The Experts below are selected from a list of 50856 Experts worldwide ranked by ideXlab platform
Tony Breton - One of the best experts on this subject based on the ideXlab platform.
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evidence of monolayer formation via diazonium grafting with a Radical Scavenger electrochemical afm and xps monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Thibaud Menanteau, Eric Levillain, Alison Downard, Tony BretonAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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Evidence of monolayer formation from diazonium grafting with Radical Scavenger: electrochemical, AFM and XPS monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Tony Breton, Thibaud Menanteau, Eric Levillain, Alison DownardAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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electrografting via diazonium chemistry from multilayer to monolayer using Radical Scavenger
Chemistry of Materials, 2013Co-Authors: Thibaud Menanteau, Eric Levillain, Tony BretonAbstract:A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium electroreduction is presented. The approach proposes to directly act on the polymerization mechanism by the use of a Radical Scavenger. The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting. The well-known 4-nitrobenzenediazonium electrografting was used to demonstrate the possibility of reaching a monolayer surface coverage with an excess of DPPH (2,2-diphenyl-1-picrylhydrazyl). Experimental conditions were varied to validate the efficiency of the grafting limitation and the Radical capture was confirmed by isolation of the aryl Radical/DPPH coupling product.
Ken Arai - One of the best experts on this subject based on the ideXlab platform.
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protective effects of a Radical Scavenger edaravone on oligodendrocyte precursor cells against oxidative stress
Neuroscience Letters, 2018Co-Authors: Hajime Takase, Anna C Liang, Nobukazu Miyamoto, Gen Hamanaka, Ryo Ohtomo, Takakuni Maki, Locduyen D Pham, Josephine Lok, Ken AraiAbstract:Oligodendrocyte precursor cells (OPCs) play critical roles in maintaining the number of oligodendrocytes in white matter. Previously, we have shown that oxidative stress dampens oligodendrocyte regeneration after white matter damage, while a clinically proven Radical Scavenger, edaravone, supports oligodendrocyte repopulation. However, it is not known how edaravone exerts this beneficial effect against oxidative stress. Using in vivo and in vitro experiments, we have examined whether edaravone exhibits direct OPC-protective effects. For in vivo experiments, prolonged cerebral hypoperfusion was induced by bilateral common carotid artery stenosis in mice. OPC damage was observed on day 14 after the onset of cerebral hypoperfusion, and edaravone was demonstrated to decrease OPC death in cerebral white matter. In vitro experiments also confirmed that edaravone reduced oxidative-stress-induced OPC death. Because white matter damage is a major hallmark of many neurological diseases, and OPCs are instrumental in white matter repair after injury, our current study supports the idea that Radical Scavengers may provide a potential therapeutic approach for white matter related diseases.
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a free Radical Scavenger edaravone suppresses systemic inflammatory responses in a rat transient focal ischemia model
Neuroscience Letters, 2016Co-Authors: Norio Fujiwara, Locduyen D Pham, Brian Lee, Angel T Som, Emiri T Mandeville, Ken AraiAbstract:A free Radical Scavenger edaravone is clinically used in Japan for acute stroke, and several basic researches have carefully examined the mechanisms of edaravone's protective effects. However, its actions on pro-inflammatory responses under stroke are still understudied. In this study, we subjected adult male Sprague-Dawley rats to 90-min middle cerebral artery (MCA) occlusion followed by reperfusion. Edaravone was treated twice via tail vein; after MCA occlusion and after reperfusion. As expected, edaravone-treated group showed less infarct volume and edema formation compared with control group at 24-h after an ischemic onset. Furthermore, edaravone reduced the levels of plasma interleukin (IL)-1β and matrix metalloproteinase-9 at 3-h after ischemic onset. Several molecules besides IL-1β and MMP-9 are involved in inflammatory responses under stroke conditions. Therefore, we also examined whether edaravone treatment could decrease a wide range of pro-inflammatory cytokines/chemokines by testing rat plasma samples with a rat cytokine array. MCAO rats showed elevations in plasma levels of CINC-1, Fractalkine, IL-1α, IL-1ra, IL-6, IL-10, IP-10, MIG, MIP-1α, and MIP-3α, and all these increases were reduced by edaravone treatment. These data suggest that free Radical Scavengers may reduce systemic inflammatory responses under acute stroke conditions, and therefore, oxidative stress can be still a viable target for acute stroke therapy.
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edaravone a free Radical Scavenger protects components of the neurovascular unit against oxidative stress in vitro
Brain Research, 2010Co-Authors: Brian Lee, Yasuhiro Egi, Klaus Van Leyen, Ken AraiAbstract:The concept of the neurovascular unit suggests that to be successful, stroke therapies must protect all neuronal, glial and endothelial components in brain. In this study, we tested the efficacy of the free Radical Scavenger edaravone in three cellular models of oxidative stress. HT22 neuronal cells were subjected to oxidative stress using the standard glutamate-induced glutathione depletion model. Primary rat astrocytes were exposed to H2O2. Oxidative stress was induced in human brain endothelial cells with sodium nitroprusside (SNP). Edaravone significantly reduced oxidative cell death in both HT22 neuronal cells and primary rat astrocytes in a dose-dependent manner. SNP did not kill brain endothelial cells but instead reduced their production of brain-derived neurotrophic factor (BDNF). Edaravone significantly ameliorated this response. These data suggest that free Radical Scavengers are effective in all cell types of the neurovascular unit, and should still be considered as a potential therapeutic approach for stroke.
Thibaud Menanteau - One of the best experts on this subject based on the ideXlab platform.
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evidence of monolayer formation via diazonium grafting with a Radical Scavenger electrochemical afm and xps monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Thibaud Menanteau, Eric Levillain, Alison Downard, Tony BretonAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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Evidence of monolayer formation from diazonium grafting with Radical Scavenger: electrochemical, AFM and XPS monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Tony Breton, Thibaud Menanteau, Eric Levillain, Alison DownardAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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electrografting via diazonium chemistry from multilayer to monolayer using Radical Scavenger
Chemistry of Materials, 2013Co-Authors: Thibaud Menanteau, Eric Levillain, Tony BretonAbstract:A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium electroreduction is presented. The approach proposes to directly act on the polymerization mechanism by the use of a Radical Scavenger. The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting. The well-known 4-nitrobenzenediazonium electrografting was used to demonstrate the possibility of reaching a monolayer surface coverage with an excess of DPPH (2,2-diphenyl-1-picrylhydrazyl). Experimental conditions were varied to validate the efficiency of the grafting limitation and the Radical capture was confirmed by isolation of the aryl Radical/DPPH coupling product.
Alison Downard - One of the best experts on this subject based on the ideXlab platform.
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evidence of monolayer formation via diazonium grafting with a Radical Scavenger electrochemical afm and xps monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Thibaud Menanteau, Eric Levillain, Alison Downard, Tony BretonAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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Evidence of monolayer formation from diazonium grafting with Radical Scavenger: electrochemical, AFM and XPS monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Tony Breton, Thibaud Menanteau, Eric Levillain, Alison DownardAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
Eric Levillain - One of the best experts on this subject based on the ideXlab platform.
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evidence of monolayer formation via diazonium grafting with a Radical Scavenger electrochemical afm and xps monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Thibaud Menanteau, Eric Levillain, Alison Downard, Tony BretonAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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Evidence of monolayer formation from diazonium grafting with Radical Scavenger: electrochemical, AFM and XPS monitoring
Physical Chemistry Chemical Physics, 2015Co-Authors: Tony Breton, Thibaud Menanteau, Eric Levillain, Alison DownardAbstract:This paper analyzes the impact of the use of a Radical Scavenger on organic films generated by aryldiazonium electrografting in terms of thickness, morphology and chemical composition. Glassy carbon (GC) and pyrolyzed photoresist films (PPFs) were modified by electrochemical reduction of 4-nitrobenzenediazonium salt in the presence of various amounts of 2,2-diphenyl-1-picrylhydrazyl (DPPH). The thicknesses of the organic films have been measured by atomic force microscopy (AFM) and the lower threshold values confirm that it is possible to reach a monolayer by Radical trapping. X-ray photoelectron spectroscopy (XPS) highlights a decrease in the proportion of nitrophenyl groups grafted via azo bridges as the DPPH concentration decreases and the film thickness increases. A correlation of electrochemical, XPS and AFM data confirms that not all nitrophenyl groups are electroactive in films greater than 2 nm thick.
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electrografting via diazonium chemistry from multilayer to monolayer using Radical Scavenger
Chemistry of Materials, 2013Co-Authors: Thibaud Menanteau, Eric Levillain, Tony BretonAbstract:A simple strategy to avoid the formation of polyaryl layer during the functionalization of carbon surface by diazonium electroreduction is presented. The approach proposes to directly act on the polymerization mechanism by the use of a Radical Scavenger. The kinetic gap between the surface coupling and the multilayer formation is exploited to prevent the growth of the layer without interfering with the grafting. The well-known 4-nitrobenzenediazonium electrografting was used to demonstrate the possibility of reaching a monolayer surface coverage with an excess of DPPH (2,2-diphenyl-1-picrylhydrazyl). Experimental conditions were varied to validate the efficiency of the grafting limitation and the Radical capture was confirmed by isolation of the aryl Radical/DPPH coupling product.
