All-or-none switching of photon upconversion in self-assembled organogel systems

Abstract

Aggregation-induced photon upconversion (iPUC) based on a triplet-triplet annihilation (TTA) process is successfully developed via controlled self-assembly of donor-acceptor pairs in organogel nanoassemblies. Although segregation of donor from acceptor assemblies has been an outstanding problem in TTA-based UC and iPUC, we resolved this issue by modifying both the triplet donor and aggregation induced emission (AIE)-type acceptor with glutamate-based self-assembling moieties. These donors and acceptors co-assemble to form organogels without segregation. Interestingly, these donor-acceptor binary gels show upconversion at room temperature but the upconversion phenomena were lost upon dissolution of the gels on heating. The observed changes in TTA-UC emission were thermally reversible, reflecting the controlled assembly/disassembly of the binary molecular systems. The observed on/off ratio of UC emission was much higher than that of the aggregation-induced fluorescence of the acceptor, which highlights the important role of iPUC, i.e., multi-exciton TTA for photoluminescence switching. This work bridges iPUC and supramolecular chemistry and provides a new strategy for designing stimuli-responsive upconversion systems.

Unreactive Gel Networks as Versatile Confined Spaces for Enhanced Photoinduced Processes

“…The decrease in UC emission intensity observed for the sol phase was ascribed to the quenching of excited triplet species by rapid diffusion of dissolved oxygen. The same on/off switching of UC emission has been also demonstrated for other thermoreversible supramolecular upconverting gels …”

“…The same on/ off switching of UC emission has been also demonstrated for other thermoreversible supramolecular upconverting gels. [44] Photoreduction Following the work of Kimizuka and coworkers on TTA-UC in gels under aerobic conditions, [43] our group has demonstrated the possibility to couple the generated singlet acceptor (S 1 ) and a single electron transfer (SET) to activate a reactant under mild conditions. [45] As a proof of concept, the intragel photoreduction of aryl halides in air by green-to-blue photon UC was successfully performed in air inside upconverting gels made of a mixture of LBG, PtOEP and DPA at suitable concentrations.…”

Recent Progress in Photon Upconverting Gels

“…Matrix-free upconverting organogels have also been reported by the Yanai and Kimizuka group [38]. Chiral nanoassemblies were self-assembled from lipophilically modified donor/acceptor pairs, which showed effective triplet energy migration in the gel nanofibers.…”

Anregen und tauschen

“…Veranschaulichung thermoschaltbarer Triplett-Triplett-Annihilation-Aufkonversion, die auf der spontanen Anordnung von Akzeptor-(L-1 oder D-1, 10 mM) und Donormolekülen (L-2, 20 µM) basiert. 9) Abb. 6…”