable-three-level Box–Behnken design (BBD). The effects of three variables, i.e., initial solution pH, adsorbent mass and initial concentration of Pb(II) ions on the removal efficiency for Pb(II) ions were evaluated. The optimal conditions for the lead removal were found to be 6, 0.05 g, and 74.4 mg/L, for the initial solution pH, adsorbent mass and the initial concentration of Pb(II) ions, respectively. Under these conditions, maximum lead removal efficiency was obtained to 98.26% that was in respectable agreement with the model (97.19%). The modified quadratic model exhibited excellent stability for Pb(II) adsorption by goethite/chitosan nanocomposite. The results of adsorption study by goethite/chitosan nanocomposite revealed that Pb(II) uptake was enhanced by chitosan film using goethite nanoparticles.

Effect of Size-Selective Retention on the Cotransport of Hydroxyapatite and Goethite Nanoparticles in Saturated Porous Media.

Attributable to their nanoscale size and slow phosphorus (P) release kinetics, hydroxyapatite nanoparticles (HANPs) are increasingly advocated as a promising P nanofertilizer. Additionally, HANPs have been extensively used to remediate soils, groundwater, and nuclear wastewaters contaminated with metals and radionuclides. Increasing application of HANPs for agronomic and environmental advantages will expedite their dissemination in subsurface environments. Because the biogeochemical cycling of P is intimately coupled with iron, it is anticipated that HANPs and released P from HANPs interact with iron oxides, particularly naturally occurring goethite nanoparticles (GNPs) because of their nanoscale size and high reactivity toward P. Here, we investigated the cotransport and retention of HANPs and GNPs in water-saturated sand columns under environmentally relevant transport conditions (pH and natural organic matter type and concentration). Our results indicated that the "size-selective retention", i.e., preferential retention of larger particles near the column inlet and elution of smaller particles occurred during cotransport of HANPs and GNPs, and the cotransport of both NPs is highly sensitive to solution chemistry that determines NPs dissolution, homo- and heteroaggregation, and co- and competitive-retention. These findings have important insights into application of HANPs as a promising P nanofertilizer and an in situ amendment for contaminated site remediation.

Proton Dynamics on Goethite Nanoparticles and Coupling to Electron Transport.

The surface chemistry of metal oxide particles is governed by the charge that develops at the interface with aqueous solution. Mineral transformation, biogeochemical reactions, remediation, and sorption dynamics are profoundly affected in response. Here we report implementation of replica-exchange constant-pH molecular dynamics simulations that use classical molecular dynamics for exploring configurational space and Metropolis Monte Carlo walking through protonation space with a simulated annealing escape route from metastable configurations. By examining the archetypal metal oxide, goethite (α-FeOOH), we find that electrostatic potential gradients spontaneously arise between intersecting low-index crystal faces and across explicitly treated oxide nanoparticles at a magnitude exceeding the Johnson-Nyquist voltage fluctuation. Fluctuations in adsorbed proton density continuously repolarize the surface potential bias between edge-sharing crystal faces, at a rate slower than the reported electron-polaron hopping rate in goethite interiors. This suggests that these spontaneous surface potential fluctuations will control the net movement of charge carriers in the lattice.

Anomalous Particle Size Dependence of Magnetic Relaxation Phenomena in Goethite Nanoparticles

By use of Mossbauer spectroscopy we have studied the magnetic properties of samples of goethite nanoparticles with different particle size. The spectra are influenced by fluctuations of the magnetization directions, but the size dependence is not in accordance with the Neel-Brown expression for superparamagnetic relaxation of the magnetization vectors of the particles as a whole. The data suggest that the magnetic fluctuations can be explained by fluctuations of the magnetization directions of small interacting grains within the particles.

Impact of Pahokee Peat humic acid and buffer identity on goethite aggregation and reactivity

High concentrations of Pahokee Peat humic acid block reactive sites resulting in well-dispersed and less reactive goethite nanoparticles.

Use of micrometer hematite particles and nanodispersed goethite as sorbent for heavy metals

Sorption properties of micrometer hematite particles and goethite nanoparticles were studied. Goethite nanoparticles were produced by chemical precipitation from iron nitrate and stabilized with potassium hydrotartrate. Data on how the sorption properties of goethite nanoparticles depend on temperature and acidity of the medium were used to determine the optimal values of these parameters, at which the maximum sorption of metals are obtained. The higher sorption properties of goethite nanoparticles with respect for all the heavy metal ions under study were found as compared with the micrometer hematite and published data. The results obtained can be used in purification of wastewater containing heavy metal ions.

Magnetic properties of ultra-small goethite nanoparticles

Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mössbauer spectroscopy. The ‘ultra-small’ size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low temperatures most likely due to freezing of spins in canted spin structures. From hysteresis curves we estimate the saturation magnetization from uncompensated magnetic moments to be σs = 0.044 A m2 kg−1 at room temperature. Inelastic neutron scattering measurements show a strong signal from excitations of the uniform mode (q = 0 spin waves) at temperatures of 100–250 K and Mössbauer spectroscopy studies show that the magnetic fluctuations are dominated by ‘classical’ superparamagnetic relaxation at temperatures above ∼170 K. From the temperature dependence of the hyperfine fields and the excitation energy of the uniform mode we estimate a magnetic anisotropy constant of around 1.0 × 105 J m−3.

Studies on Structural and Conducting Properties of Goethite Nanoparticles Doped HPMC Polymer Films

We have carried out systematic studies on Goethite nanoparticles doped (dispersed) HPMC polymer films to quantify the changes in their structural properties, the conductivity, and IR absorbance of films. It is observed that the addition of nanoparticles has significant influence on changing structural parameters and hence enhancing the conductivity of the polymer composite considerably. These polymer composites are water soluble.

Goethite nanoparticle aggregation: effects of buffers, metal ions, and 4-chloronitrobenzene reduction

The rates at which highly oxidized species are reduced by Fe(ii) sorbed onto iron mineral surfaces can change dramatically with small changes in solution conditions, mainly through changes in nanoparticle aggregation state.

Magneto-optical effect in a system of colloidal particle having anisotropic dielectric property

Spherical, non-cubic crystal nanoparticles with an anisotropic dielectric constant and a weak intrinsic magnetic moment, such as goethite nanoparticles, can be considered to be equivalent to a magnetic dielectric ellipsoid. For colloids based on such ellipsoids, the dielectric constant is isotropic in zero magnetic field. However, when a magnetic field is applied, the moments’ Brownian rotation, which is connected with the rotation of the ellipsoids themselves, will induce order in the orientation of the dielectric ellipsoids, so that the dielectric constant of the colloids becomes anisotropic to exhibit magneto-optical effect. As the orientation of the dielectric ellipsoids has been ordered by the magnetic field, the mechanism of optical effects is different from general ferrofluids and liquid crystals, and can be viewed as an optically anisotropic action which results from the coupling of both the magnetic and dielectric properties, i.e. the optical effects only come up when a magnetic field is applied because all the dielectric ellipsoids become aligned. It is confirmed from theory and experiment that for magnetic colloid based on spherical nanoparticles with cubic crystal structure, the magneto-optical effects cannot be due to the reaction of single particles.

Atomic Scale Study on the Thermal Evolution of Local Structure and Magnetic Properties in Oleic Acid Coated Iron Oxide Nanoparticles

The physics of the binding of nanoparticles of goethite and cubic iron oxide as capped by oleic acid has been elucidated in the present study based on the thermal evolution of local structure and magnetic properties using Mössbauer spectroscopy. It is observed that the goethite nanoparticles predominantly undergo topotactic transformation to hemeatite while the assembly of identical bare (not oleic acid capped) nanoparticles composed of goethite and magnetite are subjected to annealing beyond 520 K. In contrast to the results obtained on the bare nanoparticles, accelerated reduction of oleic acid coated nanoparticles of goethite to fully stoichiometric magnetite and subsequently to wustite and α-Fe is observed in the 750–875 K annealing interval. Atomic scale characterization of core–shell structures of different iron oxide phases obtained during the evolution of oleic acid coated nanoparticles of iron oxides has also been provided. The understanding of the present study could be utilized to obtain desired core–shell structures of iron oxides, providing the scope for studying the exchange interaction between the core and shell structures, which exhibit different magnetic ordering.

Separation and identification of soil nanoparticles by conventional and synchrotron X-ray diffraction

Separation and collection of environmental nanoparticles (ENPs) in natural systems are of paramount importance in research on their nature and physicochemical properties for understanding their associated properties of adsorbing or binding to organic and trace metal contaminants. However, efficient separation and collection of ENPs in nature system remain obscure. This study aimed to use an automated ultrafiltration device (AUD) to demonstrate efficient collection of ENPs from highly weathered red soils. Synchrotron and conventional X-ray diffraction (XRD) with oriented and random powder specimens were employed to identify the composition of clay minerals with various particle-size fractions (PSFs, <2000, 450–2000, 100–450, and 1–100nm). The AUD was used successfully to overcome the problem of efficiently collecting ENPs in large quantities in red soils. This study showed that the major clay minerals in the <2000 and 450–2000nm size fractions were illite, kaolinite, and minor constituents of goethite and hematite by synchrotron and conventional XRD analyses. Illite and kaolinite were confirmed to be presented in the 1–100nm size fraction by conventional XRD analysis with oriented specimens. From synchrotron random powder XRD analysis, illite, kaolinite, goethite, and hematite nanoparticles were present. Synchrotron XRD patterns and transmission electron microscopy (TEM) images provided unequivocal evidence of goethite and hematite existence in the 1–100nm size fraction. The AUD has the characteristics of automation, easy operation, and high efficiency in the separation of nanoparticles and would, thus, facilitate future research and developments in environmental nanoscience, nanotechnology and their impacts on the ecosystem.

Large Uptake of Titania and Iron Oxide Nanoparticles in the Nucleus of Lung Epithelial Cells as Measured by Raman Imaging and Multivariate Classification

It is a challenging task to characterize the biodistribution of nanoparticles in cells and tissue on a subcellular level. Conventional methods to study the interaction of nanoparticles with living cells rely on labeling techniques that either selectively stain the particles or selectively tag them with tracer molecules. In this work, Raman imaging, a label-free technique that requires no extensive sample preparation, was combined with multivariate classification to quantify the spatial distribution of oxide nanoparticles inside living lung epithelial cells (A549). Cells were exposed to TiO2 (titania) and/or α-FeO(OH) (goethite) nanoparticles at various incubation times (4 or 48 h). Using multivariate classification of hyperspectral Raman data with partial least-squares discriminant analysis, we show that a surprisingly large fraction of spectra, classified as belonging to the cell nucleus, show Raman bands associated with nanoparticles. Up to 40% of spectra from the cell nucleus show Raman bands associated with nanoparticles. Complementary transmission electron microscopy data for thin cell sections qualitatively support the conclusions.

Water Vapor Adsorption on Goethite

Goethite (α-FeOOH) is an important mineral contributing to processes of atmospheric and terrestrial importance. Their interactions with water vapor are particularly relevant in these contexts. In this work, molecular details of water vapor (0.0-19.0 Torr; 0-96% relative humidity at 25 °C) adsorption at surfaces of synthetic goethite nanoparticles reacted with and without HCl and NaCl were resolved using vibrational spectroscopy. This technique probed interactions between surface (hydr)oxo groups and liquid water-like films. Molecular dynamics showed that structures and orientations adopted by these waters are comparable to those adopted at the interface with liquid water. Particle surfaces reacted with HCl accumulated less water than acid-free surfaces due to disruptions in hydrogen bond networks by chemisorbed waters and chloride. Particles reacted with NaCl had lower loadings below ∼10 Torr water vapor but greater loadings above this value than salt-free surfaces. Water adsorption reactions were here affected by competitive hydration of coexisting salt-free surface regions, adsorbed chloride and sodium, as well as precipitated NaCl. Collectively, the findings presented in this study add further insight into the initial mechanisms of thin water film formation at goethite surfaces subjected to variations in water vapor pressure that are relevant to natural systems.

Immobilization of P by oxidation of Fe(II) ions leading to nanoparticle formation and aggregation

Ferrous iron was oxidized at pH 6.0 in the presence of dissolved oxygen and increasing concentrations of phosphate. The resulting precipitates were characterized by TEM, SEM, XRD, IR spectroscopy, Mössbauer spectroscopy, EXAFS spectroscopy, and chemical analyses. The kinetics and the stoichiometry of oxidation were also determined. Chemical analyses revealed that all the P introduced was immobilized up to an introduced P/Fe molar ratio of 0.6–0.7. In the presence of excess phosphate, the maximum P/Fe ratio of the precipitates was found to be equal to about 0.86. Incorporation of phosphate hindered the sorption of dissolved carbonates, but favored the immobilization of monovalent cations such as Na or K. The number of OH− ions per Fe atom introduced during the reaction decreased from 2 in the absence of P to about 1.5±0.1 in the presence of excess phosphate. In all cases, no residual Fe(II) could be detected. In the absence of phosphate, the samples were composed of poorly crystallized ferrihydrite, lepidocrocite and goethite nanoparticles. Even just a small amount of phosphate (P/Fe=0.02) was sufficient to effectively restrict the formation of goethite. In contrast, the formation of lepidocrocite was detected by XRD for P/Fe ratios as high as 0.1. At higher P/Fe ratios, only non-crystalline particles were detected. For 0.1<P/Fe<0.5, the characteristic size of all particles was smaller than 10nm. For P/Fe>0.5, a new category of particles with characteristic length scales larger than 10nm appeared and became prominent as P/Fe increased. The transition was accompanied by a change in color of the suspension, from dark red to light yellow. For an introduced P/Fe ratio larger than 1, only the larger particles remained. As the introduced P/Fe ratio increased further, the incorporated P/Fe ratio increased only slightly. In contrast the size of the particles increased significantly, reaching a size larger than 50nm in the presence of a large excess of PO43-. The kinetics of oxidation and hydrolysis were shown to obey a typical autocatalytic process in the presence as well as in the absence of PO43-.

Atomic scale study of thermal reduction of nano goethite coexisting with magnetite

Evolution of the local structure and magnetic properties of nano particles of goethite having magnetite as a composite due to controlled annealing treatments in vacuum has been studied using Mossbauer spectroscopy. Importance of size, defect associated with structural OH- for the observed structural and magnetic properties of goethite has been emphasized in this study. Present Mossbauer results show that thermal annealing at low temperatures (420-550 K) lead to a partial conversion / reduction of orthorhombic goethite to cubic spinel oxides such as maghemite and off-stochiometric magnetite. This study further establishes that annealing treatments beyond 650 K predominantly results in topotactic conversion of goethite to haematite. Underlying physics of the transitions of goethite to iron oxides and the important role of desorbed hydrogen for the orthorhombic to cubic structural transitions has been elucidated in this study.

Adsorption of trimethyl phosphate and triethyl phosphate on dry and water pre-covered hematite, maghemite, and goethite nanoparticles

Adsorption of trimethyl phosphate (TMP) and triethyl phosphate (TEP) on well-characterized nanoparticles of hematite (α-Fe2O3), maghemite (γ-Fe2O3), and goethite (α-FeOOH) has been studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), 2D correlation DRIFTS analysis, and X-ray photoelectron spectroscopy (XPS) on dry and water pre-covered surfaces. It is shown that, at room temperature and low coverage, both TMP and TEP coordinate to Lewis acid Fe sites through the O phosphoryl atom on hematite and maghemite, while hydrogen bonding to Brønstedt acid surface OH groups dominates on goethite. At room temperature, slow dissociation of TMP occurs on the iron (hydr)oxide nanoparticles, whereby a methoxy group is displaced to form surface methoxy, leaving adsorbed dimethyl phosphate (DMP). Methoxy is further decomposed to formate, suggesting an oxidative degradation pathway in synthetic air on the oxide particles. Relatively, larger amounts of DMP and surface methoxy form on maghemite, while more formate is produced on hematite. Upon TMP adsorption on dry goethite nanoparticles, no oxidation surface products were detected. Instead, a slow TMP hydrolysis pathway is observed, yielding orthophosphate. It is found that pre-adsorbed water stimulates the hydrolysis of TMP. In contrast to TMP, TEP adsorbs molecularly on all iron hydr(oxide) nanoparticles. This is attributed to the longer aliphatic chain, which stabilizes the loss of charge on the methoxy CO bonds by charge redistribution upon phosphoryl O coordination to Fe surface atoms. The presented results implicate different reactivity depending on specific molecular structure of the organophosphorus compound (larger functional groups can compensate loss of charge due to surface coordination) and iron (hydr)oxide surface structure (exposing Lewis acid or Brønstedt acid sites).