Ricerc@Sapienza

Solar energy plays a central role in life, providing a direct or indirect energy source for most organisms on the Earth. Photosynthesis makes use of sunlight to convert carbon dioxide into useful biomass. In view of the potential technological applications for alternative energy sources development, several interdisciplinary works have been inspired to uncover the physical mechanisms ruling this photosynthetic process. Despite huge efforts, bio-inspired artificial systems remain still less efficient and less stable than their natural counterparts. In order to realize efficient artificial photosystems, it is crucial to determine the involved electronic energy levels and relevant energy pathways in natural light harvesters. Unravelling the coupling between molecular electronic and vibrational degrees of freedom would provide the chance to unveil the physical mechanism responsible for efficient coherent energy transfer in these prototypical compounds. This project employs combined time-resolved vibrationally and electronically sensitive experimental approaches to elucidate the molecular mechanisms of light-harvesting (LH) in natural pigment-protein photosynthetic complexes and optimize them for artificial LH systems. The aim of this project is to perform high time resolution ultrafast optical spectroscopy on highly controlled samples of both natural (from plants and mosses) and artificial (organic photovoltaic materials) LH systems. The experimental results of natural LH complexes will be compared with the ones obtained for mutant and artificial matrices, where site-directed mutagenesis will be exploited for modifying the excitonic level structure and the coupling to vibrations. This will allow us to elucidate the molecular mechanisms and the role played by quantum coherences in LH processes, and their relation to the systems structural and electronic properties, paving the way to artificial materials design through bio-inspired strategies.