Electronic properties, electroactive

CNTs have been one of the most actively studied electrode materials in the past few years due to their unique electronic and mechanical properties. From a chemistry point of view, CNTs are expected to exhibit inherent electrochemical properties similar to other carbon electrodes widely used in various electrochemical applications. Unlike other carbon-based nanomaterials such as C60 and C70 [31], CNTs show very different electrochemical properties. The subtle electronic properties suggest that carbon nanotubes will have the ability to mediate electron transfer reactions with electroactive species in solution when used as the electrode material. Up to now, carbon nanotube-based electrodes have been widely used in electrochemical sensing [32-35], CNT-modified electrodes show many advantages which are described in the following paragraphs. 

Electrolytes as well as electrodes should have high diffusivities for the electroactive species in order to allow high currents. The two phases should have very different electronic properties, however. For electrolytes the conductivity of the electrons must be low. This has to be mainly caused by electronic species of low mobility rather than low concentration. Otherwise, small variations in the stoichiometry of the electrolyte, e.g. by the application of two different electrodes, would result in a relatively large change in the concentration which could cause high electronic... 

The covalent chemistry of fullerenes has developed very rapidly in the past decade in an effort to modify fuUerene properties for a number of applications such as photovoltaic cells, infrared detectors, optical limiting devices, chemical gas sensors, three-dimensional electroactive polymers, and molecular wires [8, 25, 26, 80-82]. Systematic studies of the redox properties of Cgo derivatives have played a crucial role in the characterization of their unique electronic properties, which lie at the center of these potential applications. Furthermore, electrochemical techniques have been used to synthesize and separate new fullerene derivatives and their isomers as well as to prepare fullerene containing thin films and polymers. In this section, to facilitate discussion of their redox properties, Cgo derivatives have been classified in three groups on the basis of the type of attachment of the addend to the fullerene. In group one, the addends are attached via single bonds to the Cgo surface as shown in Fig. 6(a) and are referred to as singly bonded functionalized derivatives. The group includes... 

Conductivity within conducting electroactive polymers (CEPs) is a complex issue. A polymer that can exhibit conductivity across a range of some 15 orders of magnitude most likely utilizes different mechanisms under different conditions. In addition to the electronic conductivity exhibited by CEPs, they possess ionic conductivity because of the solvent or electrolyte incorporated during synthesis. The experimental parameters encountered during synthesis (as listed and discussed in Chapter 2) have an effect on the polymer conductivity. In particular, the electrochemical conditions, the solvent, the counterion, and monomers used during synthesis influence the electronic properties of the resulting polymer. 

Photoluminescence (PL) experiments were performed on methylstilbene-equipped peptides (Aib-Stb-D and Aib-Stb-O) in TFE to assess the effect of the relative orientation of electroactive side chains on their electronic properties. Aib-Stb-D and Aib-Stb-O show identical absorption spectra (data not shown) and display monomeric methylstilbene emission with a peak maximum at 357 nm (Figure 6) however, they exhibit notably different PL intensities. Aib-Stb-O... 

Schlettwein, D. (2001) Electronic properties of molecular organic semiconductor thin films, in Supramolecular Photosensitive and Electroactive Materials (ed. H. Nalwa), Academic Press, San Diego,... 

Polypyrroles are a class of conjugated polymers that have been extensively studied due to their low oxidation potential leading to stable conductors, along with the compatibility of their electroactivity in aqueous media. Since the first report on the electrochemical preparation of conductive polypyrrole films [84—87], interest in the electronic properties of this polymer and its derivatives has increasingly grown. 

Bdlanger A, Vijh AK (1982),The hydrogen evolution reaction on Ag-Pd alloys influence of electronic properties on electroactivity, Surf Technol, 5,59-78. 

In summary, fused heterocycles provide several atrributes for the parent polymer that include the following a propensity for aromatization and localization of electron density on heteroatoms increased ability for extensive conjugation within the whole polymeric backbone multiple possibilities for interchain interactions through short contacts between heteroatoms increased electroactivity and stabilization of multiple polarons/bipolarons. These features provide complexity in electronic properties that are manifested entirely through the incorporation of fused heterocycles into the conjugated backbone of a polymer. 

A film of electroactive polymer [Os(bpy)2(vpy)2p, sandwiched between Pt and Au electrodes, becomes conductive when both the electrode potentials have appropriate values such that the mixed valent state, Os(III)/(II), is generated. Such arrangements are used in two-terminal and three-terminal diodes Solid-state organic heterojunctions utilizing two conducting polymers [PA and poly(A-methylpyrrole) junctions] were reported The electronic properties can be modified chemically. A field-effect transistor was fabricated utilizing chemically prepared poly(A-methyl-pyrrole)... 

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. 

Diamond is sp hybridized and nonconductive, but doping diamond with boron significantly alters the electronic properties, allowing diamond to support ET. Patten et al. used SECCM as a way to correlate the heterogeneous surface of polycrystalline BDD (pBDD) electrodes with the electroactivity of various redox probes (an outer sphere [FcTMA+], an inner sphere [Fe " ], and a complex redox process [serotonin]). ... 

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