The Experts below are selected from a list of 213 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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Enhancing the performance of a diazonium-modified carbon supercapacitor by controlling the grafting process
Electrochemistry Communications, 2016Co-Authors: Thibaud Menanteau, Tony Breton, Corentin Benoit, Charles CougnonAbstract:The activated Norit carbon was modified by grafting the 4-Nitrobenzenediazonium salt in the presence or in the absence of a radical scavenger (DPPH: 2,2-diphenyl-1-picrylhydrazyl) to produce modified carbon powders having different surface organic layers going from monolayer to multilayer. The surface chemistry and pore texture of carbon products were studied by TGA, chemical elemental analysis and nitrogen gas adsorption measurements. The resulting powders were used as active components in supercapacitors working in alkaline media to investigate the impact of the grafting on the electrochemical performances. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the charge/ discharge process in aqueous 1 M KOH. The present work demonstrates that the high double-layer capaci-tance and the low ionic resistance of the pristine carbon can be preserved by limiting the growth of the grafted layer with DPPH.
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Enhancing the performance of a diazonium-modified carbon supercapacitor by controlling the grafting process
Elsevier, 2016Co-Authors: Thibaud Menanteau, Tony Breton, Corentin Benoit, Charles CougnonAbstract:The activated Norit carbon was modified by grafting the 4-Nitrobenzenediazonium salt in the presence or in the absence of a radical scavenger (DPPH: 2,2-diphenyl-1-picrylhydrazyl) to produce modified carbon powders having different surface organic layers going from monolayer to multilayer. The surface chemistry and pore texture of carbon products were studied by TGA, chemical elemental analysis and nitrogen gas adsorption measurements. The resulting powders were used as active components in supercapacitors working in alkaline media to investigate the impact of the grafting on the electrochemical performances. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the charge/discharge process in aqueous 1 M KOH. The present work demonstrates that the high double-layer capacitance and the low ionic resistance of the pristine carbon can be preserved by limiting the growth of the grafted layer with DPPH. Keywords: Diazonium salts, Radical scavenger, DPPH, Activated carbon, Supercapacitors, Graftin
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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.
Thibaud Menanteau - One of the best experts on this subject based on the ideXlab platform.
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Impact of the Diazonium Grafting Control on the Interfacial Reactivity: Monolayer versus Multilayer
'Wiley', 2017Co-Authors: Thibaud Menanteau, S. Dabos, E. Levillain, T. BretonAbstract:A very simple strategy to prepare, in two steps, a versatile and sustainable monolayer platform for on-surface chemistry is presented. The first step consists of the electroreduction of well-known 4-Nitrobenzenediazonium in the presence of a radical scavenger, leading to a covalent monolayer surface modification. Then, a dense reactive phenylamine monolayer is obtained through the full electroreduction of the nitrophenyl moieties. The platform thus obtained is available for post-functionalization with carboxyl derivatives through a usual peptide coupling. Attachment of a TEMPO unit, offering both redox and electrocatalytic properties, validates this approach and leads to high surface coverage and fast electron transfer. A comparison of the electrochemical properties of the modified surface with a classical multilayered post-functionalized one highlights important differences in terms of interfacial reactivity. The results presented here justify the interest in preparing a reactive monolayer platform for molecule grafting and paves the way for simple and controlled surface chemistry without the need of synthesis
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Enhancing the performance of a diazonium-modified carbon supercapacitor by controlling the grafting process
Electrochemistry Communications, 2016Co-Authors: Thibaud Menanteau, Tony Breton, Corentin Benoit, Charles CougnonAbstract:The activated Norit carbon was modified by grafting the 4-Nitrobenzenediazonium salt in the presence or in the absence of a radical scavenger (DPPH: 2,2-diphenyl-1-picrylhydrazyl) to produce modified carbon powders having different surface organic layers going from monolayer to multilayer. The surface chemistry and pore texture of carbon products were studied by TGA, chemical elemental analysis and nitrogen gas adsorption measurements. The resulting powders were used as active components in supercapacitors working in alkaline media to investigate the impact of the grafting on the electrochemical performances. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the charge/ discharge process in aqueous 1 M KOH. The present work demonstrates that the high double-layer capaci-tance and the low ionic resistance of the pristine carbon can be preserved by limiting the growth of the grafted layer with DPPH.
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Enhancing the performance of a diazonium-modified carbon supercapacitor by controlling the grafting process
Elsevier, 2016Co-Authors: Thibaud Menanteau, Tony Breton, Corentin Benoit, Charles CougnonAbstract:The activated Norit carbon was modified by grafting the 4-Nitrobenzenediazonium salt in the presence or in the absence of a radical scavenger (DPPH: 2,2-diphenyl-1-picrylhydrazyl) to produce modified carbon powders having different surface organic layers going from monolayer to multilayer. The surface chemistry and pore texture of carbon products were studied by TGA, chemical elemental analysis and nitrogen gas adsorption measurements. The resulting powders were used as active components in supercapacitors working in alkaline media to investigate the impact of the grafting on the electrochemical performances. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the charge/discharge process in aqueous 1 M KOH. The present work demonstrates that the high double-layer capacitance and the low ionic resistance of the pristine carbon can be preserved by limiting the growth of the grafted layer with DPPH. Keywords: Diazonium salts, Radical scavenger, DPPH, Activated carbon, Supercapacitors, Graftin
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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.
Andreas Stein - One of the best experts on this subject based on the ideXlab platform.
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receptor based detection of 2 4 dinitrotoluene using modified three dimensionally ordered macroporous carbon electrodes
ACS Applied Materials & Interfaces, 2012Co-Authors: Melissa A Fierke, Eric J Olson, Philippe Buhlmann, Andreas SteinAbstract:Detection of explosives, such as 2,4,6-trinitrotoluene (TNT), is becoming increasingly important. Here, 2,4-dinitrotoluene (DNT, a common analogue of TNT) is detected electrochemically. A receptor based electrode for the detection of DNT was prepared by modifying the surface of the walls of three-dimensionally ordered macroporous (3DOM) carbon. Nitrophenyl groups were first attached by the electrochemical reduction of 4-Nitrobenzenediazonium ions, followed by potentiostatic reduction to aminophenyl groups. Chemical functionalization reactions were then performed to synthesize the receptor, which contains two urea groups, and a terminal primary amine. Detection of DNT using cyclic voltammetry was impeded by a large background current that resulted from the capacitance of 3DOM carbon. Detection by square wave voltammetry eliminated the background current and improved the detection limit. Unfunctionalized 3DOM carbon electrodes showed no response to DNT, whereas the receptor-modified electrodes responded to ...
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Receptor-Based Detection of 2,4-Dinitrotoluene Using Modified Three-Dimensionally Ordered Macroporous Carbon Electrodes
2012Co-Authors: Melissa A Fierke, Eric J Olson, Philippe Bühlmann, Andreas SteinAbstract:Detection of explosives, such as 2,4,6-trinitrotoluene (TNT), is becoming increasingly important. Here, 2,4-dinitrotoluene (DNT, a common analogue of TNT) is detected electrochemically. A receptor based electrode for the detection of DNT was prepared by modifying the surface of the walls of three-dimensionally ordered macroporous (3DOM) carbon. Nitrophenyl groups were first attached by the electrochemical reduction of 4-Nitrobenzenediazonium ions, followed by potentiostatic reduction to aminophenyl groups. Chemical functionalization reactions were then performed to synthesize the receptor, which contains two urea groups, and a terminal primary amine. Detection of DNT using cyclic voltammetry was impeded by a large background current that resulted from the capacitance of 3DOM carbon. Detection by square wave voltammetry eliminated the background current and improved the detection limit. Unfunctionalized 3DOM carbon electrodes showed no response to DNT, whereas the receptor-modified electrodes responded to DNT with a detection limit of 10 μM. Detection of DNT was possible even in the presence of interferents such as nitrobenzene
Alison J. Downard - One of the best experts on this subject based on the ideXlab platform.
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Electrografting of 4‑Nitrobenzenediazonium Ion at Carbon Electrodes: Catalyzed and Uncatalyzed Reduction Processes
2016Co-Authors: Lita Lee, Paula A. Brooksby, Philippe Hapiot, Alison J. DownardAbstract:Cyclic voltammograms for the reduction of aryldiazonium ions at glassy carbon electrodes are often, but not always, reported to show two peaks. The origin of this intriguing behavior remains controversial. Using 4-nitrobenzenediazonium ion (NBD), the most widely studied aryldiazonium salt, we make a detailed examination of the electroreduction processes in acetonitrile solution. We confirm that deposition of film can occur during both reduction processes. Film thickness measurements using atomic force microscopy reveal that multilayer films of very similar thickness are formed when reduction is carried out at either peak, even though the film formed at the more negative potential is significantly more blocking to solution redox probes. These and other aspects of the electrochemistry are consistent with the operation of a surface-catalyzed reduction step (proceeding at a clean surface only) followed by an uncatalyzed reduction at a more negative potential. The catalyzed reduction proceeds at both edge-plane and basal-plane graphite materials, suggesting that particular carbon surface sites are not required. The unusual aspect of aryldiazonium ion electrochemistry is that unlike other surface-catalyzed reactions, both processes are seen in a single voltammetric scan at an initially clean electrode because the conditions for observing the uncatalyzed reaction are produced by film deposition during the first catalyzed reduction step
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scanning tunneling and atomic force microscopy evidence for covalent and noncovalent interactions between aryl films and highly ordered pyrolytic graphite
Journal of Physical Chemistry C, 2014Co-Authors: Paula A. Brooksby, Philippe Hapiot, S A Brown, Sara J Fraser, Keith C Gordon, Yann R Leroux, Alison J. DownardAbstract:Electroreduction of 4-Nitrobenzenediazonium ions at highly ordered pyrolytic graphite (HOPG) gives a nitrophenyl film that is shown by noncontact atomic force microscopy (AFM) to be continuous and of multilayer thickness. Investigation of the same surface by ultrahigh vacuum scanning tunneling microscopy (UHV-STM) reveals molecular species immobilized on the step edges, but only mobile species on the basal planes. After several scans across an area of basal plane, atomic-level resolution images of clean, defect-free graphite surfaces are obtained. The same behavior is observed with a film deposited by reduction of 4-((triisopropylsilyl)ethynyl)benzenediazonium ion. Throughout extensive STM measurements we find no evidence for covalent attachment of aryl groups to the basal plane and conclude that our results can be best explained by the formation of films of physisorbed oligomeric species. After heating above 300 °C, nitrophenyl films are more stable to STM imaging but no longer contain nitro groups. Incr...
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Scanning Tunneling and Atomic Force Microscopy Evidence for Covalent and Noncovalent Interactions between Aryl Films and Highly Ordered Pyrolytic Graphite
2014Co-Authors: Lita Lee, Paula A. Brooksby, Philippe Hapiot, S A Brown, Sara J Fraser, Keith C Gordon, Yann R Leroux, Alison J. DownardAbstract:Electroreduction of 4-Nitrobenzenediazonium ions at highly ordered pyrolytic graphite (HOPG) gives a nitrophenyl film that is shown by noncontact atomic force microscopy (AFM) to be continuous and of multilayer thickness. Investigation of the same surface by ultrahigh vacuum scanning tunneling microscopy (UHV-STM) reveals molecular species immobilized on the step edges, but only mobile species on the basal planes. After several scans across an area of basal plane, atomic-level resolution images of clean, defect-free graphite surfaces are obtained. The same behavior is observed with a film deposited by reduction of 4-((triisopropylsilyl)ethynyl)benzenediazonium ion. Throughout extensive STM measurements we find no evidence for covalent attachment of aryl groups to the basal plane and conclude that our results can be best explained by the formation of films of physisorbed oligomeric species. After heating above 300 °C, nitrophenyl films are more stable to STM imaging but no longer contain nitro groups. Increased cross-linking within the film from coupling of radicals formed by thermal decomposition of nitrophenyl groups may be responsible for the more robust film structure
Melissa A Fierke - One of the best experts on this subject based on the ideXlab platform.
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receptor based detection of 2 4 dinitrotoluene using modified three dimensionally ordered macroporous carbon electrodes
ACS Applied Materials & Interfaces, 2012Co-Authors: Melissa A Fierke, Eric J Olson, Philippe Buhlmann, Andreas SteinAbstract:Detection of explosives, such as 2,4,6-trinitrotoluene (TNT), is becoming increasingly important. Here, 2,4-dinitrotoluene (DNT, a common analogue of TNT) is detected electrochemically. A receptor based electrode for the detection of DNT was prepared by modifying the surface of the walls of three-dimensionally ordered macroporous (3DOM) carbon. Nitrophenyl groups were first attached by the electrochemical reduction of 4-Nitrobenzenediazonium ions, followed by potentiostatic reduction to aminophenyl groups. Chemical functionalization reactions were then performed to synthesize the receptor, which contains two urea groups, and a terminal primary amine. Detection of DNT using cyclic voltammetry was impeded by a large background current that resulted from the capacitance of 3DOM carbon. Detection by square wave voltammetry eliminated the background current and improved the detection limit. Unfunctionalized 3DOM carbon electrodes showed no response to DNT, whereas the receptor-modified electrodes responded to ...
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Receptor-Based Detection of 2,4-Dinitrotoluene Using Modified Three-Dimensionally Ordered Macroporous Carbon Electrodes
2012Co-Authors: Melissa A Fierke, Eric J Olson, Philippe Bühlmann, Andreas SteinAbstract:Detection of explosives, such as 2,4,6-trinitrotoluene (TNT), is becoming increasingly important. Here, 2,4-dinitrotoluene (DNT, a common analogue of TNT) is detected electrochemically. A receptor based electrode for the detection of DNT was prepared by modifying the surface of the walls of three-dimensionally ordered macroporous (3DOM) carbon. Nitrophenyl groups were first attached by the electrochemical reduction of 4-Nitrobenzenediazonium ions, followed by potentiostatic reduction to aminophenyl groups. Chemical functionalization reactions were then performed to synthesize the receptor, which contains two urea groups, and a terminal primary amine. Detection of DNT using cyclic voltammetry was impeded by a large background current that resulted from the capacitance of 3DOM carbon. Detection by square wave voltammetry eliminated the background current and improved the detection limit. Unfunctionalized 3DOM carbon electrodes showed no response to DNT, whereas the receptor-modified electrodes responded to DNT with a detection limit of 10 μM. Detection of DNT was possible even in the presence of interferents such as nitrobenzene
