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Synthesis and identification of Zn(BTC)-(MOF) as a metal–organic framework for its application in the impedimetric determination of thyroxine hormone in human blood samples

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Abstract

This study discusses the determination of thyroxine hormone in blood serum samples by a novel MOF composite electrode. The used MOF was Zn(BTC)-(MOF) which was constructed from 1,3,5-benzenetricarboxylic acid ligand (BTC) and zinc ions in DMF solvent. Using cysteine as the linker, the MOF was plated on the surface of a gold electrode, formerly covered by a layer of gold nanoparticles immersed in conductive polymer polypyrrole (PPy). Different analytical methods, such as FTIR, XRD, SEM, EIS, CV, and BET, were utilized to investigate the morphology and performance of the prepared materials. The modified electrode exhibited excellent electrocatalytic ability to reduce thyroxine without interference from common coexisting substances such as different salts. The fabricated electrode has been successfully used to determine thyroxine in a linear concentration range of 10–210 nM with a detection limit of 8 nM.

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A metal organic framework with a unique form was prepared using the conventional microwave and changing the ratio between metal (zinc) and ligand (1,3,5 tricarboxylic acid). The powder X-ray diffraction (PXRD) shows that the increase of metal content in the synthesis give materials more crystallinity as seen in the scanning electron microscope (SEM). Moreover, by SEM the ratio 1:4 (ligand:metal) exhibited a unique cauliflower like sctruture with average size of 16.9 4.7 µm.
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A novel and task-specific nano-magnetic Schiff base ligand with phosphate spacer using 2-aminoethyl dihydrogen phosphate instead of usual coating agents, i.e. tetraethoxysilane and 3-aminopropyltriethoxysilane, for coating of nano-magnetic Fe3O4 is introduced. The nano-magnetic Schiff base ligand with phosphate spacer as a novel catalyst was synthesized and fully characterized using infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopies, thermogravimetry, derivative thermogravimetry, vibrating sample magnetometry, atomic force microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The resulting task-specific nano-magnetic Schiff base ligand with phosphate spacer was successfully employed as a magnetite Pd nanoparticle-supported catalyst for Sonogashira and Mizoroki-Heck C-C coupling reactions. To the best of our knowledge, this is the first report of the synthesis and applications of magnetic nanoparticles of Fe3O4@O2PO2(CH2)2NH2 as a suitable spacer for the preparation of a designable Schiff base ligand and its corresponding Pd complex. So the present work can open up a new and promising insight in the course of rational design, synthesis and applications of various task-specific magnetic nanoparticle complexes.
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Four metal–organic framework (MOF) materials were synthesized via the newly prepared copper or zinc hydroxides with two different organic ligands under ultrasonic conditions at room temperature. The products were characterized by powder X-ray diffraction patterning, scanning electron microscopy, thermal gravimetric analysis and nitrogen adsorption–desorption. The successful synthesis of the MOFs herein highlights the possibilities of producing other MOFs conveniently and efficiently via this method. In addition, the MOFs were used as the adsorbents to remove DBT from liquid fuel after activation, which showing comparable desulfurization performance with conventional MOFs gained via batch solvothermal or hydrothermal method. This means well applying potential of the facile synthesized MOFs.
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Six different synthetic methods (solvothermal, microwave-assisted, atmospheric pressure and reflux, ultrasonic and mechanochemical conditions) for the metal–organic framework [Cu3(btc)2(H2O)3] (btc = benzene-1,3,5-tricarboxylate) were compared. The advantages and disadvantages of the various synthetic methods were discussed including the influence of different solvents and reaction conditions on product formation, microporosity and crystallisation. Therefore, pressure and temperature for the solvothermal synthesis (autoclave and microwave) were monitored during the reaction. The characterization of the samples was performed by X-ray powder diffraction, scanning electron microscopy, infrared-spectroscopy, thermogravimetric analysis and specific surface determination using the BET method. The experimental results show that microwave-assisted solvothermal synthesis is the best method to produce crystalline [Cu3(btc)2(H2O)3] in a short time associated with high purity, high specific pore volume (0.79 cm3/g) and quantitative yield. Noteworthy, the solvent-assisted mechanochemical approach gave a comparable specific pore volume of 0.74 cm3/g. Furthermore, synthesis conditions were explored which enable to control the product formation of either [Cu3(btc)2(H2O)3] or [Cu2(btc)(OH)(H2O)]. Finally, it is shown that water stability of [Cu3(btc)2(H2O)3] at higher temperatures is low, if the adsorbed and coordinated water is not removed rapidly upon heating.
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A supramolecular metal–organic framework (MOF) constructed by two-dimensional (2D) infinite coordination polymers, [Zn(BDC)(H2O)]n (1, BDC=1,4-benzenedicarboxylate), was synthesized by the reaction of zinc acetate with H2BDC in dimethylformamide (DMF) under ultrasonic irradiation at ambient temperature and atmospheric pressure. Yield of 1 varied from 43.4% to 53.2% for the reaction time of 10–90min. Samples with different morphologies, i.e. nanobelts, nanosheets, and microcrystals, were obtained under ultrasound irradiation for different reaction times. Fluorescence emission of nanosheets of [Zn(BDC)(H2O)]n was found to be highly sensitive to ethylamine, and solid state fluorescence intensity decreased with increasing contents of ethylamine in acetonitrile solution due to weak fluorescence quenching effect.
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A rapid, accurate, and sensitive method has been developed for the quantitative determination of iodoamino acids, namely thyroxine (3,5,3′,5′-tetra-iodothyronine, (T4) and 3,5,3′-tri-iodothyronine (T3). These compounds are essential indicators in the clinical diagnosis of thyroid gland diseases.An Inertsil ODS-3, 150 × 4.0 mm, 5 μm analytical column was used with a mixture of CH3OH-H2O with 2% acetic acid, at a volume ratio 65:35, with a flow rate 1 mL/min. Detection was performed with a variable wavelength UV-visible detector at 240 nm, resulting in detection limits of 1 ng and 2 ng for T3 and T4, respectively, per 20 μL injection.For the quantitative determination, anthraquinone was used as internal standard at a concentration of 1.0 ng/μL. A rectilinear relationship was observed up to 28 and 40 ng/μL for T3 and T4, respectively.Analysis time was approximately 10 min (retention time of internal standard) while the two compounds are eluted within 5 min. The statistical evaluation of the method was examined, performing intra-day (n = 8) and inter-day calibration (n = 8) and was found to be satisfactory with high accuracy and precision results.The method was applied to the analysis of the iodothyronines in biological fluids, blood serum and urine, after solid phase extraction for sample clean-up and analyte retention, using diol cartridges. Percentage recovery of iodothyronines in spiked samples ranged from 79.90 to 103.15 for T3 and from 83.65 to 106.15 for T4, over the range of 0.5–3 ng/μL.No interferences were observed from endogenous compounds of human serum and urine.
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Differential pulse polarograms of thyroxine and of triiodothyronine recorded from 0.1 M sodium carbonate exhibit a well-defined peak at —1.060 and —1.050 V vs.Ag/AgCl, respectively, and the peak current is proportional to the concentration in the range 10-6—5 × 10-5 M. A simple and rapid method is proposed for the determination of the drugs in tablets. The procedure does not involve time-consuming extractions or decomposition of organic matter, and it is suitable for control of content uniformity in pharmaceutical formulations.
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The reduction of thyroxine (T//4), liothyronine, diiodothyronine, diiodotyrosine, and monoiodotyrosine has been studied at silver rotating disk electrodes in 0. 10 M NaOH. All compounds give one reduction wave; the potential for the reduction of T//4 on silver is about one-half volt more positive than on mercury, where it reduces stepwise. The reduction is shown to be convective diffusion controlled at the rotating silver disk electrode. Potential step and coulometric experiments are employed to show that, in the case of T//4, the reduction is an eight-electron process which results in cleavage of four iodine atoms from the T//4 molecule. Detection limits for these compounds are reported.
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A chemiluminescence (CL) flow system for determination of thyroxine (Thy) is presented. It is based on the catalytic effect of cobalt(II) on the CL reaction between luminol and hydrogen peroxide. The iodinated chemical structure of Thy causes a heavy atom effect. The luminol CL signals show significant quenching by Thy. The calibration graph for Thy is linear for 15–70 μg ml−1 and the 3σ detection limits are 27 μg ml−1 for d-Thy and 23 μg ml−1 for l-Thy.
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In this work, isolated fine silver nanoparticles and polypyrrole/silver nanocomposites with diameters of about 10 nm on gold substrates were first prepared by electrochemical methods. First, an Ag substrate was cycled in a deoxygenated aqueous solution containing 0.1 M HCl from −0.30 to +0.30 V versus Ag/AgCl at 5 mV/s with 30 scans. Subsequently the Ag working electrode was immediately replaced by an Au electrode and a cathodic overpotential of 0.2 V was applied under controlled sonication to synthesize Ag nanoparticles on the Au electrode. Then pyrrole monomers were encouragingly found to be polymerized on the deposited Ag nanoparticles. This polymerization is distinguishable from the known chemical or electrochemical one, due to the electrochemical activity of unreduced species of Agn+ clusters inside the nanoparticles. Also, this polymerization may be ascribed to the oxidizing agent of AuCl4−, which is present on the Au electrode.
Article
Highly active polypyrrole electrodes for redox supercapacitors were prepared by electrodeposition on Ti foil via cyclic voltammetry at a scan rate of 200 mV/s in oxalic acid solution and subsequently characterized in 1 M KCl. Scanning electron microscopy showed that the polypyrrole has a highly porous nanostructure leading to a very high specific capacitance of about 480 ± 50 F/g. The electrode exhibted a high stability during cycle life test. The effects of the mass of polypyrrole electrode materials on the specific capacitance were also investigated.
Article
The use of biological data to complement chemical analysis and the development of biosensors and other biological approaches have grown steadily in recent years.Biomonitoring is an essential tool for the complete implementation of new European Union Directives (e.g., the Water Framework Directive and the related Marine Strategy Framework Directive). In addition, the unique properties of nanoscale materials offer excellent prospects for interfacing biological recognition events with electronic signal transduction and for designing a new generation of bioelectronic devices exhibiting novel functions.Recent technological developments in miniaturizing electronics and wireless-communication technology have led to the emergence of environmental sensor networks, which will greatly enhance monitoring of the natural environment and, in some cases, open up new techniques for taking measurements or allow previously impossible deployments of sensors.This article reviews the principles, the advantages and the limitations of biosensors for screening and diagnosis of organic compounds in the environment with special emphasis in those based on nanomaterials. It also reviews new technologies for remote biosensing.
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We present for the first time, to the best of authors’ knowledge, surface acoustic wave (SAW) gas sensors featuring polypyrrole nanofibers as the active component for hydrogen (H2) and nitrogen dioxide (NO2) detection at room temperature. Polypyrrole nanofibers were synthesized through a template-free chemical route by introducing bipyrrole as an initiator to speed up the polymerization of pyrrole in the presence of iron (III) chloride (FeCl3) as the oxidizing agent. Polypyrrole nanofibers were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopic (FT-IR) techniques which indicated that the average diameter of the nanofibers was 18 nm with lengths in the order of several microns. The polypyrrole nanofibers were dispersed onto the surface of a ZnO/36°YX LiTaO3 SAW transducer. Gas testing towards H2 and NO2 was conducted in an enclosed environmental cell at room temperature. Measured frequency shifts due to sensor responses were 20 kHz towards 1% of H2 and 4.5 kHz towards 2.1 ppm NO2, respectively. The sensor performance was assessed during a five-day period and repeatable results were obtained.