Triplet–triplet annihilation-based photon-upconversion to broaden the wavelength spectrum for photobiocatalysis

Abstract

Photobiocatalysis is a growing field of biocatalysis. Especially light-driven enzyme catalysis has contributed significantly to expanding the scope of synthetic organic chemistry. However, photoenzymes usually utilise a rather narrow wavelength range of visible (sun)light. Triplet–triplet annihilation-based upconversion (TTA-UC) of long wavelength light to shorter wavelength light may broaden the wavelength range. To demonstrate the feasibility of light upconversion we prepared TTA-UC poly(styrene) (PS) nanoparticles doped with platinum(II) octaethylporphyrin (PtOEP) photosensitizer and 9,10-diphenylanthracene (DPA) annihilator (PtOEP:DPA@PS) for application in aqueous solutions. Photoexcitation of PtOEP:DPA@PS nanoparticles with 550 nm light led to upconverted emission of DPA 418 nm. The TTA-UC emission could photoactivate flavin-dependent photodecarboxylases with a high energy transfer efficiency. This allowed the photodecarboxylase from Chlorella variabilis NC64A to catalyse the decarboxylation of fatty acids into long chain secondary alcohols under green light (λ = 550 nm).

Exciting Enzymes: Current State and Future Perspective of Photobiocatalysis

“…Following such examples, chiral as well as achiral organo‐ and metal‐organocatalysts can be linked to protein backbones generating novel promising catalysts for asymmetric syntheses. Current limitations of the quantum yield and narrow absorption spectra of photoenzymes will be improved using antennae complexes for light harvesting [99–101] …”

“…Current limitations of the quantum yield and narrow absorption spectra of photoenzymes will be improved using antennae complexes for light harvesting. [99][100][101] The possibilities that originate from the combination of photocatalytic reactions (natural and chemical) with further biocatalytic steps (EPC-systems, Figure 1d) can be easily extended far beyond what is described today. Challenges remain when the reactivities triggered by light, e. g., the generation of excited oxygen, interferes with other reactions in the cascade, or light induces destruction of the applied enzymes.…”

Coulomb interactions for mediator-enhanced sensitized triplet–triplet annihilation upconversion in solution

“…Triplet-triplet annihilation upconversion is an interesting photophysical phenomenon capable of converting two lowenergy photons into one high-energy photon, and this process has been explored towards applications in various fields. [1][2][3][4][5][6][7][8][9][10] For sensitized triplet-triplet annihilation upconversion (sTTA-UC) typically a light-harvesting unit (sensitizer) that introduces the possibility to populate a triplet state is combined with an annihilator, that is after energy transfer able to convert these two excited triplet states by triplet-triplet annihilation to one singlet state with higher energy. [11][12][13][14] In recent years, different systems were successfully designed to enhance the sTTA-UC efficiency by using a mediated energy transfer approach (Fig.…”

Triplet–Triplet Annihilation Upconversion-Based Oxygen Sensors to Overcome the Limitation of Autofluorescence

“…33−36 However, implementation of this technique in nanosensors is still limited. There are a few reports of this mechanism being used to report pH, enzymatic activity and K + , 23,37,38 but to our knowledge, reports of nanoparticles that report changes in oxygen concentration are somewhat limited. As a result, in this work, we leveraged the TTA-UC mechanism to make an oxygen nanosensor.…”

“…The concept of TTA-UC is not a new one as it has been used in various systems such as fiber optic cables, semiconductors, solar cells, and optode films as conjugated dye systems. – However, implementation of this technique in nanosensors is still limited. There are a few reports of this mechanism being used to report pH, enzymatic activity and K + , ,, but to our knowledge, reports of nanoparticles that report changes in oxygen concentration are somewhat limited.…”