Magnetic hydroxyapatite nanoparticles: An efficient adsorbent for the separation and removal of nitrate and nitrite ions from environmental samples

A novel type of magnetic nanosorbent, hydroxyapatite‐coated Fe₂O₃ nanoparticles was synthesized and used for the adsorption and removal of nitrite and nitrate ions from environmental samples. The properties of synthesized magnetic nanoparticles were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray powder diffraction. After the adsorption process, the separation of γ‐Fe₂O₃@hydroxyapatite nanoparticles from the aqueous solution was simply achieved by applying an external magnetic field. The effects of different variables on the adsorption efficiency were studied simultaneously using an experimental design. The variables of interest were amount of magnetic hydroxyapatite nanoparticles, sample volume, pH, stirring rate, adsorption time, and temperature. The experimental parameters were optimized using a Box–Behnken design and response surface methodology after a Plackett–Burman screening design. Under the optimum conditions, the adsorption efficiencies of magnetic hydroxyapatite nanoparticles adsorbents toward NO₃^? and NO₂^? ions (100 mg/L) were in the range of 93–101%. The results revealed that the magnetic hydroxyapatite nanoparticles adsorbent could be used as a simple, efficient, and cost‐effective material for the removal of nitrate and nitrite ions from environmental water and soil samples.     

Characterization of modified styrene-co-2-acrylamido-2-methylpropane sulfonic acid magnetite nanoparticles

This work provides an insight into the effect of incorporating of magnetite nanoparticles on the rheology of fluids. In this respect, polymer-stabilized magnetite nanoparticles were obtained using sodium salt of poly (2-acrylamido-2-methylpropanesulfonate (PAMPS-Na). Monodisperse polymer coated magnetite nanoparticles Fe₃O₄/poly(styrene-AMPS) copolymer nanoparticles with diameters of 50–300 nm were prepared by radical polymerization in the presence of a ferrofluid coated with PAMPS-Na. The magnetic nanoparticles were easily separated in a magnetic field. The structure of the obtained magnetic nanoparticles was characterized by Fourier transform infrared spectroscopy (FTIR). The morphology and size of the magnetic nanoparticles were determined by transmission electron microscopy (TEM). FTIR and TEM revealed that the Fe₃O₄ nanoparticles were incorporated into the shells of poly(styrene-AMPS). Aqueous dispersed solutions of a charged hydrophobically modified Fe₃O₄/poly(styrene-AMPS) copolymer nanoparticles exhibit high viscosities even at low polymer concentrations (0.1 wt %), which is an interesting feature in connection with enhanced oil recovery. Effects of temperature and addition of sodium chloride on the viscosity properties of a semidilute dispersed solution of Fe₃O₄/poly(styrene-AMPS) copolymer nanoparticles are examined. The results indicated that Fe₃O₄/poly(styrene-AMPS) copolymer nanoparticles disclose strong interactions between magnetite and coated polymers of both PAMPS-Na and styrene-AMPS copolymers.     

Magnetic poly(N‐propargylacrylamide) microspheres: Preparation by precipitation polymerization and use in model click reactions

Magnetic poly(N‐propargylacrylamide) (PPRAAm) microspheres were prepared by the precipitation polymerization of N‐propargylacrylamide (PRAAm) in a toluene/propan‐2‐ol medium in the presence of magnetic nanoparticles (oleic acid‐coated Fe₃O₄). The effects of several polymerization parameters, including the polarity of the medium, polymerization temperature, the concentration of monomer, and the amount of magnetite (Fe₃O₄) in the polymerization feed, were examined. The microspheres were characterized in terms of their morphology, size, particle‐size distribution, and iron content using transmission and scanning electron microscopies (TEM and SEM) and atomic absorption spectroscopy (AAS). A medium polarity was identified in which magnetic particles with a narrow size distribution were formed. As expected, oleic acid‐coated Fe₃O₄ nanoparticles contributed to the stabilization of the polymerized magnetic microspheres. Alkyne groups in magnetic PPRAAm microspheres were detected by infrared spectroscopy. Magnetic PPRAAm microspheres were successfully used as the anchor to enable a “click” reaction with an azido‐end‐functionalized model peptide (radiolabeled azidopentanoyl‐GGGRGDSGGGY(¹²⁵I)‐NH₂) and 4‐azidophenylalanine using a Cu(I)‐catalyzed 1,3‐dipolar azide‐alkyne cycloaddition reaction in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Monodisperse Magnetite Nanoparticles Coupled with Nuclear Localization Signal Peptide for Cell‐Nucleus Targeting

Functionalization of monodisperse superparamagnetic magnetite (Fe₃O₄) nanoparticles for cell specific targeting is crucial for cancer diagnostics and therapeutics. Targeted magnetic nanoparticles can be used to enhance the tissue contrast in magnetic resonance imaging (MRI), to improve the efficiency in anticancer drug delivery, and to eliminate tumor cells by magnetic fluid hyperthermia. Herein we report the nucleus‐targeting Fe₃O₄ nanoparticles functionalized with protein and nuclear localization signal (NLS) peptide. These NLS‐coated nanoparticles were introduced into the HeLa cell cytoplasm and nucleus, where the particles were monodispersed and non‐aggregated. The success of labeling was examined and identified by fluorescence microscopy and MRI. The work demonstrates that monodisperse magnetic nanoparticles can be readily functionalized and stabilized for potential diagnostic and therapeutic applications.     

DNA Hybridization at Magnetic Nanoparticles with Electrochemical Stripping Detection

A simple and practical method for electrochemical DNA hybridization assay has been developed to take advantage of magnetic nanoparticles for ssDNA immobilization and zinc sulfide nanoparticle as oligonucleotide label. Magnetic nanoparticles were prepared by coprecipitation of Fe²⁺ and Fe³⁺ with NH₄OH, and then amino silane was coated onto the surface of magnetite nanoparticles. The magnetic nanoparticles have the advantages of easy preparation, easy surface modification and low cost. The target ssDNA with the phosphate group at the 5′ end was then covalently immobilized to the amino group of magnetite nanoparticles by forming a phosphoramidate bond in the presence of 1‐ethyl‐3‐(3‐dimeth‐ylaminopropyl)carbodiimide (EDAC). The zinc sulfide (ZnS) nanoparticle‐labeled oligonucleotides probe was used to identify the target ssDNA immobilized on the magnetic nanoparticles based on a specific hybridization reaction. The hybridization events were assessed by the dissolution of the zinc sulfide nanoparticles anchored on the hybrids and the indirect determination of the dissolved zinc ions by anodic stripping voltammetry (ASV) at a mercury film glassy carbon electrode (GCE). The proposed method couples the high sensitivity of anodic stripping analysis for zinc ions with effective magnetic separation for eliminating nonspecific adsorption effects and offers great promise for DNA hybridization analysis.     

The Synthesis of Magnetic Lysozyme‐Imprinted Polymers by Means of Distillation–Precipitation Polymerization for Selective Protein Enrichment

A protein imprinting approach for the synthesis of core–shell structure nanoparticles with a magnetic core and molecularly imprinted polymer (MIP) shell was developed using a simple distillation–precipitation polymerization method. In this work, Fe₃O₄ magnetic nanoparticles were first synthesized through a solvothermal method and then were conveniently surface‐modified with 3‐(methacryloyloxy)propyltrimethoxylsilane as anchor molecules to donate vinyl groups. Next a high‐density MIP shell was coated onto the surface of the magnetic nanoparticles by the copolymerization of functional monomer acrylamide (AAm), cross‐linking agent N,N′‐methylenebisacrylamide (MBA), the initiator azodiisobutyronitrile (AIBN), and protein in acetonitrile heated at reflux. The morphology, adsorption, and recognition properties of the magnetic molecularly imprinted nanoparticles were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and rebinding experiments. The resulting MIP showed a high adsorption capacity (104.8 mg g^?1) and specific recognition (imprinting factor=7.6) to lysozyme (Lyz). The as‐prepared Fe₃O₄@Lyz‐MIP nanoparticles with a mean diameter of 320 nm were coated with an MIP shell that was 20 nm thick, which enabled Fe₃O₄@Lyz‐MIP to easily reach adsorption equilibrium. The high magnetization saturation (40.35 emu g^?1) endows the materials with the convenience of magnetic separation under an external magnetic field and allows them to be subsequently reused. Furthermore, Fe₃O₄@Lyz‐MIP could selectively extract a target protein from real egg‐white samples under an external magnetic field.     

Self-Organization of Magnetic Nanoparticles and Inclusion of Hydrogen by Borohydride Reduction

 Different structures of the interglobular space or voids between self-organized nanoparticles lead to differences in the measurable magnetic properties of single-domain particle chains of similar composition, grain size, and amorphous structure of the single globules. The volumes and radii of nanoparticles obtained by application of a magnetic field (3 to 15 nm) are larger than those determined without application of a magnetic field during the borohydride reduction process. Two types of hydrogen containing nanotubes with diameters of up to 2 (small-size containers) and 5 nm (large-size containers) are produced using as a driving force the domain wall formation energy between ferromagnetic nanoparticles with quantum size effected dimensions prepared by this reduction method at room temperature and ambient atmosphere. Nanoscale hydrogen containers can be used instead of MeH nanoparticle electrodes as perfect energy charge transfer media of high efficiency (close to 100%) using Li ion electrolytes. No influence on the electrode temperature and no participation of OH⁻ and H₂O in the main charge/discharge transfer reactions were observed.     

Chloro-Modified Magnetic Fe3O4@MCM-41 Core–Shell Nanoparticles for L-Asparaginase Immobilization with Improved Catalytic Activity,Reusability, and Storage Stability

This paper describes a new support that permits to efficient immobilization of L-asparaginase (L-ASNase). For this purpose, Fe₃O₄ magnetic nanoparticles were synthesized and coated by MCM-41. 3-chloropropyltrimethoxysilane (CPTMS) was used as a surface modifying agent for covalent immobilization of L-ASNase on the magnetic nanoparticles. The chemical structure; thermal, morphological, and magnetic properties; chemical composition; and zeta potential value of Fe₃O₄@MCM-41-Cl were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction patterns (XRD), and zeta-potential measurement. The immobilization efficiency onto Fe₃O₄@MCM-41-Cl was detected as 63%. The reusability, storage, pH, and thermal stabilities of the immobilized L-ASNase were investigated and compared to that of soluble one. The immobilized enzyme maintained 42.2% of its original activity after 18 cycles of reuse. Furthermore, it was more stable towards pH and temperature compared with soluble enzyme. The Michaelis–Menten kinetic properties of immobilized L-ASNase showed a lower V_max and a similar K_m compared to soluble L-ASNase. Immobilized enzyme had around 47 and 32.5% residual activity upon storage a period of 28 days at 4 and 25 °C, respectively. In conclusion, the Fe₃O₄@MCM-41-Cl@L-ASNase core–shell nanoparticles could successfully be used in industrial and medical applications.

     

Stability, rheological, magnetorheological and volumetric characterizations of polymer based magnetic nanofluids

The Fe₃O₄ nanoparticles and Fe₃O₄ nanoparticles coated with oleic acid have been dispersed in base fluid of poly(ethylene glycol) (PEG). Stability and particle size distribution of these nanofluids have been studied by result analysis of UV–Vis spectroscopy, zeta potential and dynamic light scattering. Blue shift of UV–Vis spectra has been related to quantum effects such as band gap enlargement with particle size decreasing and also to effect of oleic acid on the ultraviolet wavelength. Flow behavior and suspension structure of Fe₃O₄ nanoparticles dispersed in PEG have been determined by rheological properties. Viscosity values of Fe₃O₄-PEG nanofluid as a function of temperature have also been investigated. The chain-like structure of Fe₃O₄ nanoparticles coated with oleic acid in base fluid of PEG has been verified by measuring the magnetorheological properties. The effect of temperature on magnetorheological properties of Fe₃O₄ nanoparticles coated with oleic acid has also been investigated in base fluid of PEG. The volumetric properties of Fe₃O₄-PEG and Fe₃O₄ coated with oleic acid–PEG nanofluids and PEG–oleic acid solution have also been measured at different temperatures to specify the suspension structure and also interactions of Fe₃O₄, PEG and oleic acid molecules.     

Self-Organization of Magnetic Nanoparticles and Inclusion of Hydrogen by Borohydride Reduction

Summary.  Different structures of the interglobular space or voids between self-organized nanoparticles lead to differences in the measurable magnetic properties of single-domain particle chains of similar composition, grain size, and amorphous structure of the single globules. The volumes and radii of nanoparticles obtained by application of a magnetic field (3 to 15 nm) are larger than those determined without application of a magnetic field during the borohydride reduction process. Two types of hydrogen containing nanotubes with diameters of up to 2 (small-size containers) and 5 nm (large-size containers) are produced using as a driving force the domain wall formation energy between ferromagnetic nanoparticles with quantum size effected dimensions prepared by this reduction method at room temperature and ambient atmosphere. Nanoscale hydrogen containers can be used instead of MeH nanoparticle electrodes as perfect energy charge transfer media of high efficiency (close to 100%) using Li ion electrolytes. No influence on the electrode temperature and no participation of OH⁻ and H₂O in the main charge/discharge transfer reactions were observed. Received October 25, 2001. Accepted (revised) January 3, 2002     

Magnetic solid‐phase extraction based on a polydopamine‐coated Fe3O4 nanoparticles absorbent for the determination of bisphenol A,tetrabromobisphenol A, 2,4,6‐tribromophenol,and (S)‐1,1’‐bi‐2‐naphthol in environmental waters by HPLC

Polydopamine‐coated Fe₃O₄ magnetic nanoparticles synthesized through a facile solvothermal reaction and the self‐polymerization of dopamine have been employed as a magnetic solid‐phase extraction sorbent to enrich four phenolic compounds, bisphenol A, tetrabromobisphenol A, (S)‐1,1′‐bi‐2‐naphthol and 2,4,6‐tribromophenol, from environmental waters followed by high‐performance liquid chromatographic detection. Various parameters of the extraction were optimized, including the pH of the sample matrix, the amount of polydopamine‐coated Fe₃O₄ sorbent, the adsorption time, the enrichment factor of analytes, the elution solvent, and the reusability of the nanoparticles sorbent. The recoveries of these phenols in spiked water samples were 62.0–112.0% with relative standard deviations of 0.8–7.7%, indicating the good reliability of the magnetic solid‐phase extraction with high‐performance liquid chromatography method. In addition, the extraction characteristics of the magnetic polydopamine‐coated Fe₃O₄ nanoparticles were elucidated comprehensively. It is found that there are hydrophobic, π–π stacking and hydrogen bonding interactions between phenols and more dispersible polydopamine‐coated Fe₃O₄ in water, among which hydrophobic interaction dominates the magnetic solid‐phase extraction performance.     

超顺磁性高分子微球的制备与表征

用化学共沉淀方法制备了Fe3O4纳米微粒,并用油酸(十八烯酸)和十二烷基苯磺酸钠为双层表面活性剂进行表面修饰,制备了稳定的水分散性纳米Fe3O4可聚合磁流体.在Fe3O4磁流体存在下,将苯乙烯与甲基丙烯酸通过乳液聚合方法制备了磁性高分子微球.透射电镜研究表明,Fe3O4微粒的平均粒径在10nm左右,乳液聚合形成的磁性高分子微球的粒径平均约为130nm;用超导量子干涉仪对微粒及高分子微球进行了磁性表征,结果表明,合成的Fe3O4纳米微粒以及磁性高分子微球均具有超顺磁性.同时,还用红外光谱及X射线衍射表征了磁性高分子微球的化学成分和晶体结构.用热失重方法测得磁性高分子微球中磁性物质的含量为23.6%.     

Preparation of Fe3O4 magnetic fluid by one-step method with a microemulsion reactor

A W/O microemulsion was prepared with Span80-PS (petroleum sulfonate) as complex emulsifier, isopropanol as cosurfactant and kerosene as oil phase. The optimal constituents of microemulsion were found from pseudoternary phase diagrams: the mass ratio of Span80 to PS was 4:1 and complex surfactant to cosurfactant was 1:1. The Fe₃O₄ magnetic fluid was obtained by one-step method with the W/O microemulsion as microreactor to synthesize magnetic nanoparticles (reaction temperature was 30 °C and reaction time was 5 h) and kerosene as carrier liquid. The magnetic fluid was investigated by TEM, XRD and fluorescence microscope. The magnetism was determined by Gouy magnetic balance. The average particle size of Fe₃O₄ was 7.4 nm, and magnetic particles were well-dispersed. The stable Fe₃O₄ magnetic fluid with good magnetism may be produced by one-step method in the W/O microemulsion. Accordingly, the traditional preparation method of magnetic fluid can be simplified greatly. __________ Translated from Chinese Journal of Applied Chemistry, 2005, 22 (7) (in Chinese)     

Synthesis and characterization of chitosan coating of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles for biomedical applications

Nickel ferrite nanoparticle is a soft magnetic material whose appealing properties as well as various technical applications have rendered it as one of the most attractive class of materials; its technical applications range from its utility as a sensor and catalyst to its utility in biomedical processes. The present paper focuses first on the synthesis of NiFe₂O₄ nanoparticles through co-precipitation method resulting in calcined nanoparticles that were achieved at different times and at a constant temperature (773 k). Afterward, they were dispersed in water that was mixed by chitosan. Chitosan was bonded on the surface of nanoparticles by controlling the pH of media. In order to assess the structural and magnetic properties of nanoparticles, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analyses were conducted at room temperature. As per the results of XRD analysis, the pure NiFe₂O₄ was synthesized. Additionally, nanoparticles grew in size by extending the calcination process duration. TEM micrographs were used to determine the size and shape of particle; the obtained results indicate that the particle size was in a range of 17–30 nm and of a circular shape. The proper chitosan covering was also indicated by FTIR results. The VSM analysis also revealed that the saturated magnetization of NiFe₂O₄ nanoparticles stood in a range of 29 emu/g and 45 Q_e. A stable maximum temperature ranging from 30 to 42 was successfully achieved within 10 min. Also, a specific absorption rate of up to 8.4 W/g was achieved. The study results revealed that the SAR parameter of the coated nickel ferrite nanoparticle is more than that of pure nickel ferrite or cobalt ferrite nanoparticles.     

Fe3O4‐SAHPG‐Pd0 nanoparticles: A ligand‐free and low Pd loading quasiheterogeneous catalyst active for mild Suzuki–Miyaura coupling and C?H activation of pyrimidine cores

This paper reports a green magnetic quasiheterogeneous efficient palladium catalyst in which Pd⁰ nanoparticles have been immobilized in self‐assembled hyperbranched polyglycidole (SAHPG)‐coated magnetic Fe₃O₄ nanoparticles (Fe₃O₄‐SAHPG‐Pd⁰). This catalyst has been used for effective ligandless Pd catalyzed Suzuki–Miyaura coupling reactions of different aryl halides with substituted boronic acids at room temperature and in aqueous media. Herein, SAHPG is used as support; it also acts as a reducing agent and stabilizer to promote the transformation of Pd^II to Pd⁰ nanoparticles. Also, this environmental friendly quasiheterogeneous catalyst is employed for the first time in the synthesis of new pyrimido[4,5‐b]indoles via oxidative addition/C? H activation reactions on the pyrimidine rings, which were obtained with higher yield and faster than when Pd(OAc)₂ was used as the catalyst. Interestingly, the above‐mentioned catalyst could be recovered in a facile manner from the reaction mixture by applying an external magnet device and recycled several times with no significant decrease in the catalytic activity.     

Selective extraction of berberine from Cortex Phellodendri using polydopamine‐coated magnetic nanoparticles

A new extraction agent featuring dopamine self‐polymerized on magnetic Fe₃O₄ nanoparticles has been successfully synthesized and evaluated for the SPE of berberine from the extract of the traditional Chinese medicinal plant, Cortex Phellodendri. The nanoparticles prepared possessed a core–shell structure and showed super‐paramagnetism. It was found that these polydopamine‐coated nanoparticles exhibited strong and selective adsorption for berberine. Among the chemical components present in C. Phellodendri, only berberine was adsorbed by the nanoparticles and extracted by a following SPE procedure. Various conditions such as the amount of polydopamine‐coated nanoparticles, desorption solvent, desorption time and equilibrium time were optimized for the SPE of berberine. The purity of berberine extracted from C. Phellodendri was determined to be as high as 91.3% compared with that of 9.5% in the extract. The established SPE protocol combined advantages of highly selective enrichment with easy magnetic separation, and proved to be a facile efficient procedure for the isolation of berberine. Further, the prepared polydopamine‐coated magnetic nanoparticles could be reused for multiple times, reducing operational cost. The applicability and reliability of the developed SPE method were demonstrated by isolating berberine from three different C. Phellodendri extracts. Recoveries of 85.4–111.2% were obtained with relative standard deviations ranging from 0.27–2.05%.     

Superassembled Hierarchical Asymmetric Magnetic Mesoporous Nanorobots Driven by Smart Confined Catalytic Degradation

Micro/nanoscale robotics has received great attention in many important fields. However, it is still a great challenge to construct nanorobots simultaneously possessing multifunctionality, well-controlled directionality, and fast and durable motion as well as fully compatible and biodegradable components. Here, a hierarchical, asymmetric, hollow, catalytic, magnetic, and mesoporous nanorobot has been fabricated through a multistep interfacial superassembly strategy. The multilayer composites consist of hollow silica nanoflasks sequentially coated with a highly magnetic responsive Fe₃O₄ layer, a mesoporous silica layer with homogeneous vertical channels, and a layer of catalytic gold nanoparticles on both the inner and outer surfaces. Furthermore, para-nitrophenol was used as a model pollutant to trigger self-motility of the nanoflasks by confined catalytic degradation (CCD). We found that the bottleneck morphology and mesoporous surface both improved the catalytic nanoparticle loading capability and CCD effect, thus enabling efficient self-motility and a durable movement capacity of ∼100 h. In addition, the catalytic performance was improved by 180 % compared with that of solid spherical nanoparticles.     

Magnetic molecularly imprinted composite for the selective solid‐phase extraction of p‐aminosalicylic acid followed by high‐performance liquid chromatography with ultraviolet detection

A new method for the selective extraction of p‐aminosalicylic acid from aqueous and urine samples has been developed using magnetic molecularly imprinted polymer nanoparticles before determination by high‐performance liquid chromatography. The Fe₃O₄ nanoparticles were first prepared through the chemical coprecipitation of Fe²⁺ and Fe³⁺ and then coated with a vinyl shell. Subsequently, a layer of molecularly imprinted polymers was grafted onto the vinyl‐modified magnetic nanoparticles by precipitation polymerization. FTIR spectroscopy, scanning electron microscopy, vibrating sample magnetometry, and thermogravimetric analysis were applied to characterize the sorbent properties. Moreover, the predominant parameters affecting the magnetic solid phase extraction such as sample pH, sorption and elution times, the amount of sorbent, and composition and volume of eluent were investigated thoroughly. The maximum sorption capacity of the imprinted polymer toward p‐aminosalicylic acid was 70.9 mg/g, which is 4.5 times higher than that of the magnetic nonimprinted polymer. The magnetic molecularly imprinted polymer nanoparticles were applied for the selective extraction of p‐aminosalicylic acid from aqueous and urine samples and satisfactory results were achieved. The results illustrate that magnetic molecularly imprinted polymer nanoparticles have a great potential in the extraction of p‐aminosalicylic acid from environmental and biological matrices.     

Magnetic ion imprinted polymer nanoparticles for the preconcentration of vanadium(IV) ions

An ion imprinted polymer coated onto magnetite (Fe₃O₄) nanoparticles is shown to be a useful magnetic sorbent for the fairly selective preconcentration of vanadium. The sorbent was prepared by radical copolymerization of 3-(triethoxysilyl)propyl methacrylate (the monomer), ethylene glycol dimethacrylate (the cross-linker), and the vanadium(IV) complex of 1-(2-pyridylazo-2-naphthol) in the presence of magnetite nanoparticles. The material was characterized by IR spectroscopy, scanning electron microscopy, and thermal analysis. The vanadium(IV) ions were removed from the imprint by a solution containing thiourea and HCl, and the eluent was submitted to AAS. The analytical efficiency and relative standard deviation are 99.4 and ±2.3 %, respectively, under optimum conditions, and the limit of detection is 20 ng mL^?1. The method was successfully applied to the preconcentration and determination of vanadium(IV) ions in crude oil. Figure

An ion imprinted polymer is coated on to magnetite nanoparticles as a useful magnetic sorbent for the fairly selective preconcentration of vanadium which can be used for vanadium determination in crude oil.     

Magnetic Nanoparticles Supported Ionic Liquids Improve Firefly Luciferase Properties

Ionic liquids as neoteric solvents, microwave irradiation, and alternative energy source are becoming as a solvent for many enzymatic reactions. We recently showed that the incubation of firefly luciferase from Photinus pyralis with various ionic liquids increased the activity and stability of luciferase. Magnetic nanoparticles supported ionic liquids have been obtained by covalent bonding of ionic liquids-silane on magnetic silica nanoparticles. In the present study, the effects of [γ-Fe₂O₃@SiO₂][BMImCl] and [γ-Fe₂O₃@SiO₂][BMImI] were investigated on the structural properties and function of luciferase using circular dichroism, fluorescence spectroscopy, and bioluminescence assay. Enzyme activity and structural stability increased in the presence of magnetic nanoparticles supported ionic liquids. Furthermore, the effect of ingredients which were used was not considerable on K _m value of luciferase for adenosine-5′-triphosphate and also K _m value for luciferin.