Application of Pneumatic Flow Injection-Tandem Spectrometer System for Chromium Speciation

In this approach, a pneumatic flow injection-tandem spectrometer system, without a delivery pump, has been developed to study chromium speciation. In this system, suction force of pneumatic nebulizer of a flame atomic absorption spectrometer has been used for solution delivery through the manifold. Cr(VI) and total Cr concentrations were determined using UV-Vis and FAAS spectrometers, respectively. The Cr(III) was determined by difference. The calibration curves were linear up to 10 μg mL−1 and 20 μg mL−1 for Cr(VI) and total Cr with detection limit of 0.12 μg mL−1 and 0.07 μg mL−1 for Cr(VI) and Cr(III), respectively. The midrange precision and accuracy are less than 1.98% and ± 2.50% for two species, respectively, at a sampling rate of 100 h−1. This system was applied for the determination of the chromium species in spiked and natural waters as well as industrial waters

A simple strategy to increase inhibitory activity of chitosan towards iron corrosion in acidic media

The chitosan as a natural and inexpensive polymer is considered as an appropriate choice towards the corrosion inhibitory. Here, the corrosion and inhibition efficacy of iron sheets is examined in the H2SO4 solution and the presence of chitosan and potassium iodide as an inhibitor through gravimetry, potentiodynamic polarization, and impedance analyses. The inhibition performance is found to be enhanced by adding chitosan concentration. The experimental data demonstrate that the doping iodide ion to chitosan is efficient on the surface coverage and the inhibition performance. The introduced inhibitors are of the interface inhibitors → liquid phase → mixed type with the physical adsorption. The adsorption of iodized chitosan on the iron surface is followed Langmuir isotherm. These inhibitors, by changing the electrical double layer, increase the resistance of charge transfer. The existence of iodide in the chitosan structure improves the electron density of polymer and strengthens the interaction between inhibitor and metal

A simple strategy to increase inhibitory activity of chitosan towards iron corrosion in acidic media

227-234The chitosan as a natural and inexpensive polymer is considered as an appropriate choice towards the corrosion inhibitory. Here, the corrosion and inhibition efficacy of iron sheets is examined in the H2SO4 solution and the presence of chitosan and potassium iodide as an inhibitor through gravimetry, potentiodynamic polarization, and impedance analyses. The inhibition performance is found to be enhanced by adding chitosan concentration. The experimental data demonstrate that the doping iodide ion to chitosan is efficient on the surface coverage and the inhibition performance. The introduced inhibitors are of the interface inhibitors → liquid phase → mixed type with the physical adsorption. The adsorption of iodized chitosan on the iron surface is followed Langmuir isotherm. These inhibitors, by changing the electrical double layer, increase the resistance of charge transfer. The existence of iodide in the chitosan structure improves the electron density of polymer and strengthens the interaction between inhibitor and metal

The Effects of Fe2O4Zn Nanoparticles on Thyroid Hormones and Evaluation of Changes Tissue Thyroid in Male Rat

Background &amp; Objectives: Despite the numerous potential applications of nanoparticles in different sciences due to their unique properties, their adverse effects on human health have not been fully studied. The aim of this study was to evaluate the effects of Fe2O4Zn nanoparticle on thyroid and thyroid hormones in male rats. Materials &amp; Methods: Male Wistar rats were randomly divided into three groups: Control rats received 0.5 ml saline for 7 consecutive days. Group 1 and 2 rats received 0.5 ml of Fe2O4Zn nanoparticle solution at doses of 100 and 200 ppm, respectively. Injections were carried out intraperitoneally. Serum biochemical parameters were evaluated in rats, after 2, 7 and 14 days of beginning the experiment. On the 14th days, thyroid tissue was removed and used for histological assessment. Results: Administration of Fe2O4Zn nanoparticle in concentrations of 100 ppm and 200 ppm significantly decreased TSH levels compared with that of control samples (P0.05). Fe2O4Zn nanoparticle treatments significantly increased serum levels of T4 (P<0.05). Nanoparticle treatments in view of textural properties showed severe blood, mild inflammation and larger follicle size and, by increasing the concentration of the nanoparticles, these effects were observed more severe. Conclusion: Due to the variations observed in the levels of thyroid hormones and the histological changes of thyroid tissue, it can be concluded that Fe2O4Zn nanoparticle had toxic effects on thyroid function. More studies to investigate the toxic effects of nanoparticles in different doses and different times of exposure to Fe2O4Zn nanoparticles seem to be necessary

Presentation of anodic electrocatalyst for polymeric fuel cell: Pt nanoparticles immobilized on NdFeO3 nanocrystals and carbon nanotubes

9-22Current catalysts for the methanol oxidation in fuel cells (typically noble metals-based) are susceptible to poisoning with intermediates like CO. Hence superseded catalysts have been desirable for methanol oxidation based on incorporation of mixed oxides. The different types of nanocomposites have been prepared with Pt nanoparticles (PtNPs), functionalized CNTs, perovskite NdFeO3 nanoparticles (NdFeO3NPs) and chitosan (CH) polymer and their catalytic activity toward methanol oxidation have been investigated by the electrochemical studies. The equations of current density versus time are obtained via the fitting and simulation of experimental data. In the following, the amount of transferred charge during methanol oxidation versus time has been calculated through the lower Riemann sum of curve correspond to experimental data and the integration of mentioned equations both. A direct methanol fuel cell (DMFC) is designed, assembled and tested with the suggested PtNPs-CNTs-NdFeO3NPs-CH nanocomposites as an anodic catalyst at variety conditions. The effect of experimental factors on DMFC performances has been investigated and optimized

Au Nanoparticles on 4-Thiophenol-Electrodeposited Carbon Surfaces for the Simultaneous Detection of 8-Hydroxyguanine and Guanine

In this proof-of-concept study, gold nanoparticles (AuNPs) were immobilized on glassy carbon electrode (GCE) surfaces using a surface-anchored diazonium salt of 4-aminothiophenol (GCE-Ph-S-AuNPs). X-ray photoelectron spectroscopy (XPS) studies confirmed the attachment of the AuNPs via 4-thiophenol onto the surface of the modified electrode. Differential pulse voltammetry (DPV) was performed for the simultaneous determination of guanine (G) and 8-hydroxyguanine (8-OH-G). The calibration curves were linear up to 140 µM and 60 µM with a limit of detection of 0.02 µM and 0.021 µM for G and 8-OH-G, respectively. Moreover, chronoamperometric studies were carried out for the determination of diffusion coefficients of 8-OH-G and G. The GCE-Ph-S-AuNPs were also applied in genomic DNA-spiked samples for the determination of G and 8-OH-G with recovery rates between 98.5% and 103.3%. The novel electrochemical surface provided a potential platform for the sensitive detection of 8-OH-G related to oxidative stress-induced DNA damage in clinical studies

Hybrid Nanomaterial of Graphene Oxide Quantum Dots with Multi-Walled Carbon Nanotubes for Simultaneous Voltammetric Determination of Four DNA Bases

In this proof-of-concept study, a novel hybrid nanomaterial-based electrochemical sensor was developed for the simultaneous detection of four DNA bases. For the modification of the working electrode surface, graphene oxide quantum dots (GOQDs) were synthesized using a solvothermal method. GOQDs were then used for the preparation of a hybrid nanomaterial with multi-walled carbon nanotubes (GOQD-MWCNT) using a solvothermal technique for the first time. Transmission electron microscopy (TEM) was used to characterize the GOQDs-MWCNTs. A glassy carbon electrode (GCE) was modified with the GOQDs-MWCNTs using Nafion™ to prepare a GOQD-MWCNT/GCE for the simultaneous determination of four DNA bases in phosphate buffer solution (PBS, pH 7.0) using differential pulse voltammetry (DPV). The calibration plots were linear up to 50, 50, 500, and 500 µM with a limit of detection at 0.44, 0.2, 1.6, and 5.6 µM for guanine (G), adenine (A), thymine (T) and cytosine (C), respectively. The hybrid-modified sensor was used for the determination of G, A, T, and C spiked in the artificial saliva samples with the recovery values ranging from 95.9 to 106.8%. This novel hybrid-modified electrochemical sensor provides a promising platform for the future development of a device for cost-effective and efficient simultaneous detection of DNA bases in real biological and environmental samples

Nanocomposite of Ellagic Acid with Multi-Walled Carbon Nanotubes for the Simultaneous Voltammetric Detection of Six Biomolecules

In this proof-of-concept study, a highly sensitive electrochemical sensor using a graphite paste electrode modified with ellagic acid and multi-walled carbon nanotubes (MGPE/MWCNTs-EA) was developed for the simultaneous determination of six biomolecules: ascorbic acid (AA), dopamine (DA), uric acid (UA), tryptophan (Trp), xanthine (XA), and caffeine (CA). Differential pulse voltammetry (DPV) was performed at a potential range from 0.1–1.2 V vs. Ag/AgCl in phosphate electrolyte (pH 2.0). The modified GPE enabled the simultaneous determination of biomolecules under investigation in human urine and blood serum samples with detection limits ranging from 11–91 nM with recoveries of 94.0–106.0%. The electrochemical performance of the modified GPE for the analytes was stable and reproducible and checked with standard high performance liquid chromatography technique. The data suggested that the modified GPE provided a promising platform for routine quantitative determination of the biomolecules under investigation in quality control studies of real samples collected from food and pharmaceutical products

Electrografting a Hybrid Bilayer Membrane via Diazonium Chemistry for Electrochemical Impedance Spectroscopy of Amyloid-&beta; Aggregation

Herein, a novel hybrid bilayer membrane is introduced as a platform to study the aggregation of amyloid-&beta;1&ndash;42 (A&beta;1&ndash;42) peptide on surfaces. The first layer was covalently attached to a glassy carbon electrode (GCE) via diazonium electrodeposition, which provided a highly stable template for the hybrid bilayer formation. To prepare the long-chain hybrid bilayer membrane (lcHBLM)-modified electrodes, GCE surfaces were modified with 4-dodecylbenzenediazonium (DDAN) followed by the modification with dihexadecyl phosphate (DHP) as the second layer. For the preparation of short-chain hybrid bilayer membrane (scHBLM)-modified electrodes, GCE surfaces were modified with 4-ethyldiazonium (EDAN) as the first layer and bis(2-ethylhexyl) phosphate (BEHP) was utilized as the second layer. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to characterize the bilayer formation. Both positively charged [Ru(NH3)6]3+ and negatively charged ([Fe(CN)6]3-/4-) redox probes were used for electrochemical characterization of the modified surfaces using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). EIS results showed a decrease in charge transfer resistance (Rct) upon incubation of A&beta;1&ndash;42 on the hybrid bilayer-modified surfaces. This framework provides a promising electrochemical platform for designing hybrid bilayers with various physicochemical properties to study the interaction of membrane-bound receptors and biomolecules on surfaces