Energy conversion harvesting

We have seen that, in photosynthetic bacteria, visible light is harvested by the antenna complexes, from which the collected energy is funnelled into the special pair in the reaction centre. A series of electron-transfer steps occurs, producing a charge-separated state across the photosynthetic membrane with a quantum efficiency approaching 100%. The nano-sized structure of this solar energy-conversion system has led researchers over the past two decades to try to imitate the effects that occur in nature. 

Importantly, Cl s seems to be involved in many classes of physical, chemical and biological processes, from pericyclic reactions to the complex light harvesting and energy conversion functions of chromophores in proteins (See in this volume) and others amply described in this conference. In contrast, direct experimental information on the passage of the vibrational wavepacket through or near Cl s is less abundant. It mostly concerns, femtosecond pump-probe experiments on isolated organic molecules in the gas phase. 

Greene RM, Geider RJ, Kolber Z, Falkowski PG (1992) Iron-induced changes in light harvesting and photochemical energy conversion processes in eukaryotic marine algae. Plant Physiol 100(2) 565-575... 

F. M. Mac Donnell is Professor of Inorganic Chemistry at the University of Texas at Arlington (UTA). He received his PhD at Northwestern University in 1993. After a postdoctoral stint at the Chemistry Department of Harvard University, he joined the Chemistry and Biochemistry Department at UTA in 1995. His research interests are in the design of photocatalysts for light harvesting and energy conversion and has pubhshed over 100 articles in these areas. 

Here, we will mainly focus on two other important aspects of photosensitization the fundamental role of deeply colored compounds as light-harvesting antenna chromophores for solar energy conversion and the possibility of reaching spectroscopically hidden, but photochemically active excited state levels by means of spectral sensitization. 

The two photochemical reactions are performed by two photosystems. Each photosystem consists of a so-called reaction centre, where the primary energy conversion takes place, associated with a few hundred pigment molecules (chlorophylls and carotenoids see Fig. 2) serving as light-harvesting antennas, which transfer the absorbed energy as electronic excitation energy to the reaction centres. 

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