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Christopher M.a. Brett - One of the best experts on this subject based on the ideXlab platform.
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A novel amperometric sensor for ascorbic acid based on poly(Nile Blue A) and functionalised multi-walled carbon nanotube modified electrodes
Talanta, 2013Co-Authors: Dilek Kul, Rasa Pauliukaite, M. Emilia Ghica, Christopher M.a. BrettAbstract:A new type of modified electrode sensor for ascorbic acid has been prepared by deposition of multi-walled carbon nanotubes (MWCNT) and poly(Nile Blue A) on the surface of glassy carbon electrodes. Nile Blue A was electropolymerised either beneath (directly on glassy carbon) or onto the MWCNT layer by potential cycling in phosphate buffer solution at pH 6.0. Characterisation of the modified electrodes was carried out by cyclic voltammetry and electrochemical impedance spectroscopy. Quantitative determination of ascorbate was achieved by cyclic voltammetry and fixed potential amperometry in phosphate buffer solution at pH 5.3. The modified electrodes exhibited good sensitivity, wide linear range, a detection limit of 1.6 μM and good stability, showing that they can be used as sensors for ascorbic acid. There is no interference from compounds commonly found in clinical and pharmaceutical samples and the determination of ascorbic acid in commercial tablet samples was successfully performed.
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Electrosynthesis and characterisation of poly(Nile Blue) films
Journal of Electroanalytical Chemistry, 2011Co-Authors: Dilek Kul, Rasa Pauliukaite, Christopher M.a. BrettAbstract:Abstract The phenoxazine dye, Nile Blue-A, has been electropolymerised on glassy carbon electrodes by potential cycling in phosphate buffer solution at pH 5.3, 6.0, and 7.0. The electrochemical behaviour was studied by cyclic voltammetry and electrochemical impedance spectroscopy in phosphate buffer solution, also adding KCl, NaCl, LiCl, K2SO4, or Na2SO4 in order to evaluate counterion effects. The redox process of the polymer film presented an equal number of electrons and protons and the studies with different electrolyte compositions showed influence of the cations and anions on the electrochemical behaviour. The best polymer electrochemical properties were obtained in pH 5.3 electrolyte for the polymer prepared at pH 6.0, important information for application in electrochemical sensors and biosensors.
Chenxin Cai - One of the best experts on this subject based on the ideXlab platform.
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Single-walled carbon nanotubes functionalized with poly(Nile Blue A) and their application to dehydrogenase-based biosensors
Electrochimica Acta, 2007Co-Authors: Shuna Liu, Chenxin CaiAbstract:Abstract This paper reports a new type of nanocomposite of poly(Nile Blue A) with single-walled carbon nanotubes (PNb–SWNTs). This nanocomposite was fabricated by the functionalization of SWNTs with poly(Nile Blue A), which was formed by electropolymerizing an Nb monomer through the use of cyclic voltammetry. Scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–vis), cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to characterize the PNb–SWNTs. The cyclic voltammetric results indicated that PNb–SWNTs were able to electrocatalyze the oxidation of NADH at a very low potential (ca. −80 mV versus SCE) and lead to a substantial decrease in the overpotential by more than 700 mV compared with the bare glassy carbon (GC) electrode. A biosensor, ADH–PNb–SWNT/GC, was developed by immobilizing alcohol dehydrogenase (ADH) onto the PNb–SWNT/GC electrode surface. The biosensor showed electrocatalytic activity toward the oxidation of ethanol with a good stability, reproducibility, and higher biological affinity. Under optimal conditions, the electrochemical response to detect ethanol has the typical characteristics of Michaelis–Menten kinetics with an apparent Michaelis–Menten constant of K M app ∼ 6.30 mM, and depends linearly on the concentration of ethanol from 0.1 to 3.0 mM (with a correlation coefficient of 0.998), with a detection limit of ∼50 μM (at a signal-to-noise ratio of 3). The facile procedure of immobilizing ADH used in the present work can promote the development of electrochemical research for enzymes (proteins), biosensors, biofuel cells and other bioelectrochemical devices.
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Electrocatalysis of NADH oxidation with electropolymerized films of Nile Blue A
Analytica Chimica Acta, 1997Co-Authors: Chenxin Cai, K.-h. XueAbstract:Abstract A stable electroactive thin film of poly(Nile Blue A) (PNB) has been deposited on the surface of a glassy carbon electrode by cyclic voltammetry in an aqueous solution containing Nile Blue A (NB). Cyclic voltammograms of PNB indicate the presence of two redox couples and the formal potential shifts toward negative direction with increasing solution pH. The PNB modified glassy carbon electrode shows excellent electrocatalytic activity toward NADH oxidation in phosphate buffer solution (pH 6.8), with an overpotential which is more than 660 mV lower than that of the bare electrode. The catalytic rate constant of the modified glassy carbon electrode for the oxidation of NADH is determined by cyclic voltammetry and rotating disk electrode measurements.
Katherine A. Willets - One of the best experts on this subject based on the ideXlab platform.
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Unforeseen distance-dependent SERS spectroelectrochemistry from surface-tethered Nile Blue: the role of molecular orientation
The Analyst, 2016Co-Authors: Andrew J. Wilson, Katherine A. WilletsAbstract:Covalent immobilization of redox-active dyes is an important strategy to evaluate structure–activity relationships in nanoscale electrochemistry by using optical readouts such as surface-enhanced Raman scattering (SERS). Here we investigate the role of the tether length in the SERS spectroelectrochemistry of surface-attached Nile Blue. Differential pulse voltammetry and a potential-dependent SERS derivative analysis reveal that the Nile Blue molecules adopt a different orientation with respect to the electrode surface as the number of carbons in a carboxylic acid-terminated alkanethiol monolayer is varied, which leads to unique SERS spectroelectrochemical behaviors. We use the relative molecular orientations and spectral characteristics to propose a model in which tethers shorter than the length of the molecule limit molecular motion under electrochemical perturbation, but tethers longer than the length of the molecule allow dye intercalation into the hydrophobic self-assembled monolayer, producing an unexpected decrease in the SERS intensity when the molecule is in the oxidized form.
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Modification of the Electrochemical Properties of Nile Blue through Covalent Attachment to Gold As Revealed by Electrochemistry and SERS
The Journal of Physical Chemistry C, 2016Co-Authors: Andrew J. Wilson, Natalia Y. Molina, Katherine A. WilletsAbstract:Conventional electrochemistry and surface-enhanced Raman scattering (SERS) spectroelectrochemistry are used to probe the redox reaction of Nile Blue immobilized on gold electrodes. Covalent attachment of Nile Blue (NB) to gold through carbodiimide cross-linking shows the appearance of a second, new redox reaction, unobserved by solution phase or physisorbed NB. Each redox reaction is characterized by differential pulse voltammetry to reveal two individual one-proton, one-electron electrochemical reactions. SERS spectroelectrochemistry along with electrochemical characterization of structurally similar Cresyl Violet are used to assign the electrochemical (de)protonation of the terminal amine and phenoxazine nitrogen to the lower and higher energy redox reactions, respectively. Analysis of covalently bound NB via azide–alkyne click chemistry supports the hypothesis that the electron-withdrawing carbonyl formed during the carbodiimide cross-linking induces a change in the electronic structure of NB, causing ...
Abbas Farmany - One of the best experts on this subject based on the ideXlab platform.
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Silver nanoparticle-based spectrophotometric method for quantification of Nile Blue A in river water
Journal of Industrial and Engineering Chemistry, 2014Co-Authors: S. S. Mortazavi, Reza Sahraei, Abbas FarmanyAbstract:Abstract A novel and sensitive spectrophotometric method is developed for the determination of nanomolar level of Nile Blue A in water samples based on its catalytic effect of silver nanoparticles on the oxidation of Nile Blue A by hexacyanoferrate (III) in acetate-acetic acid medium and at 25 °C. The absorbance is measured at 595.5 nm with the fixed-time method. The optimization of the operating conditions regarding concentration of the reagents, temperature and interferences is also investigated. The calibration curve is linear over the concentration range between 85 and 2000 nM of Nile Blue A with good precision and accuracy. The detection limit of the method is down to 54. The relative standard deviation for a standard solution of 100.0 nM of Nile Blue A is 1.63% (n = 10). The proposed method provides a highly sensitive, selective and relatively rapid assay for Nile Blue A at nanomolar level without any pre-concentration and separation step. The method was applied to the determination of Nile Blue A in river water samples.
Dilek Kul - One of the best experts on this subject based on the ideXlab platform.
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A novel amperometric sensor for ascorbic acid based on poly(Nile Blue A) and functionalised multi-walled carbon nanotube modified electrodes
Talanta, 2013Co-Authors: Dilek Kul, Rasa Pauliukaite, M. Emilia Ghica, Christopher M.a. BrettAbstract:A new type of modified electrode sensor for ascorbic acid has been prepared by deposition of multi-walled carbon nanotubes (MWCNT) and poly(Nile Blue A) on the surface of glassy carbon electrodes. Nile Blue A was electropolymerised either beneath (directly on glassy carbon) or onto the MWCNT layer by potential cycling in phosphate buffer solution at pH 6.0. Characterisation of the modified electrodes was carried out by cyclic voltammetry and electrochemical impedance spectroscopy. Quantitative determination of ascorbate was achieved by cyclic voltammetry and fixed potential amperometry in phosphate buffer solution at pH 5.3. The modified electrodes exhibited good sensitivity, wide linear range, a detection limit of 1.6 μM and good stability, showing that they can be used as sensors for ascorbic acid. There is no interference from compounds commonly found in clinical and pharmaceutical samples and the determination of ascorbic acid in commercial tablet samples was successfully performed.
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Electrosynthesis and characterisation of poly(Nile Blue) films
Journal of Electroanalytical Chemistry, 2011Co-Authors: Dilek Kul, Rasa Pauliukaite, Christopher M.a. BrettAbstract:Abstract The phenoxazine dye, Nile Blue-A, has been electropolymerised on glassy carbon electrodes by potential cycling in phosphate buffer solution at pH 5.3, 6.0, and 7.0. The electrochemical behaviour was studied by cyclic voltammetry and electrochemical impedance spectroscopy in phosphate buffer solution, also adding KCl, NaCl, LiCl, K2SO4, or Na2SO4 in order to evaluate counterion effects. The redox process of the polymer film presented an equal number of electrons and protons and the studies with different electrolyte compositions showed influence of the cations and anions on the electrochemical behaviour. The best polymer electrochemical properties were obtained in pH 5.3 electrolyte for the polymer prepared at pH 6.0, important information for application in electrochemical sensors and biosensors.