脉冲恒电位一步法制备聚3,4-乙烯二氧噻吩石墨烯复合材料构建无酶葡萄糖传感器

本研究利用石墨烯(rGO)与3,4-乙烯二氧噻吩(EDOT)单体芳香环之间的π-π*相互作用和氢键作用,采用脉冲恒电位一步法制备了聚3,4-乙烯二氧噻吩石墨烯(PEDOT-rGO)复合膜,将纳米镍(NiNPs)电沉积在此复合膜(PEDOT-rGO)表面,制备了NiNPs/PEDOT-rGO修饰玻碳电极(NiNPs/PEDOT-rGO/GCE),研究了此修饰电极对葡萄糖的电催化氧化性能.实验结果表明,此NiNPs/PEDOT-rGO/GCE可以作为无酶传感器实现对葡萄糖的检测.本方法稳定性高,选择性好,线性范围宽(2μmol/L~58 mmol/L),检出限低至0.7μmol/L,可以用于对葡萄糖的快速、灵敏检测.     

Over‐Oxidized Poly (Phenol Red) Film Modified Glassy Carbon Electrode for Anodic Stripping Voltammetric Determination of Ultra‐Trace Antimony (III)

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over‐oxidized poly(phenol red) modified glassy carbon electrode (PPhRed_ox/GCE) in 0.1 mol L^‐1 HCl medium. The formation of both poly(phenol red) and over‐oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRed_ox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRed_ox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 ‐ 1.218 μg L⁻¹ and 3.40 – 18.26 μg L⁻¹ with a detection limit of 0.0075 μg L⁻¹. The proposed over‐oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE‐EnviroMAT™ EP−L‐2).     

In situ Electrochemical Synthesis of a Composite Film Containing Nickel Hexacyanoferrate and Bentonite Clay for the Sensitive Determination of Acetaminophen and Dopamine

A composite film of nickel hexacyanoferrate (NiHCF) and bentonite (Bt) clay (abbreviated as NiHCF?Bt) is synthesized by an in situ electrochemical method. For this synthesis, nickel ions are immobilized on Bt clay by an ion‐exchange process, equilibrating Bt clay with nickel nitrate. On a glassy carbon electrode (GCE), the nickel ion‐exchanged Bt clay (Ni²⁺?Bt) is coated to get the modified electrode which is represented as GCE/Ni²⁺?Bt. The NiHCF?Bt composite film is prepared on the GCE surface using the GCE/Ni²⁺?Bt and scanning the electrode potentials between ?0.10 to 1.00 V continuously in an aqueous solution containing potassium hexacyanoferrate and potassium chloride. This NiHCF?Bt modified GCE (GCE/NiHCF?Bt) exhibits redox peaks due to the oxidation and reduction of the central metal ion, Fe²⁺. The electro‐generated Fe³⁺ present in the GCE/NiHCF?Bt, electrocatalytically oxidizes a range of drugs like acetaminophen (AC), dopamine (DA), and tyrosine (TY) at decreased overpotentials with high current. This property is advantageously used for the precise quantification of AC, DA, and TY. Sensitivity, limit of detection, and linear calibration range for the determination of AC are found to be 0.20 μA μM^?1 cm^?2, 1.5 μM, and 25.0–1000.0 μM, respectively. Further, the amount of AC present in pharmaceutical products is satisfactorily quantified which demonstrated the use of the NiHCF?Bt composite film in electroanalysis.     

Fabrication of Acid Violet 34/Nickel Hydroxide Ultrathin Film and Its Electrocatalytic Performance for Glucose

This article reports the fabrication of Acid Violet 34 (AV34)/nickel hydroxide nanosheets ultrathin film on the glassy carbon electrode (GCE) via the electrostatic layer‐by‐layer (LBL) technique, and its electrocatalytic oxidation for glucose was demonstrated. UV‐vis absorption and electrochemical impedance spectra indicate the uniform deposition of the LBL film, with a continuous and smooth film surface observed by SEM and AFM. The electrochemical performance of the ultrathin film was studied by cyclic voltammetry and chronoamperometry. The (AV34/Ni(OH)₂)₅ ultrathin film modified electrode displays a fast direct electron transfer attributed to the Ni²⁺/Ni³⁺ redox couple as well as remarkable electrocatalytic activity towards the oxidation of glucose. The linear response was obtained in the range 0.5–13.5 mM (R=0.9994) with a low detection limit (14 µM), high sensitivity (25.9 µA mM^?1 cm^?2), rapid response (less than 1 s) and excellent anti‐interference properties to the species including ascorbic acid (AA), uric acid (UA), acetamidophenol (AP) and structurally related sugars. Therefore, the AV34/Ni(OH)₂ ultrathin film can be potentially used as a feasible electrochemical sensor for the determination of glucose.     

Electrochemical Sensor‐Based Ruthenium Nanoparticles on Reduced Graphene Oxide for the Simultaneous Determination of Ethinylestradiol and Amoxicillin

The composite material of reduced graphene and Ru nanoparticles (rGO/RuNP) was obtained by electrochemical oxidation of ruthenium nanoparticles immobilised on the glassy carbon electrode (GCE) surface and used for simultaneous electroanalysis of drugs. There are many discussions in the scientific community about the decrease in therapeutic efficacy of contraceptives when associated with antibiotics. The antibiotic effect of the antagonist can increase the contraceptive excretion levels in urine, indicating a reduction in the body and thus a decrease in the desired effect. Using the DPV technique, it was possible to quantify ethinylestradiol (EE2) and amoxicillin (AMX) with a linear response range, 5.50x10⁻⁸ – 1.20x10⁻⁶ mol L⁻¹, and LOD, 2.04 nmol L⁻¹ and 1.63 nmol L⁻¹, respectively. The results for the electrochemical behaviour of EE2 and AMX using GCE/rGO/RuNP were compared with GCE/rGO and GCE. The GCE/rGO/RuNP showed greater stability and separation anodic peak currents, suitable for the quantification of organic molecules in samples of environmental interest, as well as clinical and food samples.     

Selective Electroanalysis of Ascorbic Acid Using a Nickel Hexacyanoferrate and Poly(3,4‐ethylenedioxythiophene) Hybrid Film Modified Electrode

The mixed‐valent nickel hexacyanoferrate (NiHCF) and poly(3,4‐ethylenedioxythiophene) (PEDOT) hybrid film (NiHCF‐PEDOT) was prepared on a glassy carbon electrode (GCE) by multiple scan cyclic voltammetry. The films were characterized using atomic force microscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, X‐ray diffraction, and electrochemical impedance spectroscopy (AC impedance). The advantages of these films were demonstrated for the detection of ascorbic acid (AA) using cyclic voltammetry and amperometric techniques. The electrocatalytic oxidation of AA at different electrode surfaces, such as the bare GCE, the NiHCF/GCE, and the NiHCF‐PEDOT/GCE modified electrodes, was determined in phosphate buffer solution (pH 7). The AA electrochemical sensor exhibited a linear response from 5×10⁻⁶ to 1.5×10⁻⁴ M (R²=0.9973) and from 1.55×10⁻⁴ to 3×10⁻⁴ M (R²=0.9983), detection limit=1×10⁻⁶ M, with a fast response time (3 s) for AA determination. In addition, the NiHCF‐PEDOT/GCE was advantageous in terms of its simple preparation, specificity, stability and reproducibility.     

MWCNTs/Ionic Liquid/Graphene Quantum Dots Nanocomposite Coated with Nickel‐Cobalt Bimetallic Catalyst as a Highly Selective Non‐enzymatic Sensor for Determination of Glucose

In this work, a glassy carbon electrode (GCE) was modified with multiwall carbon nanotubes/ionic liquid/graphene quantum dots (MWCNTs/IL/GQDs) nanocomposite. Then, the nanocomposite was decorated with nickel‐cobalt nanoparticles (Ni?Co NPs), and it was used as a non‐enzymatic glucose sensor. Field emission scanning electron microscopy, X‐ray diffraction spectroscopy, and energy dispersive spectroscopy were employed to prove the electrodeposition of the Ni?Co NPs on the surface of MWCNTs/IL/GQDs/GCE. Also, cyclic voltammetric and amperometric methods were utilized for the investigation of the electrochemical behaviour of the Ni?Co NPs/MWCNTs/IL/GQDs/GCE for glucose oxidation. The novel amperometric sensor displayed two linear ranges from 1.0 to 190.0 μmol L^?1 and 190.0 to 4910 μmol L^?1 with a low detection limit of 0.3 μmol L^?1 as well as fast response time (2 s) and high stability. Also, the sensor showed good selectivity for glucose determination in the presence of ascorbic acid, citric acid, dopamine, uric acid, fructose, and sucrose, as potential interference species. Finally, the performance of the proposed sensor was investigated for the glucose determination in real samples. Ni?Co NPs/MWCNTs/IL/GQDs/GCE showed good sensitivity and excellent selectivity.     

A Self‐assembled L‐Cysteine and Electrodeposited Gold Nanoparticles‐reduced Graphene Oxide Modified Electrode for Adsorptive Stripping Determination of Copper

Glassy carbon electrode (GCE) modified with L‐cysteine and gold nanoparticles‐reduced graphene oxide (AuNPs‐RGO) composite was fabricated as a novel electrochemical sensor for the determination of Cu²⁺. The AuNPs‐RGO composite was formed on GCE surface by electrodeposition. The L‐cysteine was decorated on AuNPs by self‐assembly. Physicochemical and electrochemical properties of L‐cysteine/AuNPs‐RGO/GCE were characterized by scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, Raman spectroscopy, X‐ray diffraction, cyclic voltammetry and adsorptive stripping voltammetry. The results validated that the prepared electrode had many attractive features, such as large electroactive area, good electrical conductivity and high sensitivity. Experimental conditions, including electrodeposition cycle, self‐assembly time, electrolyte pH and preconcentration time were studied and optimized. Stripping signals obtained from L‐cysteine/AuNPs‐RGO/GCE exhibited good linear relationship with Cu²⁺ concentrations in the range from 2 to 60 μg L⁻¹, with a detection limit of 0.037 μg L⁻¹. Finally, the prepared electrode was applied for the determination of Cu²⁺ in soil samples, and the results were in agreement with those obtained by inductively coupled plasma mass spectrometry.     

New Method for Carbohydrates Determination in Sugarcane Bagasse by HPAEC‐RPAD Using Glassy Carbon Electrode Modified with Carbon Nanotubes and Nickel Nanoparticles

Second generation ethanol can be produced from carbohydrates released from both sugarcane bagasse cell wall and sugarcane straw. The development of new method for the analysis of carbohydrates is, in this sense, seen as extremely relevant in the area of bioenergy. Based on the above considerations, the scope of this work encompasses the identification and quantification of carbohydrates composition in sugarcane bagasse without the need of sample derivatization, developing a novel analytical method using a glassy carbon electrode modified with multi‐walled carbon nanotubes containing nickel oxyhydroxide nanoparticles (GCE/MWCNT/NiOOH) and applying the modified electrode as a detector in HPAEC (High Performance Anion‐Exchange Chromatography) with reverse pulsed amperometric detection (RPAD) towards the determination of arabinose, galactose, glucose and xylose in hydrolyzed sugarcane bagasse. The carbohydrates concentrations determined in the hydrolyzed sugarcane bagasse were 6.1×10⁻⁴ mol L⁻¹, 1.0×10⁻² mol L⁻¹ and 2.8×10⁻³ mol L⁻¹ for arabinose, glucose, and xylose respectively. Our results showed that the present method is, in essence, attractive for analysis in the course of the production process of second generation ethanol production in that it does not require sample derivatization, has rapid run time, satisfactory separation, and can be used for the detection of carbohydrates without the interference of other electroactive species.     

A Single Drop Fabrication of the Cholesterol Biosensor Based on Synthesized NiFe2O4NPs Dispersed on PDDA‐CNTs

A cholesterol biosensor based on cholesterol oxidase‐poly(diallyldimethylammonium chloride)‐carbon nanotubes‐nickel ferrite nanoparticles (ChOx‐PDDA‐CNTs‐NiFe₂O₄NPs) solution is easily fabricated by using a single dropping step on a glassy carbon electrode (GCE) surface. This technique is an alternative way to reduce complexity, cost and time to produce the biosensor. The uniformly dispersed materials on the electrode surface enhance the catalytic reaction of cholesterol oxidase and electron transfer from the oxidation of hydrogen peroxide in the system. The nickel ferrite nanoparticles were synthesized by co‐precipitation and calcination at various temperatures. These nanoparticles were then characterized using field emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and X‐ray diffraction (XRD). The synthesized material calcined at 700 °C was well defined and presented the octahedral metal stretching with cubic NiFe₂O₄NPs phase. In cyclic voltammetric study, the ChOx‐PDDA‐CNTs‐NiFe₂O₄NPs/GCE showed 0.43 s⁻¹ charge transfer rate constant (K _s), 7.79×10⁻⁶ cm² s⁻¹ diffusion coefficient value (D ), 0.13 mm² electroactive surface area (A _e) and 3.58×10⁻⁸ mol cm⁻² surface concentration ( ). This modified electrode exhibits stability in term of percent relative standard deviation (%RSD=0.62 %, n=10), reproducibility (%RSD=0.81, n=10), high sensitivity (25.76 nA per mg L⁻¹ cm⁻²), linearity from 1 to 5,000 mg L⁻¹ (R²=0.998) with a low detection limit (0.50 mg L⁻¹). Its Michaelis‐Menten constant (K _m) was 0.14 mM with 0.92 μA maximum current (I _max) and demonstrated good selectivity without the effects of electroactive species such as ascorbic acid, glucose and uric acid. The cholesterol biosensor was successfully applied to determine cholesterol levels in human blood samples, showing promise due to its simplicity and availability.     

Visible Light Photoelectrochemical Sensor for Acetaminophen Determination using a Glassy Carbon Electrode Modified with BiVO4 Nanoparticles

A new and simple photoelectrochemical (PEC) sensor using a glassy carbon electrode (GCE) modified with bismuth vanadate (BiVO₄) nanoparticles and dihexadecyl phosphate (DHP) film was useful for acetaminophen (AC) determination. In 0.2 mol L⁻¹ phosphate buffer (pH=9), the GCE without modification exhibited the smaller photocurrent (0.86 μA) when compared with GCE modified with 1.0 mg mL⁻¹ or 2.0 mg mL⁻¹ BiVO₄ nanoparticles suspension (5.9 and 34 μA, respectively). Based on the photocurrent signal generated through the interaction between GCE, BiVO₄ and the energy of visible light a chronoamperometric method for AC determination was developed. The AC linear range concentration from 0.099 to 0.99 μmol L⁻¹ and limits of detection and quantification of 0.027 and 0.091 μmol L⁻¹, respectively, was obtained. The proposed method was applied to the AC determination in commercial drugs and tap water with satisfactory accuracy and precision. Moreover, the PEC construction was easy and had a short response time, which might confer higher sample throughput for the method.     

A Novel Electrochemical Glassy Carbon Electrode Modified with Carbon Black and Glyceline Deep Eutectic Solvent within a Crosslinked Chitosan Film for Simultaneous Determination of Acetaminophen and Diclofenac

Glyceline, reline, or ethaline deep eutectic solvents and carbon black nanoparticles within a crosslinked chitosan film are investigated as glassy carbon electrode modifiers for the first time. The selected 5 mg mL⁻¹ glyceline modified GCE was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. Simultaneous determination of acetaminophen and diclofenac by differential pulse adsorptive stripping voltammetry (DPAdSV) presented limits of detection of 2.6×10⁻⁸ and 5.2×10⁻⁸ mol L⁻¹ for acetaminophen and diclofenac, respectively, in pharmaceutical and biological samples. The obtained results were compared with those obtained by HPLC at a confidence level of 95 %.     

Comparative Study on Electroanalysis of Fenthion Using Silver Amalgam Film Electrode and Glassy Carbon Electrode Modified with Reduced Graphene Oxide

Oxidation and reduction processes of the insecticide fenthion was comparatively investigated at a reduced graphene oxide modified glassy carbon electrode (RGO‐GCE) and a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) using square wave stripping voltammetry (SWSV). The influence of pH and SW parameters was investigated. The linear concentration ranges were found to be 1 × 10⁻⁶ – 2 × 10⁻⁵ and 1 × 10⁻⁷ – 2 × 10⁻⁵ mol L⁻¹ for Hg(Ag)FE and RGO‐GCE, respectively. The detection and quantification limits were calculated as 1.3 × 10⁻⁷ and 4.5 × 10⁻⁷ mol L⁻¹ for Hg(Ag)FE and 7.6 × 10⁻⁹ and 2.5 × 10⁻⁸ mol L⁻¹ for RGO‐GCE. Both of the developed electroanalytical methods offer rapid and simple detection of fenthion and were used on spiked tap and river water and apple juice samples. Scanning electron microscopy was used for RGO‐GCE surface characterization.     

Synthesis of graphene oxide nanosheet: A novel glucose sensor based on nickel-graphene oxide composite film

The graphene oxide (GO) nanosheets were produced by chemical conversion of graphite, and were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR). An electrochemical sensor based on Ni/graphene (GR) composite film was developed by incorporating Ni²⁺ into the graphene oxide film modified glassy carbon electrode (Ni/GO/GCE) through the electrostatic interactions with negatively charged graphene oxide. The Ni²⁺/graphene modified glassy carbon electrode (Ni/GR/GCE) was prepared by cyclic voltammetric scanning of Ni/GO/GCE in the potential range from ?1.5 to 0.2 V at 50 mV s^?1 for 5 cycles. The electrochemical activity of Ni/GR/GCE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni/GR/GCE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. The introduction of conductive graphene not only greatly facilitates the electron transfer of Ni²⁺, but also dramatically improves the long-term stability of the sensor by providing the electrostatic interactions. Ni/GR/GCE also shows good electrocatalytic activity toward the oxidation of glucose. The Ni/GR/GCE gives a good linear range over 10 to 2700 μM with a detection limit of 5 μM towards the determination of glucose by amperometry. This sensor keeps over 85% activity towards 0.1 mM glucose after being stored in air for a month, respectively. Furthermore, the modified sensor was successfully applied to the sensitive determination of glucose in blood samples.     

Sensitive immunoassay for the β-agonist ractopamine based on glassy carbon electrode modified with gold nanoparticles and multi-walled carbon nanotubes in a film of poly-arginine

We are presenting an electrochemical immunosensor for the determination of the β-agonist and food additive ractopamine. A glassy carbon electrode (GCE) was modified with gold nanoparticles and a film of a composite made from poly(arginine) and multi-walled carbon nanotubes. Antibody against ractopamine was immobilized on the surface of the modified GCE which then was blocked with bovine serum albumin. The assembly of the immunosensor was followed by electrochemical impedance spectroscopy. Results demonstrated that the semicircle diameter increases, indicating that the film formed on the surface hinders electron transfer due to formation of the antibody-antigen complex on the modified electrode. Under optimal conditions, the peak current obtained by differential pulse voltammetry decreases linearly with increasing ractopamine concentrations in the 0.1 nmol•L⁻¹ to 1 μmol•L⁻¹ concentration range. The lower detection limit is 0.1 nmol•L⁻¹. The sensor displays good stability and reproducibility. The method was applied to the analysis of spiked swine feed samples and gave satisfactory results.

Immunoassay for ractopamine based on glassy carbon electrode modified with gold nanoparticles and a film of a composite made from poly (arginine) and multi-walled carbon nanotubes was proposed. Under optimal conditions, the peak currents obtained by differential pulse voltammetry decreases linearly with increasing ractopamine concentrations in the 0.1 nmol•L⁻¹ to 1 μmol•L⁻¹ concentration range. The detection limit is 0.1 nmol•L⁻¹.

     

Mercury‐modified Lignosulfonate‐stabilized Gold Nanoparticles as an Alternative Material for Anodic Stripping Voltammetry of Thallium

Lignosulfonate‐stabilized gold nanoparticles (AuNPs‐LS) were synthesized and subsequently used as a complexing agent for mercury ions. The obtained AuNPs‐LS/Hg²⁺ complex was characterized by means of various physicochemical techniques such as UV‐vis spectroscopy, transmission electron microscopy and cyclic voltammetry. Furthermore, the resulting complex was evaluated as an electrode modifier for the development of amperometric sensors. Upon sufficient negative potential, the bound mercury ions are reduced to form an amalgam with AuNPs‐LS. Thus, the performance of glassy carbon electrode (GCE) modified by AuNPs‐LS/Hg film was investigated as an electrochemical sensor in the determination of Tl⁺ ions in a 0.05 M EDTA at pH 4.5. The presence of the mercury containing film improves the analyte accumulation due to its ability to form a fused amalgam with thallium. The presented data indicate that the GCE/AuNPs‐LS/Hg modified electrode shows better performance toward Tl⁺ determination in comparison to bare GCE. The stripping anodic peak current of thallium was linear over its concentration range from 1.7⋅10⁻⁷ to 5.0⋅10⁻⁶ M. The detection limit (3σ) was estimated to be 1.4⋅10⁻⁷ M. The proposed method was successfully applied for the determination of thallium ions in real samples of soil derived from the area of the copper smelter near Głogów (Poland).     

Electroanalysis of Bisphenol A at a Multiwalled Carbon Nanotubes‐gold Nanoparticles Modified Glassy Carbon Electrode

A sensitive electrochemical method was developed for the determination of bisphenol A (BPA) at a glassy carbon electrode (GCE) modified with a multiwalled carbon nanotubes (MWCNTs)‐gold nanoparticles (GNPs) hybrid film, which was prepared based on the electrostatic interaction between positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged MWCNTs and GNPs. The MWCNT‐GNPs/GCE exhibited an enhanced electroactivity for BPA oxidation versus unmodified GCE and MWCNTs/GCE. The experimental parameters, including the amounts of modified MWCNTs and GNPs, the pH of the supporting electrolyte, scan rate and accumulation time, were examined and optimized. Under the optimal conditions, the differential pulse voltammetric anodic peak current of BPA was linear with the BPA concentration from 2.0×10^?8 to 2×10^?5 mol L^?1, with a limit of detection of 7.5 nmol L^?1. The proposed procedure was applied to determine BPA leached from real plastic samples with satisfactory results.     

Electrochemical Determination of Fenitrothion Organophosphorus Pesticide Using Polyzincon Modified‐glassy Carbon Electrode

In this paper, a glassy carbon electrode (GCE) was modified with polyzincon. The modified electrode was used as a simple, inexpensive and highly sensitive electrochemical sensor for the determination of organophosphorus pesticide fenitrothion. To fabricate the electrochemical sensor, GCE was immersed in 0.10 mmol L⁻¹ zincon solutions at pH 7.0 and then successively scanned between −1.00 to 2.20 V (vs . Ag/AgCl) at a scan rate of 70 mV s⁻¹ for six cycles. The morphology and structure of the polyzincon were studied with atomic force microscopy and scanning electron microscopy. A comparison of the electrochemical behavior of fenitrothion on the unmodified and polyzincon modified‐GCE showed that in the modified electrode not only the oxidation peak current increased, but also the overpotential shifted to lower one. The experimental conditions such as sample solution pH, accumulation potential, and time were optimized. The differential pulse voltammetric responses of fenitrothion at potential about −0.60 V was used for the determination of fenitrothion. The peak current increased with increasing the concentration of fenitrothion in the range of 5 to 8600 nmol L⁻¹ with a detection limit of 1.5 nmol L⁻¹. Finally, the electrochemical sensor was used for the analysis of fenitrothion in water and fruit samples.     

Electrochemical Determination of Dicofol at Nickel Nanowire Modified Poly(p‐aminophenol) Film Electrode

An electrochemical sensor was fabricated by construction of nickel nanowires on the surface of poly(p‐aminophenol) (PPAP) modified glassy carbon electrode. The electrochemical response of dicofol, a known pesticide and used for agricultural activities such as cyclic voltammetry and differential pulse voltammetry, were investigated and the results were compared with those obtained unmodified electrodes. Following the optimization of NaOH concentration, polymerization cycle number, Ni nanowire amount, the linear range for the dicofol was studied and found as 0.83–30.7 μmol L^?1 (R²=0.9981) at Ni/PPAP/GCE with a 0.08 μmol L^?1 detection limit according to S/N=3. Finally, the proposed Ni/PPAP/GCE sensor was successfully applied for the dicofol analysis in soil samples. The characterization of the developed surface was carried out by scanning electron microscopy and X‐Ray photoelectron spectroscopy.     

Pt‐Pd Bimetallic Nanoparticles Decorated Nanoporous Graphene as a Catalytic Amplification Platform for Electrochemical Detection of Xanthine

The nanoporous graphene papers (NGPs) was prepared by the hard‐template method. The Pt−Pd modified NGPs hybrid was prepared by the self‐assembly method. Then a glassy carbon electrode (GCE) modified with Pt−Pd bimetallic nanoparticles‐functionalized nanoporous graphene composite has been prepared for the electrochemical determination of Xanthine (XA). The Pt−Pd/NGPs hybrid was characterized by transmission electron microscopy, scanning electron microscope and X‐ray diffraction. The electrochemical behavior of XA on Pt−Pd/NGPs/GCE was investigated by cyclic voltammetry and amperometric i‐t. The Pt−Pd/NGPs modified electrode exhibited remarkably electrocatalytic activity towards the oxidation reaction of XA in phosphate buffer solution (pH=5.5). Under the optimal conditions, the determination of XA was accomplished by using amperometric i‐t, the linear response range from 1.0×10⁻⁵∼1.2×10⁻⁴ M. The detection limit was 3.0×10⁻⁶ M (S/N=3). The proposed modified electrode showed good sensitivity, selectivity, and stability with applied to determine XA in human urine.