Long optical pathlength thin-layer spectroelectrochemistry: study of homogeneous chemical reactions

Gui, John Y.; Hance, Glen W.; Kuwana, Theodore

doi:10.1016/0022-0728(91)87005-o

“…Quinone di- and monoimines are, however, not stable in aqueous solutions but undergo relatively rapid hydrolysis to quinone monoimine and parent quinone . In fact, several 4‘-substituted 4-aminodiphenylamines have been shown to be hydrolytically cleaved in the oxidized state to give benzoquinone and the corresponding aniline 52c…”

Section: Resultsmentioning

confidence: 99%

“…Quinone di- and monoimines are, however, not stable in aqueous solutions but undergo relatively rapid hydrolysis to quinone monoimine and parent quinone . In fact, several 4‘-substituted 4-aminodiphenylamines have been shown to be hydrolytically cleaved in the oxidized state to give benzoquinone and the corresponding aniline 52c , Therefore, the hydrolysis of the aniline dimer surface (peak B) can be explained by a hydrolytic cleavage of the imine moiety to give the corresponding surface-bound quinone monoimine (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Post-Self-Assembly Transformation of 4-Aminothiophenol Monolayers on Gold Electrodes

Lukkari

¹

,

Kleemola

²

,

Meretoja

³

et al. 1998

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Electrochemical oxidation of a self-assembled monolayer (SAM) of 4-aminothiophenol on polycrystalline gold electrodes leads to a complex voltammetric behavior characterized by an initial irreversible oxidation at ∼+0.77 V versus SSCE (sodium saturated calomel electrode) and the formation of a pseudostable surface redox couple at +0.53 V. The oxidized form of this couple is hydrolyzed in acidic solutions to another redox pair with the formal redox potential of ∼+0.3 V. We show that the oxidation leads to a radical−radical coupling reaction between two adjacent aminothiophenol molecules, yielding an electrode surface modified with 4‘-mercapto-4-aminodiphenylamine, the thiol derivative of a head-to-tail aniline dimer. The oxidized form of the dimer, quinone diimine, undergoes hydrolysis to the corresponding quinone monoimine and, eventually, to the original surface-bound 4-aminothiophenol and benzoquinone. The mechanism of the monolayer oxidation reaction has been elucidated by a variety of electrochemical and spectroelectrochemical techniques together with electrochemical data obtained with a soluble model compound, 4-(methylthio)aniline. In addition, X-ray photoelectron spectroscopy (XPS) characterization of the 4-aminothiophenol (Au−SPhNH2), the 2-(4‘-mercaptophenylamino)benzoquinone (Au−SPhNH−BQ), and the oxidized 4-aminothiophenol SAMs is reported. The formation of an electrode surface modified with aniline dimers explains the beneficial effect that 4-aminothiophenol SAM exhibits in the electrochemical polymerization of aniline. We suggest that it favors the direct addition of aniline monomers to the oligomer chains on the surface, which results in a more ordered structure compared with the deposition of oligomers from the solution. This result is very important for the preparation of highly ordered polyaniline films for advanced applications in molecular electronics and sensor technology. The results also show that after the initial dimerization step, aniline polymerization can proceed through coupling of the neutral monomer to the oxidized oligomer.

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“…Spectroelectrochemistry has become an essential tool for the investigation of redox processes at electrodes with a diverse range of approaches used to obtain simultaneous spectral and electrochemical information. These approaches include the use of optically transparent electrodes (OTE), [1,2] optically transparent thin-layer electrochemical cells (OTTLE), [3,4] long optical pathlength cells (LOPTLC) [5][6][7][8] and cells adapted for reflection spectroscopy. [9,10] The combination of electrochemical methods with infrared attenuated total internal reflection (ATR) spectroscopy has become a standard tool for investigating dynamics at electrodes.…”

Section: Introductionmentioning

confidence: 99%

Evanescent wave broadband cavity enhanced absorption spectroscopy using supercontinuum radiation: A new probe of electrochemical processes

Schnippering

¹

,

Unwin

²

,

Hult

³

et al. 2008

Electrochemistry Communications

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An evanescent wave variant of broadband cavity enhanced absorption spectroscopy using a supercontinuum light source has been used to detect electrogenerated species at the silica-water interface. In proof-of-concept experiments [IrCl(6)](2-) was produced by electro-oxidation of [IrCl(6)](3-) in a thin layer electrochemical cell. Diffusion of the Ir(IV) across the cell to a silica interface was monitored yielding real-time concentrations within an evanescent field region at the interface. The optical response was compared with the electrochemical response during chronoamperometric step and cyclic voltammetric experiments and both were simulated by finite element modeling. The experiment is highly sensitive to interfacial processes and its wide spectral width and fast time resolution make it a potentially powerful tool for in situ spectroscopic monitoring of processes and intermediates in dynamical electrochemistry. (C) 2008 Elsevier B.V. All rights reserved

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“…Because of the large ratio of the area of the electrode to the volume in these cells, the reactions were found to be sensitive to adsorption (on Pt working electrode) and the presence of active surface groups (glassy carbon working electrode). These complications were alleviated by preadsorbing iodide onto the Pt and oxidizing the glassy carbon electrode prior to use [195].…”

Section: Long Optical Path-length Thinlayer Cell (Loptlc)mentioning

confidence: 99%

Spectroelectrochemistry: In s itu UV ‐visible Spectroscopy

Crayston

¹

2003

Encyclopedia of Electrochemistry

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The sections in this article are Introduction and Principles Introductory Remarks Theory and Techniques: Steady State Measurement Cell Transmission for a Simple Electron Transfer Reaction: Determination of E and n Effect of Follow‐up Reactions in OTTLE Cells Theory and Techniques: Kinetic Measurements Chronoabsorptometry Instrumentation for Chronoabsorptometry Slow Heterogeneous Kinetics Effect of Follow‐up Reactions Derivative Cyclic Voltabsorptometry ( DCVA ) Galvanostatic Conditions Adsorption Cell Geometries, Design, Techniques, and Instrumentation General Considerations Transmission under Thin‐layer Conditions: OTTLEs and Flow‐cells Variations on and Alternatives to the Basic OTTLE Design OTTLE Cells Intended for Both UV ‐visible and FTIR Use OTTLE Cell Electrochemical and Spectroscopic Response Semi‐infinite Cells: Optically Transparent Electrodes ( OTEs ) Reflection from Electrodes and Liquid–Liquid Interfaces Glancing Incidence Reflection, Near‐parallel or Parallel Reflection, and Diffraction Liquid–Liquid Interface and Attenuated Total Reflection Long Optical Path‐length Thin‐layer Cell ( LOPTLC ) Forced Convection, RDE and Channel Flow UV ‐vis Combined with Other Spectroscopic Techniques Applications Solution Studies of Inorganic Species Solution Studies of Organic Species Molten Salts Spectroelectrochemistry Studies of Species of Biological Interest Inorganic Thin Films and Modified Electrodes Conducting Polymers and Oligomer Models Conclusions

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Long optical pathlength thin-layer spectroelectrochemistry: study of homogeneous chemical reactions

Cited by 18 publications

References 30 publications

Electrochemical Post-Self-Assembly Transformation of 4-Aminothiophenol Monolayers on Gold Electrodes

Electrochemical Post-Self-Assembly Transformation of 4-Aminothiophenol Monolayers on Gold Electrodes

Evanescent wave broadband cavity enhanced absorption spectroscopy using supercontinuum radiation: A new probe of electrochemical processes

Spectroelectrochemistry: In s itu UV ‐visible Spectroscopy

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