An electrochemical microsensor for chloramphenicol (CAP) was fabricated by introducing magnetic Fe3O4 nanoparticles (NPs) onto the surface of activated carbon fibers. This microsensor exhibited increased electrochemical response toward CAP because of the synergetic effect of the Fe3O4 NPs and the carbon fibers. Cyclic voltammograms were acquired and displayed three stable and irreversible redox peaks in pH 7.0 solution. Under optimized conditions, the cathodic current peaks at ?0.67 V (vs. Ag/AgCl). The calibration plot is linear in the 40 pM to 1 μM CAP concentration range, with a 17 pM detection limit (at a signal-to-noise ratio of 3). The sensor was applied to the determination of CAP in spiked sediment samples. In our perception, this electrocatalytic platform provided a useful tool for fast, portable, and sensitive analysis of chloramphenicol.
Graphical abstract A sensitive carbon fiber microsensor modified with Fe3O4 nanoparticles is found to display two cathodic peaks when detecting chloramphenicol at 100 mV·s?1 and at pH 7.0. The sensor was applied to the determination of chloramphenicol in sediment samples.
A nanocomposite consisting of cetyltrimethylammonium bromide (CTAB), Fe3O4 nanoparticles and reduced graphene oxide (CTAB-Fe3O4-rGO) was prepared, characterized, and used to modify the surface of a glassy carbon electrode (GCE). The voltammetric response of the modified GCE to 4-nonylphenol (NPh) was investigated by cyclic voltammetry and revealed a strong peak at around 0.57 V (vs. SCE). Under optimum conditions, the calibration plot is linear in the ranges from 0.03 to 7.0 μM and from 7.0 to 15.0 μM, with a 8 nM detection limit which is lower that that of many other methods. The modified electrode has excellent fabrication reproducibility and was applied to the determination of NPh in spiked real water samples to give recoveries (at a spiking level of 1 μM) between 102.1 and 99.1%.
Graphical abstract A nanocomposite consisting of cetyltrimethylammonium bromide (CTAB), Fe3O4 nanoparticles and reduced graphene oxide (CTAB-Fe3O4-rGO) was prepared and used to modify the surface of a glassy carbon electrode (GCE) for the differential pulse voltammetric (DPV) determination of 4-nonylphenol (NPh).
A new approach to the synthesis of hybrid nanoparticles based on magnetic Fe3O4 nanoparticles and CdS quantum dots, combining magnetic and luminescence properties, has been suggested. Conditions for preparation of their stable aqueous suspensions have been found, and their optical properties have been studied. Nanocomposites produced at the molar ratio Fe3O4: CdS = 5: 1, which exhibited the luminescence properties) and gave stable aqueous suspensions, have turned out to be most promising. The results are evidence that the synthesized nanoparticles can be used for the development of visualizing agents for in vitro biomedical research. 相似文献
Adsorption characteristics and doxycycline (DC) removal efficiency of Fe3O4 magnetic nanoparticles as adsorbents have been determined by investigating the effects of pH, concentration of the DC, amount of adsorbents, contact time, ionic strength and temperature. The mechanism of adsorption was also studied. The adsorption of DC to the Fe3O4 magnetic nanoparticles could be described by Langmuir-type adsorption isotherms. Short contact time between the reagents, reusability of Fe3O4 for three times after recycling of the nanoparticles, good precision and accuracy, wide working pH range and high breakthrough volume are among the highlights of this procedure. The proposed extraction and determination procedure based on magnetic nanoparticles as adsorbent was successfully applied to the determination of DC spiked in honey and various water samples. The method presented here is fast, simple, cheap and robust, and it does not require the use of organic solvents. Also, the method needs only a magnet and can be performed in any laboratory without sophisticated equipment. 相似文献
This investigation examines the magnetorheological (MR) characteristics of Fe3O4 aqueous suspensions. Magnetite particles (Fe3O4) were synthesized using a colloidal process and their sizes were determined to be normally distributed with an average of
10 nm by TEM. Experimental results reveal that the MR effect increases with the magnetic field and suspension concentration.
The yield stress increases by up to two orders of magnitude when the sample is subjected to a magnetic field of 146 Oe/mm.
In comparison with other published results, concerning a concentration of approximately 10–15% v/v, this study demonstrates
that the same increase can be obtained with a concentration of nano-scale particles as low as 0.04% by volume. The viscosity
was increased by an order of magnitude while the shear rate remained low; however, the increase decayed rapidly as the shear
rate was raised. Finally, the MR effect caused by DC outperformed that caused by AC at the same current. 相似文献
The preparation and study of electrochemical properties of a graphite screen-printed electrode (SPE) modified with the GO/Fe3O4@SiO2 (GO is graphene oxide) nanocomposites are described. The morphologies of the GO/Fe3O4@SiO2 nanocomposites were examined by scanning electron microscopy. The electrochemical oxidation of vitamin B6 (pyridoxine) on SPE modified with the GO/Fe3O4@SiO2 nanocomposite was investigated by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. Under optimum conditions (pH 7.0), the vitamin B6 oxidation at the surface of the modified SPE occurs at a potential about 190 mV less positive than that at the unmodified SPE. A linear voltammetric response for vitamin B6 was obtained in the concentration range 1.0?10 6—9.0?10 4 mol L–1 with a detection limit of 5.2?10 7 mol L–1 using differential pulse voltammetry. The developed sensor was also successfully applied for determination of trace level of vitamin B6 in both the standard vitamin B6 sample and biological samples (urine). 相似文献
Fe3O4 nanorods and Fe2O3 nanowires have been synthesized through a simple thermal oxide reaction of Fe with C2H2O4 solution at 200–600°C for 1 h in the air. The morphology and structure of Fe3O4 nanorods and Fe2O3 nanowires were detected with powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy.
The influence of temperature on the morphology development was experimentally investigated. The results show that the polycrystals
Fe3O4 nanorods with cubic structure and the average diameter of 0.5–0.8 μm grow after reaction at 200–500°C for 1 h in the air.
When the temperature was 600°C, the samples completely became Fe2O3 nanowires with hexagonal structure. It was found that C2H2O4 molecules had a significant effect on the formation of Fe3O4 nanorods. A possible mechanism was also proposed to account for the growth of these Fe3O4 nanorods.
Supported by the Fund of Weinan Teacher’s University (Grant No. 08YKZ008), the National Natural Science Foundation of China
(Grant No. 20573072) and the Doctoral Fund of Ministry of Education of China (Grant No. 20060718010) 相似文献
As the solubility is a direct measure of stability, this study compares the solubilities of ZnFe2O4, Fe3O4 and Fe2O3 in high temperature water. Through literature analysis and formula derivation, it is shown that it is reasonable to assume ZnFe2O4 and Fe(OH)3 coexist when ZnFe2O4 is dissolved in water. Results indicated that the solubility of ZnFe2O4 is much lower than that of Fe2O3 or Fe3O4. The low solubility of ZnFe2O4 indicates that it is more protectively stable as an anticorrosion phase. Moreover, the gap between the solubility of ZnFe2O4 and that of Fe3O4 or Fe2O3 was enlarged with an increase of temperature. This means that ZnFe2O4 is more protective at higher temperatures. Further analysis indicated that with the increase of temperature, the solubility of ZnFe2O4 changed little while those of Fe2O3 or Fe3O4 changed a lot. Little change of the solubility of ZnFe2O4 with increase of temperature showed that ZnFe2O4 is stable. The very low and constant solubility of ZnFe2O4 suggests that it is more protective than Fe2O3 and Fe3O4, especially in water at higher temperature. 相似文献
Peculiarities of electrochemical behavior of the Fe3O4 magnetic nanoparticles immobilized on the surface of a platinum electrode in aprotic organic media were investigated. Possible scheme of electrochemical behavior of nanoparticles depending on pre-electrolysis potential (–1.3,–2.5 V) was suggested. The effect of pre-electrolysis time, potential scan rate and nature of supporting electrolyte on the processes investigated was determined. A linear dependence of electrochemical oxidation signal versus the concentration of nanoparticles in modifying suspension in the concentration range of 0.05—0.5 g L–1 was observed. The results of the performed research allow using magnetite nanoparticles as a direct signal-generating label in electrochemical immunoassay. 相似文献
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. 相似文献
The authors describe an aptamer-based fluorescent assay for adenosine (Ade). It is based on the interaction between silver nanoparticles (AgNPs) and CdTe quantum dots (QDs). The beacon comprises a pair of aptamers, one conjugated to Fe3O4 magnetic nanoparticles, the other to AgNPs. In the presence of Ade, structural folding and sandwich association of the two attachments takes place. After magnetic separation, the associated sandwich structures are exposed to the QDs. The AgNPs in sandwich structures act as the signaling label of Ade by quenching the fluorescence of QDs (at excitation/emission wavelengths of 370/565 nm) via inner filter effect, electron transfer and trapping processes. As a result, the fluorescence of QDs drops with increasing Ade concentration. The assay has a linear response in the 0.1 nM to 30 nM Ade concentration range and a 60 pM limit of detection. The assay only takes 40 min which is the shortest among the aptamer-based methods ever reported. The method was successfully applied to the detection of Ade in spiked biological samples and satisfactory recoveries were obtained.
Graphical abstract Schematic of a highly efficient and convenient adenosine (Ade) fluorometric assay. It is based on the interaction between Ag nanoparticles (NPs) and CdTe quantum dots (QDs). Ade aptamers (ABA1 and ABA2) are used as recognition unit and Fe3O4 magnetic nanoparticles act as magnetic separator. The assay exhibits superior sensitivity and speediness.
A method for the preparation of nanoand submicron spherical particles of magnetite which form agglomerates was described. At varying the reaction conditions, the particles of -50—200 nm were obtained and characterized by scanning electron microscopy, IR-spectroscopy, X-ray analysis, thermogravimetric analysis and differential scanning calorimetry. The scheme (zero approach) of the magnetite formation in the studied system was proposed. The investigation of magnetic properties proved that the obtained particles related to the hard magnetic materials. Curie temperature for the particles with different sizes was detected. 相似文献
Sulfonated polyvinylchloride (SPVC) cation-exchange membranes were coated using chitosan solutions comprising different amounts of Fe3O4 nanoparticles. Influence of chitosan immobilization as well as nanofiller concentration on the electrochemical performance of the membranes was investigated. Electrochemical properties of the membranes including permselectivity, ionic permeability, and areal resistance were studied using an equipped electrodialysis setup and NaCl solution as model electrolyte. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were employed for membrane characterization. Electrochemical performance of the SPVC membranes was improved by coating chitosan polymer. In addition, ionic permeability and permselectivity of the membranes were initially raised by increasing nanoparticles concentration from nil to 2 wt% and then decreased by further insertion of the nanofiller. The areal resistance of the plain SPVC membrane was decreased from 9.4 to 2.9 (ohm) by coating of chitosan solution including optimum value of nano-Fe3O4 due to electrical potential field enhancement across the membrane.
A hemoglobin (Hb)-modified electrode based on chitosan/Fe3O4 nanocomposite coated glassy carbon has been constructed for trichloroacetic acid (TCA) detection. The structure of chitosan/Fe3O4 nanocomposite was investigated using energy-dispersive X-ray analysis (EDS) and X-ray diffraction (XRD) patterns. The electron transfer rate constant (ks) of Hb was estimated for as high as 3.12 s?1. The immobilized Hb exhibited excellent electro-catalytic activity toward the reduction of TCA. The response current regressed to the concentration of TCA within the range of 5.70 μM to 205 μM with a detection limit of 1.9 μM (S/N = 3). 相似文献
Ultrafine magnetite particles are prepared through an electrochemical process, at room temperature, from an iron-based electrode immersed in an alkaline aqueous medium containing complexing compounds. XRD and chemical analysis indicate that the product is pure magnetite, Fe3O4. The size and morphology of the particles are studied by SEM. The magnetite nanoparticles present a magnetoresistance of almost 3%, at 300 K, under a magnetic field of 1 T. A reactive mechanism for the electrochemical process is proposed. 相似文献
A novel amperometric immunosensor was developed by immobilizing ferritin antibody (FeAb) on the surface of Fe3O4 magnetic nanoparticles/chitosan composite film modified glassy carbon electrode (GCE). This material combined the advantages
of inorganic Fe3O4 nanoparticles with the organic polymer chitosan. The stepwise assembly procedure of the immunosensor was characterized by
means of differential pulse voltammetry (DPV) and ac impedance. The K3Fe(CN)6/K4Fe(CN)6 was used as a marker to probe the interface and to determinate ferritin. The factors that could influence the performance
of the resulting immunosensor were studied in detail. After the immunosensor was incubated with ferritin for 32 min at 35 °C,
the DPV current decreased linearly with the logarithm of ferritin concentration in the range from 20 to 500 ng mL−1 with a correlation coefficient of 0.995 and a detection limit of 7.0 ng mL−1. This immunosensor was used to analyze ferritin in human serum samples. The analytical results showed that the developed
immunoassay was comparable with the radioimmunoassay (RIA), and the studied immunosensor exhibited good accuracy, high sensitivity,
and long-term stability for 3 weeks, which implies a promising alternative approach for detecting ferritin in clinical diagnosis. 相似文献
Summary The adsorption of 99Tc on the adsorbers Fe, Fe2O3 and Fe3O4 was studied by batch experiments under aerobic and anoxic conditions. The effects of pH and CO32- concentration of the simulated ground water on the adsorption ratios were also investigated, and the valences of Tc in solution after the adsorption equilibrium were studied by solvent extraction. The adsorption isotherms of TcO4- on the adsorbers Fe, Fe2O3 and Fe3O4 were determined. Experimental results have shown that the adsorption ratio of Tc on Fe decreases with the increase of pH in the range of 5-12 and increases with the decrease of the CO32- concentration in the range of 10-8M-10-2M. Under aerobic conditions, the adsorption ratios of 99Tc on Fe2O3 and Fe3O4 were not influenced by pH and CO32-concentration. When Fe was used as adsorbent, Tc existed mainly in the form of Tc(IV) after equilibrium and in the form of Tc(VII) when the adsorbent was Fe2O3 or Fe3O4 under aerobic conditions. The adsorption ratios of Tc on Fe, Fe2O3 and Fe3O4 decreased with the increase of pH in the range of 5-12 and increased with the decrease of the CO32- concentration in the range of 10-8M-10-2M under anoxic conditions. Tc existed mainly in the form of Tc(IV) after equilibrium when Fe, Fe2O3 and Fe3O4 was the adsorbent under anoxic conditions. The adsorption isotherms of TcO4- on the adsorbers Fe, Fe2O3 and Fe3O4 are fairly in agreement with the Freundlich’s equation under both aerobic and anoxic conditions. 相似文献
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.
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.
Using Fe3O4 nano-particles as seeds, a new type of Fe3O4/Au composite particles with core/shell structure and diameter of about 170 nm was prepared by reduction of Au3+ with hydroxylamine in an aqueous solution. Particle size analyzer and transmission electron microscope were used to analyze
the size distribution and microstructure of the particles in different conditions. The result showed that the magnetically
responsive property and suspension stability of Fe3O4 seeds as well as reduction conditions of Au3+to Au0are the main factors which are crucial for obtaining a colloid of the Fe3O4/Au composite particles with uniform particle dispersion, excellent stability, homogeneity in particle sizes, and effective
response to an external magnet in aqueous suspension solutions. UV-Vis analysis revealed that there is a characteristic peak
of Fe3O4/Au fluid. For particles with d(0.5)=168 nm, the λmax is 625 nm. 相似文献
