Magnetic nanoparticles (Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> &amp; Co<Subscript>3</Subscript>O<Subscript>4</Subscript>) and their applications in urea biosensing

Nanobiotechnology has opened a new and exciting opportunities for exploring urea biosensor based on magnetic nanoparticles (NPs) mainly Fe₃O₄ and Co₃O₄. These NPs have been extensively exploited to develop biosensors with stability, selectivity, reproducibility and fast response time. This review gives an overview of the development of urea biosensor based on Fe₃O₄ and Co₃O₄ for in vitro diagnostic applications along with significant improvements over the last few decades. Additionally, effort has been made to elaborate properties of magnetic nanoparticles (MNPs) in biosensing aspects. It also gives details of recent developments in hybrid nanobiocomposite based urea biosensor.     

Magnetic solid-phase extraction of triclosan using core-shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@MIL-100 magnetic nanoparticles,and its determination by HPLC with UV detection

The article describes the synthesis of core-shell magnetic nanoparticles (MNPs) of the type Fe₃O₄@MIL-100 (MIL standing for Material Institut Lavoisier), and their application as sorbent for magnetic solid-phase extraction (MSPE) of triclosan. The MNPs were prepared via circular self-assembly of ferric chloride and benzenetricarboxylic acid. The functionalized MNPs were characterized by transmission electron microscopy, FTIR and thermogravimetry. Following extraction, triclosan was eluted with ammoniacal methanol and then submitted to HPLC with UV detection. The amount of magnetic microspheres, sample pH and ionic strength, adsorption time, desorption time, desorption solvent and the volume of the eluent were optimized. Under optimum conditions, the method showed good linearity in the 0.1 to 50 mg·kg^?1 triclosan concentration range in toothpaste samples. Other features include (a) intra-day and inter-day relative standard deviations (RSD, for n = 4) of <5.5 %, (b) a 30 μg·kg^?1 limit of detection, and (c) extraction recoveries between 90.86 % and 101.1 %. The method was successfully applied to the determination of triclosan in children’s toothpaste.

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Graphical abstract The article describes the synthesis of core-shell magnetic nanoparticles (MNPs) of the type Fe₃O₄@MIL-100, and their application as sorbent for magnetic solid-phase extraction (MSPE) of triclosan.

     

Obtaining of Ni<Subscript>0.65</Subscript>Zn<Subscript>0.35</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites by thermal decomposition of complex compounds embedded in silica matrix

This article presents the results of our investigation on the obtaining of Ni_0.65Zn_0.35Fe₂O₄ ferrite nanoparticles embedded in a SiO₂ matrix using a modified sol–gel synthesis method, starting from tetraethylorthosilicate (TEOS), metal (Fe^III,Ni^II,Zn^II) nitrates and ethylene glycol (EG). This method consists in the formation of carboxylate type complexes, inside the silica matrix, used as forerunners for the ferrite/silica nanocomposites. We prepared gels with different compositions, in order to obtain, through a suitable thermal treatment, the nanocomposites (Ni_0.65Zn_0.35Fe₂O₄)_x–(SiO₂)_100–x (where x=10, 20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy. The formation of Ni–Zn ferrite in the silica matrix and the behavior in an external magnetic field were studied by X-ray diffraction (XRD) and quasi-static magnetic measurements (50 Hz).     

Ionic behavior modification of cation exchange ED membranes by using CMC-co-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles for heavy metals removal from water

A new mixed matrix polyvinyl chloride-based heterogeneous cation exchange membrane was prepared by incorporation of carboxy methyl cellulose-co-Fe₃O₄ nanoparticles through solution casting technique. The effect of simultaneous using of carboxy methyl cellulose and iron oxide nanoparticles in the casting solution on the physicochemical properties of membranes was studied. SOM images showed uniform particles distribution and uniform surfaces for the membranes relatively. The SEM images exhibited regular direction/spatial orientation for the CMC-co-Fe₃O₄ nanoparticles in the membrane matrix. XRD patterns showed that membrane heterogeneity was enhanced by using of Fe₃O₄ nanoparticles. Membrane ion exchange capacity, membrane surface hydrophilicity, membrane potential, surface charge density, transport number, selectivity, and ionic flux were increased by using CMC/Fe₃O₄ nanoparticles in membrane matrix. Results showed that membrane areal electrical resistance was declined up to 3.8 Ω cm² by utilizing CMC/Fe₃O₄ nanoparticles in the casting solution. Also PVC/CMC-co-Fe₃O₄ membrane showed higher transport number, selectivity, flux, and electrical conductivity compared to PVC/CMC membrane and unmodified ones. Electrodialysis experiment in laboratory scale showed higher dialytic rate in lead ions removal for PVC/CMC-co-Fe₃O₄ nanoparticle-mixed matrix ion exchange membrane compared to PVC/CMC membrane and pristine one.     

Effect of the Structure of Pyridine Ligands and the Substituent in the Carboxylate Anion on the Geometry of Transition Metal Complexes [M<Subscript>2</Subscript>(O<Subscript>2</Subscript>CR)<Subscript>4</Subscript>L<Subscript>2</Subscript>]

A series of binuclear tetracarboxylate-linked Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) complexes with 1,2-substituted pyridine, viz., 2,3-cyclododecenopyridine (L), were prepared. Study of the crystal structures of isolated compounds (CIF file CCDC nos. 1575855–1575859) revealed a distortion of the {Ni₂(O₂CR)₄L₂} binuclear moiety, manifested as a change in the NiNiN angle (151.67°), in the bridging function of two out of the four carboxylate groups (from μ_2- to (κ²,μ_2-)), and in the coordination environment of the metal ion (NiO₅N). The results were analyzed in comparison with known data. The magnetic properties of copper(II) and nickel(II) complexes were studied. The copper(II) complex is diamagnetic as a result of strong exchange interactions between the unpaired electrons; in the nickel(II) complex antiferromagnetic exchange interactions were detected (J_Ni–Ni =–25 cm^–1).     

MnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles with excellent catalytic activity in thermal decomposition of ammonium perchlorate

MnCo₂O₄ spinel nanoparticles (NPs) have been prepared using Aloe vera gel solution. The characterization of prepared spinel was performed applying Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron spectroscope, scanning electron microscope and dynamic light scattering. The results manifested that the prepared nanoparticles were mainly spherical plus minor agglomeration with average size distribution between 35 and 60 nm. The catalytic activity of the prepared nanoparticles upon thermal degradation of ammonium perchlorate (AP) was evaluated applying differential scanning calorimetry and thermogravimetry instruments. MnCo₂O₄ nanoparticles increased the released heat of AP from 450 to 1480 J g^?1 and decreased the decomposition temperature from 420 to 293 °C. The kinetic parameters obtained from Kissinger methods showed that the activation energy of AP thermal decomposition in the presence of MnCo₂O₄ NPs considerably decreased. Also, a mechanism has been proposed in the presence of catalyst for the process of thermal decomposition of AP.     

Effect of the preparation method of the cathode material LiNi<Subscript>0.33</Subscript>Mn<Subscript>0.33</Subscript>Co<Subscript>0.33</Subscript>O<Subscript>2</Subscript> on the electrochemical characteristics of a lithium ion cell

Complex metal oxides with the composition LiNi_0.33Mn_0.33Co_0.33O₂ prepared by various methods: sol–gel method, solid-phase method, and thermal destruction of metal-containing compounds in oil were studied. The results of elemental analysis, TGA/DSC, powder X-ray diffraction, SEM, TEM, as well as the results of electrochemical testing of the cathodes based on the obtained materials are presented. The complex metal oxides LiNi_0.33Mn_0.33Co_0.33O₂ prepared by sol–gel processes and thermal destruction of metal-containing compounds in oil consist of primary nanosized crystallites with an average size of 90 nm covered by a nanometer carbon layer, which improves the electrochemical characteristics of lithium ion batteries.     

Preparation,Characterization and Transport Properties of Novel Cation-Exchange Nanocomposite Membrane Containing BaFe<Subscript>12</Subscript>O<Subscript>19</Subscript> Nanoparticles

A new type of ion-exchange nanocomposite membranes was prepared by addition of barium ferrite nanoparticles to a blend containing sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) and sulfonated polyvinylchloride via a simple casting method. Hard magnetic BaFe₁₂O₁₉ nanoparticles were synthesized via a facile sonochemical-assisted reaction. Nanoparticles and nanocomposites were then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and alternating gradient force magnetometer. Various characterizations revealed that the addition of different amounts of inorganic fillers could affect the membrane performance. The inorganic nanoparticles not only created extra pores and water channels that led to improve ion conductivity, but also provided higher permselectivity and transport number of counter-ions.     

Thermal behavior of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> mesoporous gels

Summary Titania-based photocatalytic materials were prepared by sol-gel method using Fe³⁺ and polyethyleneglycol (PEG₆₀₀) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe³⁺ containing titania gels. The microstructure development of the Fe₂O₃/TiO₂ gel samples with and without PEG₆₀₀ admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120&deg;C and the samples preheated for 1 h to 300 and 500&deg;C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600&deg;C.     

Synthesis of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> nanoparticles by modified Pechini method and their enhanced rate capability

Layered LiNi_1/3Co_1/3Mn_1/3O₂ nanoparticles were prepared by modified Pechini method and used as cathode materials for Li-ion batteries. The pyrolytic behaviors of the foamed precursors were analyzed by use of simultaneous thermogravimetric and differential thermal analysis (TG-DTA). Structure, morphology and electrochemical performance characterization of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron macroscopy(SEM), Brunauer-Emmett-Teller (BET) specific surface area and charge–discharge tests. The results showed that the samples prepared by modified Pechini method caclined at 900 °C for 10 h were indexed to pure LiNi_1/3Co_1/3Mn_1/3O₂ with well hexagonal structure. The particle size was in a range of 100–300 nm. The specific surface area was larger than that of the as-obtained sample by Pechini method. Initial discharge capacity of 163.8 mAh/g in the range 2.8–4.4 V (vs. Li/Li⁺) and at 0.1C for LiNi_1/3Co_1/3Mn_1/3O₂ prepared by modified Pechini method was obtained, higher than that of the sample prepared by Pechini method (143.5 mAh/g). Moreover, the comparison of electrochemical results at different current rates indicated that the sample prepared by modified Pechini method exhibited improved rate capability.     

Surface chemistry of nanoscale Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> dispersed in magnetic fluids

The interaction between stabilizers and nanoparticles is one of the important factors to prepare stable magnetic fluids. The magnetic nano-size Fe₃O₄ core with single domain and the average grain size around 8–12 nm were prepared by chemical precipitation method. The O/Fe molar ratio of the particle surface was measured by X-ray photoelectron spectroscopy (XPS). The heat effects of stabilizers adsorption on nanoparticles were measured by solution calorimetry. The excess amount of oxygen was possibly the result of the hydroxygen formed on the surface of the nanoparticles. The heat effects showed that compounds containing carboxyl groups can be adsorbed chemically on magnetite by forming chemical bonds. The other stabilizers involving NH-groups, such as polyethylene-imine, can be adsorbed physically. The exothermic value is about half of the former case. Supported by the National Natural Science Foundation of China (Grant No. 50476039), and Guangdong Provincial Department of Science and Technology (Grant No. 2004A10-703001)     

Preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>-C18 nano-magnetic composite materials and their cleanup properties for organophosphorous pesticides

Magnetic Fe₃O₄-C18 composite nanoparticles of approximately 5–10 nm in size were synthesized and characterized by IR spectroscopy, atomic absorption spectroscopy, X-ray diffraction, and transmission electron microscopy. The magnetic Fe₃O₄-C18 composite nanoparticles were applied for cleanup and enrichment of organophosphorous pesticides. Comparative studies were carried out between magnetic Fe₃O₄-C18 composite nanoparticles and common C18 materials. Residues of organophosphorous pesticides were determined by gas chromatography in combination with a nitrogen/phosphorus detector. The cleanup and enrichment properties of magnetic Fe₃O₄-C18 composite nanoparticles are comparable with those of common C18 materials for enrichment of organophosphorous pesticides, but the cleanup and enrichment are faster and easier to perform. Figure Presumed mechanism for the adhesion of the OPs to the Fe₃O₄-C18 magnetic nanoparticles     

Synthesis of pyridinecarboxaldimine grafted to magnetic nanoparticles (Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>) and its application in the aerobic oxidation of primary alcohols catalyzed by CuBr<Subscript>2</Subscript>/TEMPO

A pyridinecarboxaldimine grafted to silica-coated magnetic nanoparticles was prepared. The structure and magnetic properties of the functionalized magnetic silica nanoparticles were identified by TEM, FT-IR, XRD, elemental analysis, and vibrating sample magnetometer (VSM). The supported pyridinecarboxaldimine as chelating ligand in combination with CuBr₂ and 2,2,6,6-tetramethyl-1-piperadoxyl (TEMPO) exhibited efficient catalytic performance in the aerobic oxidation of primary alcohols to aldehydes. The functionalized magnetic silica nanoparticles could be easily recovered using an external magnetic field and reused for at least 6 times with low reduction in its performance in the aerobic oxidation of benzyl alcohol.     

Magnetic and Heat Resistant Poly(imide-ether) Nanocomposites Derived from Methyl Rich 9<Emphasis Type="Italic">H</Emphasis>-xanthene: Synthesis and Characterization

In this study a new series of magnetic and heat resistant nanocomposites were prepared based on a highly soluble poly(imide-ether) (PIE) reinforced with two different types of magnetic nanoparticles via a solution intercalation technique. New PIE with good solubility and desired molar mass containing bulky xanthene rings and amide groups in the side chains was synthesized via thermal cyclization of the poly(amic acid) precursor, obtained from the reaction of a new diamine derived from 9H-xanthene and 4,4′-oxydiphthalic dianhydride (ODPA). Improved solubility was attributed to the presence of xanthene group and flexible ether linkage in the polyimide backbones that reduce the chain-chain interaction and enhance solubility by penetrating solvent molecules into the polyimide chains. Fe₃O₄ nanoparticles (MNPs) which synthesized from chemical co-precipitation route were coated with silica (SiO₂), sequentially with (3-aminopropyl)triethoxysilane and poly-melamine-terephthaldehyde (MNPs-PMT), and then separately dispersed in the poly(amic acid) solutions and thermally imidized to form PIE/Fe₃O₄ and PIE/MNPs-PMT nanocomposites. The nanostructures and properties of the resultant materials were investigated using FTIR spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The properties of the nanocomposites were strongly related to the dispersion and interaction between the nanoparticles and PIE matrix. The thermogravimetric analysis (TGA) results showed that the addition of MNPs-PMT nanoparticles resulted in a substantial increase in the thermal stability of the corresponding PIEN. The temperature at 10% weight loss (T₁₀) was increased from 416 °C to 428 °C for PIEN containing 3 wt% MNPs-PMT as compared to neat PIE, as well the char yield enhanced. Furthermore, the MNPs-PMT nanoparticles had better dispersion in the polymer matrix due to the strong intermolecular hydrogen bond interactions between the NH and C=N groups of surface-modified nanoparticles and the PIE matrix than the uncoated Fe₃O₄ nanoparticles, and exhibited a better intercalated morphology and improved thermal properties. Also, the PIEN nanocomposites under applied magnetic field exhibited the hysteretic loops of the superparamagnetic nature.     

PW based phase change nanocomposites containing <Emphasis Type="Italic">γ</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Phase change nanocomposites were prepared by dispersing γ-Al₂O₃ nanoparticles into melting paraffin wax (PW). Intensive sonication was used to make well dispersed and homogeneous composites. Differential scanning calorimetric (DSC) and transient short-hot-wire (SHW) method were employed to measure the thermal properties of the composites. The composites decreased the latent heat thermal energy storage capacity, L _s, and melting point, T _m, compared with those of the PW. Interestingly, the composites with low mass fraction of the nanoparticles, have higher latent heat capacity than the calculated latent heat capacity value. The thermal conductivity of the nanocomposites was enhanced and increased with the mass fraction of Al₂O₃ in both liquid state and solid state.     

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.     

Characterization of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles synthesized by various methods

Microwave-induced combustion with glycine, CTAB-assisted hydrothermal process with NaOH and NH3, EDTA assisted-hydrothermal methods have been applied to prepare NiFe₂O₄ nanoparticles for the first time. Structural and magnetic properties of the products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmison electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and electron spin resonance spectrometry (EPR). TEM measurements showed that morphology of the product depends on the synthesis method employed. The average cystallite size of NiFe₂O₄ nanoparticles was in the range of 14–59 nm as measured by XRD. The uncoated sample (Method A) had an EPR linewidth of 1973 Oe, the coated samples reached lower values. The magnetic dipolar interactions existing among the Ni ferrite nanoparticles are reduced by the coatings, which could cause the decrease in the linewidth of the EPR signals. Additionally, the linewidth increases with an increase in the size and the size distribution of nanoparticles.     

Application of RuO<Subscript>2</Subscript> Nanoparticles as Catalyst in Preparation of Indolo[3,2-a]Carbazoles

RuO₂ nanoparticles were readily prepared from RuCl₃·3H₂O via the formation of Ru-hydroxide precursor, followed by calcination at 550 °C. Under similar conditions, uniform dispersion of spherical RuO₂ nanoparticles over the surface of MCM-41 was also obtained. The synthesized materials were characterized by transmission electron microscopy (TEM), infrared spectroscopy (FT-IR), X-ray diffraction (XRD), BET surface area measurements, and magnetic measurements (VSM). The obtained RuO₂ nanoparticles found application as catalyst in preparation of indolo[3,2-a]carbazoles from the reaction of indoles and benzils. Under mild reaction conditions, satisfactory yields of the desired products were obtained. Stabilization of RuO₂ nanoparticles over the surface of MCM-41 (RuO₂–MCM41), however, had the advantage of easy recycling, although a slight decrease in efficiency after five successive runs was observed.     

The design of hybrid materials based on magnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles and luminescent CdS nanoparticles for cell visualization

Hybrid nanoparticles based on Fe₃O₄ and CdS combining magnetic and luminescence properties were synthesized. The possibility of visualization of various cells by 3-mercaptopropylsilane-modified CdS nanoparticles and hybrid nanoparticles based on them using a confocal microscope was demonstrated. The synthesized materials did not show a clear-cut cytotoxicity.     

High-pressure nonstoichiometric phase Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript>

Perovskite-like nonstoichiometric oxide Sm _x Cu₃V₄O₁₂ (space group Im \(\bar 3\), Z = 2, a = 7.276?7.314 Å) with cationic vacancies and a homogeneity region was prepared barothermally (p = 6.0?9.0 GPa, T = 700?1100°C) for the first time. Structural and isotropic thermal parameters, as well as bond lengths and bond angles, were determined. The compound has metal-type conductivity and paramagnetic properties.