50673-96-6Relevant academic research and scientific papers
Mechanistic insights into phenol oxidation by a copper(II) complex of a pyridine- And amide-containing copolymer in an aqueous medium
Lykourinou, Vasiliki,Ming, Li-June
, p. 375 - 381 (2015)
A CuII complex of a pyridine- and amide-containing copolymer (Cu-P1) exhibits effective activity toward phenol hydroxylation in 50% aqueous methanol solution at apparent pH 8.0 and 25°C. The complex shows significant first-order rate accelerations of 4.2 × 105 and 1.4 × 105 relative to phenol autoxidation in air and in the presence of 20 mM H2O2, respectively. The reaction mechanisms with H2O2 and air are different on the basis of (a) the different activity profiles for Cu binding, (b) the different deuterium kinetic isotope effects (2.8 in 20 mM H2O2 and 1.2 aerobically), and (c) the formation of a dinuclear substrate-(Cu-P1) complex with H2O2 but a mononuclear one aerobically. The mechanism in the presence of H2O2 is consistent with that of the type-3 dicopper tyrosinase. Although oxidized di-CuII tyrosinase can only use H2O2 for phenol hydroxylation, CuII-P1 can use either air or H2O2 for this process. The studies herein introduce a versatile chemical system for the further exploration of Cu-oxygen chemistry and other types of metal-centered chemistry and for the aerobic degradation of aromatic compounds in environmental and green chemistry.
Electrocatalysis of dopamine in the presence of uric acid and folic acid on modified carbon nanotube paste electrode
Mazloum-Ardakani, Mohammad,Abolhasani, Mahboobe,Mirjalili, Bibi-Fatemeh,Sheikh-Mohseni, Mohammad Ali,Dehghani-Firouzabadi, Afsaneh,Khoshroo, Alireza
, p. 201 - 209 (2014)
A chemically modified carbon paste electrode (CPE), consisting of 2,2'-[(1E)-(1,2-phenylenebis (azanylylidene)] bis(methanylylidene)]bis(benzene- 1,4-diol) (PBD) and multiwalled carbon nanotubes (CNTs), was used to study the electrocatalytic oxidation of dopamine using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry (DPV). First, the electrochemical behavior of the modified electrode was investigated in buffer solution. Then the diffusion coefficient, electrocatalytic rate constant, and electron-transfer coefficient for dopamine oxidation at the surface of the PBD-modified CNT paste electrode were determined using electrochemical approaches. It was found that under optimum conditions (pH = 7.0), the oxidation of dopamine at the surface of such an electrode occurred at about 200 mV, lower than that of an unmodified CPE. DPV of dopamine at the modified electrode exhibited two linear dynamic ranges, with a detection limit of 1.0 μmol/L. Finally, DPV was used successfully for the simultaneous determination of dopamine, uric acid, and folic acid at the modified electrode, and detection limits of 1.0, 1.2, and 2.7 μmol/L were obtained for dopamine, uric acid, and folic acid, respectively. This method was also used for the determination of dopamine in a pharmaceutical preparation using the standard addition method.
Carbon supported olivine type phosphate framework: A promising electrocatalyst for sensitive detection of dopamine
Nehru, Raja,Chen, Shen-Ming
, p. 27775 - 27785 (2018)
In this study, a layered olivine-type LiMnPO4/functionalized-multiwall carbon nanotube (f-MWCNTs) composite is used as an electrochemically active material for the real-time detection of dopamine. A wet-chemical ultrasonication process is used to combine LiMnPO4 with f-MWCNTs at room temperature. The composite was subjected to various structural, morphological and electrochemical studies. The blending of olivine-type LiMnPO4 into the f-MWCNTs is revealed by TEM analysis. The electrochemical activities of the LiMnPO4/f-MWCNTs composite are systematically investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) for the real-time detection of dopamine. Furthermore, the applicability of the as prepared LiMnPO4/f-MWCNTs composite was extended for the detection of human serum (E48) and rat brain-serum (C7) samples with satisfactory recoveries for the real-time applications. All these studies revealed that the layered olivine-type LiMnPO4/f-MWCNTs composite is a potential candidate in the field of electrochemical sensing.
Mechanism of the manganese-catalyzed autoxidation of dopamine
Lloyd
, p. 111 - 116 (1995)
Manganese is an essential trace element for human metabolism, but at higher concentrations it is a potent neurotoxin that presents clinical symptoms similar to those of Parkinson's disease. Since the toxicity of manganese may be related to its ability to accelerate the oxidation of catecholamines, we have examined the effect of aqueous Mn2+ on the formation and decay of the dopamine semiquinone radical ion. ESR spectroscopy was used to measure the kinetics of the disappearance of the semiquinone radical spectrum and the simultaneous appearance of the six-line spectrum of aqueous Mn2+ in Tris buffer. From the proposed mechanism for the autoxidation of dopamine to the quinone, the rate expression for semiquinone radical disappearance has the functional form - rate = k'[D(OH)2][Mn2+] at constant pH and molecular oxygen concentration, while the pH dependence is given by -log(rate) = log(constant) + (2 x pH), in agreement with the experimental results. The autoxidation of dopamine is catalyzed by manganese through the formation of a highly reactive complex. The effect of manganese is due to the fact that it can participate in a redox cycle which involves intramolecular electron transfer between manganese and the dopamine ligand.
The effect of the buffering capacity of the supporting electrolyte on the electrochemical oxidation of dopamine and 4-methylcatechol in aqueous and nonaqueous solvents
Chen, Shanshan,Tai, Kah Yieng,Webster, Richard D.
, p. 1492 - 1499 (2011)
Dopamine was electrochemically oxidized in aqueous solutions and in the organic solvents N,N-dimethyl-formamide and dimethylsulfoxide containing varying amounts of supporting electrolyte and water, to form dopamine ortho-quinone. It was found that the electrochemical oxidation mechanism in water and in organic solvents was strongly influenced by the buffering properties of the supporting electrolyte. In aqueous solutions close to pH 7, where buffers were not used, the protons released during the oxidation process were able to sufficiently change the localized pH at the electrode surface to reduce the deprotonation rate of dopamine ortho-quinone, thereby slowing the conversion into leucoaminochrome. In N,N-dimethylformamide and dimethylsulfoxide solutions, in the absence of buffers, dopamine was oxidized to dopamine ortho-quinone that survived without further reaction for several minutes at 25 °C. The voltammetric data obtained in the organic solvents were made more complicated by the presence of HCl in commercial sources of dopamine, which also underwent an oxidation process. Copyright
A facile, solid-state reaction assisted synthesis of a berry-like NaNbO3 perovskite structure for binder-free, highly selective sensing of dopamine in blood samples
Durai, Lignesh,Badhulika, Sushmee
, p. 11994 - 12003 (2019)
Herein, we report a facile synthesis of sodium niobiate (NaNbO3) perovskite nanomaterial using a solid-state reaction (SSR) via solvothermally grown niobium pentoxide (Nb2O5) nanopowder for the excellent sensitive detection of dopamine (DA) in simulated blood serum with high selectivity. The X-ray Diffraction (XRD) pattern and Raman spectrum revealed an orthorhombic phase formation for NaNbO3 and the presence of a NbO6 octahedra site, while the scanning electron microscopy (SEM) images confirmed berry-like cluster formations of NaNbO3. The NaNbO3 modified glassy carbon electrode (GCE) sensor showed an excellent selectivity against interfering species like Na+, Cl-, Ca2+, glucose, ascorbic acid (AA), anduric acid, a sensitivity of 99 nA nM-1 cm-2 in the wide dynamic range of 10 nM to 500 μM, and a limit of detection (LOD) of 6.8 nM towards DA sensing, making it suitable for detecting physiological levels of DA in human blood. The sensing mechanism for DA was ascribed to the presence of NbO6 octahedral sites in the NaNbO3 perovskite structure that interacted with the oxidase of DA (dopamine-o-quinone) through Nb5+/Nb4+ niobium states, resulting in an increase in the oxidation peak current. This sensor did not exhibit any kind of surface fouling effects due to the reduction mechanism and the Na+ ions stabilizing the perovskite structure. The as-fabricated NaNbO3/GCE sensor was further assessed for the detection of DA in simulated blood serum, which showed an excellent recovery percentage. This novel, binder-free, NaNbO3 perovskite-based modified electrode offers a promising platform for developing high performance, non-enzymatic electrochemical sensors for numerous bioanalytical applications.
Magnetic Flower-like Fe-Doped CoO Nanocomposites with Dual Enzyme-like Activities for Facile and Sensitive Determination of H2O2and Dopamine
Lian, Jiajia,He, Yanlei,Li, Ning,Liu, Pei,Liu, Zhenxue,Liu, Qingyun
, p. 1893 - 1901 (2021)
Herein, a new series of magnetic Fe-doped CoO nanocomposites (Fe-CoO NCs) with dual enzyme-like activities (peroxidase and oxidase) were successfully synthesized. The molar ratio of Fe3+/Co2+ salts during the solvothermal process determined the morphology and catalytic activity of the NCs. Among them, the flower-like 0.15Fe-CoO NCs showed high peroxidase-mimicking activity over a wider pH range of 4-5 and a temperature range of 30-50 °C. Such nanozymes were applied for constructing a facile and sensitive colorimetric sensor to detect H2O2 and dopamine (DA) in the linear ranges of 6-20 and 2-10 μM with limits of detection (LODs) of 4.40 and 1.99 μM, respectively. The excellent magnetic separation performance and successful DA detection in human urine samples validated the promising application of CoO-based nanozymes in medical diagnosis. The superior catalytic behaviors of 0.15Fe-CoO NCs could be ascribed to the high surface area, open mesoporous structure, increased surface active species, and the facile redox of Fe3+/Fe2+ and Co3+/Co2+. Based on the results of the fluorescent probe and radical trapping tests, the possible mechanism that Fe doping promoted the decomposition of H2O2 to produce hydroxyl radical (.OH) and superoxide radical (.O2-) was proposed.
Ultrathin Cell-Membrane-Mimic Phosphorylcholine Polymer Film Coating Enables Large Improvements for In Vivo Electrochemical Detection
Liu, Xiaomeng,Xiao, Tongfang,Wu, Fei,Shen, Mo-Yuan,Zhang, Meining,Yu, Hsiao-Hua,Mao, Lanqun
, p. 11802 - 11806 (2017)
Resisting biomolecule adsorption onto the surface of brain-implanted microelectrodes is a key issue for in vivo monitoring of neurochemicals. Herein, we demonstrate that an ultrathin cell-membrane-mimic film of ethylenedioxythiophene tailored with zwitterionic phosphorylcholine (EDOT-PC) electropolymerized onto the surface of a carbon fiber microelectrode (CFE) not only resists protein adsorption but also maintains the sensitivity and time response for in vivo monitoring of dopamine (DA). As a consequence, the as-prepared PEDOT-PC/CFEs could be used as a new reliable platform for tracking DA in vivo and would help understand the physiological and pathological functions of DA.
Carbon-doped h-BN for the enhanced electrochemical determination of dopamine
Ouyang, Huiying,Li, Weifeng,Long, Yumei
, (2021)
Since dopamine (DA) is one of the central neurotransmitters and plays an important role in the human metabolism, its accurate detection is crucial for the diagnosis of DA-linked diseases. Herein, we demonstrated a novel electrochemical sensor for DA detection based on carbon-doped hexagonal boron nitrogen (C-hBN). C-hBN was prepared via a thermal polymerization process using melamine borate as a precursor. The successful C-doping was evidenced by fourier transform infrared (FTIR), photoluminescent (PL) and x-ray photoelectron spectroscopy (XPS). The carbon-doping can increase reactive sites and facilitate electrons transfer in h-BN, which was confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The C-hBN modified glassy carbon electrode (C-hBN/GCE) exhibited the enhanced electrocatalytic activity toward DA redox, whose CV peak current is 2.8 and 4.3 times higher than those of pure h-BN modified and bare GCEs, respectively. Based on CV method, the C-hBN/GCE presented a low detection limit of 5.8 nM (S/N = 3) and a sensitivity of 2037 μA?mM?cm?2. The linear response ranges were over the DA concentrations of 0.01–40 μM and 40–300 μM, respectively. In addition, the sensor was applied to detect DA in real samples including human serum and urine, and satisfactory results were achieved. The results suggested that the defect-engineered h-BN holds great potential for the development of electroanalytical devices with high-performance.
A Raman and UV-Vis study of catecholamines oxidized with Mn(III)
Barreto,Ponzoni,Sassi
, p. 65 - 72 (1998)
A UV-Vis and Raman spectroscopy study of three aminochromes generated through Mn3+ oxidation of the dopamine, L-dopa and adrenaline molecules at physiological pH was performed. The UV-Vis spectra of the catecholamines oxidized using Mn3+ in buffer solution at pH 7.2 show a band at ca. 300 nm, formed by two transitions at 280 nm and 300 nm assigned to an La and Lb transition respectively, and other at ca. 470 nm assigned to an n-π* transition localized in the carbonyl group. This assignment is suggested by the UV-Vis and Raman spectra of ortho-aminoquinone generated by MnO2 oxidation of a dopamine aqueous acidic solution. The resonance Raman spectra of the three chromes at buffer pH 7.2 show a very similar feature and the most intense bands are observed in the spectral range 1100-1800 cm-1. The band around 1680 cm-1 for the three compounds is assigned to a v(C=O) stretching vibration, 1630 cm-1 to the v(C=C) ring mode, two bands at 1423, 1439 cm-1; 1427, 1438 cm-1 and 1456, 1475 cm-1 are assigned to a v(C=N+) vibration, for aminochrome, dopachrome and adrenochrome, respectively. The excitation profiles for the most intense bands for aminochrome and adrenochrome were obtained. The band assigned to the v(C=N+) present a red shift with respect to the visible band peak, however the band in adrenochrome at 1475 cm-1 shows a profile similar to v(C=O) and v(CC) modes that reflects the methyl group effect on mixing this mode more effectively with the v(CC) ring mode.
