Electrochemical Sensors

Hydroquinone (HQ) is a toxic and carcinogenic substance commonly used in cosmetics, pharmaceuticals, and various industrial applications. In this study, we report the synthesis of a novel composite material consisting of flavin adenine dinucleotide (FAD) functionalized fluorapatite (FA) combined with singlewalled carbon nanotubes (SWCNTs) (FAD/FA/SWCNT). This composite was prepared through a mechanochemical method using dimethyl sulfoxide (DMSO) as the dispersing solvent. The resulting composite was then applied on to a glassy carbon electrode (GCE) for the electrochemical detection of hydroquinone (HQ). The structural morphology and phase of the nanocomposite were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and UV-visible spectroscopy. Electrochemical techniques, including cyclic voltammetry and amperometry, were employed to evaluate the electrochemical performance of the surface-modified electrode for hydroquinone (HQ) detection. The FAD/FA/SWCNT biosensor exhibited a redox peak at-0.45 V in a 0.1 M phosphate buffer solution (PBS, pH 7.4) under blank conditions. The composite demonstrated remarkable catalytic activity, showing an increased current signal in response to HQ detection. The sensor displayed a linear response range from 0.005 mM to 258.2 mM for HQ, with a limit of detection (LOD) of 2.70 nM. Furthermore, the FAD/FA/SWCNT biosensor successfully detected HQ in spiked water samples, achieving high recovery rates between 100.4% and 103.0%, highlighting its potential for realworld applications.

The growing occurrence of antibiotic residues in pharmaceutical products and environmental matrices underscores the urgent need for sensitive, sustainable, and cost-effective sensing platforms. In this study, a green synthesised palladium/graphene (Pd/ Gr) nanohybrid was fabricated using Strobilanthes kunthiana leaf extract and employed as an efficient electrocatalytic material for the electrochemical detection of Sparfloxacin (SFX), a fluoroquinolone antibiotic. The Pd/Gr nanohybrid was coated onto a glassy carbon electrode (GCE) and thoroughly characterised using FESEM, UV-Vis, and FTIR analyses, which confirmed the successful synthesis of the nanocomposite and its high electrocatalytic properties. The as-prepared Pd/Gr/GCE sensor exhibited a linear detection range for SFX from 0.05 to 38.00 µM with the lowest detection limit (LOD) of 0.015 µM. Furthermore, this new sensor demonstrated excellent analytical performance for the detection of SFX in real-world sample with the recovery values between 100.5% and 106.8% in human urine and tap water samples.

An electrochemical sensor based on cucurbit [6] uril has been developed for sensitive detection of an important neurotransmitter, norepinephrine (NEP). On a platinum wire electrode, the cucurbit [6] uril solution was drop-casted and is known as a modified electrode. The modified sensor has been characterized by scanning electron microscopy (SEM) to understand the morphological properties of the sensor surface. Electrochemical responses of norepinephrine at a CB [6] modified sensor were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV studies of NEP at the modified electrode were carried out in the potential range of 0 V to 0.8 V in phosphate buffer solution (pH 7.0) and impedance studies at potential 0.4 V in the frequency range of 0.1 Hz to 10 3 kHz. The modified electrode showed increased current response and decreased charge transfer resistance towards the oxidation of NEP compared to the bare electrode.

The development of an efficient, simple, and cost-effective electrode material for accurately measuring the activity of neurotransmitters in the human body has become a significant focus in the research community. In this context, we have synthesized a novel composite of polyluminol (PLUM) coated graphitic carbon nitride (GCN) for the detection of epinephrine (Epi), also known as adrenaline. We employed various spectroscopic and analytical methods to analyze the crystalline and structural characteristics of both GCN and PLUM/GCN. The PLUM/GCN modified glassy carbon electrode shows excellent electrocatalytic properties for Epi detection. Notably, this sensor has a lowest detection limit of 0.00142 μM and a wide linear range of detection from 0.05 to 200 μM. The proposed PLUM/GCN sensor demonstrates good stability, strong repeatability, and limited selectivity in the presence of common interfering compounds. Furthermore, the PLUM/GCN sensor showed recovery rates between 89.20 and 106.90% for detecting Epi in spiked adrenaline injection samples and human bodily fluids, such as human blood serum and urine. This demonstrates the potential applicability of the proposed sensor in real-world samples.

Impaired 5-HT function can lead to clinical depression, which is one of the most serious problems nowadays and the number of people suffering from it is growing worldwide. Given the (patho)physiological importance of serotonin, its analysis is necessary. It plays a major role in both neurological and metabolic diseases. In this research, a platinum wire modified with platinum nanoparticles (PtNPs) was used to detect serotonin. The structural and morphological characteristics of the electrode were extensively investigated using scanning electron microscopy (SEM). To characterize the electrochemical performance of the electrodes (before and after surface modification) cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) was employed. The CV results demonstrated that incorporating PtNPs significantly increased the current response of 5-HT and impedance studies revealed that charge transfer resistance decreases. Hence, the designed electrodes have potential applications in in-vivo neurotransmitter detection in future studies.

Neste trabalho foram desenvolvidos processos de corrosao por plasma de filmes de carbono tipo diamante (DLC – Diamond Like Carbon), visando sua aplicacao em guias de onda em dispositivos de optica integrada que e a base dos dispositivos fotonicos. Os filmes de DLC apresentam diversas carateristicas fisico/quimica que o tornam excelente candidato como material estrutural em dispositivos fotonicos; eles sao inertes quimicamente, transparentes na regiao do visivel/infravermelho, materiais duros e alto lubrificantes, alem destas vantagens a deposicao por sputtering e feita a temperatura ambiente, o que o torna compativel com etapas de pos-processamento em dispositivos optoeletronicos.

Electrochemical behavior of artificial antioxidant, butylated hydroxyanisole (BHA), was investigated at a glassy carbon electrode modified with poly L-cysteine [poly (L-Cys/GCE)]. BHA exhibits a pair of well -defined redox peak on L-cysteine modified GCE with E pa =69 mV and E pc = 4 mV. The modified electrode showed good electrocatalytic activity towards the oxidation of BHA under optimal conditions and exhibited a linear response in the range from 1.0× 10 -5 to 1.0×10 -6 M with a correlation coefficient of 0.998. The limit of detection was found to be 4.1×10 -7 M. The kinetics parameters of the proposed sensor such as heterogeneous electron transfer rate, k s , and charge transfer coefficient, α, was calculated and found to be 1.20 s -1 and 0.575 respectively. The average surface concentration of BHA on the surface of poly (L-Cys/GCE) was calculated to be 3.18 × 10 -4 mol cm -2 . The analytical utility of the proposed sensor was evaluated by the successful determination of BHA in coconut oil and sesame oil samples. Keywords BHA . L-cysteine . Sensor . Heterogeneous electron transfer rate Highlights • Development of a voltammetric sensor for butylated hydroxyanisole (BHA) was described • Experimental parameters were studied and optimized • Kinetic parameters were studied • Application studies were carried out

The present study investigated the use of the cyclic voltammetric electrochemical method and the electronic tongue (e-tongue) method for detecting adulteration in lime juice. Since the measurement of citric acid content in lime juice is an accepted indicator of lime juice adulteration in laboratories, at first, attempts were made to determine its concentration using a potentiostat device and the cyclic voltammetry method, which involved various electrodes including glassy carbon, graphite, gold, and carbon nanotube and gold nanoparticle-modified glassy carbon electrodes. Different conditions were considered by testing citric acid at multiple concentrations in buffers with different pH levels. The results showed that the electrochemical behavior of citric acid was weak, so conventional electrochemical methods could not be used to check its behavior. In the second part, a portable electronic tongue system (e-tongue) was evaluated. Eight samples of adulteration levels (from 5% up to 95%) were created in lemon juice (0, 5, 10, 20, 40, 70, 95, and 100% impurity). Unsupervised models including Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA), and supervised models including Multilayer Perceptron (MLP) neural networks and Support Vector Machine (SVM) were used. Based on the results, the PCA fingerprint showed good discrimination between different levels of adulteration, and HCA further confirmed this. The results of the analysis of supervised methods showed that the MLP model outperformed the SVM model in predicting fraud levels with a success rate of 99.33% and high correlation coefficients (R2 = 0.9973, RMSE = 0.09). These results show that the proposed system can separate different levels of adulteration in lemon juice and can be used as a taste quality control system.

The persistent contamination of aquatic environments by toxic heavy metals such as Pb²⁺, Cd²⁺, Hg²⁺, and As³⁺ has necessitated the development of rapid, sensitive, and field-deployable analytical techniques. Graphene-based electrochemical sensors have emerged as highly promising platforms due to their exceptional physicochemical properties, including a theoretical specific surface area of approximately 2630 m² g⁻¹, intrinsic carrier mobility exceeding 1.5 × 10⁵ cm² V⁻¹ s⁻¹, and excellent electrochemical stability. This review provides a comprehensive and detailed account of the development of graphene-based electrochemical sensors for heavy metal detection, emphasizing synthesis protocols, functionalization strategies, sensing mechanisms, and analytical performance metrics under realistic conditions. Detection limits as low as 0.008 µg L⁻¹ for Pb²⁺ and 0.015 µg L⁻¹ for Cd²⁺ are critically discussed alongside linear dynamic ranges extending from 0.02 to 500 µg L⁻¹. The role of deposition potential of −1.2 to −0.8 V vs. Ag/AgCl, accumulation time (120–300 s), and electrode surface modification in enhancing sensitivity is analyzed in depth. The review concludes with a critical evaluation of current limitations and future research directions toward scalable, real-time monitoring systems.

Os filmes Cu 0,6 In 0,4 Se 2 foram depositados em substrato de vidro pela técnica de spray-pirólise, para utilização como camada absorvedora de células fotovoltaicas. Foram adotados os seguintes parâmetros de deposição: temperatura de substrato entre 250 e 400ºC, fluxo da solução precursora de 1 mL/min e tempo de deposição de 30 min. As propriedades estruturais, elétricas, morfológicas e óticas dos filmes preparados foram analisadas em função da variação da temperatura de substrato. A análise por difração de raios X mostrou que os picos mais intensos são de orientação (204/220) e que os filmes possuem as fases de CuSe, CuSe 2 e CuInSe 2 . Para o processo de condução elétrica foi observada uma única energia de ativação com valor médio de 0,73 eV. A resistência de folha variou entre 0,277 a 0,576 MΩ/□. Os valores de resistividade elétrica apresentaram pequenas variações tendo um valor médio de 1,44 KΩm. As análises da morfologia dos filmes realizadas por microscopia confocal revelaram que de um modo geral as amostras apresentam-se sem trincas, sendo que as superfícies dos filmes com maior temperatura de deposição foram mais uniformes. A caracterização ótica foi realizada no intervalo de comprimento de onda de 350 a 1100 nm e os filmes apresentaram coeficiente de absorção na ordem de 10 3 cm -1 no comprimento de onda de 550 nm e gap ótico com valor médio de 1,5 eV. Palavras-chave: Spray-pirólise, camada absorvedora, disseleneto de cobre e índio.

Progress in four interrelated catalysis research efforts in our laboratory are summarized: (1) catalytic photochemical function alization of unactivated CeH bonds by polyoxometalates (POMs); (2) self-repairing catalysts; (3) catalysts for air-based oxidations under ambient conditions; and (4) terminal oxo complexes of the late-transition metal elements and their oxidation chemistry.

Heavy metal contamination in water is a major concern on a global scale due to its toxicity, persistence, and bioaccumulation. Most conventional water analysis techniques typically laboratory-based, relying on bulky and expensive equipment, which result in high costs and prolonged detection time. These limitations have driven a growing interest in developing efficient testing devices. There have been many studies that attracted considerable research interest in miniaturized analytical devices, especially miniaturized electrochemical (MEC) sensors, for introducing fast, affordable, and sensitive sensing devices. Such devices minimize the need for large sample volumes and reagents, as well as bulky electrodes and other equipment. Among the various platforms, paperbased electrodes, screen-printed electrodes (SPEs), and textile-based electrodes have received much attention due to their specific properties. Carbon-based nanomaterials (CNs), such as graphene, carbon nanotubes (CNTs), graphene quantum dots (GQDs), graphene, carbon fibers, and graphene oxide (GO), have emerged as key

In the paper the results of preliminary experiments concerning bioelectrical impedance measurements using integrated impedance scanner AD5933 (Analog Devices) are described. Results of performed simulations are also presented. Design of a control circuit based on ARM microprocessor is described. Possible applications of the bioelectrical impedance spectroscopy method in measurements of selected characteristics of the human organism are discussed as well as plans for future development of dedicated, specialized equipment. Integrated impedance scanner in selected biomeasurement applications... 69

Artificial sniffing and tasting devices mimicking the olfactory and gustatory senses of mammals have been widely used separately for medical and environmental applications. However, a device that can simultaneously measure the aroma and taste of samples, as mammals usually do, has not been delivered yet. This study introduces an innovative, all-in-one, miniaturized paper-based sensor array that integrates electronic nose and electronic tongue functionalities. It effectively distinguishes between breast cancer and head and neck carcinoma, as well as healthy subjects, using microliter amounts of blood plasma. A total of 140 participants were examined, comprising 40 breast cancer cases, 40 head and neck carcinoma cases, and 60 healthy controls. The threedimensional origami design features a central sample introduction zone connected to eight lateral sensing zones through microfluidic channels in the tongue, while it contains a sample holding zone and eight sensing zones in the headspace nose, all arranged on a compact folding piece of paper. A 3D-printed miniature cubic reaction chamber established a saturated reaction environment. Arrays of eight fluorescent bimetallic nanoclusters, immobilized in designated sensing zones, interacted with plasma-derived constituents and volatile organic compounds, resulting in fluorescence intensity changes. The sensor required only 40 μL of plasma and produced measurable responses after 1 h at a temperature of 40 • C. Multidimensional imaging data revealed distinct colorimetric signatures that allowed preliminary identification of the two studied cancers with the respective 95.7 %, 97.5 % and 99.1 % accuracies using the tongue, nose, and integrated tongue-nose modalities. Overall, the device offers a compact, portable, and cost-effective platform that integrates optical sensors for smell and taste, thereby facilitating the progression of diagnostic technologies.

O. Üzengi Aktürk,1,2,3 E. Aktürk,1,2,4,* H. H. Gürel,5 and S. Ciraci2,† 1Nanotechnology Application and Research Center, Adnan Menderes University, Aydın 09010, Turkey 2Department of Physics, Bilkent University, 06800 Ankara, Turkey 3Department of Electric and Electronic Engineering, Adnan Menderes University, 09100, Aydın, Turkey 4Department of Physics, Adnan Menderes University, 09100, Aydın, Turkey 5Department of Information Systems Engineering, Kocaeli University, 41380 Kocaeli, Turkey (Received 7 April 2016; revised manuscript received 13 February 2017; published 9 March 2017)

Glyphosate is universally used broad spectrum organophosphorus herbicide to eliminate weeds. Although it's prolonged use has led to contamination of water and soil bodies and potential health issues in humans. This study highlights the necessity to monitor the level of glyphosate using electrochemical sensor. Herein, we report the development of a chitosan-cucurbit [6] uril modified platinum nanoparticle electrode for the detection of glyphosate. Platinum nanoparticle deposited electrode was modified by chitosan-cucurbit [6] uril solution by drop cast method. Electrochemical performance was examined by cyclic voltammetry and it is found that the current response of oxidation of glyphosate at modified electrode is higher than the bare and nanoparticle deposited platinum electrode.

Simultaneous determination of acetaminophen and uric acid in biological samples was performed using differential pulse voltammetry (DPV) on a glassy carbon electrode coupled with orthogonal signal correction-partial least squares (OSC-PLS). The optimum parameters were set at pH 8.0, a scan rate of 10 mV/s, and a pulse height of 50 mV. Both analytes showed peaks at about 390 mV. OSC-PLS was performed to solve the interference problem in the voltammograms. DPV calibration showed broad dynamic ranges of 10.0-220.0 and 10.0-210.0 μmol/L for acetaminophen and uric acid, respectively. The method was successfully applied to human plasma and urine samples without any pretreatment.

We are focusing on the application of biosensor technology for the successful detection of selected DNA and mutated DNA sequences based on conduting polymer nanostructures. There are several tasks in the current research which need great concerns over the sensitivity, selectivity and throughput. Therefore, developing simple, efficient and cost effective methods for routine analysis of DNA hybridization is of great importance. Compared with other techniques electrochemical technique is an attractive and many advantages including high sensitivity, inherent simplicity and miniaturization and low-cost. It is well-known that electroactive conducting polymer (such as polyaniline, polypyrrole, poly (3, 4-ethylenedioxythiophene) is widely used in biosensors due to their unique physical and chemical properties and also low cost, easy preparation, and environment stability. In this book chapter, we have discussed a new sensing platform using nanostructure conduting polymers to detect target ssDNA and mutated ssDNA Advances in Chemical Engineering

Graphene oxide (GO) was prepared from graphite (GT) with Hammer method, the GO was reduced with hydrazine hydrate to produce a reduced graphene oxide (RGO). The RGO was reacted with thiocarbohydrazide (TCH) to functionalize the RGO with 4-amino-3-symbol-1h-1, 2, 4-triazol-5 (4H) -thion group and to obtain (RGOT). All the prepared nanomaterial and the product of the functionalization RGOT were characterized with Fourier transformer infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis. RGOT mixed with ultrasonic device at different pH values of phosphate buffer solution (PBS), the mixture used to modifying a screen printed carbon electrodes SPCE and with cyclic voltammetry the sensitivity of selectivity of the new modifying electrode to examine. The results show good selectivity at pH 2 to the ampicillin and a redox reaction of the β-lactam group of the antibiotic. Keywords Graphene oxide (GO), Reduced graphene oxide (rGO), Reduced graphene oxide (rGO) functionalization with thiocarbohydrazide, Screen printed carbon electrode (SPCE), Cyclic voltammetry, Effect pH on the redox of AMP, Scan rate and limit of detection LOD

Herein we report a low cost, sensitive, supercapacitor-powered electrochemiluminescent (ECL) protein immunoarray fabricated by an inexpensive 3-dimensional (3D) printer. The immunosensor detects three cancer biomarker proteins in serum within 35 min. The 3D-printed device employs hand screen printed carbon sensors with gravity flow for sample/reagent delivery and washing. Prostate cancer biomarker proteins, prostate specific antigen (PSA), prostate specific membrane antigen (PSMA) and platelet factor-4 (PF-4) in serum were captured on the antibody-coated carbon sensors followed by delivery of detection-antibody-coated Ru(bpy) 3 2+ (RuBPY)-doped silica nanoparticles in a sandwich immunoassay. ECL light was initiated from RuBPY in the silica nanoparticles by electrochemical oxidation with tripropylamine (TPrA) co-reactant using supercapacitor power and ECL was captured with a CCD camera. The supercapacitor was rapidly photo-recharged between assays using an inexpensive solar cell. Detection limits were 300-500 fg mL -1 for the 3 proteins in undiluted calf serum. Assays of 6 prostate cancer patient serum samples gave good correlation with conventional single protein ELISAs. This technology could provide sensitive onsite cancer diagnostic tests in resource-limited settings with the need for only moderate-level training.