Biphosphor Carbon Dots/Chlorophyll System Entirely Derived from Chlorella Microalgae for Luminescent Solar Concentrators

Abstract

In this work, a singular system capable of interacting with the entire visible region of the solar spectrum is produced by combining carbon dots (CDs) and chlorophyll (Chl) pigments, entirely derived from the microalga Chlorella pyrenoidosa. The process involves the digestion of the C. pyrenoidosa cellular wall in an acetic acid:cholinium chloride (AA/ChCl) solvent, followed by a microwave reaction. The resulting CDs exhibit excitation and emission maxima at 461 and 528 nm, respectively. The Chl centers enable a secondary photoluminescence (PL) process, thus ensuring that the as-prepared CDs/Chl system (CDCS) can also interact with the farther red region of the visible spectrum. The luminescence properties of CDCS are concentration-dependent, undergoing a blue shift with dilution. Confocal microscopy provided insights into the protection of Chl pigments throughout the process. Furthermore, the consequences arising from the addition of poly(ethylene glycol) oligomers (PEG-200) are also analyzed. The results demonstrate that the interaction between CDCS and PEG-200 significantly modifies the PL intensity and emission wavelengths, especially at higher PEG-200 concentrations. This suggests that PEG-200 can act as a modulating agent, stabilizing and even preventing the CDs’ fluorescence quenching while also affecting the PL properties of Chl. This work presents interesting possibilities for the development of multifunctional luminescent systems derived from microalgae biomass by addressing how these microorganisms can function not only as precursors in the formation of advanced functional materials but also as an integrated component of these systems. As an added benefit, a luminescent solar concentrator (LSC) was fabricated, revealing photostability, as well as optical and power conversion efficiency values of 11 and 0.2%, respectively, values comparable to state-of-the-art CD-based LSCs.