Recent Advances in Light Energy Conversion with Biomimetic Vesicle Membranes

Abstract

Lipid bilayer membranes are ubiquitous in natural chemical conversions. They enable self-assembly and compartmentalization of reaction partners and it becomes increasingly evident that a thorough fundamental understanding of these concepts is highly desirable for chemical reactions and solar energy conversion with artificial systems. This minireview focusses on selected case studies from recent years, most of which were inspired by either membrane-facilitated light harvesting or respective charge transfer. The main focus is on highly biomimetic liposomes with artificial chromophores, and some cases for polymer-membranes will be made. Furthermore, we categorized these studies into energy transfer and electron transfer, with phospholipid vesicles, and polymer membranes for light-driven reactions.

Keywords: energy transfer; liposomes; luminescence; photocatalysis; vesicles.

Figure 1

The LHCs as well as PSI and PSII play a central role in valorization of sunlight energy.

Figure 2

Examples for bilayer vesicle forming molecules: Phospholipids DOPC (1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine) and DMPG (1,2‐dimyristoyl‐sn‐glycero‐3‐phosphoglycerol), galactolipid 16 : 0–18 : 1 GlcGlcDAG (1‐palmitoyl‐2‐oleoyl‐3‐bis(β‐d‐glucosyl)‐sn‐glycerol), and the block copolymers PEO₄₅‐b‐P(NCMA_x‐co‐DPA_1‐x)_n (PEO=polyethyleneoxide, NCMA=2‐nitrobenzyl ester‐photocaged carboxyl monomer, DPA=tertiary amine‐containing monomer with carbamiate side linkage) and PS‐PAA (polystyrene‐polyacrylic acid).

Figure 3

a) Accumulation of chromophores in Ld domains of liposomes for efficient energy transfer. Reproduced with permission from ref. [23]; Copyright: 2017, The Chemical Society of Japan. b) Light harvesting and energy transfer are enhanced at the membrane‐water interface using amphiphilic, strongly at 620 nm absorbing DiD as energy donor and C60‐N⁺ as energy acceptor. Reproduced with permission from ref. [24]; Copyright: 2018, Wiley‐VCH GmbH. c) Light‐absorption by a transmembrane oligoaromatic chromophore, followed energy transfer to the acceptor, eosin Y and electron transfer at the membrane interface to water. Image reproduced from ref. [25]; published 2020 by Wiley‐VCH GmbH, Creative Commons CC BY license.

Figure 4

Triplet‐triplet‐annihilation‐upconversion combined with a photochemical reaction. Reproduced with permission from ref. [26]; Copyright: 2013, Wiley‐VCH GmbH. (PS=photosensitizer, A=annihilator).

Figure 5

a) Light induced charge transfer from methyl viologen to photoexcited zinc porphyrin. Reproduced with permission from ref. [31]; Copyright: 2016, American Chemical Society. b) Charge transfer during photocatalysis. Upon photoexcitation the photosensitizer is oxidized or reduced by an acceptor (A) or donor (D) followed by electron (e⁻) or hole (h⁺) transfer to the active catalyst.

Figure 6

a) Charge separation, transmembrane electron transfer and a proton gradient were achieved with zinc‐porphyrin‐NDI dyads with suitable spacer length matching the length of lipid bilayer membrane. Reproduced with permission from ref. [42]; Copyright: 2015, Elsevier. b) TCNQ acting as electron relay across lipid bilayer membrane replacing transmembrane electron transfer proteins I and II as well as membrane soluble ubiquinone (UQ). Reproduced with permission from ref. [43]; Copyright: 2018, American Chemical Society. c) An amphiphilic, membrane embedded zinc porphyrin is photoreduced by the sacrificial electron donor EDTA in the inner aqueous compartment of liposomes. The membrane soluble electron relay, MMPH, catalytically transports the electrons across the membrane to reduce the WST1⁻ dye in the bulk to generate the strongly colored Fz1²⁻. In another scenario, the photoreduction took place at the membrane‐bulk interface in absence of the transmembrane electron relay. Reproduced from ref. [44]; published 2015 by Royal Society of Chemistry, Creative Commons Attribution 3.0 Unported Licence.

Figure 7

Energy transfer mediated by hyperbranched polymers with NBD‐Cl as energy donor encapsulated inside hyperbranched cores and rhodamine B as energy acceptors incorporated on the surface of vesicle with cyclodextrin as host (PEO=polyethyleneoxide) Reproduced with permission from ref. [59]; Copyright: 2017, John Wiley and Sons.