Title: On the interaction of carbon nanotubes with photosynthetic assembles

Abstract

The development of various bio hybrid natural or artificial systems for promotingthe solar energy conversion is of high priority in contemporary energy research. It has been suggested that single-walled carbon nanotubes (CNTs) might boost photosynthetic activity by enlarging the light spectrum region available for the photosynthetic reactions (Nat.Mater.2014, 13:400-408). The actual mechanism of this phenomenon is still unclear and the limited number of studies dealing with the CNT interplay with photosynthetic complexes provided controversial indications including both energy/charge transfers forward and from the nanotubes. We have evaluated the potential of CNTs to enhance the photosynthetic performance of microalgae and thus to open new opportunities for more efficient use of the photosynthesis based systems in the sustainable production of energy, biomass and high-value compounds. Our studies of the effects of CNTs on the photochemical reactions in the unicellular green algae Chlamydomonas reinhardtii pointed out the ability of the nanotubes to modify the growth and photosynthesis of the algal cells. Particularly, the characterisation of CNT interaction with photochemical events occurring in photosystem II (PSII) and photosystem Ivia chlorophyll fluorescence spectroscopy indicated CNT-induced alterations in the PSII electron transport and non-radiative loss of excitation energy in both photosystems. With the scope to gain further insights into the electro-optical interactions of CNTs with light dependent photosynthetic reactions we used isolated photosynthetic complex (PSCs) with different level of complexity, such as thylakoid membranes, PSII-enriched membrane fragments and light-harvesting complexes of PSII. The energy and electron fluxes in the bio hybrid (PSCs/CNTs) systems were analysed by steady-state chlorophyll fluorescence and time-resolved fluorescence spectroscopy. The possible processes involved in the energy excitation decay in the photosynthetic structures in the studded model systems will be discussed.