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1.
A novel enzyme-free electrochemical sensor for H2O2 was fabricated by modifying an indium tin oxide (ITO) support with (3-aminopropyl) trimethoxysilane to yield an interface for the assembly of colloidal gold. Gold nanoparticles (AuNPs) were then immobilized on the substrate via self-assembly. Atomic force microscopy showed the presence of a monolayer of well-dispersed AuNPs with an average size of ~4 nm. The electrochemical behavior of the resultant AuNP/ITO-modified electrode and its response to hydrogen peroxide were studied by cyclic voltammetry. This non-enzymatic and mediator-free electrode exhibits a linear response in the range from 3.0?×?10?5 M to 1.0?×?10?3 M (M?=?mol?·?L?1) with a correlation coefficient of 0.999. The limit of detection is as low as 10 nM (for S/N?=?3). The sensor is stable, gives well reproducible results, and is deemed to represent a promising tool for electrochemical sensing.
Figure
AuNPs/ITO modified electrode prepared by self-assembly method exhibit good electrocatalytic activity towards enzyme-free detection H2O2. The linear range of typical electrode is between 3.0?×?10?5 M and 1.0?×?10?3 M with a correlation coefficient of 0.999 and the limit detection is down to 1.0?×?10?8 M.  相似文献   

2.
We report on the electrochemical formation of copper oxide nanoparticles (CuO-NPs) at a carbon ceramic electrode (CCE) as a highly-porous substrate. A copper film was deposited on the surface of the CCE and derivatized in situ to give CuO-NPs by potential cycling between ?0.8 and 0.35?V in strongly alkaline solution. The electrode was characterized by scanning electron microscopy and cyclic voltammetry. The CuO-NPs exhibited excellent electrocatalytic activity toward the oxidation of L-tyrosine (L-Tyr) in responding linearly in the 2 to 1,350???M concentration range, an associated detection limit (S/N?=?3) of 160?nM, and a sensitivity of 0.61?A?M?1?cm?2.
Cyclic voltammograms of the bare CCE (a, c) and nano-copper oxide coated CCE (b, d) in 0.05?mol L?1 NaOH solution in the absence (a, b) and presence of 6?mmol L?1 L-Tyr (c, d) at scan rate of 50?mV?s?1  相似文献   

3.
《Analytical letters》2012,45(7):1321-1332
Abstract

A novel amperometric nitric oxide (NO) sensor based on a glassy carbon electrode modified with thionine and Nafion films has been developed. The oxidation peak current of NO increased significantly at the poly(thionine)/Nafion‐modified glassy carbon electrode (GCE), which can be used for the detection of NO. The oxidation peak current was linear with the concentration of nitric oxide over the range from 3.6×10?7 to 6.8×10?5 mol · L?1, and the detection limit was 7.2×10?8 mol · L?1. This nitric oxide sensor showed high selectivity to nitric oxide determination, and some potential interference could be eliminated effectively. The nitric oxide sensor has been applied to monitor NO release from rat kidney stimulated by L‐arginine. The results indicated the applicability of the NO sensor to biomedical samples.  相似文献   

4.
We report on the fabrication of an enzyme–free electrochemical sensor for glucose based on a printed film consisting of multi–walled carbon nanotubes (MWCNTs). The MWCNT–based film can be produced by means of a flexographic printing process on a polycarbonate (PC) substrate. The electrochemical response of the MWCNT–based film (referred to as MWCNT–PC) towards the oxidation of glucose at pH 7 was studied by means of cyclic voltammetry and electrochemical impedance spectroscopy. The MWCNT–PC film exhibits substantial electrocatalytic activity towards the oxidation of glucose at an anodic potential of 0.30?V (vs. Ag/AgCl). The findings reveal that the MWCNT–PC film enables non–enzymatic sensing of glucose with a detection limit as low as 2.16?μM and a sensitivity of 1045?μA?mM?1?cm?2.
Figure
Enzyme–free electrochemical sensor for glucose consisting of multi–walled carbon nanotubes was fabricated by means of flexographic printing process on polycarbonate substrate. The sensor exhibits electrocatalytic activity for glucose oxidation at an anodic potential of 0.30?V (vs. Ag/AgCl) with detection limit of 2.16?μM and sensitivity of 1045?μA?mM?1?cm?2.  相似文献   

5.
We report on a novel sensor for the electrochemical determination of thiourea (TU). It is based on an active carbon paste electrode modified with copper oxide nanoparticles. The modified electrode and the electrochemical properties of thiourea on its surface were investigated using cyclic voltammetry and differential pulse voltammetry. Under optimized conditions, the detection limit is 20 μg?L?1 of TU. The method was applied to the determination of thiourea in fruit juice, orange peel and industrial waste water.
Figure
Cyclic voltammograms of ACPE (A), CuO/ACPE (B) and CuO/CPE (C) in pH 8 phosphate buffered saline.  相似文献   

6.
We have immobilized DNA on a glassy carbon electrode (GCE) modified with graphene oxide (GO) to develop an electrochemical biosensor for catechol. Compared to carbon nanotubes, the use of GO dramatically improved the electrooxidative current of the guanine and adenine moieties in DNA but retained the low background current of unmodified GCEs. Factors such as DNA adsorption time, DNA concentration and pH of solution were investigated to optimize experimental conditions. In the presence of catechol, the voltammetric response to DNA was inhibited due to the interaction between DNA and catechol. The response to adenine is linearly proportional to the concentration of catechol in the range from 1.0?×?10?6 to 1.0?×?10?4 mol·L?1. If catechol is degraded by the combined action of UV light and hydrogen peroxide, the response to DNA is restored. Thus, the modified electrode can act as an efficient biosensor for monitoring the degradation of catechol.
Figure
GO dramatically improved the electrooxidative current of the guanine and adenine moieties in DNA but retained the low background current of unmodified GCEs. While the DNA/GO-modified electrode was applied to monitor catechol, it showed sensitive response to catechol before and after photodegradation treatment.  相似文献   

7.
We report on a highly sensitive and selective nonenzymatic glucose sensor based on a glassy carbon electrode modified with a composite prepared from nickel(II) hydroxide nanoplates and carbon nanofibers. The nanocomposite was characterized by scanning electron microscopy and powder X-ray diffraction. Electrodes modified with pure Ni(OH)2 and with the nanocomposite were characterized by electrochemical impedance spectroscopy. Cyclic voltammetric and amperometric methods were used to investigate the catalytic properties of the modified electrodes for glucose electrooxidation in strongly alkaline solution. The sensor exhibits a wide linear range (from 0.001 to 1.2 mM), a low detection limit (0.76 μM), fast response time (< 5 s), high sensitivity (1038.6 μA?·?mM?1?·?cm?2), good reproducibility, and long operational stability. Application of the nonenzymatic sensor for monitoring glucose in real samples was also demonstrated.
Figure
We report on a highly sensitive and selective nonenzymatic glucose sensor based on a glassy carbon electrode modified with a nanocomposite prepared from nickel (II) hydroxide nanoplates and carbon nanofibers. The facile preparation, high electrocatalytic activity, relatively fast response, favorable reproducibility and long-term performance stability demonstrate the potential applications of the sensor.  相似文献   

8.
We present a modified glassy carbon electrode as a sensing platform for glucose. It is based on a composite film prepared from Ni(II) ion, quercetin and graphene. The sensor was characterized by cyclic voltammetry. The electron transfer coefficient, reaction rate constant and catalytic rate constant were determined and found to be 0.53, 5.4?s?1 and 2.93?×?103?M?1 s?1, respectively. The catalytic current depends linearly on the concentration of glucose in the range from 3 to 900???M, with a detection limit of 0.5???M (at an S/R of 3). The sensor exhibits good reproducibility, stability, fast response, and high sensitivity.
Figure
Cyclic voltammograms of Ni(II)-Qu/Gr/GCE in 0.1?M NaOH solution at various scan rates (from inner to outer): 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0?V·s?1. Plot of I p versus ??1/2 and E p versus log??.  相似文献   

9.
An electrochemical sensor for theophylline (ThPh) was prepared by electropolymerizing o-phenylenediamine on a glassy carbon electrode in the presence of ThPh via cyclic voltammetry, followed by deposition of gold nanoparticles using a potentiostatic method. The effects of pH, ratio between template molecule and monomer, number of cycles for electropolymerization, and of the solution for extraction were optimized. The current of the electro-active model system hexacyanoferrate(III) and hexacyanoferrate(IV) decreased linearly with successive addition of ThPh in the concentration range between 4.0?×?10?7?~?1.5?×?10?5 mol·L?1 and 2.4?×?10?4?~?3.4?×?10?3 mol·L?1, with a detection limit of 1.0?×?10?7 mol·L?1. The sensor has an excellent recognition capability for ThPh compared to structurally related molecules, can be regenerated and is stable.
Figure
In this paper, an electrochemical sensor for theophylline (ThPh) was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode in the presence of ThPh via cyclic voltammetry, followed by deposition of gold nanoparticles to enhance the sensitivity of the sensor. Therefore, the sensor showed a high sensitivity for ThPh determining. Peak current of [Fe(CN)6]3?/[Fe(CN)6]4? varied linearly with the concentration of ThPh in the range of 4.0×10-7~1.5×10-5 mol·L-1 and 2.4×10-4~3.4×10-3 mol·L-1, and the detection limit reached 1.0×10-7 mol·L-1. Compared to structurally related molecules, the sensor also has a high recognition capability for ThPh. With excellent regeneration property and stability, the present sensor maybe provides a new class of polymer modified electrodes for sensor applications.  相似文献   

10.
We have prepared calcined silver oxide-doped zinc oxide nanoparticles (NPs) by a hydrothermal method using reducing agents in alkaline medium. The doped NPs were characterized by UV/vis, FTIR, and X-ray photoelectron spectroscopy, and by X-ray powder diffraction and field-emission scanning electron microscopy. The NPs were deposited on microchips to result in a sensor that has a fast response to methanol in the liquid phase. Features include high sensitivity, low-sample volume, reliability, reproducibility, ease of integration, long-term stability, and enhanced electrochemical responses. The calibration plot is linear (r2?=?0.9981) over the 0.25 mmolL?1 to 0.25 molL?1 methanol concentration range. The sensitivity is ~7.917 μA cm?2 mmolL?2, and the detection limit is 71.0?±?0.5 μmolL?1 at a signal-to-noise-ratio of 3.
Figure
Fabrication of highly sensitive (~7.917 μA cm?2) and selective methanol chemical sensor based on hydrothermally prepared silver oxide doped zinc oxide nanoparticles deposited tiny microchips with a detection limit as low as 71.0 μM (at an S/N of 3).  相似文献   

11.
We have fabricated, in a single step, carbon ceramic electrodes modified with a poly(acridine orange) film containing reduced graphene oxide. They display electrocatalytic activity to ascorbic acid (AA) and uric acid (UA) at pH 4.5. The anodic peak potentials of AA and UA are separated by 276 mV so that they can be well resolved in cyclic voltammetry. UA and AA were simultaneously determined in a mixture at working potentials of 170 and 400 mV, respectively. Under optimized conditions, the calibration curves for AA and UA cover the 0.8–5,000 μM and 0.6–900 μM concentration range, respectively, while detection limits are 0.3 μM and 0.2 μM. The electrode was applied to determine AA and UA in urine samples.
Figure
DPV curves of RGO–PAO/CCE in the phosphate buffer solution (pH 4.5) containing 5.0?×?10?5 mol L?1 AA with different concentration of UA (a?→?f: 0, 1, 3, 5, 7, 9?×?10?6 mol L?1)  相似文献   

12.
Functionalized gold nanoparticles capped with polyoxometalates were prepared by a simple photoreduction technique where phosphododecamolybdates serve as reducing reagents, photocatalysts, and as stabilizers. TEM images of the resulting gold nanoparticles show the particles to have a relative narrow size distribution. Monolayer and multilayer structures of the negatively charged capped gold nanoparticles were deposited on a poly(vinyl pyridine)-derivatized indium-doped tin oxide (ITO) electrode via the layer-by-layer technique. The surface plasmon resonance band of the gold nanoparticles displays a blue shift on the surface of the ITO electrode. This is due to the substrate-induced charge redistribution in the gold nanoparticles and a change in the electromagnetic coupling between the assembled nanoparticles. The modified electrode exhibits the characteristic electrochemical behavior of surface-confined phosphododecamolybdate and excellent electrocatalytic activity. The catalysis of the modified electrode towards the model compound iodate was systematically studied. The heterogeneous catalytic rate constant for the electrochemical reduction of iodate was determined by chronoamperometry to be ca. 1.34?×?105 mol?1·L·s?1. The amperometric method gave a linear range from 2.5?×?10?6 to 1.5?×?10?3 M and a detection limit of 1.0?×?10?6 M. We believe that the functionalized gold nanoparticles prepared by this photoreduction technique are advantageous in terms of fabrication of sensitive and stable redox electrodes.
Figa
Functionalized gold nanoparticles (Au-NPs) capped with polyoxometalates were prepared by a simple photoreduction technique. The negatively charged capped Au-NPs were deposited on a poly(vinyl pyridine)-derivatized indium-doped tin oxide electrode via the layer-by-layer technique. The modified electrode exhibits the characteristic electrochemical behavior of surface-confined phosphododecamolybdate, and excellent catalytic activity.  相似文献   

13.
A disposable electrochemical myeloperoxidase (MPO) immunosensor was fabricated based on the indium tin oxide electrode modified with a film composed of gold nanoparticles (AuNPs), poly(o-phenylenediamine), multi-walled carbon nanotubes and an ionic liquid. The composite film on the surface of the electrode was prepared by in situ electropolymerization using the ionic liquid as a supporting electrolyte. Negatively charged AuNPs were then adsorbed on the modified electrode via amine-gold affinity and to immobilize MPO antibody. Finally, bovine serum albumin was employed to block possible remaining active sites on the AuNPs. The modification of the electrode was studied by cyclic voltammetry and scanning electron microscopy. The factors affecting the performance of the immunosensor were investigated in detail using the hexacyanoferrate redox system. The sensor exhibited good response to MPO over two linear ranges (from 0.2 to 23.4 and from 23.4 to 300 ng.mL?1), with a detection limit of 0.05 ng.mL?1 (at an S/N of 3).
Figure
A disposable electrochemical immunosensor for myeloperoxidase based on the indium tin oxide electrode modified with an ionic liquid composite film composed of gold nanoparticles, poly(o-phenylenediamine) and carbon nanotubes.  相似文献   

14.
The food antioxidant quercetin was used as a template in an ultrathin molecularly imprinted polymer (MIP) film prepared by photopolymerization. Indium tin oxide (ITO) plates were electrografted with aryl layers via a diazonium salt precursor bearing two terminal hydroxyethyl groups. The latter act as hydrogen donors for the photosensitizer isopropylthioxanthone and enabled the preparation of MIP grafts through radical photopolymerization of methacrylic acid (the functional monomer) and ethylene glycol dimethacrylate (the crosslinker) in the presence of quercetin (the template) on the ITO. The template was extracted, and the remaining ITO electrode used for the amperometric determination of quercetin at a working potential of 0.26 V (vs. SCE). The analytical range is from 5.10?8 to 10?4 mol L?1, and the detection limit is 5.10?8 mol L?1.
Figure
This work describes the grafting of a molecularly imprinted polymer (MIP) film by combining diazonium surface chemistry and surface-initiated photopolymerization. The MIP grafts specifically and selectively recognize quercetin in pure solution in THF and in real green tea infusion.  相似文献   

15.
We report on a sensitive, simple, label-free impedance-based immunoelectrode for the determination of microcystin-LR (MCLR). The surface of the electrode was modified with a composite made from multiwalled carbon nanotubes and an ionic liquid, and with immobilized polyclonal antibody against MCLR. Cyclic voltammetry and impedance spectroscopy were applied to characterize the modified electrode. It is found that the multi-walled carbon nanotubes act as excellent mediators for the electron transfer between the electrode and dissolved hexacyanoferrate redox pair, while the ionic liquid renders it biocompatible. The method exhibits a wide linear range (0.005 μg?L-1 to 1.0 μg?L-1), a low detection limit (1.7 ng?L-1) and a long-term stability of around 60 days. The ionic liquid 1-amyl-2,3-dimethylimidazolium hexafluorophosphate gave the best impedimetric response. The new immunoelectrode is sensitive, stable, and easily prepared. It has been successfully applied to the determination of MCLR in water samples.
Figure
The immunosensor, modified with a nanocomposite of room temperature ionic liquid- multiwalled carbon nanotube, was applied to detect MCLR. The method exhibits a wide linear range (0.005 μg·L?1 to 1.0 μg·L?1), a low detection limit (1.7 ng·L-1) and a long-term stability of around 60 days.  相似文献   

16.
We report on a non-enzymatic amperometric sensor for hydrogen peroxide (H2O2). It was fabricated by electrodeposition of multi-wall carbon nanotubes and polyaniline along with platinum nanoparticles on the surface of a glassy carbon electrode. The modification was probed by scanning electron microscopy and cyclic voltammetry. The resulting sensor exhibits a high sensitivity (748.4?μA·mM?1·cm?2), a wide linear range (7.0?μM–2.5?mM), a low detection limit (2.0?μM) (S/N?=?3), a short response time (>5?s), and long-term stability, and is not interfered by common species. It was successfully applied to determine H2O2 in disinfectants.
Figure
SEM images of the obtained Pt/MWCNTs-PANI composite films with large surface-to-volume ratio and biocompatibility  相似文献   

17.
18.
A glassy carbon electrode was modified with PdO-NiO composite nanofibers (PdO-NiO-NFs) and applied to the electrocatalytic reduction of hydrogen peroxide (H2O2). The PdO-NiO-NFs were synthesized by electrospinning and subsequent thermal treatment, and then characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Factors such as the composition and fraction of nanofibers, and of the applied potential were also studied. The sensor exhibits high sensitivity for H2O2 (583.43 μA?·?mM?1?·?cm?2), a wide linear range (from 5.0 μM to 19 mM), a low detection limit (2.94 μM at an SNR of 3), good long term stability, and is resistant to fouling.
Figure
A glassy carbon electrode was modified with PdO-NiO composite nanofibers which were synthesized by electrospinning and subsequent thermal treatment. The sensor exhibited a wide linear range, high sensitivity, good stability and selectivity for the detection of hydrogen peroxide  相似文献   

19.
We report on an aptamer with high affinity against Salmonella typhimurium (S. typhimurium) and selected from an enriched oligonucleotide pool by a whole-cell SELEX process in a method for the fluorimetric determination of S. typhimurium using a graphene oxide platform. In the absence of target, the fluorescence was fairly weak as result of the FAM-labeled aptamer adjacent to graphene oxide. If, however, the fluorophore is released from the graphene oxide due to the formation of the target/aptamer complexes, fluorescence intensity is substantially increased. Under the optimum conditions, the assay displays a linear response to bacteria in the concentration range from 1?×?103 to 1?×?108 CFU·mL?1, with a detection limit of 100 CFU·mL?1. The method is selective in that fluorescence is not much enhanced in case of other bacteria. This aptasensor displays higher sensitivity and selectivity than others and is believed to possess a large potential with respect to the rapid detection of bacteria.
Figure
A useful fluorescence aptasensor based on a graphene oxide platform was constructed for Salmonella typhimurium detection, which has a great potential application in rapid detection of pathogen as it has high sensitivity and selectivity.  相似文献   

20.
We have developed a sensor for the square wave anodic stripping voltammetric determination of Pb(II). A glassy carbon electrode was modified with a thin film of an antimony/poly(p-aminobenzene sulfonic acid) composite in air-saturated aqueous solution of pH 2.0. Compared to a conventional antimony film electrode, the new one yields a larger stripping signal for Pb(II). The conditions of polymerization, the concentration of Sb(III), the pH value of the sample solution, the deposition potential and time, frequency, potential amplitude, and step increment potential were optimized. Under the optimum conditions, a linear response was observed for Pb(II) in the range of 0.5 to 150.0 μg?L?1. The detection limit for Pb(II) is 0.1 μg?L?1.
Figure
The surface of a glassy carbon electrode (GCE) was modified by electropolymerization of p-aminobenzene sulfonic acid (p-ABSA) and the modified electrode was then prepared by in situ depositing antimony and target metal on the poly(p-ABSA) coated glassy carbon electrode. The antimony/poly(p-ABSA) film electrode displays high electrochemical activity in giving a peak current that is proportional to the concentration of Pb(II) in a certain range.  相似文献   

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