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Completed Project

A Novel Photosystem II Photocell Assembled on Carbon Nanotubes

Andrew Needleman, Vassar College ’17 and Prof. Christopher Smart
Despite the complex molecular pathways required for photosynthesis to harvest usable light energy, the initial photon harvesting step is considered to be nearly energetically perfect, or at thermodynamic unity. To generate high potential electrons, the photosystems, using the energy from photons, catalyze the splitting of water and harvest the electrons from the oxygen, creating aqueous protons and diatomic oxygen as byproducts. Previous research has demonstrated that attaching a histidine tag on the CP43 subunit of photosystem II allows electron transfer to occur between the entire photosystem II complex and a linker molecule, which can then be assembled as a monolayer on gold via a gold-thiol linkage. Attaching photosystem II to a gold surface via a linker molecule and exposing the sample to light has been observed to produce a harvestable electrical potential across the material, though currently the potential is small with traditional surfaces. It has also been observed that increasing the surface area of the gold material by roughening it increases total current. We propose that growing carbon nanotubes (CNT) on a gold wire, gold plating the nanotubes, and then assembling the photosystem II monolayer on the CNT/gold system will provide a large surface area and will provide the largest current reported for a photosystem II based cell. Currently, we are cloning the histidine tagged CP43 subunitintoE. coli.