Development of Pen-type Portable Electrochemical Sensor Based on Au-W Bimetallic Nanoparticles Decorated Graphene-chitosan Nanocomposite Film for the Detection of Nitrite in Water,Milk and Fruit Juices

The development and fabrication of a simple, portable, and sensitive detection tool to precisely monitor nitrite level is of growing importance in electrochemistry research, given the strong interest in the protection of drinking water quality, treatment of wastewater, food production, and control of remediation processes. This work describes the fabrication of a simple, cost-effective, pen-type electrochemical sensor based on bimetallic gold and tungsten nanoparticles electrochemically decorated on graphene-chitosan modified pencil graphite electrode (PGE) for the trace detection of nitrite in real samples. The prepared nanocomposite was characterized using XRD, SEM, and EDS. The electrochemical behavior of the sensor was evaluated by cyclic voltammetry (CV) and impedance electrochemical spectroscopy (EIS). Results revealed that the proposed sensor displayed excellent electrocatalytic activity towards electro-oxidation of nitrite with an irreversible redox reaction. The AuNPs-WNPs@Gr-Chi/PGE sensor exhibited excellent analytical performance with a wide linear range from 10 to 250 μM towards nitrite. The LOD and LOQ were calculated to be 0.12 μM and 0.44 μM, respectively. The designed electrochemical sensor was successfully applied for the detection of nitrite in water, milk, and natural fruit juice samples.     

Sensitive Electrochemical Detection of Bisphenol A Using Molybdenum Disulfide/Au Nanorod Composites Modified Glassy Carbon Electrode

Bisphenol A, an important compound that is classified as an environmental hormone, has been proven to have harmful effects on human health and ecology. A molybdenum disulfide/Au nanorod‐modified glassy carbon electrode was prepared as an electrochemical sensor for the detection of bisphenol A using a simple and convenient approach. UV–Vis spectrophotometry and transmission electron microscopy were employed to characterize the composite. The electrochemical behavior of bisphenol A at the modified electrode was investigated via differential pulse voltammetry and cyclic voltammetry. The results show that bisphenol A exhibits a good electrochemical signal at the modified electrode under optimized conditions, and a good linear relationship was observed between the bisphenol A concentration and peak current within the range of 0.01–50 μM, with a detection limit of 3.4 nM. Furthermore, the fabricated electrodes showed good anti‐interference, reproducibility and stability. The proposed electrochemical method was successfully applied for the detection of bisphenol A in milk and water samples, and its potential for applications in pollutant detection was demonstrated.     

Determination of Bisphenol A Using an Electrochemical Sensor Based on a Molecularly Imprinted Polymer-Modified Multiwalled Carbon Nanotube Paste Electrode

A novel electrochemical sensor for bisphenol A was developed through the combination of a molecular imprinting technique with a multiwalled carbon nanotube paste electrode. A molecularly imprinted polymer and nonimprinted polymer were synthesized in the presence and absence of bisphenol A, and then used to prepare the electrode. The bisphenol A imprinted polymer was applied as a selective recognition element in the electrochemical sensor. Differential pulse voltammetry was used to characterize the electrochemical behavior of bisphenol A at the modified electrodes. The results showed that the imprinted sensor had highest response for bisphenol A. Parameters including the carbon paste composition, pH, and adsorption time for the imprinted sensor were optimized. Under the optimized conditions, the differential pulse voltammetry peak current was linear with the concentration of bisphenol A from 0.08 to 100.0 µM, with a detection limit of 0.022 µM. The imprinted sensor for bisphenol A exhibited good selectivity, stability, and reproducibility. This sensor was successfully used for the determination of bisphenol A in real water samples.     

Simultaneous electrochemical determination of nitrate and nitrite in aqueous solution using Ag-doped zeolite-expanded graphite-epoxy electrode

In this work a new electrochemical sensor based on an Ag-doped zeolite-expanded graphite-epoxy composite electrode (AgZEGE) was evaluated as a novel alternative for the simultaneous quantitative determination of nitrate and nitrite in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemical behavior of the electrode in the presence of individual or mixtures of nitrate and nitrite anions in 0.1 M Na₂SO₄ supporting electrolyte. Linear dependences of current versus nitrate and nitrite concentrations were obtained for the concentration ranges of 1-10 mM for nitrate and 0.1-1 mM for nitrite using cyclic voltammetry (CV), chronoamperometry (CA), and multiple-pulsed amperometry (MPA) procedures. The comparative assessment of the electrochemical behavior of the individual anions and mixtures of anions on this modified electrode allowed determining the working conditions for the simultaneous detection of the nitrite and nitrate anions. Applying MPA allowed enhancement of the sensitivity for direct and indirect nitrate detection and also for nitrite detection. The proposed sensor was applied in tap water samples spiked with known nitrate and nitrite concentrations and the results were in agreement with those obtained by a comparative spectrophotometric method. This work demonstrates that using multiple-pulse amperometry with the Ag-doped zeolite-expanded graphite-epoxy composite electrode provides a real opportunity for the simultaneous detection of nitrite and nitrate in aqueous solutions.     

A solid composite electrode for the determination of the electrochemical oxygen demand of aqueous samples

A composite electrode containing graphite, paraffin, AgO and CuO is described for the determination of the electrochemical oxygen demand (EOD) of waste waters. The oxidation of dissolved organic compounds at the electrode is based on a heterogeneous chemical reaction of AgO/CuO with the organic constituents of the waste water. This chemical reaction can be followed by a solid state electrochemical oxidation of the formed Ag₂O/Cu₂O. The method has been tested with various organic compounds and applied to real samples of sewage water. The EOD values correlate well to BOD and COD values.     

Molecularly Imprinted Polyresorcinol Based Capacitive Sensor for Sulphanilamide Detection

A molecularly imprinted polymer (MIP) based capacitive sensor for antibiotic detection in drinking water and milk has been developed on a gold coated silicon electrode (Au Electrode). The electrode was fabricated by electropolymerizing monomer resorcinol (RN) on Au surface in presence of sulphanilamide (SN) as a template molecule, to get insulated RN polymer antibiotic composite. The insulation of the polymer film was improved by incubation of electrode in 1‐Dodecanethiol solution. Subsequently MIP sensor was obtained by extraction of SN in ethanol and acetic acid solution. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements were performed for characterization of the developed MIP electrode at different steps of fabrication. The surface morphology of MIP electrode was characterized using atomic force microscopy (AFM), X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x‐ray spectroscopy (EDS). Performance of MIP sensor was evaluated by measuring change in capacitance against varying concentration of SN using EIS. A linear response in the range 1 to 200 μg L^?1 SN was recorded for MIP sensor with a detection limit of 0.1 μg L^?1. The developed MIP sensor exhibited good selectivity towards SN in water and milk with recoveries in the range 92 % to 105 %. The obtained results suggest the usability of MIP based sensor for SN estimation in water and milk samples.     

Nonenzymatic Electrochemical Biosensor Based on Novel Hydrophilic Ferrocene‐terminated Hyperbranched Polymer and its Application in Glucose Detection

We designed a novel water soluble topological structure polymer‐ferrocene‐ terminated hyperbranched polyurethane (HPU‐Fc) with good water solubility. The redox behaviors and the electrochemical kinetics parameters of HPU‐Fcs were explored by cyclic voltammetry (CV) according to electrochemical principle. The topological structure polymer was applied for the design and engineering of non‐enzymatic glucose sensor. The designed sensor showed good response to glucose concentration with good stability, favorable accuracy and high selectivity. The electrode was also used to detect glucose in blood samples, and the glucose contents detected by the electrode were in good agreement with those from the hospital where a common automatic biochemical analyzer (HF240–300) was used. This finding makes HPU‐Fc a promising biosensor for directly sensing glucose.     

Amperometric Determination of Lactic Acid. Applications on Milk Samples

Abstract

A hydrogen peroxide electrochemical sensor, coupled with immobilized lactate oxidase and covered with a cellulose acetate dialysis membrane has been applied in flow analysis of lactate in milk samples. The hydrogen peroxide produced by the enzymatic reaction is measured with a platinum electrode polarized at +650 mV versus Ag/AgCl. Milk samples were analyzed and compared with a spectophotometric reference method. The developed procedure is very simple and the short response time allows its use in assaying milk samples on dairy farms.     

Gold-dendrimer Nanocomposite Based Electrochemical Sensor for Dopamine

An electrochemical sensor for dopamine was developed by electrodepositing poly(propylene imine) (PPI) dendrimer and gold nanoparticles (AuNPs) onto a glassy carbon electrode (GCE). Electrochemical characterisation of the sensor was carried out by cyclic voltammetry and electrochemical impedance spectroscopy in ferri/ferrocyanide electrolyte. The nanocomposite electrode (GCE-PPI-AuNPs) showed improved electroactive surface area and electrochemical response over bare GCE. The sensor recorded a detection limit of 0.16 μM over a concentration range of 0.1 μM to 125 μM. The sensor was applied for dopamine detection in human serum samples and in the presence of interfering substances such as ascorbic acid and epinephrine.     

利用Cu0/多壁碳纳米管纳米复合物修饰玻碳电极快速非酶法检测葡萄糖和果糖(英文)

A nonenzymatic electrochemical sensor for glucose and fructose was fabricated that contained a glassy carbon electrode modified with a copper oxide (CuO)/multiwalled carbon nanotube (MWCNT) nanocomposite. The electrochemical properties of the CuO/MWCNT‐modified glassy carbon electrode were investigated. Two distinguishable anodic peaks were observed around 0.30 and 0.44 V corresponding to the oxidation of glucose and fructose, respectively, at the surface of the modified electrode. The detection limits for glucose and fructose were both 0.04 mmol/L. The sensor was used to simultaneously determine the concentrations of glucose and fructose in hydrolyzed sucrose samples, and to measure glucose in blood serum samples, demonstrating its potential as a nonenzymatic carbohydrate sensor.     

Graphene-Gold Nanoparticle-modified Electrochemical Sensor for Detection of Kanamycin Based on Target-induced Aptamer Displacement

A highly sensitive and selective label-free electrochemical sensor was developed for the determination of kanamycin. To improve the sensitivity of the electrochemical sensor, graphene-gold nanoparticles were prepared by a one-step electrochemical coreduction process and were modified on the surface of a glassy carbon electrode. The double-stranded DNA(ds-DNA) duplex probe was immobilized onto the graphene-gold nanoparticle-modified electrode. The introduction of target kanamycin induced the displacement of aptamer from the ds-DNA duplex into the solution. Methylene blue(MB) as a redox indicator monitored the current change using differential pulse voltammetry. Under optimal conditions, the designed electrochemical aptasensor exhibited a wide linear range from 0.1 pmol/L to 10 pmol/L with a detection limit of 0.03 pmol/L for kanamycin. The experimental strategy enabled the direct analysis of milk samples, and the results showed high sensitivity and good selectivity.     

Conductive 2D Metal-organic Framework (Co,NiCo, Ni) Nanosheets for Enhanced Non-enzymatic Detection of Urea

2D metal-organic framework (MOF) has potential applications in electrocatalysis owing to fast mass transfer, charge transfer and large specific surface area. Here, we had prepared three conductive 2D MOF based on Ni, NiCo and Co in a simple and rapid way. The 2D nanostructure of MOF was confirmed by SEM and TEM. The chemical composition was studied by XRD, Raman and XPS spectrum. The electrochemical oxidation and detection was investigated through cyclic voltammetry and current-time method. Their sensing performance for urea was determined by varying oxidation potentials and metal sites. The non-enzymatic Ni-, NiCo- and Co-MOF sensors had good catalytic activity for urea. Compared with NiCo- and Co-MOF, Ni-MOF had a wider linear range (0.5–832.5 μM), high sensitivity (1960 μA mM⁻¹ cm⁻²), low detection limit (0.471 μM), and fast response time. The sensors had well repeatability, reproducibility, and selectivity to specific interfering species. Furthermore, Ni- and NiCo-MOF modified electrode was also applied to detection of milk samples. The results showed that the recovery was satisfactory, which further confirmed the effectiveness of non-enzyme sensor. In general, the highly-sensitive 2D Ni- and NiCo-MOF modified electrode has great potential as nonenzymatic urea sensors for real samples detection in hydrogen energy, clinical diagnostics, and environmental protection, et al.     

Application of a Tetraamino Cobalt(II) Phthalocyanine Modified Screen Printed Carbon Electrode for the Sensitive Electrochemical Determination of L-Dopa in Pharmaceutical and Biological Samples

A novel synthesized tetraamino cobalt(II) phthalocyanine monomer was used for the fabrication of a sensor by electrochemical polymerization. A disposable electrochemical sensor based on the use of a screen printed carbon electrode covered with an electropolymerized film of tetraamino cobalt(II) phthalocyanine for the determination of L-dopa in pharmaceutical tablets and biological samples was described. Cyclic voltammetry and electrochemical impedance spectroscopy were performed for the characterization of the bare and modified electrode. For the electrochemical detection of L-dopa differential pulse voltammetry was used. The proposed method exhibits a good response towards electrooxidation of L-dopa in the linear concentration range: from 0.1 to 1000.0 μmol L⁻¹ in BRB pH=2.0, with a detection limit of 0.03 μmol L⁻¹ and from 1 to 1000 μmol L⁻¹ in PBS pH=7.4, with a detection limit of 0.33 μmol L⁻¹. Due to the fact that the developed sensor was applied in two different types of real samples, two buffer media were used, BRB pH=2.0 for pharmaceutical and urine samples and PBS pH=7.4 for whole blood samples. The proposed pCoTAPc/SPCE was successfully applied for the determination of L-dopa in pharmaceutical tablets, urine and in whole blood samples with satisfactory results.     

Development of an Innovative Nitrite Sensing Platform Based on the Construction of an Electrochemical Composite Sensor of Polymer Coated CNTs and Decorated with Magnetite Nanoparticles

Electrochemical determination of nitrite in real water samples is achieved using simple and efficient electrochemical sensor. The sensor is fabricated by electrodeposition of a thin layer of poly(3,4-ethylenedioxythiophene) sandwiched by drop-casting two thin layers of CNTs and iron oxide nanoparticles (Fe₃O₄) over a GC electrode surface. Voltammetry determination of nitrite in tap water and wastewater samples in the concentration range (0.5–150 μM) is successfully achieved with detection limits of 22 and 24 nM, respectively. Practical application of the GC/CNT/PEDOT/Fe₃O₄ sensor is efficiently assessed in real water samples for nitrite determination with acceptable recoveries, excellent anti-interference ability and long-term stability.     

Electrochemical behavior of o-sec-butylphenol at glassy carbon electrode modified with multiwalled carbon nanotubes and 1-butyl-3-methylimidazolium hexafluorophosphate

A sensitive electrochemical sensor based on immobilized multiwalled carbon nanotubes (MWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM·PF(6)) on a glassy carbon electrode (GCE) for o-sec-butylphenol (osBP) was proposed. The electro-oxidation behavior was studied, the experimental conditions were optimized and kinetic parameters were calculated. The results indicated that this electrochemical sensor has the advantages of fast electron-transfer rate, minimal fouling of electrodes, high sensitivity and stability for o-sec-butylphenol. Upon comparison with a glassy carbon electrode, this senor would effectively minimize the over-potential and increase the electrochemical response to o-sec-butylphenol. Under the optimum conditions, the peak current was linear to the osBP concentration range from 1 × 10(-7) to 2.5 × 10(-5) M with the detection limit of 8.65 × 10(-9) M (S/N = 3). The proposed method was applied to the determination of spiked water samples with satisfactory results.     

Molecularly imprinted nanoparticles-based electrochemical sensor for determination of ultratrace parathion in real samples

Molecularly imprinted polymer nanoparticles (nano-MIP), containing parathion selective sites, were synthesized by using suspension polymerization in silicon oil and then used for carbon paste electrode preparation. The obtained electrode was applied as an electrochemical sensor for parathion determination in different fruit and vegetable samples. Different factors including electrode composition, conditions of parathion extraction in the electrode and electrochemical measurement conditions were evaluated and then optimized by using various techniques of screening and response surface experimental designs. Electrode response to parathion (Res₁) and its selectivity for parathion (Res₂) were the desired responses. These responses were optimized simultaneously. After optimization, a sensor with high selectivity and picomolar detection limit were obtained. It was shown that the sensor response to parathion concentration was linear in the concentration range of 0.05 to 150?nmol?L^?1. The detection limit of designed sensor was calculated equal to 0.02?nmol?L^?1. The developed determination method was properly used for ultra-trace level assay of parathion in different fruit and cabbage samples.     

A Sensitive and Selective Nitrite Detection in Water Using Graphene/Platinum Nanocomposite

A glassy carbon electrode modified with reduced graphene oxide and platinum nanocomposite film was developed simply by electrochemical method for the sensitive and selective detection of nitrite in water. The electrochemical reduction of graphene oxide (GO) efficiently eliminates oxygen‐containing functional groups. Pt nanoparticles were electrochemically and homogeneously deposited on the ErGO surface. Field emission scanning electron microscopy (FE‐SEM), Raman spectroscopy, attenuated total reflectance‐fourier transform infrared spectroscopy (ATR‐FTIR), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were used to examine the surface morphology and electrocatalytic properties of the Pt‐ErGO nanocomposite film‐modified electrode surface. The fabricated nitrite sensor showed good electrochemical performance with two linear ranges; one from 5 to 100 µM (R²=0.9995) and the other from 100 to 1000 µM (R²=0.9972) and a detection limit of 0.22 µM. The proposed sensor was successfully applied for the detection of nitrite in tap water samples which proves performance of the Pt‐ErGO nanocomposite films.     

A Robust Electrochemical Sensor Based on Butterfly-shaped Silver Nanostructure for Concurrent Quantification of Heavy Metals in Water Samples

Heavy metals in drinking water have become a severe threat to human health. Detection of heavy metals has been achieved by electrochemical sensors that are modified with complex nanocomposites; however, reproducibility of these sensors is still a big challenge when applied in commercial settings. Here, a simple, very robust, and sensitive electrochemical sensor based on a screen-printed carbon electrode modified with butterfly-shaped silver nanostructure (AgNS/SPCE) has been developed for the concurrent determination of cadmium (II), lead (II), copper (II), and mercury (II) in water samples. The electrochemical behavior of the modified electrodes was investigated using cyclic voltammetry and differential pulse anodic stripping voltammetry. The AgNS/SPCE showed distinct peak potentials and a significant increase in the peak currents for all heavy metals, attributed to the high electrical conductivity and electrocatalytic activity of the synthesized butterfly-shaped AgNS. Moreover, the excellent stability and sensitivity towards simultaneous quantification of heavy metals have been obtained with detection limits of 0.4 ppb, 2.5 ppb, 7.3 ppb, and 0.7 ppb for Cd (II), Pb (II), Cu (II), and Hg (II), respectively. Besides, the constructed sensor was successfully applied to simultaneously quantify target heavy metals in spiked water samples. Owing to excellent sensitivity, high robustness, affordability, and fast response, the presented electrochemical sensor could be incorporated into a portable and miniaturized potentiostat device, making it a promising method for on-site water analysis.     

A Sonogel/L-Cystein and a SAM L-Cystein Modified Electrodes for Detection of Dopamine

Summary: The Sonogel-Carbon electrode is a special class of sol-gel electrode that exhibits favourable mechanics and electric properties that can be used as electrochemical sensors. In this study, a Sonogel-Carbon modified with L-Cysteine was used to prepare a novel electrochemical sensor. The objective of this new electrode modification was to seek new electrochemical performances for thedetection of dopamine (DA). The influence of natural interferents such as Ascorbic Acid (AA) and Uric Acid (UA) was explored. The concentration of theses strong interferent was increased to a certain level in order to determine to what extends AA and UA may disturb the neurotransmitters electroanalysis. Our work showed that the modified electrode offers interesting analytical performances such as: (a) Fast and linear responses towards the neurotransmitter dopamine: The differential pulse voltammetry current peak was linear with the DA concentration in the range 2 · 10⁻⁷ M to 10⁻⁵ M with a detection limit of 4 · 10⁻⁸ M (S/N = 3). (b) Simultaneous detection and well-resolved signals between the DA, AA and UA: The new sensor could sensitively and separately determine DA in the presence of 1000 and 900 times higher concentrations of AA and UA respectively. Optimization of parameters such as the amount of L-cysteine in the Sonogel-Carbon mixture, interference effect, perm-selectivity and mechanical stability of the sensor are discussed. A comparison with a SAM L-Cysteine/gold electrode was also made. On the other hand the new Sonogel modified electrode has been applied to the determination of dopamine in urine samples with satisfactory results. With good selectivity and sensitivity, the proposed sensor is a simple tool for the selective detection of DA, AA and UA in biological samples.     

磁性石墨烯修饰辛基酚印迹传感器制备及应用研究

以辛基酚(4-OP)为模板分子,多巴胺为功能单体,采用电聚合技术在磁性石墨烯修饰碳电极表面制备对辛基酚具有高选择性与灵敏性的印迹电化学传感器。采用循环伏安法(CV)和差分脉冲伏安法(DPV)对此印迹传感器的电化学性能进行详细表征;采用扫描电子显微技术对修饰电极的形貌进行表征。结果表明,此印迹电化学传感器对辛基酚具有良好的特异识别性能。采用 DPV 法考察了孵化时间和洗脱溶剂对印迹传感器性能影响,结果表明,最佳孵化时间为14 min。此印迹电化学传感器的响应电流(△IR )与辛基酚在5.0×10-6~5.0×10-9 mol/ L 范围内浓度的负对数(-lgC)呈良好的线性关系,线性方程为△IR ( mA)=-0.25lgC(mol/ L)+2.35,检出限为3.64×10-10 mol/ L (S/ N=3)。此印迹电化学传感器对辛基酚具有良好的选择性和灵敏性,成功用于实际水样中辛基酚的检测,回收率为96.0%~104.0%。