Electroactive monolayers/multilayers

Numerous bisthiols have been observed to form spontaneously multilayers on gold and silver on the basis of the oxidative formation of disulfides.15-27 Nonetheless, most of these compounds lack electroactive character, with few notable exceptions.23,27 In principle, the introduction of redox centers at the core of these molecules and their subsequent assembly into multilayers can be exploited to generate electroactive films. The concentration of redox centers within the resulting electrode coatings, as well as their thickness, can be significantly larger than those possible with electroactive thiols such as 1-4 (Fig. 7.1).11 14 In addition, the transition from electroactive monolayers to electroactive multilayers can translate into a significant enhancement in stability and a much more effective protection of the electrode surface. 

Self-assembled Monolayers and Multilayers of Electroactive Thiols... 

SELF-ASSEMBLED MONOLAYERS AND MULTILAYERS OF ELECTROACTIVE THIOLS... 

There are several reasons for the appeal of polymer modification immobilization is technically easier than working with monolayers the films are generally more stable and because of the multiple layers redox sites, the electrochemical responses are larger. Questions remain, however, as to how the electrochemical reaction of multimolecular layers of electroactive sites in a polymer matrix occur, e.g., mass transport and electron transfer processes by which the multilayers exchange electrons with the electrode and with reactive molecules in the contacting solution [9]. 

By its very nature, copolymerization offers the unique capability or opportunity for chemists to design and construct molecules with special electronic properties using established techniques. The Langmuir-Blodgett (LB) technique, for instance, enables the chemist to organize molecules into highly ordered monolayers and to manipulate a multilayer film to a desired architecture. Copolymerization enables the molecular architect or tailor to incorporate various molecules, e.g. biological components, into electroactive PP and PT polymers. The number of potential applications for these unique materials is unlimited. 

The SECM studies of nanoparticles are of great interest and diversity. Metal nanoparticles can serve as redox mediators in solution to investigate their redox activities at solid-liquid and liquid-liquid interfaces by using SECM as discussed in Chapter 3. By contrast, this section is focused on the SECM studies of monolayers and multilayers of metal nanoparticles formed at various interfaces. In these studies, SECM was employed to quantitatively investigate the lateral conductivity and interfacial electroactivity of nanoparticle films. In addition, new experimental setups were developed to address the electrocatalytic and photocatalytic activities of nanoparticle films. Moreover, significant progresses were made to deposit and pattern nanoparticles on various substrates by using SECM. 

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