Light energy conversion with chlorophyll a and pheophytin a monolayers at the optically transparent SnO2 electrode: artificial photosynthesis

Abstract

The photoelectrochemical behavior of chlorophyll a and pheophytin a monolayers, deposited on tin oxide (SnO2) optically transparent electrodes (OTE) by means of the Langmuir-Blodgett technique, has been investigated. The photocurrent action spectra coincide with the absorption spectra of photosynthetic pigment monolayers at the SnO2/solution interfaces. Anodic and cathodic photocurrents were measured at various electrode potentials. Effects of electrolyte concentration, pH, electrode potentials, type of SnO2 OTE and the nature of redox reagents on the magnitude of the photocurrent in solar energy conversion are discussed. A mechanism for the electron transfer in thin films of photosynthetic pigments in monolayers at the SnO2 OTE is proposed. On the other hand, the absorption and fluorescence spectral characteristics, and fluorescence lifetime measurements of pheophytin a in monolayers and thin films are also discussed in view of the aggregation properties of the photosynthetic pigments.