► We present a general method to prepare the core–shell magnetic MIPs nanoparticles (Fe3O4@MIPs) for sulfamethazine. ► The Fe3O4@MIPs possess a highly improved imprinting factor, fast adsorption ...kinetics and high adsorption capacity. ► The structure and affinity properties of the resulting Fe3O4@MIPs were characterized. ► We used Fe3O4@MIPs for enrichment and determination of SMZ in the poultry feed samples.
In this study, we present a general method to prepare the core–shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs) for sulfamethazine (SMZ). The resulting Fe3O4@MIPs NPs possess a highly improved imprinting effect, fast adsorption kinetics and high adsorption capacity, and can be applied to extract sulfonamide in the poultry feed. In this protocol, the magnetite NPs were synthesized by co-precipitating Fe2+ and Fe3+ in an ammonia solution first. Silica was then coated on the Fe3O4 NPs using a sol–gel method to obtain silica shell magnetic NPs. Subsequently, the vinyl groups were grated onto silica-modified Fe3O4 surface by 3-methacryloyloxypropyltrimethoxysilane. Finally, the MIPs films were formed on the surface of Fe3O4@SiO2 by the copolymerization of vinyl end groups with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule, sulfamethazine. The morphology, magnetic, adsorption and recognition properties of Fe3O4@MIPs NPs were characterized using transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometer, vibrating sample magnetometer (VSM) and re-binding experiments. The results showed that the binding sites of Fe3O4@MIPs were good accessibility, fast adsorption rate and the maximum adsorption capacity of Fe3O4@MIPs to SMZ was 344.8μgg−1. The selectivity of the obtained Fe3O4@MIPs NPs were elucidated by the different rebinding capability of SMZ and structural related sulfonamides in the mixed solution. The results indicated that the Fe3O4@MIPs had high imprinting factor 9.5 and significant selectivity. A method was developed for enrichment and determination of SMZ in the poultry feed samples with recoveries of duck and chicken feed ranging from 63.3 to 76.5% and 68.7 to 74.7%, respectively and the relative standard deviations (RSD) (<6.7%).
•A functionalized magnetic covalent organic framework (Fe3O4@COF-(NO2)2) was fabricated.•Fe3O4@COF-(NO2)2 showed excellent extraction efficiency for neonicotinoids.•The MSPE-HPLC exhibited a wide ...linear range, low LODs, and high enrichment factor.•A sensitive MSPE-HPLC method for monitoring trace insecticides residue in vegetable samples.
A functionalized magnetic covalent organic framework containing the nitro groups (Fe3O4@COF-(NO2)2) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe3O4@COF-(NO2)2 was investigated by various characterization techniques. The Fe3O4@COF-(NO2)2 exhibits the excellent thermal and chemical stability, high surface area (254.72 m2 g−1), total pore volume (0.19 cm3 g−1), high magnetic responsivity (27.7 emu g−1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe3O4@COF-(NO2)2-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1–30 ng mL−1, low limits of detection (S/N = 3) of 0.02–0.05 ng mL−1. Furthermore, high enrichment factors of 170–250 for six neonicotinoid insecticides were obtained. The applicability of Fe3O4@COF-(NO2)2 is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2%. The results indicated that the Fe3O4@COF-(NO2)2 microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples.
The molecularly imprinted polymer based on polypyrrole film with incorporated graphene oxide was fabricated and used for electrochemical determination of quercetin. The electrochemical behavior of ...quercetin on the modified electrode was studied in detail using differential pulse voltammetry. The oxidation peak current of quercetin in B-R buffer solution (pH = 3.5) at the modified electrode was regressed with the concentration in the range from 6.0 × 10(-7) to 1.5 × 10(-5) mol/L (r2 = 0.997) with a detection limit of 4.8 × 10(-8) mol/L (S/N = 3). This electrode showed good stability and reproducibility. In the above mentioned range, rutin or morin which has similar structures and at the same concentration as quercetin did not interfere with the determination of quercetin. The applicability of the method for complex matrix analysis was also evaluated.
In this study, we synthesized Fe
3O
4 magnetic nanoparticles coated estrone-imprinted polymer with controlled size using a semi-covalent imprinting strategy. In this protocol, the estrone–silica ...monomer complex (EstSi) was synthesized by the reaction 3-(triethoxysilyl)propyl isocyanate with estrone, where the template was linked to the silica coating on the iron oxide core
via a thermally reversible bond. The removal of the template by a simple thermal reaction produced specific estrone recognition sites on the surface of silica shell.The resulting estrone-imprinted polymer coating Fe
3O
4 magnetic hybrid nanoparticles exhibit a much higher specific recognition and saturation magnetization. The hybrid nanoparticles have been used for biochemical separation of estrone.
Electroosmosis has been proposed as a technique to reduce moisture and thus increase the stability of soft clay. However, its high energy consumption and uneven reinforcement effect has limited its ...popularization and application in practical engineering. This paper presents the results of some electrokinetic tests performed on clayey specimens with different electrification time and anode boundary conditions. The results indicate that the timing of the formation of electroosmotic flow (EF) by the water originally contained in different soil cross sections, from the anode to the cathode, varies. The measuring soil cross section nearest the anode first reached the limiting water content of 22%±3% and electroosmosis had to be stopped. Water injection into the anode during electroosmosis enhanced further drainage of other four measuring soil cross sections until the second soil cross section from the anode reached the limiting water content of 30%±2%. Electroosmosis with water injection into the anode technique provides more uniform reinforcement, increasing EF, and environmental protection. The experimental results highlighted the relevant and expected contribution of water injection into the anode on the effectiveness of the electroosmotic treatment as a soft clay improvement technique.
Silicon-based optoelectronics (SBO), combining the advantages of both microelectronics and optoelectronics, has entered a period of rapid development. Applications based on SBO have expanded from ...traditional communication field to other fields such as sensing, computing, and artificial intelligence. Although the SBO technology started relatively late in China, it has developed rapidly in recent years due to continuous investment and improved industrial structure. This article first reviews the early activities, and then, summarizes the current status of SBO in China. It provides a comprehensive analysis of academic and industrial advancements in recent years and discusses future development directions and main challenges.
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•CeO2–OMC composites were prepared via a hydrothermal method.•CeO2–OMC had electrocatalytic ability to oxidation of hydrazine.•The sensor had high sensitivity, excellent stability and ...reproducibility.•The sensor was successfully employed to detect hydrazine in real water samples.
A novel ceria (CeO2)–ordered mesoporous carbon (OMC) modified electrode for the sensitive amperometric determination of hydrazine was reported. CeO2–OMC composites were synthesized via a hydrothermal method at a relatively low temperature (180°C) and characterized by scanning electron microscopy (SEM), transmission electron microcopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The CeO2–OMC modified glassy carbon electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and indicated good electrocatalytic effect to the oxidation of hydrazine. Under the optimized conditions, the present sensor could be used to measure hydrazine in wide linear range from 40nM to 192μM (R2=0.999) with a low detection limit of 12nM (S/N=3). Additionally, the sensor has been successfully applied to detect hydrazine in real water samples and the recoveries were between 98.2% and 105.6%. Eventually, the sensor exhibited an excellent stability and reproducibility as a promising method for determination of hydrazine.
The oxygen evolution reaction (OER) is the efficiency-determining half-reaction process of high-demand, electricity-driven water splitting due to its sluggish four-electron transfer reaction. ...Tremendous effects on developing OER catalysts with high activity and strong acid-tolerance at high oxidation potentials have been made for proton-conducting polymer electrolyte membrane water electrolysis (PEMWE), which is one of the most promising future hydrogen-fuel-generating technologies. This review presents recent progress in understanding OER mechanisms in PEMWE, including the adsorbate evolution mechanism (AEM) and the lattice-oxygen-mediated mechanism (LOM). We further summarize the latest strategies to improve catalytic performance, such as surface/interface modification, catalytic site coordination construction, and electronic structure regulation of catalytic centers. Finally, challenges and prospective solutions for improving OER performance are proposed.
► An alternative method was developed for the synthesis of a macroporous boronate affinity monolithic column in a convenient way using MOG as a porogenic template. ► The monolithic column had the ...advantage of good macropore distribution and permeability for further high-throughput and efficient separations of glycoproteins. ► A one-step purification of transferrin from bovine serum sample was of success.
A macroporous boronate affinity monolithic column was prepared and applied to specifically capture glycoproteins using metal-organic gels (MOGs) as a porogenic template. This newly explored application of MOGs has proven to be a more convenient method for the formation of macropores in contrast to traditional porogenic methods. The poly (3-acrylamidophenylboronic acid-co-ethylene dimethacrylate) monolithic columns were synthesized in stainless columns by
in situ polymerization. To fabricate the macroporous formation with a uniformed open-channel network, the preparation conditions, such as reaction temperature, the concentration of the MOGs and the ratio of monomers were systematically investigated. The prepared macroporous monoliths were characterized by scanning electron microscope (SEM) and mercury intrusion porosimetry. Furthermore, horseradish peroxidase (HRP) and transferrin (TF) were chosen as test glycoproteins, and the chromatographic analysis demonstrated that the macroporous boronate affinity monoliths exhibited a higher selectivity and better dynamic binding capacity toward glycoproteins compared with non-glycoproteins. The resulted affinity monolithic column was successfully employed to specifically capture TF from a bovine serum sample.
A novel solid phase extraction (SPE) method for determination of tetracyclines (TCs) in milk and honey samples by molecularly imprinted monolithic column was developed. Using tetracycline (TC) as the ...template, methacrylic acid (MAA) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, methanol as the solvent, cyclohexanol and dodecanol as the mixed porogenic solvents, a TC imprinted monolithic column was prepared by in situ molecular imprinting technique for the first time, and the optimal synthesis conditions and the selectivity of TC imprinted monolithic column were investigated. The interfering substances in food samples and TCs can be separated successfully on imprinted column. Molecularly imprinted solid phase extraction (MISPE) coupling with C18 column was used to determinate the TCs in milk and honey. The recoveries of this method for six tetracyclines antibiotics such as tetracycline (TC), oxytetracycline (OTC), minocycline (MINO), chlortetracycline (CTC), metacycline (MTC) and doxycycline (DTC) were investigated, and high recoveries of 73.3–90.6% from milk samples and 62.6–82.3% from honey samples were obtained. A method for determination of TCs at low concentration level in milk and honey samples was successfully developed by using the monolithic column as the precolumn for solid phase extraction of six TCs compounds.
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