Bare Magnetite Nanoparticles Research Articles

Impact of coated and non-coated magnetic nanoparticles on oil-water separation in green surfactant-based emulsions

This study investigates the efficacy of magnetite nanoparticles as a means of demulsifying surfactant-based emulsions, focusing on light and medium crude oil emulsions. The demulsification capabilities of bare, amine-coated, and oleic acid-coated magnetite nanoparticles were tested. Nanoparticle concentrations ranged from 0.25 % to 8 %. The emulsions used Alpha Olefin Sulfonate and two environmentally friendly surfactants, Coco Glucoside and Greenzyme with sodium and potassium formate as eco-friendly alternatives and sodium chloride as the standard brine. Magnetic demulsification efficacy is highly dependent on the interplay between the nanoparticle surface charge and surfactant, thereby affecting surfactant adsorption onto the particle surface. While gravimetric separation alone has partial effectiveness, the magnetic field enhances particle movement, promoting greater instability. The nanoparticles play a key role in adsorbing surfactant species from the interfacial region, thus facilitating demulsification. Notably, magnetic demulsification is more effective with environmentally friendly surfactants, achieving 100 % separation in most cases. Demulsification of emulsions containing synthetic surfactants is most successful with light crude oil emulsions, and in select cases, achieves 100 % separation with medium crude oil emulsions.

Low toxicity of magnetite-based modified bionanocomposites with potential application for wastewater treatment: Evaluation in a zebrafish animal model

In recent years, the escalating concerns surrounding environmental pollution and the need for sustainable wastewater treatment solutions have underscored the significance of developing technologies that can efficiently treat wastewater while also reducing negative ecological effects. In this context, our study aims to contribute to the advancement of sustainable technologies for wastewater treatment, by investigating the effects that bare magnetite nanoparticles and those functionalized with the enzyme laccase could have in an aquatic animal, zebrafish, at various life cycle stages. Exposure to magnetite nanoparticles shows some effects on embryo hatching, survival rates, or larval behavior at higher concentrations. For both treatments, the hatching percentages were close to 80% compared to 93% for the control group. At the end of the observations in larvae, survival in all the evaluated groups was higher than 90%. Additionally, we evaluated the accumulation of nanoparticles in various stages of zebrafish. We found that, although there was accumulation during embryonic stages, it did not affect normal development or subsequent hatching. Iron levels in different organs such as gills, muscles, gastrointestinal tract, and brain were also evaluated in adults. Animals treated with a mix of food and nanoparticles at 10 μg/mL (Food group) presented a higher concentration of iron accumulation in muscle, gastrointestinal tract, and gills compared to the untreated control group. Although iron levels increased depending on the dose and exposure method applied, they were not statistically significant from the control groups. Our findings suggest that bionanocomposites evaluated here can be considered safe for removal of contaminants in wastewater without toxic effects or detrimental accumulation fish's health.

A comprehensive study of As(V) removal by starch-coated magnetite nano-adsorbent based on waste iron sludge

Combining natural polymer starch with magnetite nanoparticles (MNPs) can reduce the aggregation of MNPs and enhance their adsorption capacity and stability. Iron sludge from a de‑ironing water plant and starch were employed as basic ingredients in this study. Bare magnetite nanoparticles (MNPs) and starch-coated magnetite nanocomposites (ST2-MNPs) were synthesized by a “green” co-precipitation method for the removal of low-concentration As(V) solutions. TEM, XPS, FTIR, XRD, VSM, BET, and TGA techniques were used to examine the physicochemical properties of the synthesized ST2-MNPs. TEM verified that the magnetite nanoparticles in the composites were evenly distributed. The ST2-MNPs (5.26 nm) possessed a smaller average particle size than MNPs (6.24 nm). And VSM confirmed their remarkable magnetic properties. The starch-to‑iron-sludge ratio was optimized and the influence of adsorbent dosage, pH, and co-existing anions on As(V) adsorption were studied. The acquired arsenate adsorption data were found to be consistent with the Langmuir isotherm model, with maximum adsorption capacities of 23.04 mg/g for MNPs and 42.88 mg/g for ST2-MNPs. This shows that the active sites on MNPs and ST2-MNPs are energetically homogenous, and that the addition of starch coating significantly increases magnetite's adsorption capacity for As(V). The adsorption kinetics follow a Pseudo-second-order kinetic model, indicating chemisorption between As(V) and ST2-MNPs. In addition, the adsorption mechanism of As(V) by ST2-MNPs including chemical adsorption and electrostatic attraction was determined through in-depth discussion of characterization methods and adsorption experiments. This study offers references for the removal of As(V) and the resourceful application of backwash iron sludge.

Immobilization of phosphotungstic acid on the surface of chemically modified magnetite nanoparticles: An efficient heterogeneous acid catalyst for alcoholysis of epoxides

A new magnetically recoverable heterogeneous acid catalyst was easily synthesized by electrostatic interaction of phosphotungstic acid (HPW) species with 3-aminopyridine (Ampy) modified magnetite-silica heterostructure (Fe3O4/SiO2-Ampy-HPW). The step by step modification of magnetite nanoparticles along with structural stability, and maintenance of magnetization and morphology of bare magnetite nanoparticles after chemical functionalization steps were confirmed by various physicochemical techniques. The size of these nanoparticles was obtained to be 10–30 nm from TEM analysis, which was in accordance with the data estimated from XRD technique. Also, it was observed that the presence of HPW on the surface of catalyst has increased the acid content of catalyst. Catalytic property of Fe3O4/SiO2-Ampy-HPW catalyst was assessed in acid-catalyzed ring opening of epoxides with alcohols. According to the results obtained at optimum reaction condition, the prepared catalyst exhibited good performance (conversion of 93%) with high selectivity (100%) in methanolysis of styrene oxide compared to the unfunctionalized Fe3O4/SiO2, which is definitely due to the presence of HPW acidic species on the surface of Fe3O4/SiO2. Moreover, other epoxides and alcohols were tested in this catalytic system, which subsequently, reasonable results with more or less conversion were obtained based on the types of the epoxides and alcohols used.

Finely Dispersed Fe3O4 and Ag Nanoparticles Adhered by Starch Nano‐layers: an Efficient Catalyst for the Synthesis of Pyrano[2,3‐d]Pyrimidines

AbstractHot‐water‐soluble starch (HWSS) was employed as binder for fabrication of a composite from magnetite and Ag nanoparticles (NPs). Electron microscopy images showed a good dispersion of magnetite NPs in the matrix of HWSS. This observation indicates that HWSS tends to coat the maximum surface of magnetite by encapsulation of individual magnetite NPs, leading to disassembly of their aggregates. The HWSS‐coated magnetite NPs were employed as nano‐support for immobilization of fine Ag NPs generated in situ via reduction of Ag+ cations by glucose. Monitoring of the formation and growth of Ag NPs by UV–Vis spectroscopy made it possible to set up an optimal condition for fabrication of the nano‐composite and to verify the supremacy of HWSS‐coated magnetite NPs over bare magnetite NPs as support in this new protocol. Valuable insights into the texture of the nano‐composite were obtained by VSM, FT‐IR and XRD studies. The bio‐derived nano‐composite displayed an interesting magnetic property and an efficient catalytic activity in the three‐component synthesis of pyrano[2,3‐d]pyrimidines. It is a robust heterogeneous catalyst and can be simply retrieved from reaction mixtures by magnetic separation method.

Red Blood Cell Substitutes: Liposome Encapsulated Hemoglobin and Magnetite Nanoparticle Conjugates as Oxygen Carriers.

The established blood donation and transfusion system has contributed a lot to human health and welfare, but for this system to function properly, it requires a sufficient number of healthy donors, which is not always possible. Pakistan was a country hit hardest by COVID-19 which additionally reduced the blood donation rates. In order to address such challenges, the present study focused on the development of RBC substitutes that can be transfused to all blood types. This paper reports the development and characterization of RBC substitutes by combining the strategies of conjugated and encapsulated hemoglobin where magnetite nanoparticles would act as the carrier of hemoglobin, and liposomes would separate internal and external environments. The interactions of hemoglobin variants with bare magnetite nanoparticles were studied through molecular docking studies. Moreover, nanoparticles were synthesized, and hemoglobin was purified from blood. These components were then used to make conjugates, and it was observed that only the hemoglobin HbA1 variant was making protein corona. These conjugates were then encapsulated in liposomes to make negatively charged RBC substitutes with a size range of 1-2 μm. Results suggest that these RBC substitutes work potentially in a similar way as natural RBCs work and can be used in the time of emergency.

Synthesis and Characterization of Magnetic Composite Theragnostics by Nano Spray Drying.

Composites of magnetite nanoparticles encapsulated with polymers attract interest for many applications, especially as theragnostic agents for magnetic hyperthermia, drug delivery, and magnetic resonance imaging. In this work, magnetite nanoparticles were synthesized by coprecipitation and encapsulated with different polymers (Eudragit S100, Pluronic F68, Maltodextrin, and surfactants) by nano spray drying technique, which can produce powders of nanoparticles from solutions or suspensions. Transmission and scanning electron microscopy images showed that the bare magnetite nanoparticles have 10.5 nm, and after encapsulation, the particles have approximately 1 μm, with size and shape depending on the material’s composition. The values of magnetic saturation by SQUID magnetometry and mass residues by thermogravimetric analysis were used to characterize the magnetic content in the materials, related to their magnetite/polymer ratios. Zero-field-cooling and field-cooling (ZFC/FC) measurements showed how blocking temperatures of the powders of the composites are lower than that of bare magnetite, possibly due to lower magnetic coupling, being an interesting system to study magnetic interactions of nanoparticles. Furthermore, studies of cytotoxic effect, hydrodynamic size, and heating capacity for hyperthermia (according to the application of an alternate magnetic field) show that these composites could be applied as a theragnostic material for a non-invasive administration such as nasal.

Ultrasound-assisted dispersive micro-solid phase extraction of Pb(II) in water samples with in situ synthesis of magnetic Fe3O4-PbS nanocomposites followed by electrothermal atomic absorption spectrometry determination

Herein, an ultrasound-assisted dispersive magnetic micro-solid phase extraction (DM-μSPE) approach, along with electrothermal atomic absorption spectrometry (ETAAS) for the determination of lead at trace level in spring, well, river mineral and tap water samples was developed. The extraction step is based on the synthesis of PbS, following the sonochemical decomposition of L-cysteine used as sulphide precursor and its anchoring onto bare magnetite nanoparticles yielding the Fe3O4@PbS nanocomposite. Overall, DM-μSPE with in situ precipitation of PbS and retention onto magnetic sorbent requires a time as short as 6 min. After trapping Pb(II) as PbS, the magnetic nanocomposite was easily separated from the aqueous matrix by applying an external magnetic field and analyzed by ETAAS following slurry sampling. Different parameters involved in both the sorbent preparation/extraction and Pb quantification were optimized. Under optimal conditions, the method showed a detection limit of 0.02 μg L−1 Pb and a quantification limit of 0.07 μg L−1 Pb. The repeatability, expressed as relative standard deviation was 2% (for 0.6 μg L−1; n = 3). An experimental enrichment factor of 79 and an extraction efficiency of 99% were obtained. Finally, the method was applied for the determination of ultratrace levels of Pb(II) in spring, well, river mineral and tap water samples, showing quantitative recoveries in the range of 95–100%.

Alginate and Gum Arabic Coated Iron Oxide Nanoparticles as an Efficient Drug Carrier Agent

Multifunctional iron oxide nanoparticles have a vast and emerging scope in the field of nanotechnology. Out of numerous techniques available to develop multifunctional magnetite nanoparticles, co-precipitation is considered as one of the most efficient and economical techniques. Bare magnetite nanoparticles could be functionalized to act as multifunctional nanoparticles with the help of some suitable and biocompatible coating materials. In present study, surface functionalization of magnetic iron oxide nanoparticles has been carried out with alginate and gum Arabic, respectively. For the confirmation of surface functionalization, the synthesized multifunctional magnetite nanoparticles were characterized FTIR spectroscopy and thermogravimetric analysis. Further, the drug loading efficiency of these surface coated iron oxide nanoparticles has been evaluated with the help of UV-visible spectrophotometric studies

Sample preparation considerations for surface and crystalline properties and ecotoxicity of bare and silica-coated magnetite nanoparticles.

Magnetite (Fe3O4) nanoparticles (NPs) have widely used in various fields, including in medicine, due to their (super)paramagnetic properties. This requires a thorough evaluation of their possible hazardous effects. However, there is no standard procedure for the preparation of oxidation-prone NPs (such as magnetite) before subjecting them to biological assays. In this study we used Fe3O4 NPs (bare and silica-coated) as test samples to compare different preparation methods (ultrasound, centrifugation and filteration of NPs suspensions) based on X-ray and dynamic light scattering analysis and evaluation of microstructure and surface charge. After oxidation and functionalization, all samples retained their superparamagnetic behaviour. The toxicity of NP suspensions obtained by the methods described for Paramecium caudatum ciliates and Sinapis alba plants was evaluated.

Magnetite Nanoparticles Coated with PEG 3350-Tween 80: In Vitro Characterization Using Primary Cell Cultures.

Some medical applications of magnetic nanoparticles require direct contact with healthy tissues and blood. If nanoparticles are not designed properly, they can cause several problems, such as cytotoxicity or hemolysis. A strategy for improvement the biological proprieties of magnetic nanoparticles is their functionalization with biocompatible polymers and nonionic surfactants. In this study we compared bare magnetite nanoparticles against magnetite nanoparticles coated with a combination of polyethylene glycol 3350 (PEG 3350) and polysorbate 80 (Tween 80). Physical characteristics of nanoparticles were evaluated. A primary culture of sheep adipose mesenchymal stem cells was developed to measure nanoparticle cytotoxicity. A sample of erythrocytes from a healthy donor was used for the hemolysis assay. Results showed the successful obtention of magnetite nanoparticles coated with PEG 3350-Tween 80, with a spherical shape, average size of 119.2 nm and a zeta potential of +5.61 mV. Interaction with mesenchymal stem cells showed a non-cytotoxic propriety at doses lower than 1000 µg/mL. Interaction with erythrocytes showed a non-hemolytic propriety at doses lower than 100 µg/mL. In vitro information obtained from this work concludes that the use of magnetite nanoparticles coated with PEG 3350-Tween 80 is safe for a biological system at low doses.

Green synthesis and characterization of magnetite (Fe3O4) nanoparticles using Chromolaena odorata root extract for smart nanocomposite

We report a facile and green biosynthetic co-precipitation of magnetite nanoparticles using extract from the root of Chromolaena odorata. The particle sizes are in the range 5.6–16.8 nm. Absorption band edges of the particles at 205 nm and 291 nm are ascribed to surface plasmon vibrations, and estimated band gap energy of the particle is 1.97 eV. The basified extract produced 30-fold mono-phased magnetite nanoparticles with reduced band gap in comparison to bare magnetite nanoparticles. Basification of the plant extract inhibited the co-precipitation of other cations in solution; promoting the formation of water dispersible hydrophilic nanoparticles.

Adsorption of bovine serum albumin (BSA) by bare magnetite nanoparticles with surface oxidative impurities that prevent aggregation

Bare, uncoated magnetite nanoparticles, synthesized using an electrochemical surfactant-free synthesis, have highly oxidized surfaces that prevent aggregation. These particles have demonstrated highly intriguing biological activity showing extremely potent antibiotic activity against both gram-positive and gram-negative bacteria with little toxicity to rats. This difference in activity could be ascribed to the nature of the protein corona. The kinetics and thermodynamics of the binding of bovine serum albumin (BSA), used as a model serum protein, to these magnetite nanoparticles were analyzed. There is no significant change in particle diameter by dynamic light scattering following adsorption, indicating corona formation does not induce aggregation. The maximum adsorption capacity of the particles was determined to be 300 mg of BSA per gram of magnetite. The particles are able to adsorb 90% of the BSA at protein concentrations as high as 500 mg/L. The adsorption is best described using a pseudo second order model and a Langmuir Type III isotherm model. Thermodynamic analysis showed that the process is entropically driven and is spontaneous at all tested temperatures and conditions. However, it appears to be a weak to moderate physical adsorption. This moderate binding affinity could indicate the differential biological activity of these particles towards bacteria and mammalian cells and further support the contention that these are potentially useful new tools for targeting antibiotic-resistant bacteria.

Microwires of Au-Ag Nanocages Patterned via Magnetic Nanoadhesives for Investigating Proteins using Surface Enhanced Infrared Absorption Spectroscopy.

The controlled assembly of metal nanoparticles into ordered structures interacting with biological molecules is an emerging concept in surface science. Here, bare magnetite nanoparticles (Fe3O4-NPs) were employed as nanoadhesives to capture hollow metallic nanostructures (Au-Ag nanocages) from aqueous suspensions, and these coupled nanostructures were patterned onto various types of substrate via magnetolithography. Microwires of Au-Ag nanocages patterned onto an Au substrate behaved as optical antennas, providing a plasmonic enhancement exploited in surface-enhanced infrared absorption spectroscopy (SEIRAS) to investigate the proteins cytochrome c, bilirubin oxidase, alcohol dehydrogenase, bovine serum albumin, and glucose oxidase. Chemical maps containing more than 4000 spectra, acquired within only 2 min with a focal plane array detector, indicate that proteins were adsorbed along the microwires with their secondary structure preserved according to the spatial distribution of their amide groups. We believe there are significant practical aspects of the methodology proposed here to develop an alternative label-free assay for investigating biological molecules.

Binding Parameters of Magnetite Nanoparticles Interaction with Anticancer Drug Doxorubicin

Magnetic nanoparticles have received great interest for their use in cancer diagnostics and therapy. They can be loaded with the chemotherapeutic agents and used for the targeted delivery to the tumor and the retention of the drugs there under the external magnetic field. In the present paper, we investigated the interaction between magnetic Fe3O4 nanoparticles, both bare and coated with trisodium citrate, and anticancer drug doxorubicin in the base and acidic forms, respectively. The changes in the drug absorption spectra in the visible region and the shift of ferromagnetic resonance spectra taking place at the drug-nanoparticle interaction were analyzed. The spectrophotometric titration data were processed using the Langmuir model of equilibrium binding. For both systems, we report the calculated thermodynamic binding parameters including the drug-nanoparticle binding constants and binding site sizes. We show that in order to interact with the doxorubicin molecules in acidic form, the surface of the nanoparticles needs to be modified with trisodium citrate which provides their surface with the negative charge. At the same time, the bare magnetite nanoparticles are able to interact with the base form of the drug. The comparison of the binding parameters in both systems has shown that the nanoparticle-citrate-doxorubicin system is more promising in terms of biomedical application.

Facile synthesis and characterization of thermo-magneto-responsive poly(N-isopropylacrylamide)-magnetite composite hydrogel and its adsorption-desorption study on chromium (III)

Poly(N-isopropylacrylamide)-magnetite composite hydrogels with thermo-magneto-responsiveness were synthesized via layer-by-layer coatings with and without using silanization precursor, namely 3-(trimethoxysilyl)propyl methacrylate (MPS) as bridging agents for polymerizing N-isopropylacrylamide (NIPAM). Dynamic light scattering (DLS) was employed to monitor the temperature dependent change in hydrodynamic diameters, Dh of the hydrogels. The morphological transition from the stage of bare magnetite nanoparticles (MNPs) until PNIPAM-magnetite composite hydrogels was inspected by using transmission electron microscope (TEM). MPS-modified silica-PVP-MNPs showed the lowest suspension stability whereas, PVP-functionalized MNPs showed the sluggish response towards low gradient magnetic field. PNIPAM-silica-PVP-MNPs was selected as adsorbent for the Cr3+ ions the adsorption test. In the temperature manipulated adsorption-desorption test, the adsorption of Cr3+ prevailed as temperature increased from 25 °C to 50 °C and the release of Cr3+ into bulk phase took place when the reaction solution was cooled back to 25 °C as depicted by the drop in normalized adsorption capacity, qe/Ce from 36.22, 59.65 and 54.76 to 17.87, 36.21 and 41.67 for C0 of 20, 60 and 100 mg L−1.

Separation of superparamagnetic magnetite nanoparticles by capillary zone electrophoresis using non-complexing and complexing electrolyte anions and tetramethylammonium as dispersing additive.

Separations of bare superparamagnetic magnetite nanoparticles (BSPMNPs, approx. 11 nm diameter) was performed using non-complexing (nitrate) and complexing (chloride, citrate and phosphate) electrolyte ions with additions of tetramethylammonium hydroxide (TMAOH), which is commonly applied to control the synthesis of stable iron oxides. The use of TMAOH as a background electrolyte (BGE) additive for capillary electrophoresis (CE) separations provided for the first time electropherograms of BSPMNPs exhibiting symmetrical and highly reproducible peaks, free of spurious spikes characteristic of nanoparticle clusters. Consequently, accurate determination of the electrophoretic effective mobility of BSPMNPs was possible, yielding a value of -3.345E-08 m2 V-1 s-1 (relative standard deviation (RSD) of 0.500%). The obtained mobilities of BSPMNPs in the presence of various electrolyte ions show that the degree of complexation with the surface of BSPMNPs follows the order chloride < citrate < phosphate, correlating with the stabilities of Fe(III) complexes with the respective anions. Finally, bare and carboxylated iron oxide nanoparticles were successfully separated in only 10 min using 10 mM Tris-nitrate containing 20mM of TMAOH as electrolyte. Our findings show that simple and rapid CE experiments are an excellent tool to characterise and monitor properties and interactions of iron oxide nanoparticles with other molecules for surface modification purposes.

Stimulatory effect of magnetite on the syntrophic metabolism of Geobacter co-cultures: Influences of surface coating

Magnetite-mediated direct interspecies electron transfer (DIET) can facilitate syntrophic metabolism in natural microbial communities and also promote the performance of the engineered systems based on syntrophic interactions. In this study, the stimulatory effect of bare synthetic magnetite (Mt), humic acid coated magnetite, and SiO 2 coated magnetite (Mt-SiO 2 ) on DIET in defined co-cultures of Geobacter metallireducens / Geobacter sulfurreducens were studied. Magnetite coated with Aldrich humic acid (HA) and Elliott Soil humic acid (HA ES ), respectively, were prepared, and the two kinds of humic acid influenced the ability of Mt to promote syntrophic metabolism of the co-cultures in a similar way. When weight concentration was the same, pure humic acid presented the stimulatory effect on DIET similar to bare magnetite. However, the presence of HA coating on magnetite surface caused 50% and 61%, respectively, decrease in the rates of ethanol consumption ( R e ) and succinate production ( R s ) in DIET processes. Pure HA in the same weight concentration as the HA coating in Mt-HA induced the similar metabolism rates as Mt-HA. In the Mt-HA mediated DIET, most electrons from ethanol metabolism were transferred to G. sulfurreducens selectively through the HA coating, and magnetite core hardly contributed to DIET processes. The SiO 2 coating on magnetite resulted in 81% and 89%, respectively, decreases in R e and R s , mainly because the non-conductive SiO 2 layer hindered electron transfer between magnetite core and bacteria. After eight-day incubation with the co-cultures, bare magnetite nanoparticles formed relatively larger and more compact aggregates with cells than Mt-HA and Mt-SiO 2 , due to the different surface charge between bare and coated Mt. The generation of dissolved Fe(II) and HCl-extractable Fe(II) due to microbial reduction of magnetite by G. metallireducens and vivianite formation were observed along with DIET processes in all DIET experiments. Based on these results, different pathways of electron transfer in defined co-cultures of Geobacters with bare and coated magnetite nanoparticles were proposed. The findings in this study demonstrate the significant effects of surface properties on the ability of magnetite to stimulate DIET, which needs to be considered in order to comprehensively understand the role and mechanisms of mineral-mediated DIET in natural and engineered systems.

Aqueous aggregation behavior of citric acid coated magnetite nanoparticles: Effects of pH, cations, anions, and humic acid

Improving the colloidal stability of magnetite nanoparticles (MNPs) is essential for their successful applications. In this study, the surface zeta potential and particle size evolutions of citric acid coated magnetite nanoparticles (CA-MNPs) were measured under varied aqueous conditions using dynamic light scattering (DLS). The effects of pH (5.0–9.0), ionic strength (IS), cations (Na+ and Ca2+), anions (phosphate, sulfate, and chloride) and humic acid on the aggregation behaviors of CA-MNPs were explored. Compared with bare MNPs, the stability of CA-MNPs were greatly improved over the typical pH range of natural aquatic environments (pH = 5.0–9.0), as the coated CA-MNPs were highly negatively charged over the pH range due to the low pKa1 value (3.13) of citrate acid. CA-MNPs were more stable in the presence of monovalent cation (Na+) compared with divalent cation (Ca2+), as Ca2+ could neutralize the surface charge of MNPs more significantly than Na+. In the presence of anions, the surface charges of CA-MNPs became more negative, and the stability of CA-MNPs followed the order: in phosphate > sulfate > chloride. The observed aggregation trend could be explained by the differences in the valences of the anions and their adsorption behaviors onto CA-MNPs, which altered the surface charges of CA-MNPs. The measured critical coagulation concentrations (CCC) values of CA-MNPs in these electrolyte solutions agreed well with Derjaguin–Landau–Verwey–Overbeek (DLVO) calculations. With the addition of Humic acid (HA), the aggregation of CA-MNPs was inhibited in all electrolyte solutions even with the critical coagulation concentrations. This is due to the adsorption of HA onto CA-MNPs, which enhanced the electrostatic and steric repulsive forces between CA-MNPs. Considering the good stability of CA-MNPs in solutions with varied pH and electrolyte compositions, as well as with the easy synthesis of CA-MNPs and their non-toxicity, this study suggested CA coating as a good strategy to increase the stability of MNPs.

Magnetic iron oxide nanoparticles for the collection and direct measurement of adsorbed alpha-emitting radionuclides from environmental waters by liquid scintillation analysis.

Radioactive contamination, be it from accidental or intentional release, can create an urgent need to assess water and food supplies and the environment, and monitor human health. In the event of such an emergency, rapid and efficient methods may be needed to assess contamination levels in scores of samples within a short time frame. Internalized exposure to radionuclides that decay by alpha (α) emission can be especially hazardous, given the strongly ionizing nature of the α particle. Unfortunately, the determination of α-emitting radionuclides using traditional radioanalytical methods is typically labor and resource intensive and time consuming. In an effort to devise methods that are fast, require little labor and laboratory expendables, and minimize the use of toxic or corrosive reagents, researchers at PNNL have evaluated superparamagnetic nanoparticles as extracting agents for α-emitting radionuclides from chemically unmodified and acidified (pH 2) aqueous systems. It is demonstrated that bare magnetite nanoparticles exhibit strong affinity for two representative α-emitting radionuclides (241Am and 210Po) from two representative aqueous matrices (river and ground water). Furthermore, use of the superparamagnetic properties of these nanomaterials to concentrate the analyte-bearing solids from the bulk aqueous solution has been demonstrated. The nanoparticle concentrate can be either directly dispensed into a scintillation cocktail, or first dissolved and then added to a scintillation cocktail as a solution for an α-emission assay by liquid scintillation analysis. Despite the severe quenching caused by the metal oxide suspensions in the cocktail, the authors have demonstrated that modern liquid scintillation analyzers can report accurate α activity count rates; the upper limits of nanoparticle suspension concentrations in a cocktail are reported for cases wherein normal instrument count mode and a quench correction protocol are used. Discussions are provided on the presented sample processing and analysis method, the improvement (lowering) of minimum detectable activity concentrations using the nanoparticle-based assay method, and the quenching effects of nanoparticle suspensions in a scintillation cocktail.