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1.
The electrochemical reduction of three common insecticides such as cypermethrin (CYP), deltamethrin (DEL) and fenvalerate (FEN) was investigated at glassy carbon electrode (GCE), multiwalled carbon nanotubes modified GCE (MWCNT‐GCE), polyaniline (herein called as modifier M1) and polypyrrole (herein called as modifier M2) deposited MWCNT/GCE using cyclic voltammetry. Influences of pH, scan rate, and concentration were studied. The surface morphology of the modified film was characterized by scanning electron microscopy (SEM) and X‐ray diffraction analysis (XRD). A systematic study of the experimental parameters that affect differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived at. The calibration plots were linear over the insecticide's concentration range 0.1–100 mg L?1 and 0.05–100 mg L?1 for all the three insecticides at MWCNT‐GCE and MWCNT(M1)‐GCE respectively. The MWCNT(M2)‐GCE performed well among the three electrode systems and the determination range obtained was 0.01–100 mg L?1 for CYP, DEL and FEN. The limit of detection (LOD) was 0.35 μg L?1, 0.9 μg L?1 and 0.1 μg L?1 for CYP, DEL and FEN respectively on MWCNT(M2)‐GCE modified system. Suitability of this method for the trace determination of insecticide in spiked soil sample was also determined.  相似文献   

2.
An electrochemical sensing platform was developed for the amperometric detection of β-nicotinamide adenine dinucleotide (NADH) through the integration of a multi-walled carbon nanotube (MWCNT) into electropolymerized phenothiazine dyes. The composite containing MWCNT and poly(phenothiazine) was prepared by electro-oxidative polymerization of phenothiazine derivatives, Azure B, Azure A and thionine, into an MWCNT/ poly(diallyldimethylammonium chloride) (PDDA) multilayer, which was constructed by electrostatic layer-by-layer assembly on a glassy carbon electrode. The three phenothiazine monomers used in this study exhibited similar electrochemical behaviors. Azure B was used extensively as a model monomer for the investigation. Electrochemical techniques and scanning electron microscopy were used to demonstrate that the porous composite was formed and that the carbon nanotube served as a nano-sized backbone for the loading of polymeric phenothiazine. The electrocatalytic current for NADH oxidation was enhanced as the number of layers increased, implying that the increase of NADH-accessible poly(phenothiazine) and the three-dimensional arrangement of the poly(phenothiazine)-coated MWCNT in the composite facilitated electron and NADH transfer. Under optimal conditions, the detection limit for NADH decreases to 7.0 × 10?8?M at a potential of 0.1 V (versus Ag/AgCl) using a {MWCNT/PDDA}8?poly(Azure B) composite modified glassy carbon electrode, with a response time of about 5 s. This work demonstrates that the electropolymerization of the phenothiazine monomer into a pre-formed multilayer containing MWCNT can be used for the controllable preparation of stable MWCNT/poly(phenothiazine) composites on electrode surfaces, which have the potential to provide a platform for electrochemical biosensors based on NAD+-dependent dehydrogenase enzymes.  相似文献   

3.
The synthesis and electropolymerization of a pyrrolic concanavalin A derivative (pyrrole‐Con A) onto a multiwalled carbon nanotube (MWCNT) deposit is reported. Glucose oxidase was then immobilized onto the MWCNT‐poly(pyrrole‐Con A) coating by affinity carbohydrate interactions with the polymerized Con A protein. The resulting enzyme electrode was applied to the amperometric detection of glucose exhibiting a high sensitivity of 36 mA cm?2 mol?1 L and a maximum current density of 350 μA cm?2.  相似文献   

4.
A new biomimetic functional system having an impure multiwalled carbon nanotube (MWCNT‐Fe)–chitosan biopolymer (H2N–CHIT) chemically modified glassy carbon electrode (GCE/[MWCNT‐Fe:H2N‐CHIT]) has been developed and demonstrated efficient hydrogen peroxide electrocatalytic and electrochemical sensing applications in pH 7 phosphate buffer solution (PBS). The hybrid system showed a stable and well‐defined surface confined redox peak at an apparent electrode potential, E°′=?0.22 V versus Ag/AgCl with surface excess value 13.63 nmol cm?2. Physicochemical characterizations of the hybrid by using FESEM, TEM, Raman spectroscopy, FTIR, and various control electrochemical experiments revealed that the iron impurity in the MWCNT interacted with the amino functional group of the chitosan polymer and thereby formed an unique complex‐like structure ([MWCNT‐FeIII/II:NH2‐CHIT]), similar to heme peroxidase with a central FeIII/II‐redox‐active site. The biomimetic system followed Michaelis–Menten‐type reaction kinetics for the H2O2 reduction reaction with a KM value of 0.23 mM . At pH 7, amperometric it sensing and flow‐injection analysis of H2O2 on the biomimetic system showed calibration plots in windows 5–500 and 50–2500 μM , with detection‐limit values of 2.3 and 9.7 μM , respectively. Unlike most of the previously reported systems that undergo serious interferences in physiological pH, the biomimetic system displayed a remarkable tolerance to other co‐existing interferants (such as cysteine, ascorbic acid, uric acid, nitrate, and nitrite), at a H2O2 detection potential similar to the peroxidase enzyme. The ability of the biosensor system to perform routine analyses was demonstrated by the detection of H2O2 present in simulated milk and clinical and cosmetic samples with appreciable recovery values.  相似文献   

5.
Nitrogen‐doped mesocellular carbon foam (denoted as MCF? CNx) with high surface area and large pore volume was prepared and characterized in detail. The MCF? CNx was further functionalized by oxidation with HNO3 (denoted as MCF? CNx‐O) in order to effectively improve its hydrophilicity and biocompatibility. Both MCF? CNx and MCF? CNx‐O were used for immobilization of Hb and design of electrochemical biosensors. The activity of Hb immobilized on MCF? CNx‐O is two times higher than that of Hb immobilized on MCF? CNx. The Hb‐MCF? CNx‐O‐Nafion modified electrode displays fast response, high sensitivity and low detection limit to the detection of hydrogen peroxide. The sensitivity of Hb‐MCF? CNx‐O‐Nafion modified electrode (477 μA mM?1 cm?2) is twice that of Hb‐MCF? CNx‐Nafion modified electrode.  相似文献   

6.
The present work describes the development of a selective and sensitive voltammetric sensor for simultaneous determination of catechol (CC) and hydroquinone (HQ), based on a glassy carbon (GC) electrode modified with manganese phthalocyanine azo‐macrocycle (MnPc) adsorbed on multiwalled carbon nanotubes (MWCNT). Scanning electron microscopy and scanning electrochemical microscopy were used to characterize the composite material (MnPc/MWCNT) on the glassy carbon electrode surface. The modified electrode showed excellent electrochemical activity towards the simultaneous oxidation and reduction of CC and HQ. On the MnPc/MWCNT/GC electrode, both CC and HQ can generate a pair of quasi‐reversible and well‐defined redox peaks. Under optimized experimental and operational conditions, the cathodic peak currents were linear over the range 1–600 µmol L?1 for both CC and HQ, with limits of detection of 0.095 and 0.041 µmol L?1, respectively. The anodic peak currents were also linear over the range 1–600 µmol L?1 for both CC and HQ, with limits of detection of 0.096 and 0.048 µmol L?1, respectively. The proposed method was effectively applied for the simultaneous detection of hydroquinone and catechol in water samples and the results were in agreement with those obtained by a comparative method described in the literature.  相似文献   

7.
A highly sensitive and stable amperometric tyrosinase biosensor has been developed based on multiwalled carbon nanotube (MWCNT) dispersed in mesoporous composite films of sol–gel‐derived titania and perfluorosulfonated ionomer (Nafion). Tyrosinase was immobilized within a thin film of MWCNT–titania–Nafion composite film coated on a glassy carbon electrode. Phenolic compounds were determined by the direct reduction of biocatalytically‐liberated quinone species at ?100 mV versus Ag/AgCl (3 M NaCl) without a mediator. The present tyrosinase biosensor showed good analytical performances in terms of response time, sensitivity, and stability compared to those obtained with other biosensors based on different sol–gel matrices. Due to the large pore size of the MWCNT–titania–Nafion composite, the present biosensor showed remarkably fast response time with less than 3 s. The present biosensor responds linearly to phenol from 1.0×10?7 M to 5.0×10?5 M with an excellent sensitivity of 417 mA/M and a detection limit of 9.5×10?8 M (S/N=3). The enzyme electrode retained 89% of its initial activity after 2 weeks of storage in 50 mM phosphate buffer at pH 7.0.  相似文献   

8.
The electrochemical behaviour of hydrazine at a 1‐benzyl‐4‐ferrocenyl‐1H‐[1,2,3]‐triazole‐triazole/carbon nanotube modified glassy carbon electrode has been studied. The modified electrode shows an excellent electrocatalytic activity for the oxidation of hydrazine and accelerates electron transfer rate. The electrocatalytic current increases linearly with hydrazine concentration in the range 0.5–700.0 μm and the detection limit for hydrazine was 33.0 ± 2.0 nm . The diffusion coefficient (D = 2.5 ± 0.1 × 10?5 cm2 s?1) and kinetic parameters such as the electron transfer coefficient, (α = 0.52) and the heterogeneous rate constant (k′ = 5.5 ± 0.1 × 10?3 cm s?1) for hydrazine were determined using electrochemical approaches. Finally, the method was employed for the determination of hydrazine in water samples. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

9.
Electron transfer (ET) reactions in bioelectrocatalysis of enzymes at electrode surfaces require not only the efficient immobilization, but also highly conductive nanostructured platform, which allows for retaining its bioactivity and structural conformation. The novel architecture of spatially separated electrochemically reduced graphene oxide (ERGO) by multi‐walled carbon nanotubes functionalized with 4‐(pyrrole‐1‐yl) benzoic acid (MWCNT/PyBA) with the accurate porous structure could be an alternative for earlier approaches to the construction of bioelectrocatalytic systems with rapid diffusion of reagents from the solution to the enzyme molecule. The formation of ERGO/MWCNT/PyBA system was confirmed by electrochemical, spectroscopic and microscopic methods. The cyclic voltammetry experiments revealed that the presence of ERGO in the conductive material affects the electronic communication between the enzyme molecule and modified electrode surface greatly improving its ET properties resulting in a double increase of the heterogeneous ET rate constant value (ks=6.5 s?1). The fabricated glucose oxidase based biosensor sensitively detects glucose, therefore, ERGO/MWCNT/PyBA architecture could provide a novel and efficient platform for immobilization of redox enzymes.  相似文献   

10.
The nickel tetrasulfonated phthalocyanine (NiTsPc) functionalized multiwalled carbon nanotube (MWCNT) nanocomposite was prepared by a simple sonochemical method. Here, NiTsPc served as a dispersing agent for MWCNT via π? π interaction between MWCNT and NiTsPc. The activated glassy carbon electrode (AGCE) modified with MWCNT‐NiTsPc composite exhibited a good electrocatalytic ability toward dopamine and displayed a good linear dependence in the concentration range of 20 nM–1.384 mM with a sensitivity of 0.17 µA µM?1 cm?2. The detection limit is 1 nM based on the signal‐to‐noise ratio of 3.  相似文献   

11.
A simple but highly snesitive electrochemical sensor for the determination of dihydromyricetin (DMY) based on graphene‐Nafion nanocomposite film modified Glassy carbon electrode (GCE) was reported. The characteristic of the sensor was examined by scanning electron microscopic (SEM) and electrochemical impedance spectroscopy (EIS). Compares with bare GCE, pre‐anodized glassy carbon electrode (GCE(ox)) and Nafion modified electrode, the sensor exhibited the more superior ability of detecting DMY, due to the synergetic graphene and Nafion. Other, the dependence of the current on pH, instrumental parameters, accumulation time and potential were investigated to optimize the experimental conditions in the determination of DMY. Under the selected conditions, the response peak currents were linear relationship with the DMY concentrations in the range of 8.0 × 10?8 ~ 2.0 × 10?5 mol L?1 with a detection limit of 2.0 × 10?8 mol L?1. And, the method was also applied successfully to detect DMY in Ampelopsis grossedentata samples.  相似文献   

12.
A simple and efficient electrochemical method is utilized to functionalize aligned carbon nanotubes (ACNTs) by the electrochemical reduction of 4‐carboxyphenyl diazonium salt. Thus hemoglobin (Hb) molecules were covalently immobilized on the diazonium‐ACNTs surface via carbodiimide chemistry. Direct electrochemistry and bioelectrocatalytic activity of the immobilized Hb were then investigated by cyclic voltammetry (CV) and amperometry techniques. It is showed that the Hb film on the diazonium‐ACNTs electrode had well‐defined redox peaks with a formal potential (E°) at ?312 mV (vs. Ag/AgCl), and the Hb‐ACNTs electrode displayed good electrocatalytic activity to H2O2 reduction. Owing to the high Hb covering on the ACNTs surface (Γ*=2.7×10?9 mol cm?2), the catalytic current were significantly improved when compared to the current measured at an Hb‐tangled carbon nanotubes electrode. The Hb‐ACNTs electrode exhibited high sensitivity, long‐term stability and wide concentration range from 40 μM to 3 mM for the amperometric detection of H2O2. The heterogeneous reaction rate constant (ks) was 0.95±0.05 s?1 and the apparent Michaelis–Menten constant (K was 0.15 mM.  相似文献   

13.
The interactions of furazolidone (Fu) with double‐stranded calf thymus DNA (dsDNA) on the multi‐walled carbon nanotubes‐ionic liquid‐modified carbon paste electrode (MWCNT‐IL‐CPE) have been studied by cyclic voltammetry. In the presence of DNA, the cathodic peak current of Fu decreased and the peak potential shifted to a positive potential, indicating the intercalative interaction of Fu with DNA. The binding constant of Fu with DNA and stoichiometric coefficient has been determined according to the Hill's model. This electrochemical method was further applied to the determination of DNA. Two linear calibration curves were obtained for DNA detection in the concentration ranges of 0.03–0.10 and 0.10–4.0 μg l?1 with a detection limit of 0.027 μg l?1. The method was successfully applied to analyze Fu in serum samples.  相似文献   

14.
A novel enzyme immobilization technique based on thionine‐bovine serum albumin conjugate (Th‐BSA) and gold colloidal nanoparticles (nano‐Au) was developed. Thionine was covalently bound onto the BSA film with glutaraldehyde(GA) as cross‐linker to achieve Th‐BSA conjugate. The free amino groups of thionine were then used to attach nano‐Au for the immobilization of horseradish peroxidase (HRP). Such nano‐Au/Th‐BSA matrix shows a favorable microenvironment for retaining the native activity of the immobilized HRP and thionine immobilized in this way can effectively shuttle electrons between the electrode and the enzyme. The proposed biosensor displays excellent catalytic activity and rapid response for H2O2. The linear range for the determination of H2O2 is from 4.9×10?7 to 1.6×10?3 M with a detection limit of 2.1×10?7 M at 3σ and a Michaelies‐Menten constant K value of 0.023 mM.  相似文献   

15.
We report a simple approach to the production of carbon fiber‐based amperometric microbiosensors for selective detection of hydrogen peroxide (H2O2), which was achieved by electrometallization of carbon fiber microelectrodes (CFMs) by electrodeposition of Pt nanoparticles. The Pt‐carbon hybrid sensing interface provided a sensitivity of 7711±587 μA ? mM?1 ? cm?2, a detection limit of 0.53±0.16 μM (S/N=3), a linear range of 0.8 μM–8.6 mM, and a response time of <2 sec. The morphologies of the Pt nanoparticle‐modified CFMs were characterized by scanning electron microscopy. To achieve selectivity, permseletive layers, polyphenylenediamine (PPD) and Nafion, were deposited resulting in exclusion of the anionic and cationic interferents, ascorbic acid and dopamine, respectively, at their physiologically relevant concentrations. The resultant sensors displayed a sensitivity to hydrogen peroxide of 1381±72 μA ? mM?1 ? cm?2, and a detection limit of 0.86±0.19 μM (S/N=3). This simple and rapid metallization method converts carbon fiber microelectrodes, which are readily accessible, to microscale Pt electrodes in 2 min, providing a platform for oxidase‐based amperometric biosensors with improved spatial resolution over more commonly used platinum electrode array microprobes.  相似文献   

16.
In this work, an electrochemical sensor based on pyrolytic graphite electrode (PGE), cobalt phthalocyanine (CoPc) and multiwalled carbon nanotube (MWCNT) composite designed as PGE‐MWCNT/CoPc was developed and validated for pyridoxine (vitamin B6) determination employing Differential Pulse Voltammetry (DPV). The electrochemical behaviour of pyridoxine at the PGE‐MWCNT/CoPc has been evaluated and the charge transfer coefficient, α, and the charge transfer rate constant, κ, were calculated as 0.30 and 11.67±0.43 s?1, respectively, which indicates that, although this system is irreversible, it is viable kinetically to be used as a sensor. The optimized experimental conditions were pH 5.5 in 0.30 mol L?1 phosphate buffer. The linear range found was 10 to 400 μmol L?1 of pyridoxine, with r=0.9987. The limits of detection and quantification were 0.50 and 1.67 μmol L?1, respectively, showing the good sensitivity of the method. The method was successfully applied for the pyridoxine determination in real samples of pharmaceutical formulation with RSD% lower than 5 % indicating that it can be used for routine quality control pharmaceutical formulations containing pyridoxine. Furthermore, it has the advantages of a fast response, a low detection limit and low cost.  相似文献   

17.
An amperometric tyramine biosensor based on poly‐L‐lysine (PLL) and Fe3O4 nanoparticles (Fe3O4NP) modified screen printed carbon electrode (SPCE) was developed. PLL was formed on the SPCE by the electropolymerization of L‐lysine. Subsequently, Fe3O4NP suspension prepared in chitosan (CH) solution was casted onto the PLL/SPCE. Tyrosinase (Ty) enzyme was immobilized onto the modified Fe3O4?CH/PLL/SPCE and the electrode was coated with Nafion to fabricate the Ty/Fe3O4?CH/PLL/SPCE. Different techniques including scanning electron microscopy, chronoamperometry (i–t curve), cyclic voltammetry and electrochemical impedance spectroscopy were utilized to study the fabrication processes, electrochemical characteristics and performance parameters of the biosensor. The analytical performance of the tyramine biosensor was evaluated with respect to linear range, sensitivity, limit of detection, repeatability and reproducibility. The response of the biosensor to tyramine was linear between 4.9×10?7–6.3×10?5 M with a detection limit of 7.5×10?8 M and sensitivity of 71.36 μA mM?1 (595 μA mM?1 cm?2). The application of the developed biosensor for the determination of tyramine was successfully tested in cheese sample and mean analytical recovery of added tyramine in cheese extract was calculated as 101.2±2.1 %. The presented tyramine biosensor is a promising approach for tyramine analysis in real samples due to its high sensitivity, rapid response and easy fabrication.  相似文献   

18.
A robust and effective composite film combined the benefits of Nafion, room temperature ionic liquid (RTIL) and multi‐wall carbon nanotubes (MWNTs) was prepared. Hemoglobin (Hb) was successfully immobilized on glassy carbon electrode surface by entrapping in the composite film. Direct electrochemistry and electrocatalysis of immobilized Hb were investigated in detail. A pair of well‐defined and quasi‐reversible redox peaks of Hb was obtained in 0.10 mol·L?1 pH 7.0 phosphate buffer solution (PBS), indicating that the Nafion‐RTIL‐MWNTs film showed an obvious promotion for the direct electron transfer between Hb and the underlying electrode. The immobilized Hb exhibited an excellent electrocatalytic activity towards the reduction of H2O2. The catalysis current was linear to H2O2 concentration in the range of 2.0×10?6 to 2.5×10?4 mol·L?1, with a detection limit of 8.0×10?7 mol·L?1 (S/N=3). The apparent Michaelis‐Menten constant (Kmapp) was calculated to be 0.34 mmol·L?1. Moreover, the modified electrode displayed a good stability and reproducibility. Based on the composite film, a third‐generation reagentless biosensor could be constructed for the determination of H2O2.  相似文献   

19.
This work describes the development of a biosensor for paracetamol (PAR) determination based on a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes (MWCNT) and laccase enzyme (LAC), which was immobilized by means of covalent crosslinking using glutaraldehyde. Voltammetric investigations were carried out by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The biosensor was characterized by Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FT‐IR). The results showed that the use of MWCNT/LAC composite increased the sensor sensitivity, compared to bare glassy carbon electrode. Factors affecting the voltammetric signals such as pH, ionic strength, scan rate and interferents were assessed. Linear range, limit of detection (LOD) and limit of quantitation (LOQ) obtained were 10–320 μmol L?1, 7 μmol L?1 and 10 μmol L? 1, respectively. The developed biosensor was successfully applied to PAR determination in urine and pharmaceutical formulations samples, with recovery varying from 99.96 to 106.20 % in urine samples and a relative standard deviation less than 1.04 % for PAR determination in pharmaceutical formulations. Therefore, the MWCNT‐LAC/GCE exhibits excellent sensitivity and can be used to PAR determination as a viable alternative in clinical analyzes and quality control of pharmaceutical formulations, through a simple, fast and inexpensive methodology.  相似文献   

20.
At present, a highly sensitive hydrogen peroxide (H2O2) sensor is fabricated by ferrocene based naphthaquinone derivatives as 2,3‐Diferrocenyl‐1,4‐naphthoquinone and 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone. These ferrocene based naphthaquinone derivatives are characterized by H‐NMR and C‐NMR. The electrochemical properties of these ferrocene based naphthaquinone are investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) on modified glassy carbon electrode (GCE). The modified electrode with ferrocene based naphthaquinone derivatives exhibits an improved voltammetric response to the H2O2 redox reaction. 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone show excellent non‐enzymatic sensing ability towards H2O2 response with a detection limitation of 2.7 μmol/L a wide detection range from 10 μM to 400 μM in H2O2 detection. The sensor also exhibits short response time (1 s) and good sensitivity of 71.4 μA mM?1 cm?2 and stability. Furthermore, the DPV method exhibited very high sensitivity (18999 μA mM?1 cm?2) and low detection limit (0.66 μM) compared to the CA method. Ferrocene based naphthaquinone derivative based sensors have a lower cost and high stability. Thus, this novel non‐enzyme sensor has potential application in H2O2 detection.  相似文献   

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