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Shaojun Dong - One of the best experts on this subject based on the ideXlab platform.
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copper hexacyanoferrate multilayer films on glassy carbon electrode modified with 4 Aminobenzoic Acid in aqueous solution
Talanta, 2006Co-Authors: Guocheng Yang, Yan Shen, Mingkui Wang, Hongjun Chen, Shaojun DongAbstract:4-Aminobenzoic Acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation during the electrooxidation process in 0.1 M KCl aqueous solution. X-ray photoelectron spectroscopy (XPS) measurement proves the presence of 4-carboxylphenylamine on the GCE. Electron transfer processes of Fe(CN)6 3- in solutions of various pHs at the modified electrode are studied by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Changing the solution pH would result in the variation of the terminal group's charge state, based on which the surface pKa values were estimated. The copper hexacyanoferrate (CuHCF) multilayer films were formed on 4-ABA/GCE prepared in aqueous solution, and which exhibit good electrochemical behavior with high stability.
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electrochemical behavior and assembly of tetranuclear dawson derived sandwich compound cd4 h2o 2 as2w15o56 2 16 on 4 Aminobenzoic Acid modified glassy carbon electrode
Analytica Chimica Acta, 2005Co-Authors: Yan Shen, Junguang Jiang, Erkang Wang, Shaojun DongAbstract:Abstract The transition metal-substituted heteropolyoxoanion, Cd4(H2O)2(As2W15O56)212− (As4W30Cd4), is one of the trivacant Dawson derivatives. Its redox electrochemistry has been studied in Acid buffer solutions using cyclic voltammetry. It exhibited three steps of four-electron redox waves attributed to redox processes of the tungsten-oxo framework. Through layer-by-layer assembly, the compound was first successfully immobilized on a 4-Aminobenzoic Acid modified glassy carbon electrode surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)2Cl]2+/+ (denoted as QPVP-Os). Thus, prepared multilayer films have been characterized by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy (UV–vis). The electrocatalytic activities of the multilayer films containing As4W30Cd4 have been investigated on the reduction of three substrates of important analytical interests, NO2−, BrO3− and IO3−. And with the increase of the number of As4W30Cd4 layers, the catalytic current towards the reduction of BrO3− was enhanced and the catalytic potential shifted positively.
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assembly of the transition metal substituted polyoxometalates znw11m h2o o rm _ 39 n m mn cu fe co cr ni zn on 4 Aminobenzoic Acid modified glassy carbon electrode and their electrochemical study
Electroanalysis, 2002Co-Authors: Jianyun Liu, Long Cheng, Shaojun DongAbstract:Through layer-by-layer assembly, a series of undecatungstozincates monosubstituted by first-row transition metals, ZnW11M(H2O)O-39(n-) (M=Cr, Mn, Fe, Co, Ni, Cu. or Zn) were first successfully immobilized on a 4-Aminobenzoic Acid modified glassy carbon electrode surface. The electrochemical behaviors of these polyoxometalates were investigated. They exhibit some special properties in the films different from those in homogeneous aqueous solution. The Cu-centered reaction mechanism in the ZnW11Cu multilayer film was described. The electrocatalytic behaviors of these multilayer film electrodes to the reduction of H2O2 and BrO3- were comparatively studied.
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Investigation of the model compounds at 4-Aminobenzoic Acid modified glassy carbon electrode by scanning electrochemical microscopy
Journal of Electroanalytical Chemistry, 2001Co-Authors: Jianyun Liu, Shaojun Dong, Zhiquan Zhang, Yuanhua ShaoAbstract:In this paper, we studied the reactions of both potassium ferricyanide and hexaammineruthenium(III) chloride at a 4-Aminobenzoic Acid (4-ABA) modified glassy carbon electrode (GCE) by scanning electrochemical microscopy (SECM) in different pH solutions. The surface of the modified electrode has carboxyl groups, the dissociation of which are strongly dependent upon the solution pH values. The rate constant kb of the oxidation of ferrocyanide on the modified electrode can be obtained by fitting the experimental tip current-distance (I-T-d) curves with the theoretical values. The surface pK(a) of the 4-ABA modified GCE was estimated from the plot of standard rate constant k(o) versus the solution pH and is equal to 3.2, which is in good agreement with the reported result. The SECM approach curves for Ru(NH3)(6)(3+) both on the bare and the modified electrodes show similar diffusion control processes. These results can be explained by the electrostatic interactions between the modified electrode surface and the model compounds with different charges. (C) 2001 Elsevier Science BN. All rights reserved.
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covalent modification of a glassy carbon surface by 4 Aminobenzoic Acid and its application in fabrication of a polyoxometalates consisting monolayer and multilayer films
Langmuir, 2000Co-Authors: Jianyun Liu, Long Cheng, And Baifeng Liu, Shaojun DongAbstract:4-Aminobenzoic Acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation process of the amino-containing compound. X-ray photoelectron spectroscopy measurement proves the presence of 4-carboxylphenylamine monolayer on the GCE. The redox responses of various electroactive probes were investigated on the 4-ABA-modified GCE. Electron transfer to Fe(CN)63- in solutions of various pHs was studied by both cyclic voltammetry and electrochemical impedance analysis on the modified electrode. Changes in the solution pH value result in the variation of the terminal group charge state, based on which surface pKa values are estimated. The 4-ABA-modified GCE was used as a suitable charged substrate to fabricate polyoxometalates-consisting (POM-consisting) monolayer and multilayer films through layer-by-layer assembly based on electrostatic attraction. Cyclic voltammetry shows the uniform growth of these three-dimensional multilayer films. Taking K10...
John W Chen - One of the best experts on this subject based on the ideXlab platform.
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myeloperoxidase propagates damage and is a potential therapeutic target for subacute stroke
Journal of Cerebral Blood Flow and Metabolism, 2015Co-Authors: Reza Forghani, Gregory R Wojtkiewicz, Lionel Bure, Yue Wu, Makoto Hayase, Yi Zheng, Michael A Moskowitz, John W ChenAbstract:Few effective treatment options exist for stroke beyond the hyperacute period. Radical generation and myeloperoxidase (MPO) have been implicated in stroke. We investigated whether pharmacologic reduction or gene deletion of this highly oxidative enzyme reduces infarct propagation and improves outcome in the transient middle cerebral artery occlusion mouse model (MCAO). Mice were treated with 4-Aminobenzoic Acid hydrazide (ABAH), a specific irreversible MPO inhibitor. Three treatment regimens were used: (1) daily throughout the 21-day observational period, (2) during the acute stage (first 24 hours), or (3) during the subacute stage (daily starting on day 2). We found elevated MPO activity in ipsilateral brain 3 to 21 days after ischemia. 4-Aminobenzoic Acid hydrazide reduced enzyme activity by 30% to 40% and final lesion volume by 60% (P<0.01). The MPO-knockout (KO) mice subjected to MCAO also showed a similar reduction in the final lesion volume (P<0.01). The ABAH treatment or MPO-KO mice also improved n...
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myeloperoxidase propagates damage and is a potential therapeutic target for subacute stroke
Journal of Cerebral Blood Flow and Metabolism, 2015Co-Authors: Reza Forghani, Gregory R Wojtkiewicz, Lionel Bure, Makoto Hayase, Yi Zheng, Michael A Moskowitz, Hyeon Ju Kim, Ying Wei, John W ChenAbstract:Few effective treatment options exist for stroke beyond the hyperacute period. Radical generation and myeloperoxidase (MPO) have been implicated in stroke. We investigated whether pharmacologic reduction or gene deletion of this highly oxidative enzyme reduces infarct propagation and improves outcome in the transient middle cerebral artery occlusion mouse model (MCAO). Mice were treated with 4-Aminobenzoic Acid hydrazide (ABAH), a specific irreversible MPO inhibitor. Three treatment regimens were used: (1) daily throughout the 21-day observational period, (2) during the acute stage (first 24 hours), or (3) during the subacute stage (daily starting on day 2). We found elevated MPO activity in ipsilateral brain 3 to 21 days after ischemia. 4-Aminobenzoic Acid hydrazide reduced enzyme activity by 30% to 40% and final lesion volume by 60% (P<0.01). The MPO-knockout (KO) mice subjected to MCAO also showed a similar reduction in the final lesion volume (P<0.01). The ABAH treatment or MPO-KO mice also improved neurobehavioral outcome (P<0.001) and survival (P=0.01), but ABAH had no additional beneficial effects in MPO-KO mice, confirming specificity of ABAH. Interestingly, inhibiting MPO activity during the subacute stage recapitulated most of the therapeutic benefit of continuous MPO inhibition, suggesting that MPO-targeted therapies could be useful when given after 24 hours of stroke onset.
P Ramasamy - One of the best experts on this subject based on the ideXlab platform.
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synthesis growth structural optical thermal laser damage threshold and computational perspectives of 4 nitrophenol 4 Aminobenzoic Acid monohydrate 4npaba single crystal
Journal of Molecular Structure, 2019Co-Authors: P Karuppasamy, P Ramasamy, T Kamalesh, V Mohankumar, Abdul S Kalam, Muthu Senthil Pandian, Sunil Verma, Venugopal S RaoAbstract:Abstract A new organic compound 4-nitrophenol 4-Aminobenzoic Acid monohydrate (4NPABA) was synthesized and crystals were grown by slow evaporation solution technique (SEST). The crystal structure of 4NPABA was confirmed by single crystal X-ray diffraction (SXRD) and it was found to be monoclinic system with the centrosymmetric space group P21/c. The powder XRD (PXRD) was carried out for analysis of diffracting planes of grown crystal and also indexed by the Rietveld refinement using FullProf code. The 1H NMR and 13C NMR spectral analysis was used to confirm the chemical environment of various protons and carbons present in a 4NPABA structure. The various functional groups of the grown crystal were identified using Fourier transform infrared (FTIR) and FT-Raman spectroscopy. The transmittance of the grown crystal was analyzed by using UV–Visible–NIR spectral analysis and the cut-off wavelength was found to be 400 nm. The thermal stability of the grown crystal has been investigated by TGA-DTA studies. Laser damage threshold (LDT) value of the grown crystals has been determined using a nanosecond (ns) Nd:YAG laser operating at 532 nm. The third-order nonlinear optical property of 4NPABA crystal was studied by Z-scan technique to determine its nonlinear absorption (β) and nonlinear refraction (n2). The charge transfer characteristic of the grown crystal was studied by frontier molecular orbital (FMOs) analysis. The hydrogen bonding of the present molecule was confirmed by NBO analysis. The polarizability and hyperpolarizability of the 4NPABA were calculated at the B3LYP/6–311++G (d,p) level using Gaussian 09W package. The calculated values of linear polarizability (α*) and first order hyperpolarizability (β*) are 2.683 × 10−23 (esu) and 11.865 × 10−30 (esu) respectively.
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synthesis growth structural optical and thermal properties of an organic single crystal 4 nitroaniline 4 Aminobenzoic Acid
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014Co-Authors: A Silambarasan, P Rajesh, P RamasamyAbstract:Abstract The organic single crystals of 4-nitroaniline 4-Aminobenzoic Acid (4NAABA) were grown from ethanol solvent. The lattice parameters of the grown crystal have been confirmed from single crystal XRD analysis. The powder XRD pattern shows the various planes of grown crystal. The FTIR and 1 H NMR spectral analysis confirm the presence of various functional groups and the placement of proton in 4NAABA compound respectively. The UV absorption was carried out which shows the cutoff wavelength around 459 nm. The optical band gap of the crystal has been evaluated from the transmission spectra and absorption coefficient by extrapolation technique. In addition, a fluorescence spectral analysis is carried out for 4NAABA crystals. The thermal properties of crystals were evaluated from thermogravimetrical analysis. It shows that the grown crystal is stable up to 160 °C and the crystal has sharp melting point at 151 °C.
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crystal growth optical and thermal studies of 4 nitroaniline 4 Aminobenzoic Acid a fluorescent material
2014Co-Authors: A Silambarasan, P Rajesh, P RamasamyAbstract:The organic single crystals of 4-nitroaniline 4Aminobenzoic Acid (4NAABA) were grown from ethanol solvent. The grown crystals have been confirmed from single crystal XRD analysis. The UV absorption was carried out which shows the cutoff wavelength around 459 nm. The optical band gap of the crystal has been evaluated from the absorption spectra and absorption coefficient by extrapolation technique. The fluorescence spectral analysis is carried out for 4NAABA crystals. The thermal stability of the crystal was evaluated from thermogravimetric and differential thermal analysis.
Jianyun Liu - One of the best experts on this subject based on the ideXlab platform.
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assembly of the transition metal substituted polyoxometalates znw11m h2o o rm _ 39 n m mn cu fe co cr ni zn on 4 Aminobenzoic Acid modified glassy carbon electrode and their electrochemical study
Electroanalysis, 2002Co-Authors: Jianyun Liu, Long Cheng, Shaojun DongAbstract:Through layer-by-layer assembly, a series of undecatungstozincates monosubstituted by first-row transition metals, ZnW11M(H2O)O-39(n-) (M=Cr, Mn, Fe, Co, Ni, Cu. or Zn) were first successfully immobilized on a 4-Aminobenzoic Acid modified glassy carbon electrode surface. The electrochemical behaviors of these polyoxometalates were investigated. They exhibit some special properties in the films different from those in homogeneous aqueous solution. The Cu-centered reaction mechanism in the ZnW11Cu multilayer film was described. The electrocatalytic behaviors of these multilayer film electrodes to the reduction of H2O2 and BrO3- were comparatively studied.
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Investigation of the model compounds at 4-Aminobenzoic Acid modified glassy carbon electrode by scanning electrochemical microscopy
Journal of Electroanalytical Chemistry, 2001Co-Authors: Jianyun Liu, Shaojun Dong, Zhiquan Zhang, Yuanhua ShaoAbstract:In this paper, we studied the reactions of both potassium ferricyanide and hexaammineruthenium(III) chloride at a 4-Aminobenzoic Acid (4-ABA) modified glassy carbon electrode (GCE) by scanning electrochemical microscopy (SECM) in different pH solutions. The surface of the modified electrode has carboxyl groups, the dissociation of which are strongly dependent upon the solution pH values. The rate constant kb of the oxidation of ferrocyanide on the modified electrode can be obtained by fitting the experimental tip current-distance (I-T-d) curves with the theoretical values. The surface pK(a) of the 4-ABA modified GCE was estimated from the plot of standard rate constant k(o) versus the solution pH and is equal to 3.2, which is in good agreement with the reported result. The SECM approach curves for Ru(NH3)(6)(3+) both on the bare and the modified electrodes show similar diffusion control processes. These results can be explained by the electrostatic interactions between the modified electrode surface and the model compounds with different charges. (C) 2001 Elsevier Science BN. All rights reserved.
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covalent modification of a glassy carbon surface by 4 Aminobenzoic Acid and its application in fabrication of a polyoxometalates consisting monolayer and multilayer films
Langmuir, 2000Co-Authors: Jianyun Liu, Long Cheng, And Baifeng Liu, Shaojun DongAbstract:4-Aminobenzoic Acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation in the electrooxidation process of the amino-containing compound. X-ray photoelectron spectroscopy measurement proves the presence of 4-carboxylphenylamine monolayer on the GCE. The redox responses of various electroactive probes were investigated on the 4-ABA-modified GCE. Electron transfer to Fe(CN)63- in solutions of various pHs was studied by both cyclic voltammetry and electrochemical impedance analysis on the modified electrode. Changes in the solution pH value result in the variation of the terminal group charge state, based on which surface pKa values are estimated. The 4-ABA-modified GCE was used as a suitable charged substrate to fabricate polyoxometalates-consisting (POM-consisting) monolayer and multilayer films through layer-by-layer assembly based on electrostatic attraction. Cyclic voltammetry shows the uniform growth of these three-dimensional multilayer films. Taking K10...
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layer by layer assembly of multilayer films consisting of silicotungstate and a cationic redox polymer on 4 Aminobenzoic Acid modified glassy carbon electrode and their electrocatalytic effects
Analytica Chimica Acta, 2000Co-Authors: Long Cheng, Jianyun Liu, Shaojun DongAbstract:A novel 4-Aminobenzoic Acid (4-ABA) monolayer film is formed on glassy carbon electrode (GCE) by amino cation radical method. Silicotungstic heteropolyanion (SiW12O404-, denoted as SiW12)-containing multilayer films have been fabricated on the 4-ABA modified GCE surface by alternate deposition with a quaternized poly(4-vinylpyridine) partially complexed with [Os(bpy)(2)Cl](2+/+) (denoted as QPVP-Os). Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) and X-ray reflectivity (XR) have been used to characterise the as-prepared multilayer films. It is proved that the multilayer films are uniform and stable. The average thickness for a bilayer of QPVP-Os/SiW12 in the multilayer film is 30.2 Angstrom. The electrocatalytic activities of the multilayer films have been investigated on the reduction of three substrates of important analytical interests, HNO2, BrO3- and H2O2. Especially, the influence of layer number of the multilayer films on the electrocatalytic reduction of HNO2 has been investigated in detail. (C) 2000 Elsevier Science B.V. All rights reserved.
Larry J Campbell - One of the best experts on this subject based on the ideXlab platform.
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studying gas phase interconversion of tautomers using differential mobility spectrometry
Journal of the American Society for Mass Spectrometry, 2016Co-Authors: Larry J Campbell, Amy Mengci Yang, Luke R Melo, Scott W HopkinsAbstract:In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-Aminobenzoic Acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-Aminobenzoic Acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.
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probing electrospray ionization dynamics using differential mobility spectrometry the curious case of 4 Aminobenzoic Acid
Analytical Chemistry, 2012Co-Authors: Larry J Campbell, J Yves Le C Blanc, Bradley B SchneiderAbstract:Here, we present the separation of two ions that differ only by the site of protonation of the analyte molecule using differential mobility spectrometry (DMS). Protonated 4-Aminobenzoic Acid molecules (4-ABA) generated by positive-mode electrospray ionization [ESI(+)] can exist with the proton residing on either the amine nitrogen (N-protonated) or the carboxylic Acid oxygen (O-protonated), and the protonation site can differ on the basis of the solvent system used. In this study, we demonstrate the identification and separation of N- and O-protonated 4-ABA using DMS, with structural assignments verified by: (1) the presence of distinct peaks in the DMS ionogram, (2) the observed effects resulting from altering the ESI(+) solvent system, (3) the observed 13C NMR chemical shifts arising from altering the solvent system, (4) the observation of distinct MS/MS fragmentation patterns for the two DMS-separated ions, (5) the unique hydrogen–deuterium exchange behavior for these ions, and (6) the fundamental beha...
