Triplet Excitons in Natural Photosynthetic and Artificial Light Harvesting Systems: Measurement and Modeling.

Under full sunlight, unprotected (Bacterio)Chlorophyll ((B)Chl) molecules photodegrade in a matter of minutes. This is the result of the generation of highly reactive singlet oxygen (1O2) by energy transfer from the (B)Chl triplet state (3(B)Chl) to the oxygen ground state. Natural photosynthetic systems must protect themselves from 1O2, typically done by positioning carotenoids within a few angstroms of each (B)Chl molecule to quench 3(B)Chl states. Using phosphorescence spectroscopy and computational modeling, we investigated alternative, carotenoid independent, mechanisms which nature may employ to prevent 1O2 sensitization by lowering the energy of 3(B)Chl below that of 1O2. The two proposed triplet lowering mechanisms investigated were: triplet state lowering by strong pigment-pigment interactions (i.e. triplet exciton formation) and triplet state lowering by pigment-protein interactions. Possible natural examples employing these mechanisms are two structures found in green sulfur bacteria: the chlorosome (an antenna containing ~100000 coupled BChl c, d, or e molecules with unexpectedly high photostability) and the Fenna-Matthews-Olson (FMO) complex (an auxiliary antenna containing eight seemingly unprotected BChl a molecules).

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics & Astronomy

Year

2015

Author dc:creator

• Hartzler, Daniel Allen

Contributors dc:contributor

• Sergei Savikhin
• Yulia Pushkar
• Ken P Ritchie
• Paul F Muzikar

• Bacteriochlorophyll
• Chlorophyll
• Coupling
• Exciton
• Phosphorescence
• Triplet

Repository record dc:identifier

https://docs.lib.purdue.edu/open_access_dissertations/1414

OAI identifier oai:identifier

oai:docs.lib.purdue.edu:open_access_dissertations-2630