Magnetic response of chlorophyll self-assembly within hydrogel: a mechanistic approach towards enhanced photoharvesting

Abstract

Self-assembly of chlorophyll-a (Chl-a) molecules within a protein environment serves as the key factor behind controlled and efficient light energy harvesting in natural photosystems. Long-range ordering among supramolecular structures in terms of spin–orbit coupling and edge effect helps in untrapping of excitons in the disordered energy landscape. Mimicking the photosynthetic machinery would give a new paradigm for organic photovoltaic material design where a large amount of disorder exists. In this paper, we report the experimental evidence of room temperature magnetic domain wall formation and edge effect along with spin flop canting in self-assembled Chl-a within hydrogel matrix via SQUID magnetometry. This was further correlated with intermolecular coupling and exciton delocalization through specific arrangements of self-assembly as evident from NMR spectral and photophysical characteristics. The data cumulatively suggest electronic backscattering protection which is also substantiated by the ferroelectric behavior coming from coexisting symmetry lowering. Here the polarization evolves through primary distribution of π electronic density along with a photoresponsive IV loop, similar to the photoprotection of photosynthesis. This work thus proposes a promising design principle for room temperature Chl-a based biomimetic systems efficient in photoharnessing.