Steering Nanohelix and Upconverted Circularly Polarized Luminescence by Using Completely Achiral Components.

Abstract

Enormous attention has been paid to upconverted circularly polarized luminescence (UC-CPL). However, so far, chiral species are still needed in UC-CPL materials, either through the covalent or noncovalent bond. Here, we report a general supramolecular coassembly approach for the fabrication of UC-CPL systems from completely achiral components. We have found that an achiral <i>C</i>₃-symmetric molecule could form a chiral nanohelix through symmetry breaking, which could serve as a general helical platform to endow achiral guests with induced chirality and CPL activity. Two different photon upconversion systems, namely, triplet-triplet annihilation photon upconversion (TTA-UC) donor/acceptor pairs and inorganic lanthanide upconversion nanoparticles (UCNPs), are selected. When these two systems coassembled with the chiral nanohelix made from an achiral <i>C</i>₃-symmetric molecule, hybrid nanohelix structures formed and UC-CPL activity was induced. Through such an approach, we demonstrated that the fabrication of the UC-CPL materials does not require any chiral molecules. Moreover, we have shown that the polarization of UC-CPL can be tuned by the helicity of the nanohelix, which could be controlled through the seeded vortex. Our work provides a general approach for designing tunable UC-CPL materials from completely achiral motifs, which largely expands the research scope of the CPL materials.