Aqueous Photon Upconversion by Anionic Acceptors Self-Assembled on Cationic Bilayer Membranes with a Long Triplet Lifetime

Abstract

Anionic 9,10-diphenylanthracene chromophores electrostatically bound to cationic, chiral bilayer membranes show ordered self-assembly in water. The integrity of the chromophore-accumulated aqueous bilayer membranes is ensured by multiple hydrogen-bond networks introduced in the bilayer, which allowed adaptive accommodation of the guest chromophores at the inner surface of the bilayer while maintaining their cohesive interactions. The regular chromophore alignment in the aqueous assembly is confirmed by differential scanning calorimetry, circular dichroism, and circularly polarized luminescence spectra. Excitonic migration of triplet energy occurs among the chromophores densely organized at the inner surface of the bilayer, which lead to triplet–triplet annihilation-based photon upconversion (TTA-UC). This acceptor-bilayer self-assemblies show a notably long triplet lifetime of 8.0 ms, which allows TTA-UC at sufficiently low excitation light intensity. These results demonstrate the usefulness of the simple electrostatic accumulation approach for TTA-UC chromophores where the suitable molecular design of the TTA-UC chromophore-integrated bilayer membranes plays a key role.

Avoiding Oxygen Removal for Photochemical Reactions – towards Water as the Solvent

“…[14] This strategy was applied for an oxygen tolerant upconversion process. [5,15] Micelles Micelles self-assemble in water due to the amphipilic nature of the surfactants and within different compartments of the micelles, unique microenvironments arise with a number of previously showcased benefits in the context of photochemical reactivity [16] -one of them being an increased oxygen tolerance. [17,18] Hence, the micelle could potentially provide the perfect environment for oxygen sensitive photoreactions to take place.…”

“…The anionic headgroup of the designed surfactant acts further as a barrier for oxygen and consequently the desired oxygen sensitive photochemical pathway could occur to a satisfactory extent without the need for oxygen removal [14] . This strategy was applied for an oxygen tolerant upconversion process [5,15] …”

A supramolecular assembly-based strategy towards the generation and amplification of photon up-conversion and circularly polarized luminescence

“…D. Asthana et al reported a lipid-based supramolecular system in which the acceptor arranges itself along the bilayer structure. 74 Lipid structures also helps in solubilizing the donor (PtOEP) which being hydrophobic in nature will have a tendency to get precipitated in water. A mixture of a cationic lipid–anionic acceptor (DPA-SO 3 − ) complex and a PtOEP donor gets easily dispersed in water and exhibits TTA-UC under mild irradiation conditions ( I th = 25 mW cm −2 ).…”