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The aim of this study is to develop an electroanalytical method for the determination of serotonin, a very important neurotransmitter for neuroscience in food products, with an electrochemically produced sulfur-doped graphene oxide modified pencil graphite electrode (EGO/PGE). The S-doped graphene oxide electrode was fabricated by chronoamperometry, a fast, environmentally friendly, and, more importantly, functional group doping technique in one step. Techniques such as atomic force microscopy, electrochemical impedance spectroscopy, cyclic voltammetry, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy were used for the structural and morphological characterization of the produced sensor. The limit of detection and limit of quantitation were calculated as 0.026 and 0.09 [micro]M, respectively, using differential pulse voltammetry under optimum experimental conditions with the prepared EGO/PGE. Recovery tests were performed by spiking different concentrations into walnut and milk samples to investigate the applicability of the developed method in food samples. Good results between 93.1 and 105.8% were obtained in recovery studies. These results showed that the developed S-doped graphene oxide modified pencil graphite electrode platform was practically applicable in food samples due to its simplicity, low cost, fast response time, easy manufacturing, good selectivity, and high sensitivity., Author(s): Zeynep Serbest [sup.1] , Ozge Gorduk [sup.1] , Yucel Sahin [sup.1] Author Affiliations: (1) grid.38575.3c, 0000 0001 2337 3561, Yildiz Technical University, Faculty of Arts and Science, Department of [...]

This study introduces a novel label-free immunosensor that has the potential to be utilized for clinical screening and diagnosis of prostate cancer. The electrochemical immunosensor's performance was enhanced by combining 3,4-ethylenedioxythiophene (EDOT), 3-methylthiophene (3MT), and gold nanoparticles (AuNPs), enabling the accurate and sensitive determination of serum prostate specific antigen (PSA) concentrations. The immunosensor platform used [Fe(CN)6]3−/4− as a redox probe to obtain the signal, and the DPV technique was used to correlate the signal with the PSA concentration. The linear range of AuNPs/p(EDOT-co-3MT)/PGE is 0.1 to 50 000 pg mL−1, with a detection limit of 0.083 pg mL−1. In interference studies with interferences such as bovine serum albumin, carcinoembryonic antigen, uric acid, ascorbic acid, vitamin B12, vitamin B9, L -tyrozine, L -phenylalanine, Cu2+, Fe2+, and Zn2+ the immunosensor showed excellent anti-interference properties. The designed sensor platform is facile, inexpensive, highly sensitive, and selective, and has a high surface area, excellent electrical conductivity, and biocompatibility. Furthermore, this technology is highly suitable for industrial-scale production and can be easily converted into point-of-care detection devices due to its low cost, reproducibility, selectivity, and accuracy. [ABSTRACT FROM AUTHOR]

In this study, an anodically pretreated pencil graphite electrode (Ptre/PGE) which has oxygen-containing groups was used for the electrochemical determination of Allura Red (AR) by differential pulse voltammetry (DPV) method for the first time in the literature. In order to be more selective and sensitive the pencil graphite electrode, the anodic pretreatment process was performed by applying a constant +1.8 V potential for 250 s in pH 9 phosphate buffer solution using chronoamperometry method. The characterisation studies of the sensor were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. Interference effects of sunset yellow, tartrazine, amaranth, aspartame, glucose, gelatin, and ascorbic acid on AR determination with Ptre/PGE were investigated. The limit of detection and quantitation values was found as 75 and 251 nmol L−1, respectively. The Ptre/PGE has been used for the determination of AR in cherry juice and energy drink samples, where it provides recovery ranging from 98.40% to 100.8%. [ABSTRACT FROM AUTHOR]

The desire for real-time and continuous human health monitoring and uninterrupted human–machine interaction has been increasing exponentially day by day. This has opened new windows in the development of wearable devices. In particular, graphene oxide as a new 2D material has become interesting in wearable sensors thanks to its superior thermal, mechanical and electrical properties. Conductive inks containing graphene materials have been shown to be an attractive approach to produce flexible, disposable, wearable and miniature devices with desirable properties. In this study, a conductive ink containing sulfur-doped graphene oxide (S-GO), polyvinylidene fluoride (PVDF) and N-methyl-2-pyrrolidone (NMP) was synthesized and was coated on a polyester/cotton blended fabric substrate by the "dip and dry" method. Then, conductive fabric electrodes (CFEs) were prepared. S-GO was synthesized in one-step, inexpensive, easy, and environmentally friendly with a constant potential. FTIR, EIS, SEM-EDS, AFM, XRD, XPS, Raman spectroscopy and tensile tests were used for the characterization of the CFEs. The electrochemical behaviors of biological substances such as dopamine (Dop), ascorbic acid (AA), NADH and uric acid (UA) were investigated using the CFE for the first time in the literature. It is predicted that the CFE developed according to the obtained results can offer new opportunities for the required flexible, low-cost, wearable electronics and sensors. [ABSTRACT FROM AUTHOR]

Tyrosine (l-Tyr), which is found in basic foods, is a nonessential amino acid and a metabolite of phenylalanine, has many roles in human metabolism, and is important in maintaining nutritional balance. In this study, an electrochemical method has been presented to determine low levels of l-Tyr using an electrochemically treated pencil graphite electrode (EPGE) via overoxidation of graphite surface and intercalation of Li+ ions into graphite by cyclic voltammetry in the potential range between −0.3 and 2.0 V. Characterization studies of the EPGEs were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and cyclic voltammetry. The determination of l-Tyr was performed by differential pulse voltammetry, and the investigation of electrochemical properties of l-Tyr was conducted by cyclic voltammetry. The results showed that the EPGE presents high electrocatalytic performance and has a low detection limit (0.12 μM) for determining l-Tyr with a wide linear range from 1.0 to 500 μM. The selectivity of prepared EPGE was investigated in the presence of organic species. The determination of l-Try was performed in yoghurt and milk samples and good results were obtained with recoveries between 95.7% and 103.1%. Stability and repeatability studies further demonstrate the applicability of the sensor. [ABSTRACT FROM AUTHOR]

The rapid and accurate determination of phosphate is necessary for human health and the environment. In this study, three species of inorganic phosphate were sensitively determined by the use of poly(vinyl chloride) (PVC)-coated molybdenum blue (MB) modified pencil graphite electrodes (PGEs) for the first time. The prepared electrodes were characterized by electrochemical and microscopic methods. For the determination of inorganic phosphate species, PMo12O43–, PMo11O39H47– and PMo10O38H811– complexes were formed by the interaction of molybdenum blue and phosphate under the optimized conditions. Peaks observed in the differential pulse voltammograms (DPVs) were due to the PO43–, HPO42– and H2PO4– complexes and the number of molybdenum atoms in molybdenum blue. For the electrochemical determination of these complexes, each had an oxidation peak at a distinctive potential in the differential pulse voltammograms. The electrodes also showed good selectivity for the different phosphate species since they formed unique complex structure with phosphate species. The limits of detection and quantitation were determined to be 0.141 µM and 0.47 µM for PO43– (PMo10O38H811–), 0.11 µM and 0.334 µM for HPO42– (PMo12O403–), and 0.129 µM and 0.432 µM for H2PO4– (PMo11O39H47–), respectively. [ABSTRACT FROM AUTHOR]

Sunset Yellow (E110) is an azo food artificial dye and has a wide range of applications. When ingested in excess, it can lead to many serious health problems, so it is significant to rapidly determine Sunset Yellow. In this study, a modified electrode was developed by making use of electroactive properties of Sunset Yellow. Using a chronoamperometry method, an electrochemically prepared graphene oxide modified pencil graphite electrode was prepared in one-step by applying a + 1.9 V constant potential for 60 seconds in 5.0 M sulfuric acid. Cyclic voltammetry, electrochemical impedance spectroscopy, X-ray powder diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy were used to characterize the electrochemical properties and surface morphology of the modified electrode. Electrochemical measurements were carried out using differential pulse voltammetry. The influence of pH on the electrochemical determination of Sunset Yellow was investigated. The effects of possible substances that may interfere and the repeatability and reproducibility of the developed sensor platform were examined. Under the optimized conditions, the limits of detection and quantitation were 0.057 µM and 0.19 µM, respectively. The applicability of the developed protocol to real samples was investigated and good recovery values were achieved. The developed sensor platform stands out with features such as short preparation and analysis time, simplicity, low cost, sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

In this study, acid-activated multi-walled carbon nanotubes (AA-MWCNT) and poly(3,4-ethylenedioxythiophene) (PEDOT) were deposited on a pencil graphite electrode (PGE) surface for electrochemical sensing applications. The acid-activated multi-walled carbon nanotube/over-oxidized poly(3,4-ethylenedioxythiophene) modified pencil graphite electrode (AA-MWCNT/OO-PEDOT/PGE) was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The sensing properties of the obtained surface were examined for the voltammetric determination of serotonin in a phosphate buffer solution. The effects of the pH, adsorption time, over-oxidation and polymerization parameters on the electrochemical properties of serotonin were investigated. The effects of possible interfering substances were evaluated. The detection limit was determined to be 0.092 µM based on a signal-to-noise ratio of 3. Analytical applications of AA-MWCNT/OO-PEDOT/PGE were successfully tested for the determination of serotonin in human blood serum samples. [ABSTRACT FROM AUTHOR]

AbstractThere is a pressing requirement to synthesize stable electrode components that possess enhanced capabilities for creating electrochemical sensors, which are sensitive and discerning, to swiftly detect dangerous noxious substances. A sensitive electrochemical sensor has been developed in this study for hydrazine (HY) oxidation, utilizing gold nanoparticles (AuNPs) and poly(brilliant blue) (p(BB)) modifiers on the surface of the pencil graphite electrode (PGE). The features of the sensor for detecting hydrazine were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). Additionally, when examined under optimal parameters using CV and amperometry, the proposed hydrazine sensor presents favorable electrochemical and analytical figures of merit. The AuNPs/p(BB)/PGE provides the determination of low levels of hydrazine in water samples with a detection limit of 0.14 µM. A wide linear range from 1.0 to 800 μM was obtained. The findings indicate that the AuNPs/p(BB)/PGE sensor exhibits good stability, repeatability, and reproducibility for hydrazine. The proposed sensor was effectively used to determine hydrazine in both water and mineral water samples. [ABSTRACT FROM AUTHOR]