Micelles, electrochemical methods

A somewhat different micelle-disruption method was used to prepare thin reactive films on electrode surfaces. For this purpose, micelles containing ferrocenyl surfactant 9 and a dissolved dye, e.g. phthalocyanine or quinone, were electrolyzed. The ferrocenyl micelles broke up into monomers whenever the iron atoms were oxidized electrochemically. The dissolved dyes then precipitated as transparent nanometre films onto the electrode surface. ... 

Harima, Y. and K. Yamashita (1989). Electrochemical characterization of phthalocyanine thin films prepared by the electrolytic micelle disruption method. J. Phys. Chem. 93, 4184-4188. 

The aim of this chapter is to describe electrochemistry in micelles and microemulsions in fundamental and practical terms. A major focus is on the use of these media to purposely influence the desired outcome of electrochemical reactions. The chapter also describes how electrochemical methods can be used for structural characterization of these fluids. In the next section (Sect. 4.4.2), we discuss structures, properties, and dynamics of micelles and microemulsions. Subsequent sections present relevant aspects of direct electrochemistry and electrochemical catalysis in micelles and microemulsions. 

Transition-metal nanopartides are of fundamental interest and technological importance because of their applications to catalysis [22,104-107]. Synthetic routes to metal nanopartides include evaporation and condensation, and chemical or electrochemical reduction of metal salts in the presence of stabilizers [104,105,108-110]. The purpose of the stabilizers, which include polymers, ligands, and surfactants, is to control particle size and prevent agglomeration. However, stabilizers also passivate cluster surfaces. For some applications, such as catalysis, it is desirable to prepare small, stable, but not-fully-passivated, particles so that substrates can access the encapsulated clusters. Another promising method for preparing clusters and colloids involves the use of templates, such as reverse micelles [111,112] and porous membranes [106,113,114]. However, even this approach results in at least partial passivation and mass transfer limitations unless the template is removed. Unfortunately, removal of the template may re-... 

Several transition metals such as V, Nb, Ta, and Pd can form stable bulk hydrides, so-called interstitial hydrides the bonding in the hydride phase is not ionic but mostly metallic in character, and the hydrogen to metal ratio is not necessarily stoichiometric. Especially, nanoparticles of noble metals such as Pd are relatively easy to prepare by various methods, such as vapor phase deposition on substrates, reductions of salts in solution (electrochemically or electroless), and the inverse micelle templated growth. They are not easily oxidized, and, in recent years, several methods have been developed to precisely control the size of the particles or clusters. Furthermore, growth in solution in the presence of surfactants and stabilizers allows control over the shape of the final particles [35, 36, 42]. 

The electrochemical behavior of ascorbic acid (1) and uric acid (3) in the presence of micelles and their selective determination were investigated. Aqueous cetylpyridinium bromide (cpb) and sodium dodecylbenzenesulfonate (sdbs) miceUar solutions have been used. The oxidation peak potentials for 1 and 3 are separated by 270 mV in the presence of cpb in aqueous phosphate buffer solution (pH 6.8), thus allowing their selective determination, as well as the selective determination of 3 in the presence of excess of 1. The method is simple, inexpensive and rapid with no need to modify the electrode surface by tedious procedures, and it was applied to 3 determination in samples of human urine and serum. Abnormal levels of uric acid in urine and serum are symptomatic of several diseases (gout, hyperuricaemia and Lesch-Nyhan syndrome) . 

In recent years, there has been a rapid growth in the number of publications that report the use of surfactant monomers or micelles to improve the analytical perfommice of various spectroscopic (UV-visible spectrophotometry, fluorimetry, phosphorimetry, chemiluminescence and atomic spectroscopy), and electrochemical (especially amperometry) methods [1]. The unique properties of surfactants have been recognized as being very helpful to overcome many problems associated with the use of organic solvents in these methods. Surfactant-modified procedures yield sensitivity and/or selectivity improvements in determinations commonly performed in homogeneous solution, whereas certain analytic methods (such as room-temperature phosphorescence in solution) can be exclusively conducted in organized media. 

Liu Y, Qiu X, Chen Z, Zhu W (2002) A new supported catalyst for methanol oxidation prepared by a reverse micelles method. Electrochem Commun 4 550-553... 

By integrating CNTs with PANi nanofibers, high density and high-suiface areas are possible that can lead to improvements in the conductivity and the development of electronic devices with superior properties [78]. The composites of PANi-CNT can be synthesized by various methods such as electrochemical processing, surfactant free aqueous polymerization, micelle-CNT hybrid template directed synthesis, inverse emulsion pathways, interfacial polymerization, plasma polymerization, in-situ and ex-situ polymerization. The details of these methods have been discussed by Oueiny et al. [8]. In-situ polymerization is one of the most important methods developed so far to integrate CNTs and polyaniline. Polymerization methods include stirring, static placement, sonication and emulsion polymerization [78]. 

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