Why Photoinduced Electron Transfer

Since PET lies at the heart of natural photosynthesis, there is a wealth of information available to device designers. Some of this data has arisen from exploratory photochemistry, while some have their origins in artificial photosynthesis research.  

Since electrons are of rather low mass, PET rates can be extremely fast with transit times in the ps-ns range. Molecular switches where the only moving part is an electron are likely to be much faster than those involving nuclear motion. Since they require ion movement, photoionic devices based on PET will operate at slower rates. However these are fast enough compared to the human timescales. 

Electron transfer rates are naturally subject to molecular-scale electric fields. Therefore, ion binding to a molecule is an effective way of controlling PET within it. Since PET is an excited state deactivation pathway, the competing radiative route, i.e. luminescence, also becomes exposed to ionic manipulation. Under favorable conditions, PET rates can be much faster (lO s ) than luminescence (10 -10 ° s ). At the other extreme, conditions can be arranged under which PET is effectively non-existent. Therefore, luminescence can be ionically switched between off and on states representing digital action.  

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