First step towards converting solar energy using artificial leaf.

ISLAMABAD, July 01, 2009 (Balochistan Times) -- An international team of researchers has achieved the first step in converting solar energy using an artificial leaf. The researchers have modified chlorophyll from an alga so that it resembles the extremely efficient light antennae of bacteria, BBC reported. The team was then able to determine the structure of these light antennae. This is the first step to converting sunlight into energy using an artificial leaf. Two things are needed to generate fuel from sunlight: an antenna that harvests light, and a light-driven catalyst. The fastest light harvesters are to be found in nature: in green leaves, algae and bacteria. The light antennae of bacteria chlorosomes are the fastest of all. They have to be capable of harvesting minimal quantities of light particles in highly unfavourable light conditions, such as deep in the sea. These chlorosomes are made up of chlorophyll molecules. The art is to imitate these systems very precisely. German colleagues from the University of Wurzburg in Huub de Groots team modified chlorophylls from the alga Spirulina, such that they resembled the pigments of bacteria. De Groots Leiden group then studied the structure of these semi-synthetic light antennae. According to De Groot, Nanotechnology and supramolecular systems are becoming increasingly important, but it is very difficult to determine their structure. So-called cartoons are frequently made that give a schematic indication of what their structure could be. De Groot and his colleagues successfully determined the detailed molecular and supramolecular structure of their artificial self-assembled light antennae. They did this using a combination of solid state NMR and X-ray diffraction (see attachment). X-ray diffraction enabled them to determine the overall structure and NMR allowed them to penetrate deeply into the molecules. We already knew that the light antennae in bacteria form a structure rather like the annual rings of a tree trunk, said De Groot. The molecules in these semi-synthetic antennae seem to stack in a different way; they are flat. But this, too, is one of four ways we had thought in advance were possible, he added. The researchers still have to determine how the light antennae of modified Spirulina chlorophylls work in practice.

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