An electrochemical nanoaptasensor is described that is based on the use of a glassy carbon electrode (GCE) modified with electrodeposited silver nanoparticles (AgNPs). An aptamer (Apt) against trinitrotoluene (TNT) was then immobilized on the AgNPs. The addition of TNT to the modified GCE leads to decrease in peak current (typically measured at a potential of ?0.45 V vs. Ag/AgCl) of riboflavin which acts as an electrochemical probe. Even small changes in the surface (as induced by binding of Apt to TNT) alter the interfacial properties. As a result, the LOD is lowered to 33 aM, and the dynamic range extends from 0.1 fM to 10 μM without sacrificing specificity.
Graphical abstract Schematic presentation of a nanoaptasensor which is based on a glassy carbon electrode (GCE) modified with electrodeposited silver nanoparticles (AgNPs) and aptamer (Apt). It was applied to the detection of 2,4,6-trinitrotoluene (TNT) with the help of riboflavin (RF) as a redox probe.
A nanocomposite prepared from reduced graphene oxide (rGO) and silver nanoparticles (AgNPs) is used in an electrochemical aptasensor for the sensitive and selective determination of the antibiotic chloramphenicol (CAP). The nanocomposite was obtained by electrostatic assembly of AgNPs on the surface of polyelectrolyte-functionalized rGO and then used to modify a glassy carbon electrode. The biosensor is then obtained by immobilizing the aptamer against CAP. When incubated with solutions of CAP, the sensor surface is loaded with CAP due to aptamer recognition. The captured CAP can be electrochemically reduced to yield a current that is strongly enhanced as a result of the excellent electrocatalysis property of the graphene/AgNP-nanocomposite. Under optimum conditions, the calibration plot is linear in the 0.01 to 35 μM concentration range, with a 2 nM detection limit (at 3σ). The sensor is reproducible, stable, selective over homologous interferents, and performs excellently when analyzing CAP in milk samples.
Graphical Abstract A graphene/silver nanoparticle-based electrochemical aptasensor is designed for the selective determination of the antibiotic chloramphenicol (CAP). The excellent electrocatalytic reduction of CAP specifically captured onto the electrode surface enables the sensitive electrochemical signal transduction of the biosensor by linear sweep voltammetry (LSV).
We report on a nonenzymatic glucose sensor based on a glassy carbon electrode that was electrochemically modified with a nanocomposite prepared from nickel hydroxide and graphene. Scanning electron microscopy revealed that the nickel hydroxide in the nanocomposite was present in the form of a nanostructure of three-dimensional spheres that were assembled by many densely arranged nanosheets. The electrocatalytic activity of the electrode toward the oxidation of glucose was investigated by chronoamperometry. The current response was linearly related to the glucose concentration in the range from 1 to 10?μM, with a sensitivity of 494?μA?mM–1?cm–2 and a correlation coefficient of 0.9990, and a second range (from 10 to 1000?μM with a sensitivity of 328?μA?mM–1?cm–2 and a correlation coefficient of 0.9990). The detection limit was 0.6?μM at a signal-to-noise ratio of 3, and the response time was as short as 2?s.
Figure
As seen in the scanning electron microscopic image, three-dimension Ni(OH)2 spheres was decorated on the surface of graphene. Due to its excellent electrochemical properties and large specific surface area, the addition of graphene obviously promoted the current response to glucose at the Ni(OH)2 modified electrode. 相似文献
We report on the modification of a glassy carbon electrode with a composite consisting of silver nanoparticles (AgNPs), polydopamine, and graphene to give an electrochemical sensor for catechol. The composite was characterized by transmission electron microscopy, and the electrochemical behavior of catechol at the modified electrode was studied by cyclic voltammetry. The electrochemical response is greatly enhanced and thought to result from a combination of beneficial effects including the good conductivity and large surface area of the AgNPs, the high conductivity of graphene, the synergistic effects of the composite, and the increased quantity of catechol that is adsorbed on the surface of the electrode. Differential pulse voltammetric responses are proportional to the concentration of catechol between 0.5 and 240?μM levels of catechol, and the detection limit is 0.1?μM (S/N?=?3). The performance of the sensor was evaluated with catechol-spiked water samples, and recoveries range from 96.5 % to 103.1 %. The results indicated that the composite presented here is a promising substrate for use in electrochemical sensing.
Graphical abstract
We report on the modification of a glassy carbon electrode with a composite consisting of silver nanoparticles, polydopamine, and graphene to obtain an electrochemical sensor for catechol. 相似文献
We report on a simple, rapid, and efficient method for the extraction of volatile organic compounds (VOCs; including methanol, tetrahydrofuran, 2-hexanone and benzene) from air and solid samples. The system is based on the use of a laboratory-made syringe as the extractor. The needle of the syringe is placed in a chamber cooled by liquid nitrogen. The tip of the needle is placed in the headspace of a vial containing the sample. The headspace components then are circulated with a pump to pass the needle, and this results in freeze-trapping of the VOCs on the inner surface of the needle. The circulation of the headspace components is continued for 15 min, and the syringe is then removed and placed in a GC injector. The effects of volume of the sample vial, headspace flow rate, temperature and time of extraction and desorption were optimized. The overall time for sampling and analysis is <30 min. The method displays an extraction efficiency of >80%) and a good sample transfer efficiency into the GC column due to the absence of a sorbent inside the needle. No carry-over was observed after 30?s desorption at 260?°C. An external standard method was used for quantitative analysis. The relative standard deviation values are below 10% and the limits of detection range from 1.3 to 4.6?ng?g?1.
Fiugre
The scheme of sorbentless cryogenic needle trap device 相似文献
A glassy carbon electrode (GCE) modified with polymeric nanocomposite consisting of palladium nanoparticles and a conductive polymeric ionic liquid was prepared. The modified GCE was applied to sensitive and fairly selective electrochemical determination of the mycotoxin zearalenone. Electrocatalytic oxidation is performed in a solution containing 20 % (V/V) acetonitrile and 80 % (V/V) of 1 M perchloric acid. Cyclic voltammetry and square wave voltammetry revealed a well-defined electrocatalytic peak current at overpotential of +0.69 V versus Ag/AgCl. Under optimized experimental conditions, there is a linear relationship between anodic peak current and zearalenone concentration in the range from 0.03 to 35 ng?mL￣1, and the detection limit is 0.01 ng?mL￣1. The method was successfully applied to the analysis of zearalenone in spiked food samples and gave recoveries between 95.6 and 104.0 %.
Graphical abstract The nanocomposite (PdVC-PIL) was prepared by polymerization of ionic liquid monomer (PIL) in presence of Pd nanoparticles on Vulcan XC-72R carbon (PdVC). The solution containing nanocomposite was placed on the glassy carbon electrode (GCE). The voltammetry activity of modified electrode (PdVC-PIL/GCE) was compared to a bare GCE for zearalenone determination.
A voltammetric sensor is described for the determination the antibiotic sulfamethoxazole (SMZ). It is based on the use of a glassy carbon electrode (GCE) modified with a nanocomposite prepared from graphitic carbon nitride and zinc oxide (g-C3N4/ZnO). The nanorod-like ZnO nanostructure were synthesized sonochemically. The g-C3N4/ZnO nanocomposite was then prepared by mixing g-C3N4 with ZnO, followed by ultrasonication. The morphology and structure of the nanocomposite were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy and transmission electron microscopy. Under the optimal conditions, the response of the electrode, typically measured between 0.8 and 0.9 V (vs. Ag/AgCl), increases linearly in the 20 nM to 1.1 mM SMZ concentration range, and the lower detection limit is 6.6 nM. This is better than that of many previously reported sensors for SMZ. The modified electrode is highly selective, well reproducible and maintains its activity for at least 4 weeks. It was applied to the determination of SMZ in spiked human blood serum samples in with satisfactory results.
Graphical abstract Schematic presentation of the voltammetric sensor for sulfamethoxazole. It consists of a glassy carbon electrode modified with a nanocomposite prepared from graphitic carbon nitride (g-C3N4/ZnO) that was supported with zinc oxide nanorods.
A novel nitrite sensor was fabricated based on a graphene/polypyrrole/chitosan nanocomposite film modified glassy carbon electrode. The nanocomposite film was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The electron transfer behaviour of the modified electrodes was investigated in [Fe(CN)(6)](3-)/(4-) redox probe using cyclic voltammetry and electrochemical impedance spectroscopy. Differential pulse voltammetry and amperometry were used to study the electrochemical properties of the proposed sensor. Under optimum conditions, the sensor exhibited good reproducibility and stability for nitrite determination. Linear response was obtained in the range of 0.5-722 μM with a detection limit of 0.1 μM (S/N = 3) for nitrite determination. 相似文献
Microchimica Acta - The article describes an electrochemical sensor for the detection of uric acid (UA) by using a glassy carbon electrode (GCE) modified with a composite consisting of... 相似文献
The authors describe a dopamine (DA) sensor based on a glassy carbon electrode modified with a composite film composed of carbon dots (C-dots) and graphene functionalized with an ionic liquid. The C-dots were functionalized with carboxy groups whose negative charge promotes electrostatic attraction to the protonated amino groups in DA. The presence of an imidazole cation in the IL facilitates interaction with the C-dots and DA via electrostatic interactions and π-stacking forces. Under optimal conditions, the modified GCE display improved electrochemical response to DA compared to a bare GCE, or a GCE modified with C-dots or IL-graphene only. The oxidation current, measured best at a potential of 0.22 V (vs. Ag/AgCl) is linearly related to the DA concentration in the 0.1 to 600 μM range, with a 30 nM detection limit at a signal-to-noise ratio of 3. Ascorbic acid does not interfere even in large excess, and the sensor is stable for at least a month. The modified GCE was applied to the determination of DA in spiked fetal bovine serum and gave satisfactory results. 相似文献
We describe a sensitive electrochemical immunosensor for the detection of deoxynivalenol (DON). It is based on a glassy carbon electrode modified with a composite made from fullerene (C60), ferrocene and the ionic liquid. The components were immobilized on the surface of the electrode using chitosan cross-linked with epichlorohydrin. Then, the antibody to DON was covalently conjugated to the surface which then was blocked with serum albumin. The performance of the immunosensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. It offers good repeatability (RSD?=?1.2%), selectivity, a stability of more than 180?days, an impedimetric response to DON in the range of 1?pgmL?1 to 0.3?ng?mL?1, and a detection limit (at S/N?=?3) of 0.3?pgmL?1. The limit of detection is better than that of GC, HPLC, GC-MS, HPLC-MS and LC-MS-MS. The effects of omitting C60 or the ionic liquid were also examined. The results indicate that the sensitivity of the biosensor is 2-fold better if C60 and ionic liquids are used. This demonstrates that C60 facilitates electron transfer on the surface of the modified electrode due to its unique electrochemical properties, while the ionic liquid provides a biocompatible microenvironment for the antibody. This results in increased sensitivity and stability. The method was satisfactorily applied to the determination of DON in food samples.
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Fullerene, ferrocene, chitosan and ionic liquid offer remarkable synergistic contributions towards improve electrochemical performance of DON sensor. This results that novel sensor exhibits a good repeatability (RSD=1.2%), selectivity, very low detection limit (S/N=3) of 0.0003 ng mL-1, an impedimetric response to DON in the range from 0.001 ng mL-1 to 0.3 ng mL-1 and a stability of more than 180 days. Cyclic voltammograms of, Ab/C60-FC-IL-GCE a and Ab/FC-IL-GCE b相似文献
