Interfacial electron transfer processes

Duonghung D, Ramsden J, Gratzel M (1982) Dynamics of interfacial electron-transfer processes in colloidal semiconductor systems. J Am Chem Soc 104 2977-2985... 

The attention devoted to supramolecular sensitizers containing multifold chromophoric and electroactive centers arises from the construction of molecular devices based on nanometric and well-defined molecular architectures [4]. The use of these species for sensitization of titanium dioxide has provided fundamental insights into interfacial electron-transfer processes. 

C. Remote and Stepwise Interfacial Electron-Transfer Processes... 

Figure 12 Schematic representation of thermodynamic and kinetic parameters influencing interfacial electron-transfer processes between the semiconductor and an adsorbed redox specie.

Interfacial Electron Transfer Processes at Modified Semiconductor Surfaces... 

Niemeyer et al. have reported the design of quantum dot/enzyme nanohybrids that are capable of catalyzing an organic transformation upon optical excitation of semiconductor quantum dots (QDs) [31]. The hybrid device was composed of semiconductor CdS nanoparticles and cytochrome p450BSp enzyme. It has been proposed that irradiation of QDs leads to formation of excitons (h+-e pairs) that on dissociation generate superoxide and hydroxyl radicals in interfacial electron transfer process (see Chapter 7). These radicals in turn activate the enzyme adsorbed at the QD surface. The activated enzyme is able to catalyze mono-oxygenation of fatty acids, but has a lower activity than the native enzyme [31]. 

Interfacial Electron Transfer Processes In Micellar Solutions... 

The sensitization of electrodes to visible light by dye molecules is an old area of science with a rich history [2]. A dye-sensitized photoefifect was measured at a semiconductor surface as early as 1887 in Vienna [3]. The accepted mechanisms for the dye sensitization of electrodes emerged from photoelectrochemical studies in the 1960s and 1970s [4-6]. These studies were motivated by a desire to quantify interfacial electron transfer processes and develop cells useful for solar energy conversion. The two most common approaches are shown schematically in Figure 1. 

There are two possible excited state interfacial electron transfer processes that can occur from a molecular excited state, S, created at a metal surface (a) the metal accepts an electron from S to form S+ or (b) the metal donates an electron to S to form S . Neither of these processes has been directly observed. The two processes would be competitive and unless there is some preference, no net charge will cross the interface. In order to obtain a steady-state photoelectrochemical response, back interfacial electron transfer reactions of S+ (or S ) to yield ground-state products must also be eliminated. Energy transfer from an excited sensitizer to the metal is thermodynamically favorable and allowed by both Forster and Dexter mechanisms [20, 21]. There exists a theoretical [20] and experimental [21] literature describing energy transfer quenching of molecular excited states by metals. How-... 

Two limiting cases could be considered that would, however, let us treat in a simple way the interfacial electron transfer process as involving a single prepared excited state of the sensitizer ... 

Prokopuk N. and Lewis N. S. (2004), Energetics and kinetics of interfacial electron-transfer processes at chemically modified InP/hquid junctions , J. Phys. Chem. B 108, 4449-4456. 

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