Biphasic Voltammetry of N,N,N′,N′‐Tetraphenyl‐para‐phenylenediamine Microdroplets, Microparticles and Microparticle Suspensions

Halls, Jonathan E.; Wadhawan, Jay D.

doi:10.1002/elan.201000633

Cited by 5 publications

(3 citation statements)

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“…In contrast to work on microemulsions and liquid dispersions, there is only very little work on electrosynthetic transformation with dispersed solids, although the potential for application has been realised for many years. 105,106 In a recent review some of the developments and the fundamental background have been summarised. 107 Solid-to-solid redox transformations for immobilised solids have been studied intensely for immobilised particles mainly on carbon electrode surfaces.…”

Section: Solid | Liquid | Solid Systemsmentioning

confidence: 99%

“…In contrast to work on microemulsions and liquid dispersions, very little work has been done on electrosynthetic transformation with dispersed solids, although the potential for application has been realized for many years. , A recent review summarizes some of the developments and the fundamental background . Solid-to-solid redox transformations for immobilized solids have been studied intensely for immobilized particles, mainly on carbon electrode surfaces. , This includes a range of organic and organometallic solids that demonstrate E-type (redox conversion) as well as EC-type (redox conversion followed by a chemical reaction step) solid–solid redox transformations.…”

Section: Solid|liquid|solid Systemsmentioning

confidence: 99%

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Multiphase Methods in Organic Electrosynthesis

Marken

Wadhawan

2019

Acc. Chem. Res.

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With water providing a highly favoured solution environment for industrial processes (and in biological processes), it is interesting to develop water-based electrolysis processes for the synthesis and conversion of organic and biomass-based molecules. Molecules with low solubility in aqueous media can be dispersed/solubilised (i) by physical dispersion tools (by milling, by power ultrasound, or by high shear ultra-turrax processing), (ii) in some cases by pressurising/super-saturation (e.g. for gases), (iii) by adding co-solvents or "carriers" such as chremophor EL, or (iv) by adding surfactants to generate micelles, microemulsions, and/or stabilised biphasic conditions. This review examines and compares methodologies to bring the dispersed or multi-phase system into contact with an electrode. Both the microscopic process based on the individual particle impact as well as the overall electro-organic transformation are of interest. Distinct mechanistic cases for multi-phase redox processes are considered.Most traditional electroorganic transformations are performed in homogeneous solution with reagents, products, electrolyte, and possibly mediators or redox catalysts all in the same (usually organic) solution phase. This may lead to challenges in the product separation step and in the re-use of solvents and electrolytes. When exploiting aqueous electrolyte media, reagents and products (or even electrolyte) may be present as microdroplets or nanoparticles. Redox transformations then occur during interfacial "collisions" under multiphase conditions or

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Section: Solid | Liquid | Solid Systemsmentioning

confidence: 99%

Section: Solid|liquid|solid Systemsmentioning

confidence: 99%

Multiphase Methods in Organic Electrosynthesis

Marken

Wadhawan

2019

Acc. Chem. Res.

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“…In a previous work, we developed a unifying global theory for the facile quantification of axiosymmetric diffusion anisotropy, exploiting the transition between planar unidimensional transport and convergent, two-dimensional diffusion at microdisk electrodes, using potential-step chronoamperometry. We have subsequently initiated a systematic investigation of electron transport through three-dimensional, autoassembled molecular electrochemical nanosystems based on lyotropic liquid crystals, where the medium into which the electrode is immersed has some form of long-range redox structure, with a view to exploit these lightweight, self-annealing and flexible soft-matter systems for technological application, for example, as conduits for information transfer or energy storage and conversion.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Estimation of Diffusion Anisotropy ofN,N,N′,N′-Tetramethyl-para-phenylenediamine within the Normal Hexagonal Lyotropic Mesophase of Triton X 100/Light Water: When Can the Effects of Cross-Pseudophase Electron Transfer be Neglected for Partitioned Reagents?

2011

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The H(1) lyotropic liquid crystalline phase of Triton X 100 with aqueous 0.1 M potassium chloride is examined as a medium in which to determine the axiosymmetric anisotropy in the diffusion flux of N,N,N',N'-tetramethyl-para-phenylenediamine using electrochemical methods (voltammetry and potential step chronoamperometry) at both planar electrodes and two-dimensional flux microdisk electrodes. Comparison of experiment with theory suggests the ratio of anisotropic diffusion coefficients in the directions tangential and perpendicular to the electrode surface varies over two orders of magnitude (from 0.04 to 3.3) with increasing concentration of the redox analyte. This is understood through the occurrence of a long-range charge transfer across the pseudophase | pseudophase boundary interface, occurring as a result of differential diffusivities of the redox probe within the surfactant and aqueous subphases. These data and their dependence on the analyte concentration empower, in a proof-of-concept, the estimation of the partition equilibrium constant (K(P)); the value estimated for the small electroactive-drug mimetic considered is log K(P) = 2.01 ± 0.05 (at 294 ± 2 K) and is in agreement with that envisaged for its partition between n-octanol and water. It is suggested that only measurements at low analyte loadings allow for interphase electron transfers to be neglected, since then percolation effects appear to dominate the Faradaic current.

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Electrochemical goniometry: keystone reactivity at the three-phase boundary

Varley,

Lawrence,

Wadhawan

2024

J Solid State Electrochem

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Contact angles of liquid, spherical cap droplets immobilised on an electrode surface and bathed by a fluid are important, quantifiable measures of the liquid/fluid interfacial tension. Optical goniometry, even if computer assisted, suffers when the contact angle is 10° or less. In this work, an alternative method of measurement is considered: electrochemical techniques (voltammetry and chronoamperometry), which rely on the transport of material from within the droplet to the conductive surface. As a result of the reactions that take place at the triple phase boundary, these are demonstrated to provide information on the size and the shape of the droplet, including its contact angle, for the cases when the droplets have a redox analyte and either have a supporting electrolyte, or not. The voltammetric behaviour is seen to change from exhaustive, thin film characteristics, to quasi-steady-state signals as the droplet becomes bigger, or the scan rate becomes larger, or diffusion of the redox material inside the droplet becomes slower. One of the surprising outcomes is that there is a zone of planar diffusion only in the case of the supported droplets, with both the droplet size and its contact angle determining whether this is seen at conventional combinations of scan rates and diffusion coefficients. Experimental data are provided which emphasize key features pertaining to the nature of the redox system and illustrate the facile nature of the contact angle estimation process, albeit to within 10% uncertainty.

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Biphasic Voltammetry of N,N,N′,N′‐Tetraphenyl‐para‐phenylenediamine Microdroplets, Microparticles and Microparticle Suspensions

Cited by 5 publications

References 46 publications

Multiphase Methods in Organic Electrosynthesis

Multiphase Methods in Organic Electrosynthesis

Electrochemical Estimation of Diffusion Anisotropy ofN,N,N′,N′-Tetramethyl-para-phenylenediamine within the Normal Hexagonal Lyotropic Mesophase of Triton X 100/Light Water: When Can the Effects of Cross-Pseudophase Electron Transfer be Neglected for Partitioned Reagents?

Electrochemical goniometry: keystone reactivity at the three-phase boundary

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