Electrochemical Behavior of LB Films Containing a Mixture of Viologen and a Phospholipid

Abstract

The electrochemical behavior of mixed monolayers of N-tetradecyl-N′-methyl viologen (TMV) and L-Rdimyristoylphosphatidic acid (DMPA) has been studied. Mixed monolayers of TMV/DMPA ) 1:2 have been obtained at the air-water interface and transferred by the Langmuir-Blodgett (LB) method at π ) 40 mN m -1 onto In and Sn oxide (ITO) electrodes. These LB films were used as the working electrode in a conventional electrochemical cell and immersed in aqueous solutions with different electrolytes. The influence of the type and the electrolyte concentration on the voltammetric peaks related to the two one-electron processes of TMV has been studied. The formation of an insoluble salt of viologen perchlorate on the surface of the electrode is observed when concentrations of perchlorate higher than 0.3 M are used. Due to this, a reorientation of the polar group of the viologen in the transferred mixed monolayer from a flat to a perpendicular position is postulated.

Electrochemical investigation on hybrid viologen tetracyanoquinodimethanide LB films

“…In order to interpret these voltammograms, we should take into account the various effects that may result in different electrochemical behaviour. These factors include: (i) the counter anion present either in the solution or in the films, given that interactions of anions with the electrode surface could cause bending of the Fermi level at the electrode surface [29]; (ii) the extensive association chemistry of bimp 2+ results in difficult behaviour of viologens, depending on which species are formed [30,31] and obviously, different chemical complexes give different electrochemical responses; (iii) the energetic considerations inherent in an electron transfer process depend on the specific chemical composition of the species undergoing the electron transfer, i.e., on the rate at which charge is transferred across the interface at that site [3]; (iv) the degree of order, structure, and architecture of the films have been proved [2,5,6,11,[32][33][34] to have a profound effect on the electrochemical behaviour of immobilized species at the electrode.…”

“…They are redox chromophores having three oxidation states and a high reversibility of their redox reactions. The electrochemical properties of viologens immobilized at the electrode surface have shown great dependence on several parameters including: (i) the degree of order and architecture of the films [4][5][6][7][8][9][10] (the presence of different conformations of the viologens at the electrode surface, possible interactions between the parent and the reduced species, formation of radical dimers, steric hindrance that prevents dimer formation, and so on); (ii) the nature of the bipyridilium substituents [11] (number and length of the alkyl chains joined to the viologen unit, other functional groups attached to the bipyridilium, etc. ); (iii) the type of counterion [3,12,13]; (iv) the electrolyte used during electrochemical experiments [6,8] and aging effects [14,15].…”

Influence of the Hofmeister series of anions on the molecular organization of positively ionized monolayers of a viologen derivative

“…The properties and consequently applications of viologens are sensitive to a variety of factors, including the nature of anions X − [12]. In contrast to the large body of published work dealing with the electrochemistry of thin solid films of viologen derivatives [25][26][27][28][29][30][31][32][33] there is little data available for the detailed organization and properties of amphiphilic viologens arranged in thin solid films together with different counterions X − . This has motivated us to analyze the influence of the Hofmeister series of anions on the film forming behaviors of a viologen amphiphile, and determine how these anions may affect the organization of the viologen moieties within the Langmuir monolayers.…”

Oxygen storage/release in cobalt porphyrin electrodeposited films

“…More details about this monolayer preparation have been published elsewhere [22]. The mixed monolayer was compressed at 40 mN m −1 and transferred by using the vertical dipping technique at a lifting rate of 5 mm min −1 , on Co-porphyrin-MIE or the bare ITO electrode.…”

“…Thus, the viologen in a mixed monolayer, containing an amphiphilic anchor DMPA in a molar ratio TDMV/DMPA = 1:2, was transferred both onto CoTSPP-MIE and CoTMPyP-MIE with different number of CVs, and then used as working electrodes in 0.1 M KClO 4 aqueous solution without porphyrin, and under N 2 atmosphere. The structure and electrochemical behavior of the viologen mixed film have been previously studied [22,41]. Fig.…”