Highly efficient light-converting films based on diketopyrrolopyrrole with deep-red aggregation-induced emission for enhancing the lipid productivity of Chlorella sp.

Abstract

The spectral modification of sunlight from less efficient green (500-600 nm) to more efficient red (600-700 nm) by light-converting fluorescent dyes has been widely studied for enhancing the microalgal biomass productivity. In particular, deep-red (650-700 nm) photons, which are mainly used by photosynthetic pigments of microalgae for photosynthesis, play a key role in promoting microalgal growth. In this study, we have synthesized three different deep-red emitting diketopyrrolopyrrole (DPP) dyes and utilized two of them to fabricate light-converting films for microalgal cultivation. The introduction of free-rotatable triphenylamine (TPA) moieties into DPP dyes enabled them to exhibit excellent solid state emission via aggregation-induced emission (AIE). As a result, cultured microalgae showed different biomass and lipid productivity according to the degree of increase in the photosynthetic photon flux density (PPFD) of the light-converting films. In detail, strong deep-red emission of the light-converting film prepared using dye E2 increased the total fatty acid methyl ester (FAME) content of microalgae up to 62.4%. In contrast, the weak deep-red emission of the lightconverting film based on dye M2 resulted in an enhancement of only 28.8%. These results show that the deep-red emitting AIE-DPPs could potentially be applied in light-converting film materials for accelerating the mass production of microalgae.