Self-assembled cellulosic superstructures with unanticipated high quantum yields

TL;DR

Researchers created cellulosic superstructures with unexpectedly high fluorescence efficiency by using self-assembly and oxygen clusters.

Contribution

The novel contribution is the creation of macroscale cellulosic superstructures with high fluorescence quantum yields through oxygen cluster engineering.

Findings

Cellulose nanocrystals co-assembled into helices with 86% fluorescence quantum yield.

Porous bowl-shaped microparticles achieved 91% fluorescence quantum yield.

High yields are attributed to oxygen clusters and non-covalent interactions enhancing electron delocalization.

Abstract

Nonconventional luminophores devoid of traditional, large π-conjugates often suffer from low solid-state fluorescence quantum yields (FLQYs). In parallel, self-assembled bowl-shaped and helical architectures at the micro- and macroscale are unusual (mostly reported at the nanoscale). Here, we report that surface-stearoylated cellulose nanocrystals and cellulose stearoyl esters co-assemble into macroscale helices (FLQY: 86%) with diameters of 32−104 μm. Meanwhile, surface-lauroylated cellulose nanocrystals and cellulose lauroyl esters co-assemble into porous bowl-shaped microparticles (FLQY: 91%) with diameters of 8−19 μm. The high FLQYs are ascribed to the synergism of the dense oxygen clusters and abundant van der Waals interactions and hydrogen bonds between side stearoyl or lauroyl groups, which can promote through-space electron delocalization, ultimately improving fluorescence performance. These results were rationalized by theoretical calculations. Such superstructures exhibit great potential for stable anti-counterfeiting materials due to the excellent regeneration ability as well as structural stability of the oxygen clusters.

Nonconventional luminophores generally suffer from low solid-state quantum yields. Here, the authors report self-assembled cellulosic superstructures with high solid-state fluorescence quantum yields via oxygen cluster engineering and tailored non-covalent interactions.

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