Electrochemical Sensor Based on Biomass Yeast Integrated Sulfur-doped Graphene and Carboxylated Carbon Nanotubes/MoS2 for Highly-sensitive Detection of Pb2+

Glassy carbon electrodes (GCEs) modified with sulfur-doped graphene (SG)/carboxylated carbon nanotube (CNT−COOH)/MoS₂/yeast composite were prepared for electrochemical detection for lead ions by the simple hydrothermal methods and ultrasonic methods. The combination of SG and CNT−COOH could form a double-layer carbon structure, providing more active detection sites for detection for lead, which could also contribute to adherence of yeast and MoS₂. The SG/CNT−COOH/MoS₂/yeast exhibited a high response in detecting low concentrations of lead ions. And then the SG/CNT−COOH/MoS₂/yeast was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission electron microscope (TEM), Scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Compared with traditional detection technology, the linear range of the sensor was 10⁻⁶∼10⁻¹⁴ g/L. And the lower of detection (LOD) down to 2.61×10⁻¹⁵ g/L was achieved. The sensor showed prospective applications in detection of Pb²⁺ in real serum samples.     

基于核酸酶的新型阻抗传感器检测纺织品中的铅

建立一种基于核酸酶的电化学阻抗传感器检测纺织品中铅含量的方法。采用金纳米粒子修饰的金电极作为基底电极,以一种新型的核酸酶17EDNAzyme体系作为铅离子的生物识别元件,构建了一种新型的电化学阻抗传感器用于高灵敏选择性检测铅离子。在最佳实验条件下,传感器对溶液中铅离子的线性检测范围为1.0μg/L~10mg/L,检出限为0.6μg/L。测定结果的相对标准偏差小于5.4%(n=6),加标回收率在93.5%~106.0%之间。采用该法对实际纺织品样品进行测试,并与国标方法测定值进行对比,实验结果表明两种方法的测定值无显著性差异。该方法操作简便,对铅离子的检测具有良好的选择性,可用于现场样品的在线、快速测定。     

Lead(II)-Selective Membrane Electrode Based on Tetraphenylporphyrin

ABSTRACT

A PVC membrane electrode for Pb² ions based on tetraphenylporphyrin was prepared. The sensor exhibits a Nernstian response for lead ions over a wide concentration range (1.0 x 10^?5-1.0 x 10^?2 M). The limit of detection is 8.5 x 10^?6M. It has a response time of 15 s and can be used for at least three months without any divergence in potential. The proposed electrode shows a fairly good discriminating ability towards Pb² ion in comparison to some alkali, alkaline earth, transition and heavy metal ions. The electrode can be used in the pH range 5.0 to 7.5. It was used as an indicator electrode in potentiometric titration of lead ion.     

基于L-半胱氨酸/CdTe量子点修饰电极的电化学传感器的制备及其对Pb~(2+)的检测

成功制备了由L-半胱氨酸和CdTe量子点作为修饰材料的电化学传感器并用于水体中Pb~(2+)的检测。巯基丙酸修饰的CdTe量子点通过水相合成,表面含有大量羧基,与L-半胱氨酸表面的氨基形成酰胺键,修饰于金电极表面。通过荧光分光光度计、透射电子显微镜、红外光谱、X射线衍射对L-Cys/CdTe QDs复合材料进行表征。采用循环伏安法(CV)研究了L-Cys/CdTe QDs修饰成分在金电极上的电化学性能及CdTe量子点的最佳自组装时间。采用差分脉冲溶出伏安法(DPSV)研究了铅离子在修饰电极上的电化学行为。在优化实验条件下,Pb~(2+)浓度在1.0×10~(-6)~1.0×10~(-2) mol/L范围内与其峰电流呈良好的线性关系,相关系数(r2)为0.993 8,检出限(3σ,n=5)为4.0×10~(-7) mol/L。该传感器具有良好的重现性和稳定性,有望用于实际水样中铅离子的检测。     

Fabrication of Electrochemical Sensor Modified with Porous Graphene for Determination of Trace Calycosin

In this study, the porous graphene (PG) with excellent structure was successfully prepared by a simple pyrolysis process, and applied to construct electrochemical sensor (PG@GCE) for detection of calycosin (CYS). PG was characterized by Raman spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. Also, the electrochemical properties of the proposed sensors were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the results indicated that sensors had relatively large specific surface area and higher electron transport rate. Based on all those characteristics, CYS, a traditional Chinese medicine (TCM) active ingredient, displayed a great response on the surface of PC@GCE. Under the optimized conditions, the sensors displayed a good linear relationship between the peak current and the CYS concentration in the range of 1.8 × 10^–7–4.4 × 10^–5 M with the detection limit of 5.8 × 10^–8 M (S/N = 3). This study provided a novel analytical method for detection of CYS, rapid identification of Radix Hedysari and Radix Astragali, and gave another way for the trace analysis of CYS in biological samples. Furthermore, it would also deepen the application of PG in the field of pharmaceutical analysis.     

Lead(II) complexes of proline

Three new proline (pro) lead(II) complexes were synthesized and characterized by elemental analyses, IR, ¹H NMR, and ¹³C NMR spectroscopy. Single crystal X-ray structural analysis of [Pb(pro)(H₂O)] _n shows the complex to be a novel 1D chain polymer as a result of water bridging. Coordination number of Pb(II) is six, with a ‘stereo-chemically active’ electron lone pair, and the coordination sphere is hemidirected. The chains interact with each other via weak Pb?···?O intractions and hydrogen bonding to create a 2D framework.     

Sensitive and Simple Electrochemical Detection of Lead(II) with Carbon Ionic Liquid Electrode

In this paper a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid 1‐ethyl‐3‐methylimidazolium ethylsulphate ([EMIM]EtOSO₃) as the modifier and further used as the working electrode for the sensitive anodic stripping voltammetric detection of Pb²⁺. The characteristics of the CILE were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In pH 4.5 NaAc‐HAc buffer Pb²⁺ was accumulated on the surface of CILE due to the extraction effect of IL and reduced at a negative potential (‐1.20 V). Then the reduced Pb was oxidized by differential pulse anodic stripping voltammetry with an obvious stripping peak appeared at ?0.67 V. Under the optimal conditions Pb²⁺ could be detected in the concentration range from 1.0 × 10^?8 mol/L to 1.0 × 10^?6 mol/L with the linear regression equation as I_p(μA) = ?0.103 C (μmol/L) + 0.0376 (γ = 0.999) and the detection limit as 3.0 × l0^?9 mol/L (3σ). Interferences from other metal ions were investigated and Cd²⁺ could be simultaneously detected in the mixture solution. The proposed method was further applied to the trace levels of Pb²⁺ detection in water samples with satisfactory results.     

Polyethyleneimine Methylenephosphonic Acid for the Solid-Phase Sorption of Lead(II)

Abstract

In the first part of this work, polyethyleneimine methylenephosphonic acid (PEIMPA) was used as an effective sorbent for solid-phase extraction of Pb(II) ions from an aqueous solution. Conditions for effective sorption are optimized with respect to different experimental parameters in a batch process. The results showed that the amount of extraction decreases with solution pH in the range between 3.5 and 5.8. The sorption capacity is 609 mg·g^?1. The second part of the study focuses on the recovery of Pb(II) from a synthesized binary solution of Pb(II)–Zn(II) and from real Zn(II)-electrolyzed wastewaters. The presence of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), and Zn(II) in large concentrations has a significantly negative effect on extraction properties.     

Electrochemical Sensor Based on Thioether Oligomer Poly(N‐vinylpyrrolidone)‐modified Gold Electrode for Bisphenol A Detection

Presently, bisphenol A (BPA) has been added to the list of substances of very high concern as endocrine disruptors. According to the literature, exposure to bisphenol A even at low doses may result in adverse health effects. In this study, electrochemical sensor of Bisphenol A based on thioether DDT‐Poly(N‐vinylpyrrolidone) oligomer has been developed. The thioether oligomer, which is capable of recognizing BPA, was prepared and used for gold electrode modification. The characterization of the modified gold electrode and the synthesized thioether oligomer were carried out by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), Fourier‐transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR) and Size exclusion chromatography (SEC). Obtained results indicate that the modified electrode shows good electrochemical activity, good sensitivity and reproducibility for BPA detection. It exhibited a good linear relationship ranging from 1 to 20 pg/mL, and the detection limit was found to be 1.9 pg/mL at S/N=3. Several interfering species such as hydroquinone, phenol and resorcinol were used and their behaviors on the modified gold electrode were investigated.     

Selective Preconcentration and Ion Chromatography of Trace Lead(II) in Environmental Samples Using a Porous Graphitic Carbon Column

Abstract

Highly selective ion analysis of sub-ppm Pb(II) on a porous graphitic carbon (PGC) column, is described using ion chromatography with acidified aqueous mobile phases, post-column detection using PAR and spectrophotometric detection. Sensitivity is enhanced by on-line preconcentration of the metal prior to the chromatography using one millilitre injection volumes applied to a calix[4]arene-tetrahydroxamate based chelating precolumn. The method is applied to water samples collected from a river subjected to an industrial effluent discharge and results obtained compare favourably with those obtained using flame atomic absorption spectroscopy.     

Development of an Electrochemical Sensor for Selective Determination of Dopamine Based on Molecularly Imprinted Poly(p-aminothiophenol) Polymeric Film

In this study, a molecularly imprinted electrochemical sensor (MIP/DA) was investigated for selective and sensitive determination of dopamine (DA) by electrochemical polymerization of p-aminothiophenol in the presence of DA on gold electrode. According to electrochemical behaviour of the sensor, gained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), MIP/DA sensor showed distinctive electron transfer characteristics in comparison to the non-imprinted (NIP/DA) sensor. Besides the MIP/DA sensor showed high selectivity for dopamine through its analyte specific cavities. The sensor had a broad working range of 5.0×10⁻⁸–2.0×10⁻⁷ M with a limit of detection (LOD) of 1.8×10⁻⁸ M and the developed sensor was successfully applied for determination of dopamine in pharmaceutical samples.     

A New Sensor with Increased Lifetime Based on a Mixed Diazonium Thick Film/Gold Nanoparticles Interface for Hg(II) Trace Detection

This work describes a novel strategy for surface functionalization, the aim of which is to significantly increase the lifetime of an electrochemical sensor dedicated to Hg(II) trace determination. In order to tailor stable mixed organic/inorganic interfaces, gold nanoparticles were electrodeposited onto a glassy carbon electrode previously functionalized by a thick 4‐thiophenol diazonium film, which affords a good anchoring to the nanoparticles. AFM and FEG‐SEM were used to characterize the film thickness and the nanoparticles average size and density, respectively. By using square wave anodic stripping voltammetry, the sensor exhibited a linear response between 1 and 10 nM Hg(II) and a normalized sensitivity 0.03 μA nM^?1 min^?1. Compared to previous works, the storage lifetime of the interface was at least three times longer, being more than three weeks.     

Copper (II) Sensor Based on a Cephaloridine Antibiotic PVC Matrix

ABSTRACT

A poly (vinyl chloride) (PVC) based membrane of cephaloridine as a novel ionophore exhibits good potentiometric response for Cu²⁺ over a wide concentration range (10^?5-10^? M) with a slope of 28.5 mV per decade. The detection limit is 3.5 × 10^?6 M. The response time of the sensor is < 60 s. The electrode has been used for a period of one month and exhibits good selectivity towards Cu²⁺ in comparison to alkali, alkaline earth, transition and heavy metal ions, with no interference caused by Pb²⁺ Cd²⁺ and Fe²⁺ which are known to interfere with many other copper electrodes. The electrode can be used in the pH range from 4.0 to 6.5 and it can also be used in partially non-aqueous medium having up to 10 (v/v) non aqueous content and in the presence of cationic surfactants at concentrations less than 10^?3 M.     

Ag(I)与Co(II)离子对阳极析氧过程的电催化作用

Influence of Ag(Ⅰ), Co(Ⅱ) and Ni(Ⅱ) ions on oxygen anodic evolution at Pt and Ti/Pt/PbO2 electrodes was investigated in surphuric acid solutions. The oxygen evolution reaction at Ti/Pt/PbO2 electrode in surphuric acid solutions is characterized by two linearφ~ lgi relationships. At low c.d. it is close to 2.303RT/(1+β)F, whereas at high c.d. it is close to 2.303RT/βF. In the presence of Ag(Ⅰ) or Ni(Ⅱ) ions in the electrolytic solution the Tafel slope of oxygen evolution tends to be low, 2.303RT/(1+β)F (withβ=0.5). However, the oxygen evolution reaction at Pt electrodes in H2SO4 or CoSO4﹢H2SO4 solutions is characterized by one linearφ~ lgi relationship. The Tafel slope is close to 2.303RT/βF. In the presence of Ag(Ⅰ) or Ni(Ⅱ) ions in the electrolytic solution the Tafel slope of oxygen evolution tends to be low, 2.303RT/(1+β)F. The oxygen anodic evolution reactions are catalyzed by Ag(Ⅰ), Co(Ⅱ) and Ni(Ⅱ) ions in the electrolytic solution. When Ag(Ⅰ) or Ni(Ⅱ) was mixed with Co(Ⅱ), a promising catalyst for oxygen anodic evolution with higher catalyst activity than either of them alone was found. A comparison of the PbO2 electrode and the Pt electrode has also been given.     

Electrochemical Detection of Lead Ion Based on a Peptide Modified Electrode

A novel biosensor harnessing a peptide layer which has specific affinity to lead ion proved to be highly effective for electrochemical analysis of lead ions. The peptide modified electrode was used for the electrochemical analysis of various trace metal ions by square wave voltammetry. Compared to the other ions investigated, the peptide modified electrode was found to be highly selective to Pb²⁺ in the range of 50–700 nM. Furthermore, the biosensor exhibited a high reusability and good spike recovery in the tap water containing various concentration of Pb²⁺.     

Lead(IV) oxide-graphite composite electrodes: application to sensing of ammonia, nitrite and phenols

Carbon powder modified with lead(IV) oxide was synthesised by a wet impregnation procedure from concentrated lead(II) nitrate solution. The impregnated powder was subsequently thermally treated at 823 K. Electrochemical and spectroscopic characterisation of the modified powder showed that lead(IV) oxide has been formed during the procedure. A novel composite lead(IV) oxide modified carbon powder epoxy electrode was developed for electrocatalytic sensing of gaseous, inorganic and organic analytes. The behaviour and analytical advantages of the composite electrode are evaluated with respect to determination of ammonia, nitrite ions and several different phenols. It has been demonstrated that the composite electrode can be used to analyze these analytes in standard aqueous solutions with competitively low limits of detection.     

Determination of Trace Amount of Lead(II) in Sweet Fruit‐Flavored Powder Drinks by Differential Pulse Adsorptive Stripping Voltammetry at Carbon Paste Electrode

A new method is described for the determination of lead based on the cathodic adsorptive stripping of the lead–nuclear fast red (NFR) at a carbon paste electrode (CPE). The differential pulse voltammograms of the adsorbed complex of lead–NFR are recorded from ?0.10 to ?0.60 V (versus Ag/AgCl electrode). Optimal conditions were found to be an electrode containing 25% paraffin oil and 75% high purity graphite powder, 4.0×10^?5 mol L^?1 NFR; buffer solution (pH of 3.0), accumulation potential and time, ?0.20 V, 60 and 120 s (for high and low concentration of lead), respectively. The results show that the complex can be adsorbed on the surface of the CPE, yielding one peak at ?0.34 V, corresponding to reduction of NFR in the complex at the electrode. The detection limit was found to be 0.2 ng mL^?1 with a 120s accumulation time. The linear ranges are from 0.5 to 50 (t_acc=120 s) and 50 to 200 ng mL^?1 (t_acc=60 s). Application of the procedure to the determination of lead in lake water, bottled mineral water, synthetic samples and sweet fruit‐flavored powder drinks samples gave good results.     

Lead(II) ion-selective electrode based on polyaminoanthraquinone particles with intrinsic conductivity

A new polyvinylchloride membrane electrode was facilely prepared by using polyaminoanthraquinone (PAAQ) microparticles with an intrinsically electrical conductivity as a lead(II) ionophore. It is found that the electrode performance will significantly be improved with adding 1 wt% PAAQ microparticles and decreasing the membrane thickness. A 90 μm-thick membrane electrode consisting of PAAQ(salt):polyvinyl chloride:dioctylphthalate:sodium tetraphenylborate of 1:33:66:1 (wt) but without any traditional lead(II) ionophore achieved the optimal performance and exhibited a good Nernstian response for Pb(II) ions over a wide concentration range from 2.5 × 10⁻⁶ to 0.1 M with a slope of 28.9 mV/decade and a detection limit down to 776 nM. A reasonably short response time of 12 s was revealed together with a long lifetime over a period of around 4 months in a wide pH range between 2.8 and 5.2. A fixed interference method indicated that the electrode has an excellent selectivity for lead(II) ion over alkali, alkaline earth and other heavy metal ions. The proposed electrode has been also found to be a powerful indicator electrode for potentiometric titration of Pb(II) ions with EDTA. The electrode can be used to accurately monitor the Pb(II) pollution in environmental waters.     

Fast Simultaneous Adsorptive Stripping Voltammetric Determination of Ni(II) and Co(II) at Lead Film Electrode Plated on Gold Substrate

A fast adsorptive stripping voltammetric procedure for simultaneous determination of Ni(II) and Co(II) in the presence of nioxime as a complexing agent at an in situ plated lead film electrode was described. The time of determination of these ions was shortened due to the application of gold as a substrate for lead film. At gold substrate lead film formation and accumulation of Ni(II) and Co(II) complexes with nioxime proceeds simultaneously. To obtain a stable signals for both ions a simple procedure of activation of the electrode was proposed. Calibration graphs for an accumulation time of 20 s were linear from 5×10^?9 to 1×10^?7 mol L^?1 and from 5×10^?10 to 1×10^?8 mol L^?1 for Ni(II) and Co(II), respectively. The procedure with the application of a lead film electrode on a gold substrate was validated in the course of Ni(II) and Co(II) determination in certified reference materials.     

Reversible and Highly Selective Fluorescent Sensor for Mercury(II) Based on a Water‐Soluble Poly(para‐phenylene)s Containing Thymine and Sulfonate Moieties

A novel water‐soluble poly(para‐phenylene) derivative with pendant thymine and sulfonate units (PBTS) has been prepared and its metal ion sensing properties have been investigated. PBTS exhibited a reversible and selective fluorescence quenching behavior toward Hg²⁺ ions as compared to Ag⁺, Ni²⁺, Mg²⁺, Ca²⁺, Hg²⁺, Co²⁺, Cd²⁺, Cu²⁺, Pb²⁺, Ba²⁺, Fe³⁺, and Zn²⁺ ions in aqueous solution. The fluorescence quenching resulted from the interpolymeric π‐stacking aggregation which was induced by the specific thymine–Hg–thymine interaction.