Universiteit Leiden

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Photosynthetic light reactions at the gold interface

Promotor: T.J. Aartsma, Co-promotor: R.N. Frese

M. Kamran
07 mei 2014
Thesis in Leiden Repository

In the project described in this thesis we studied a simple bio-electronic device for solar energy conversion by surface-assembly of photosynthetic pigment-protein complexes on a bare gold-electrode. Optical excitation of the photosynthetic pigments gives rise to charge separation in the so-called reaction center complex. Energy conversion is completed by subsequent electron transfer to the electrode, generating a light-induced electric current. The efficiency of the initial steps of charge separation is very high, the challenge lies in interfacing the protein complexes with conducting surfaces in an efficient manner to exploit the larger part of the harvesting energy. We have interfaced photosynthetic proteins with the Gold electrode by different techniques namely, simple incubation from solution, 2D crystallization and Langmuir-Blodgett deposition and measured photocurrent and current-voltage characteristics of these complexes. We conclude that Langmuir-Blodgett deposition gives a uniformly oriented mono-layer of protein complexes, which enhance the electron transfer efficiency between the electrode and proteins, resulting in highest ever photo-current density and internal quantum efficiency of a mono-layer of protein complexes. 2D crystals of photosynthetic proteins provide native like environment which is desirable for any application of the proteins.2D crystal packing of proteins seem to compete the excitation quenching by the gold electrode.