Coated Magnetite Nanoparticles Research Articles

Application of silica coated magnetite nanoparticles modified with Cu(I)-neocuproine as nanosorbent to simultaneous separation-preconcentration of trace amounts of nitrate and nitrite

A novel, inexpensive and sensitive type of magnetic nanosorbent based on the functionalized silica-coated Fe3O4 nanoparticles was prepared and used for the adsorption of trace amounts of nitrite and nitrate ions. The work is based on selective ion-pairing complex formation of nitrate and nitrite with Cu(I)-neocuproine which are covalently bounded on nanoparticles. Nitrite was determined according to its reaction with barbituric acid to give violuric acid and determination of nitrate was based on its reduction to nitrite in the presence of Zn/NaCl. After formation of violuric acid, the absorbance was measured spectrophotometrically at 310 nm. The quantitative recoveries were obtained at pH 5.5 for the analytes. Under optimum conditions, the limits of detection in the original solutions were 0.49 μg L−1 and 0.40 μg L−1 for nitrate and nitrite, respectively. The linearity ranges were found to be 1.5 to 2.8 × 103 μg L−1(NO3−) and 1.2 to 1.9 × 103 μg L−1 (NO2−). The preconcentration factor was 120 for nitrate and 150 for nitrite. This method has been successfully applied to the determination of trace amounts of nitrite and nitrate in various water and food samples and also accuracy was confirmed by the analysis of the spiked recovery test.

Adsorption kinetics and thermodynamics studies of gold(III) ions using thioctic acid functionalized silica coated magnetite nanoparticles

Thioctic acid functionalized silica coated magnetite nanoparticles, RS-SR-NH-SiO2-Fe3O4, has been synthesized and its ability for the recovery of Au(III) in aqueous solutions was assessed. The results of the adsorption thermodynamics and kinetics showed that this magnetic adsorbent has good adsorption capacity for Au(III) and the best interpretation for the experimental data was given by the Langmuir isotherm model. The adsorption kinetics of RS-SR-NH-SiO2-Fe3O4 was well fitted with the pseudo-second-order rate equation. The thermodynamic parameters ΔG, ΔH and ΔS were also evaluated and the overall adsorption process was exothermic and spontaneous in nature.

Synthesis and Characterization Of Dextran Coated Magnetite Nanoparticles Loaded With Curcumin And In Vitro Cytotoxicity Study In MCF-7 Cancer Cells

Synthesis and Characterization Of Dextran Coated Magnetite Nanoparticles Loaded With Curcumin And In Vitro Cytotoxicity Study In MCF-7 Cancer Cells

Self-cleaning superhydrophobic epoxy coating based on fibrous silica-coated iron oxide magnetic nanoparticles

Inspired by the self-cleaning lotus leaf, a facile method of fabricating superhydrophobic silica coated magnetite nanoparticles using a cost-effective process is presented in this work. The structural characterizations and magnetic properties of the obtained core-shell magnetic nanoparticles were characterized by means of X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). TEM analysis revealed that the particles present flower‐like dendrimeric fibers morphology. The particles were uniformly dispersed on the surface of an epoxy resin coating with the purpose to increase the roughness and reduce the surface energy of the surface. The resulting superhydrophobic surface provides robust water-repellent surface under harsh conditions, thanks to its self-cleaning characteristic. The superhydrophobicity of this surface was confirmed based on the measurements of a water contact angle around 175°, which surpasses the theoretical limit of the superhydrophobicity. The simplicity and the cost-effectiveness of the process developed in this study appears to be a promising route for the preparation of other magnetic superhydrophobic organic-inorganic hybrid materials that would be beneficial in a wide variety of applications.

Adsorption of As(V) from contaminated water over chitosan coated magnetite nanoparticle: Equilibrium and kinetics study

The efficacy of chitosan/magnetite nanocomposite (CTN) for remediation of arsenate ions [As(V)] from water was investigated. The prepared material could efficiently perform several cyclic runs with high As(V) removal efficiency and has the advantages over many established method. Different characterization techniques were performed to investigate the binding and structural properties of prepared materials. The study also focused on the effect of competing ions viz. phosphate and chloride on removal efficiency. The initial As(V) concentration (0.6mg/L) was found to decrease to less than 0.01mg/L at a contact time of 120min with an adsorbent dose of 1g/L. Increase in initial ion concentration of arsenate ions decreased the sorption rate, but the ion uptake capacity was increased. The sorption was reasonably explained with Langmuir (RL∼0.9851) and Freundlich isotherm models (n∼1.78). At low concentrations Langmuir monolayer sorption was followed but heterogeneity appeared at higher arsenate concentrations. The maximum adsorption capacity (Qo) calculated from Langmuir isotherm was found to be 10.81mg As(V)/g at room temperature and neutral pH. The sorption process was found to be governed by pseudo second order kinetics.

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.

Fe3O4@SiO2@KIT-6 as an Efficient and Reusable Catalyst for the Synthesis of Novel Derivatives of 3,3'-((Aryl-1-phenyl-1H-pyrazol-4- yl)methylene)bis (1H-indole).

Korea advanced institute of science and technology cubic ordered mesoporous silica (KIT-6 mesoporous) silica coated magnetite nanoparticles, is an effective, ecobenign and recyclable catalyst for the electrophilic substitution reactions of indoles with various synthetized aldehydes to afford the corresponding novel diindolylmethanes in high yields and short reaction times. The catalyst can be recovered and reused without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification. The present methodology offers several advantages such as aqueous media, excellent yields, simple procedure, mild conditions and reduced environmental consequences. All of synthesized compounds are new and were characterized by IR, NMR and elemental analyses. A mixture of synthetized pyrazolecarbaldehydes [24] (2.0mmol), indole (4.0mmol) and Fe3O4@SiO2@KIT-6 (0.04mmol) and H2O (10mL) were stirred at room temperature for the required reaction time according to Table 2. After completion of the reaction, the product was solved in CHCl3 (3×10 mL) and insoluble catalyst was removed by filtration in the presence of an efficient magnetic bar. The organic phase including the product and CHCl3 was evaporated under vacuum. The resulting crude material was purified by recrystallization from EtOH to afford pure products. As part of our on interest for the development of efficient and environmentally friendly procedures for the synthesis of heterocyclic and pharmaceutical compounds, an efficient, facile and aqueous media was introduced for the synthesis of novel derivatives of diindolylmethanes containing pyrazole moiety. A variety of synthetized aldehyde compounds reacted smoothly with indoles to produce diindolylmethanes under these reaction conditions. The electron deficiency and the nature of the substituents on the aromatic ring show some effects on this conversion. All the reactions were run with catalytic amounts of catalysts. The best results gained with 0.04mmol of Fe3O4@SiO2@KIT-6 as a strong Lewis acid at room temperature in aqueous media. In conclusion, we have investigated the synthesized KIT-6 mesoporous silica coated magnetite nanoparticles (MMNPs) as a mild and efficient catalyst for the synthesis of novel diindolylmethanes coupled with pyrazole moiety in aqua media. The simplicity, easy workup together with the use of inexpensive, environmentally friendly and reusable catalyst, is the notable features of this catalytic procedure. To the best of our knowledge, this is the first report for the synthesis of a new library of diindolylmethane compound bearing pyrazole moiety that enhance the biological and pharmacological activity.

NH2-coordinately immobilized tris(8-quinolinolato)iron onto the silica coated magnetite nanoparticle: Fe3O4@SiO2-FeQ3 as a selective Fenton-like catalyst for clean oxidation of sulfides

A green, robust and eco-friendly procedure for the oxidation of aromatic organic sulfides to sulfones using H2O2 catalyzed by NH2-coordinately immobilized tris(8-quinolinolato)iron onto the silica coated magnetite (Fe3SiO6) has been developed. Physicochemical properties of the resulting nanoparticles were investigated by means of techniques including X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, vibrating sample magnetometer, atomic adsorption spectroscopy and FT-IR spectroscopy. The catalytic activity of sulfides oxidation showed that this atom-economical protocol provided great yields of various sulfones and allowed the sulfide function reaction conducting under the mild conditions thus to prevent the sulfide being over-oxidized to sulfoxides. The Fe3O4@SiO2-FeQ3 catalysts are magnetically separable and kept stable after recycling for 7 consecutive runs without detectable activity loss.

Chromium(VI) concurrent detoxification and immobilization by gallate: Kinetics, equilibrium, thermodynamics, and mechanism studies

Gallic acid (GA), with a reducing and in situ coordinating capability towards to reducible metal ions, was successfully conjugated onto the amine-silane coated magnetite nanoparticles by stable amide bond through 1-ethyl-3-(3-dimethylaminepropyl) carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) chemistry, with the aim of engineering a magnetically-separable Fe3O4@TEOS@AMEO@GA applicable for Cr(VI) concurrent reduction and removal, together with explicating reduction-adsorption mechanism. The structure, composition, and morphology of the nanocomposite were systematically characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM), low-temperature nitrogen adsorption/desorption experiment, X-ray spectroscope (EDS), X-ray photoelectronic spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), total organic carbon (TOC), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and fluorescence spectra, showing a core-shell, cubic inverse spinel structure of the nanocomposite with superparamagnetism roughly containing 7.8% (w/w) GA on its surface. Cr(VI) reduction-adsorption kinetics, equilibrium, and thermodynamics studies were carried out under solution pH of 6.0, where partially deprotonated phenolic hydroxyl dominated the nanoadsorbent surface. Results showed that pseudo-first order kinetic model and Freundlich isotherm model described the Cr(VI) reduction-adsorption well. Thermodynamics studies indicated an endothermic, spontaneous, and feasible process of such Cr(VI) reduction-adsorption. Furthermore, Cr(VI) reduction-adsorption mechanism was explicated by EDS and XPS technology, finding that phenolic hydroxyls of those conjugated gallates were only functional and active groups. Based on these, we intend to offer a predictable, and hence controllable approach for Cr(VI) reductive immobilization that may be a potential direction for those poisonous and reducible metal ions thorough detoxification and in situ removal based on magnetite-supported materials in practical application.

Using polymer coated nanoparticles for adsorption of micropollutants from water

In this study, polyvinylpyrrolidone (PVP)-coated magnetite nanoparticles were synthesized to adsorb six emerging contaminants (Tonalide, Bisphenol-A, Triclosan, Metolachlor, Ketoprofen and Estriol) from aqueous solutions. The PVP-coated NPs were characterized by dynamic light scattering (DLS) measurements, thermal analysis, and X-ray diffraction. Results indicated that PVP-coated NPs were successfully used as a separable adsorbent for removing the micropollutants from water. Adsorption results were modeled using Langmuir and Freundlich isotherms, which showed a better fit of data to the Langmuir model. The adsorbent showed good adsorption performance in which Bisphenol-A and Ketoprofen were the most effectively removed micropollutants, with 98 and 95% removal using only 0.1mg of the adsorbent within 15min of contact time, respectively. Kinetic studies were performed using the pseudo-second-order model to compare the performance of PVP-coated NPs with granular activated carbon (GAC) revealing the superiority of PVP-coated NPs over GAC. Thermodynamic parameters of the adsorption of the micropollutants onto the adsorbate showed the adsorption process was endothermic and spontaneous. Adsorbate regeneration studies were performed with methanol, ethanol, and the UV/H2O2 process in five regeneration cycles. Methanol treatment ensured the highest level of regeneration.

Coherent source interaction, third-order nonlinear response of synthesized PEG coated magnetite nanoparticles in polyethylene glycol and its application

Third-order nonlinear response of synthesized polyethylene glycol coated Fe3O4 nanoparticles dispersed in a suitable solvent, polyethylene glycol has been studied. The structural characterization of the synthesized magnetite nanoparticles were carried out. The linear optical property of the synthesized magnetite nanoparticles was investigated using UV-visible technique. Both closed and open aperture Z-scan techniques have been performed at 532nm with pulse width 5ns and repetition rate 10Hz. It was found that polyethylene glycol coated magnetite exhibits reverse saturable absorption, with significant nonlinear absorption coefficient. Two-photon absorption intensity dependent positive nonlinear refraction coefficients indicate self focusing phenomena. Results show that higher concentration gives better nonlinear and optical limiting properties.

Studies on the role of unsaturation in the fatty acid surfactant molecule on the thermal conductivity of magnetite nanofluids

To study the role of unsaturation in the surfactant molecule on the thermal conductivity of magnetite nanofluids, four different fatty acid (stearic, oleic, linoleic, and linolenic acids with different degree of unsaturation) coated magnetite nanoparticles of comparable size are prepared and dispersed in toluene. It is found that the nanofluid with the saturated fatty acid coated nanoparticles show larger viscosity than the fluid with the unsaturated fatty acid coated particles at all concentrations. Thermal conductivity studies show enhancement only above a critical concentration for all fluids. The critical concentration for thermal conductivity enhancement varies with the surfactant, possibly due to the difference in the degree of aggregation of the nanoparticles in the fluid, because of the difference in the conformation of the surfactant molecules on the nanoparticle’s surface. The experimental thermal conductivity follows the Maxwell model at higher concentrations. From the overall studies, it is observed that the thermal conductivity of the fluids with aggregated or assembled nanoparticles shows slightly larger enhancement than that of the fluids with isolated particles. However, in the presence of a magnetic field, the fluids with isolated nanoparticles showed relatively larger enhancement, possibly due to the easy response of the isolated magnetite nanoparticles to the applied field.

Effective removal of phosphate from aqueous solution using humic acid coated magnetite nanoparticles

Effective removal of excess phosphate from water is critical to counteract eutrophication and restore water quality. In this study, low cost, environmentally friendly humic acid coated magnetite nanoparticles (HA-MNP) were synthesized and applied for the remediation of phosphate from aqueous media. The HA-MNPs, characterized by FTIR, TEM and HAADF-STEM showed the extensive coating of humic acid on the magnetite surface. The magnetic nanoparticles with diameters of 7–12 nm could be easily separated from the reaction mixture by using a simple hand held magnet. Adsorption studies demonstrate the fast and effective separation of phosphate with maximum adsorption capacity of 28.9 mg/g at pH 6.6. The adsorption behavior follows the Freundlich isotherm suggesting the formation of non-uniform multilayers of phosphate on the heterogeneous surface of HA-MNP. The adsorption kinetic fits the pseudo-second order model well with rate constants of 0.206 ± 0.003, 0.073 ± 0.002 and 0.061 ± 0.003 g mg−1min−1 for phosphate (P) concentrations of 2, 5 and 10 mg/L respectively. The removal of phosphate was found higher at acidic and neutral pH compared to basic conditions. The nanoparticles exhibit good selectivity and adsorption efficiency for phosphate in presence of co-existing ions such as Cl−, SO42−and NO3− with some inhibition effect by CO32−. The effect of temperature on the adsorption reveals that the process is endothermic and spontaneous. HA-MNPs are promising, simple, environmentally friendly materials for the removal of phosphate from aqueous media.

Role of base fluid on the thermal conductivity of oleic acid coated magnetite nanofluids

Thermal conductivity enhancement of nanofluids of oleic acid coated magnetite nanoparticles dispersed in four different base fluids (toluene, xylene, mesitylene, kerosene) is studied to understand the role of the solvent (base fluid). From the correlation of the thermophysical properties of the base fluid with the thermal conductivity of the corresponding nanofluid, it is found that the nanofluid with the base fluid of lower intrinsic thermal conductivity and dielectric constant shows relatively larger enhancement in the thermal conductivity. A linear increase in the thermal conductivity with increasing viscosity is observed for all four nanofluids studied. The concentration dependent thermal conductivity studies showed enhancement only above a particular concentration, within the sensitivity of the measurement, and this critical concentration is different for the different nanofluids. The nanofluid with kerosene showed the lowest critical concentration for thermal conductivity enhancement compared to the other nanofluids. The difference between the experimental thermal conductivity and the calculated value using the Maxwell model is found to depend on the critical concentration. By assuming the critical concentration as the zero concentration, it is found that all the studied nanofluids almost follow the Maxwell model of thermal conductivity. Thus, for the dispersions of the same oleic acid coated magnetite nanoparticles, the base fluid affects the critical concentration for thermal conductivity enhancement, probably due to the interfacial effects arising from the surfactant-solvent interactions.

Electrochemical preparation and characterization of chitosan-coated superparamagnetic iron oxide (Fe3O4) nanoparticles

ABSTRACTIn this work, a novel and one-step synthesis protocol is proposed to prepare naked and chitosan (CS) coated magnetite nanoparticles (MNPs). Well-defined Fe3O4 nanoparticles were prepared through cathodic electrochemical deposition (CED) under the mild conditions. The crystalline and completely spherical nanoparticles of naked Fe3O4 with uniform size of 8nm were electrodeposited from mixed iron chloride/nitrate aqueous solution by applying current density of 10 mA cm–2 for 30 min. The uniform chitosan coated MNPs with size of 10 nm were also prepared from 0.005M [FeCl2+Fe(NO3)3] + 1 g/L chitosan aqueous solution with only applying 10 mA cm–2 for 30 min. The prepared naked and chitosan coated MNPs were characterized through XRD, IR, FE-SEM, TEM,DSC-TGA, DLS and VSM techniques. The chitosan layer of the surface of MNPs was confirmed by FT-IR, DLS and DSC-TG analyses. The magnetic analysis via VSM revealed that both synthesized NPs exhibit excellent superparamagnetic behavior and can be used for a wide range of biomedical applications. The CS coated MNPs have negligible remnant magnetization (Mr = 0.26 emu g–1) and coercivity (Ce = 0.5 Oe) as compared with those of naked NPs (Mr≈0.75 emu g–1 and Ce≈2.3 Oe). In final, the possible mechanism of the Fe3O4 deposition on cathode surface was proposed and discussed in details. Bas on the obtained results, the CED strategy is introduced as an easy, fast and efficient preparation route of uniform MNPs with proper phase, size and magnetic characters for biomedical applications.

Ultrasound-assisted synthesis of pH-responsive nanovector based on PEG/chitosan coated magnetite nanoparticles for 5-FU delivery

pH-responsive magnetic carriers at the nanoscale are one of the most important agents for the targeted treatment of cancer. In this study, Fe3O4 nanoparticles were prepared by co-precipitation method and functionalized with three types of PEG using ultrasound waves. PEGlated particles were modified with chitosan shell through ultrasound-assisted double emulsion method. The prepared material which was used as a pH responsive carrier for pinpointed 5-FU delivery. The chemico-physical properties of prepared nanoparticles have been investigated. Results demonstrated that pure Fe3O4 had a mean diameter of 20nm with the regular spherical shape which was increased after modification step depending on the type of PEG. 5-FU loading properties and releasing behaviors studies in different pHs which showed that 5-FU can be efficiently loaded in the Fe3O4@Cs-PEG. Also, in the case of release, the amount of 5-FU released at pH=5.8 is noticeably higher compared to the released amount at pH=7.4 in all three samples at any distinct time. For instance at pH=7.4, 27% of the 5-FU was released from the Fe3O4@Cs-PEG2 during 48h; as the pH decreases to 5.8, the cumulative amount of 5-FU released enhanced to 52%. The in vitro MTT assay results demonstrated that the cell viability decreases in all synthesized nanoparticles as the pH medium of MCF-7 culture became to 5.8. For example, cell viability of Fe3O4@Cs-sPEG decreased from 44±2% to 36±1.9% at a concentration of 5 (μg/ml) as the pH varied from 7.4 to 5.8.

Adsorptive Removal of Carbamazepine and Diatrizoate in Iron Oxide Nanoparticles Amended Sand Column Mimicing Managed Aquifer Recharge

The sorption–desorption of recalcitrant pharmaceuticals in sand/soil columns can be used to infer performance of managed aquifer recharge. Removal of carbamazepine (CBZ) and diatrizoate (DTZ) from synthetic wastewater, containing 100 µg·L−1 of each pharmaceuticals, was studied in recirculating sand columns amended with uncoated or methacrylic acid (MAA) coated magnetite nanoparticles. Removal of CBZ and DTZ in MAA-magnetite column (68.34% and 61.91%, respectively) was much higher than that with uncoated magnetite (53.47% and 50.26%, respectively). Rapid decrease of dissolved organic carbon concentrations across nanoparticle amended columns (between 42.28% and 50.08% on Day 1), followed by slow recuperation suggests adsorption–desorption dynamics and competition of dissolved organic matter for sorption sites. Core-level binding energy and charge analysis for Fe(2s) and O(1s) in X-ray photoelectron spectroscopy suggests involvement of physisorption process on the NP surfaces.

A novel preparation method for surface coated superparamagnetic Fe3O4 nanoparticles with vitamin C and sucrose

In this letter, we report a one-step electro-synthesis protocol for preparation of sucrose- and vitamin C coated magnetite nanoparticles (MNPs). The coated MNPs are electrodeposited through very simple and efficient procedure of direct current (DC) deposition by applying 5mAcm−2 into sucrose and/or vitamin C added aqueous solution of iron(II) chloride/iron(III)nitrate salts. The XRD results confirmed the pure magnetite phase for the prepared MNPs. Morphological observations of the prepared MNPs through SEM and TEM exhibited the uniform particle morphology with 10nm in size. IR analysis presented all vibrations related to chemical bounds in the sucrose and vitamin C. TG analysis exhibits 10% vitamin C and 17% sucrose in MNPs composition. Magnetic analysis via VSM proved the superparamagnetic nature of the prepared MNPs.

Spectroscopic and magnetic studies of highly dispersible superparamagnetic silica coated magnetite nanoparticles

Superparamagnetic behavior in aqueously well dispersible magnetite core-shell Fe3O4@SiO2 nanoparticles is presented. The magnetic properties of core-shell nanoparticles were measured with use of the DC, AC magnetometry and EPR spectroscopy. Particles where characterized by HR-TEM and Raman spectroscopy, showing a crystalline magnetic core of 11.5±0.12nm and an amorphous silica shell of 22±1.5nm in thickness. The DC, AC magnetic measurements confirmed the superparamagnetic nature of nanoparticles, additionally the EPR studies performed at much higher frequency than DC, AC magnetometry (9GHz) have confirmed the paramagnetic nature of the nanoparticles. Our results show the excellent magnetic behavior of the particles with a clear magnetite structure, which are desirable properties for environmental remediation and biomedical applications.

In situ ultrasound-assisted preparation of Fe3O4@MnO2 core-shell nanoparticles integrated with ion co-precipitation for multielemental analysis by total reflection X-ray fluorescence

In this work, a new analytical approach based on in situ ultrasound-assisted preparation of manganese dioxide coated magnetite nanoparticles (Fe3O4@MnO2 NPs) was applied for extraction and preconcentration of Ni, Cu, Zn, Tl, Pb, Bi and Se. The Fe3O4@MnO2 core-shell nanocomposite was synthesized by application of high-intensity sonication to an aqueous reaction medium in the presence of the target analytes, which are trapped during NPs formation. In this way, synthesis of the nanosorbent and extraction can be simultaneously accomplished within only 30s. After the extraction step, the resulting Fe3O4@MnO2 NPs enriched with the target analytes were separated by an external magnetic field, so that filtration or centrifugation steps were unnecessary. A 10μL aliquot of the solid phase was deposited onto a sample carrier (quartz reflector) and directly analyzed by total-reflection X-ray fluorescence (TXRF) without the need for an elution step. A comprehensive characterization of the Fe3O4@MnO2 NPs was carried out by transmission electron microscopy and TXRF. Detection limits ranged from 0.19 to 0.98μgL−1 depending on the analyte. Enrichment factors in the range of 402–540 were obtained. The repeatability expressed as relative standard deviation was around 1.7% (N=5). The accuracy of the proposed method was assessed by analyzing the certified reference material BCR®-610 (groundwater). An effective, simple, rapid and sensitive procedure for multielemental analysis of water samples was accomplished.