Near-infrared-light-driven artificial photosynthesis by nanobiocatalytic assemblies

Artificial photosynthesis in nanobiocatalytic assemblies aims to reconstruct man-made photosensitizers, electron mediators, electron donors, and redox enzymes for solar synthesis of valuable chemicals through photochemical cofactor regeneration. Herein, we report, for the first time, on nanobiocatalytic artificial photosynthesis in near-infrared (NIR) light, which constitutes over 46% of the solar energy. For NIR-light-driven photoenzymatic synthesis, we synthesized silica-coated upconversion nanoparticles, Si-NaYF4:Yb,Er and Si-NaYF4:Yb,Tm, for efficient photon-conversion through Förster resonance energy transfer (FRET) with rose bengal (RB), a photosensitizer. We observed NIR-induced electron transfer by using linear sweep voltammetric analysis; this indicates that photoexcited electrons of RB/Si-NaYF4:Yb,Er are transferred to NAD+ through a Rh-based electron mediator. RB/Si-NaYF4:Yb,Er nanoparticles, which exhibit higher FRET efficiency due to more spectral overlap than RB/Si-NaYF4:Yb,Tm, perform much better in the photoenzymatic conversion.