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The C3-symmetry ionic polymer PPyTri has been designed with multi-walled carbon nanotubes (MWCNTs) or graphene nanoplatelets (GNPs) and studied as an ultrasensitive electrochemical sensor for trace Hg(II) detection. The synthesis approach incorporated attaching three pyridinium cationic components with chloride anions to the triazine core. The precursors, BPy, were synthesized using a condensation process involving 4-pyridine carboxaldehyde and focused nicotinic hydrazide. The polymer PPyTri was further modified with either MWCNTs or GNPs. The resulting ionic polymer PPyTri and its fabricated nanocomposites were characterized using infrared (IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and powder X-ray diffraction (XRD). The analysis revealed that both the polymer and its nanocomposites have semi-crystalline structures. The electroactivity of the designed nanocomposites toward Hg + 2 ions revealed that among the nanocomposites and bare copolymer, the glassy carbon electrode (GCE) adapted with the PPyTri GNPs-5% exhibited the greatest current response over a wide range of Hg + 2 concentrations. The nanocomposite-modified electrode presented an excellent sensitivity of 83.33 µAµM − 1 cm − 2, a low detection limit of 0.033 nM, and a linear dynamic range of 0.1 nM to 0.01 mM (R2 = 0.9945). [ABSTRACT FROM AUTHOR]

Dietary supplements are drastically growing as a category of consumer products all over the world. The abuse of supplements marketed for slimming purposes and physical fitness has been observed worldwide in recent years, which raises concerns in terms of public health. In this study, different types of dietary supplements marketed and delivered through the e-commerce were studied for the determination of thallium as a hazardous inorganic contaminant. The total content of thallium was determined by a sensitive voltammetric method after a microwave-assisted oxidative digestion of the sample. In addition, a comparative spectrometric method was applied for validation of the results in the samples. The maximum concentration found for thallium was found to be 2.89 mg kg−1, which well agree with the comparative measurement. Considering the 32 studied formulations, it can be pointed out that ∼24% of the of dietary supplements presented Tl concentrations at concentrations higher than 1 mg kg−1. The results permitted the assessment of the health risk related to thallium from contaminated samples, based on the calculation of the estimated daily intake (EDI) and the risk quotient (HQ). The highest daily intake of thallium was calculated as 82.0 µg day−1 in a protein-based supplement, which is equivalent to an EDI of 1.17 µg kg−1 day−1. This work highlights the need to develop regulations on the limits of toxic elements such as thallium in widely consumed dietary supplements, as well as an in-depth look at the adverse effects caused by this element in the human body. [ABSTRACT FROM AUTHOR]

In order to prepare fiber-type nanohybrid composites for electrochemical and antimicrobial applications, polypyrrole was combined with carboxymethylcellulose and multiwalled carbon nanotubes (PPy/CMC/MWCNTS). These composite materials were synthesized using ultrasonication and in situ polymerization. By using analytical methods, the structure and morphology of the synthesized nanohybrid composite material were confirmed. Slurry of fiber-type PPY/CMC/MWCNT composites synthesized in ethanol was deposited as a thin-uniform layer with conductive nafion (5% ethanolic solution of nafion) binder. Based on electrochemical measurements in a phosphate buffer medium, Sb3+ ions have linear responses between 0.1 nM and 0.01 mM, which is known as linear dynamic range (LDR). A sensor's sensitivity (22.4304 µAµM−1cm−2) is calculated using the LDR slope by considering the GCE surface area (0.0316 cm2). A signal-to-noise ratio of 3 is used to estimate the lower limit of detection which is equal to 96.82 ± 4.84 pM. Moreover, the antibacterial activity of the obtained polypyrrole/carboxymethylcellulose/MWCNT composite has also been evaluated "against Gram-positive bacteria B. subtilis along with S. aureus, as well as Gram-negative bacteria, P. aeruginosa along with Escherichia coli by utilizing" autoclave of agar media. In electrochemical analysis, the proposed Sb3+ cationic sensor exhibits appreciable reproducibility, response time, stability, and outstanding outcome in analysis of real samples. In the field of metal ion sensor, this reliable method might be prospective in the recent future. [ABSTRACT FROM AUTHOR]

An applied electrochemical method in the form of a chronocoulometry technique is proposed for measuring Fick's diffusion constant of a thin protective coating layer over the conductive base materials. Using this method, the capacitance is monitored for a capacitor formed using the base material, an electrolyte such as aqueous NaCl, and an insulating coating layer in between. The capacitance increases when the distance between the base material and the electrolyte decreases in the diffusion of the electrolyte through the insulating coating layer. Therefore, the change in the capacitance provides a diffusion rate related to Fick's diffusion constant. Conventional gravimetric methods require a long measurement time to reach saturation, and thin coating layers of minimal weight increment through water diffusion were demonstrated to be inadequate for the methods. However, the new electrochemical method is appropriate for thin coating layers and requires a limited duration after the onset of diffusion. Experimental for 1-mm thick PA6 films provided Fick's diffusion constants of safer side with the new method of 15h by reflecting the heterogeneous properties of the surface, while the conventional gravimetric method in 360h provided smaller or danger-side values. [ABSTRACT FROM AUTHOR]

In Sri Lanka wastewater originated from prawn-farms contain an excessive amount of nitrate that is becoming a crucial issue on human health and environment. Currently, there are no proper practices to treat the wastewater. This study was aimed to develop an electrochemical method to remove nitrate from the wastewater and to investigate the effect of pH, retention time (RT), current, and surface area (SA) of the electrodes using Taguchi method. The maximum removal efficiency of nitrate (72%) by using copper cathode was obtained and the removal efficiency rates with copper cathode were higher than that with carbon and aluminum cathode. [ABSTRACT FROM AUTHOR]

Carbon-based quantum dots, zero-dimensional carbon nanomaterials that can be widely used with a particle size of 1-10nm, can be widely used in fluorescent carbon nanomaterials in thousands of households. This article will first elaborate on carbon-based quantum dots and metal nanomaterials and explain the related methods of making them. First, the top-down method is used to prepare carbon quantum dots, the fluorescence mechanism of carbon-based quantum dots is used, and the electrochemical method is used at high temperature. Carbonization burning method and laser ablation method, the mixture of graphite powder and polyethylene glycol ester is hot pressed, baked, and cut in an argon atmosphere to obtain strong fluorescent carbon-based quantum dots, and then explain the immune algorithm to prepare nanocomposites for cermet mold materials, use the diversity of antibodies to calculate the concentration and quantity, and calculate its viability. Through regression coefficients, it can be shown that the immune algorithm is used to optimize the component optimization design of Ti(C,N)-based nanocomposite cermet mold materials. The effect is better. [ABSTRACT FROM AUTHOR]

Exosomes, small vesicles with the diameters of 40–160 nm, play an important role in intercellular transport and communication. Exosomes are rich in many kinds of biomolecules, and differential expression of exosomal contents directly reflects the state of the original cells. Therefore, the tumor exosomes are appearing as promising biomarkers in liquid biopsy, and highly sensitive and specific detection of tumor exosomes may provide the information for the early diagnosis, real-time monitoring and treatment of the tumors. In this review, we summarized the recent advances in the detection of tumor exosomes, mainly focusing on the use of different analytical techniques, such as optical and electrochemical methods as well as that combination with newly-emerging microfluidic techniques, thereby providing valuable information for the application in the clinical diagnosis and management of the tumors. [ABSTRACT FROM AUTHOR]

In this study, nano-size MgO was synthesized from seawater and bittern obtained from local salt industry in Pamekasan, Madura, Indonesia, using electrochemical method. The main purpose was to study the effects of seawater pre-concentration and bittern dilution on the structure and morphology of the MgO nanoparticles produced. Electrochemical process was performed in a two-compartment electrochemical cell with a fixed potential of 18 V, for 4 h at ambient temperature, and without adjusting the pH. Solid Mg(OH)2 produced was converted into MgO by calcination treatment at 500 °C for 4 h, and then characterized using XRD and SEM technique. The characterization results revealed that spherical or cubic crystalline MgO were successfully produced, with the particle sizes in the range of 60–100 nm. [ABSTRACT FROM AUTHOR]

The α-bromination of carbonyl compounds is one of the most important transformations and also important precursors in synthetic organic chemistry. Particularly, the side chain monobromination of carbonyl compounds has been a challenging task, because during the reaction a small amount of disubstituted or ring brominated products as an impurity is always accompanied with monosubstituted product in the reaction mixture. In recent years substantial advances have been made for the synthesis of brominated aromatic carbonyl compounds with high selectivity. In this review, we have summarized various methods for the synthesis of α-bromo aromatic carbonyl compounds. [ABSTRACT FROM AUTHOR]

Gluten is a protein found in cereal grain such as wheat, barley, and rye. A small amount of gluten causes an autoimmune disease that leads to damage in the digestive system as well as a skin body system. The detection of gluten in food attracts tremendous attention. Surface modification by molecularly imprinted polymers electrode has been studied for specific detection of gluten using electrochemical superparamagnetic iron oxide nanoparticles trapped into a polymer matrix to improve gluten sensitivity with a magnetic property. A gold screen-printed electrode was modified by the magnetic molecularly imprinted polymers using surface polymerization of methyl methacrylate as monomer and gluten as a template. The magnetic iron oxide with a particle size less than 100 nm was modified and characterized using VSM, DLS and TEM techniques. SEM techniques confirmed the surface morphology of gold screen-printed electrodes modified with the MMIP. Finally, MMIP electrodes were used to detect gluten by an electrochemical method. [ABSTRACT FROM AUTHOR]

A novel sulfhydryl-modified covalent organic framework was designed for the selective determination of lead(II) using square wave anodic stripping voltammetry. The introduction of sulfhydryl groups enhanced the selectivity and sensitivity of the covalent organic framework for analytes. The sulfhydryl-modified covalent organic framework was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Under the optimized conditions, a sulfhydryl-modified covalent organic framework/gold electrode was successfully used for the determination of lead(II) in water samples. The newly developed square wave anodic stripping voltammetry method exhibited wide linearity (0.05 to 20 ng mL−1, r = 0.991), a low limit of detection (0.015 ng mL−1) and good precision, with a relative standard deviation values <5.1%. The limit of detection was lower than 10 ng mL−1, the level of lead(II) in drinking water permitted by the World Health Organization. The recoveries of three spiked samples ranged from 90.0% to 104.0%, with relative standard deviations <4.9%. Satisfactory reproducibility and good repeatability demonstrated that the newly developed method is very suitable for the detection of lead(II) in real water samples, with significant advantages over existing methods. [ABSTRACT FROM AUTHOR]

Synergistic result of cationic gemini surfactant (GS) 1,2-bis(N-hexadecyl-N,N-dimethylammonium) ethane dibromide (16-2-16) and organic salt (Sodium tosylate; NaTos) on mild steel corrosion in 1 M HCl solution at various temperatures (30, 40, 50 and 60 °C) has been examined using gravimetric, electrochemical and surface morphology measurement. Investigational result shows that the inhibition efficiency (η) of 16-2-16 GS enhanced in the existence of a set quantity of NaTos. The synergism parameter (Sθ) values are larger than unity, representing large inhibition efficiency, generated via the accumulation of NaTos to 16-2-16 GS is owing to adsorption supportive. The electrochemical results revealed that the 16-2-16 GS in the absence and presence of NaTos act as mixed-type inhibitors. The inhibitor adsorption on the mild steel surface in 1 M HCl solution obeys Langmuir adsorption isotherm. Surface morphology was studied using scanning electron microscopy (SEM). [ABSTRACT FROM AUTHOR]

In this study, poly(acrylic acid) and multiwalled carbon nanotubes (PAA/MWNTs) composite nanofiber thin film was prepared on fluorine doped indium tin oxide–coated glass substrate through electrospinning method. The electrospun PAA/MWNTs nanofiber thin film was modified with layer–by–layer (LbL) self–assembled multilayers of glucose oxidase (GOD) and poly(dialyldimethylammoniumchloride) (PDADMAC) prior to employ for glucose detection. The obtained nanofiber thin film was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The prepared nanofibers thin film shows a good potential for detection of glucose at constant applied potential through an electrochemical method. [ABSTRACT FROM AUTHOR]

Early detection of Parkinson's disease (PD), as a dangerous neurodegenerative disease, is a key factor in the therapy or prevention of further development of this disease. We developed an electrochemical nanobiosensor for early detection of PD based on the quantification of circulating biomarker, miR-195. Exfoliated graphene oxide (EGO) and gold nanowires (GNWs) were used to modify the surface of screen-printed carbon electrode. A single-strand thiolated probe was designed for specific hybridization with target miRNA (miR-195), and doxorubicin was used as an electrochemical indicator for differential pulse voltammetry measurements. The results of scanning electron microscope imaging and cyclic voltammetry experiments confirmed the accuracy of the working electrode modification steps. The results of analytical performance nanobiosensor showed a high sensitivity of the biosensing with 2.9 femtomolar detection limit and dynamic range of 10.0-900.0 femtomolar. In addition, good selectivity for target miRNA over non-specific oligonucleotides (one and three base replacement in target miRNA, and non-complementary) was achieved. The results of real human serum analysis did not show any interference in the function of the biosensor. Based on the results, the miR-195 electrochemical nanobiosensor could be suggested for clinicians in the medical diagnosis of PD. [ABSTRACT FROM AUTHOR]

A new category of thermally stable hybrid polyarylidene(azomethine-ether)s and copolyarylidene(azomethine-ether)s (PAAP) based on diarylidenecycloalkanones has been synthesized using solution polycondensation method. For potential cationic sensor development, a thin layer of PAAP onto a flat glassy carbon electrode (GCE, surface area: 0.0316 cm2) was prepared with conducting nafion (5%) coating agent to fabricate a sensitive and selective arsenic (III) [As3+] ion in short response time in neutral buffer system. The fabricated cationic sensor was measured the analytical performances such as higher sensitivity, linear dynamic range, detection limit, reproducibility, and long-term stability towards As3+ ions. The sensitivity and detection limit were calculated as 2.714 μAμM−1cm−2 and 6.8 ± 0.1 nM (SNR of 3; 3N/S) respectively from the calibration curve. This novel approach can be initiated a well-organized route of an efficient development of heavy selective arsenic sensor for hazardous pollutants in biological, environmental, and health care fields. Real sample analysis for various environmental sample was performed with PAAP-modified-GCE. [ABSTRACT FROM AUTHOR]

This work reports the fabrication of poly(3-aminobenzoic acid), (PABA)/multiwalled carbon nanotubes (MWNTs) composite thin film modified with layer-by-layer (LbL) self-assembled multilayers of cytochrome C (Cyt C) and poly(diallyldimethylammonium chloride) (PDADMAC) for hydrogen peroxide (H2O2) sensing on indium tin oxide-coated glass substrate. An electropolymerized PABA/MWNTs composite thin film was employed for the covalent attachment of Cyt C. The subsequent multilayers of PDADMAC and Cyt C were then fabricated using LbL deposition technique. The fabricated film was characterized by UV-vis spectroscopy, Raman spectroscopy, SEM and AFM. The modified thin film was finally used for successive detection of H2O2at constant applied potential through an electrochemical method. [ABSTRACT FROM AUTHOR]

The use of adsorption and electrochemical treatment technologies for wastewater treatment has significantly increased in recent years. In the present study, carbon prepared from biomass waste can be used as electrode material in the electrochemical process is shown. Given that the electrode material is quite expensive, low-cost manufacturing is gaining more and more importance. Electroadsorption of textile dye (Burdem Orange II) by using activated carbon prepared from waste material, which is cherry stones, was investigated with the variation in the parameters of pH, initial dye concentration, solution flow rate, applied potential, and supporting electrolyte. The removal efficiency of textile dye up to 98% were achieved by electrochemical method. [ABSTRACT FROM AUTHOR]

The corrosion of steel tubes in sea water was controlled by cathodic protection. The impressed current technique was used. The rate of reaction was evaluated as a function of the temperature, pH and solution velocity. In this technique, the polarization method was used to determine the protection potential and current. The rate of zinc consumption, the protection potential, and the protection current are highly dependent on the variables of the study. The boundary element technique was suitable for modelling corrosion problems. The average percentage of error among the experimental and theoretical data was 1.27%. [ABSTRACT FROM AUTHOR]

The multiwalled carbon nanotube-nickel hydroxide composite film used to modify glassy carbon electrode was prepared and confirmed by transmission electron microscopy and cyclic voltammetry. The process and mechanism of film formation were discussed in detail. The electrode modified with the composite film exhibited good catalytic activity toward electrochemical oxidation of hydrogen peroxide in 0.1 mol/L sodium hydroxide solution. Various factors affecting the electrocatalytic activity of nickel hydroxide film were investigated. The anodic peak current increased with the increased concentration of hydrogen peroxide. The linear range for the determination of hydrogen peroxide was from 1.5 × 10-6 mol/L to 2.5 × 10-3 mol/L with the detection limit 6.1 × 10-7 mol/L (S/N = 3). And the proposed method was applied to the determination of hydrogen peroxide in disinfector with higher sensitivity and lower detection limit. [ABSTRACT FROM AUTHOR]

The effect of ethylenediaminetetraacetate (EDTA) on the removal of cyanide (CN-) from electroplating wastewater was investigated using an electrochemical process. Decay of 100 mg/L CN- was carried out as a function of electrical current (I = 0.5–5.0 A) and molar ratios of EDTA to CN- (2.6–15.7) at pH 13.0. The experiments showed that electrooxidation of CN- follows first-order kinetics with respect to CN- ion. The first-order rate constant, k, showed linearity with the applied current (r2 = 0.99). At a molar ratio of 2.6 ([EDTA]: [CN-]) and electric current, I = 2.5 A, the oxidation of CN- proceeded by a slower rate than in the absence of EDTA. Under similar conditions, the oxidation rate of cyanide increased at molar ratios ranging from 5.2 to 15.7. Consequently, the energy consumption for the electrooxidation of CN- varies with the amount of EDTA present in the solution. [ABSTRACT FROM AUTHOR]

The charge-transfer complexes of formula D(TCNQ)2 are formed between π-acceptor TCNQ (7,7',8,8'-tetracyanoquinodimethane) and phenolic donors such as p-aminophenol, α-naphthol, 2,4,5-trichlorophenol, and p-cresol. Solution growth and an electrochemical method were used to synthesize the complexes. Their structural analyses were performed using elemental analysis (C, H, N, and halogen), X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) photographs, dc electrical conductivity, and spectral properties (electronic and 1H NMR), which reveals that these quasi-one-dimensional monoclinic crystalline compounds are synthesized in the single phase with space group P2/1/n and are of semiconductor nature at room temperature. The stoichiometric ratio of donor and acceptor in the complex D(TCNQ)2 is found to be in a 1:2 ratio, respectively. [ABSTRACT FROM AUTHOR]

The state of the art of voltammetric and amperometric methods used in the study and determination of pesticides in crops, food, phytopharmaceutical products, and environmental samples is reviewed. The main structural groups of pesticides, i.e., triazines, organophosphates, organochlorides, nitrocompounds, carbamates, thiocarbamates, sulfonylureas, and bipyridinium compounds are considered with some degradation products. The advantages, drawbacks, and trends in the development of voltammetric and amperometric methods for study and determination of pesticides in these samples are discussed. [ABSTRACT FROM AUTHOR]