Azobenzene-based ultrathin peptoid nanoribbons for the potential on highly efficient artificial light-harvesting

The development of artificial light-harvesting systems based on long-range ordered ultrathin organic nanomaterials (i.e., below 3 nm), which were assembled from stimuli-responsive sequence-controlled biomimetic polymers, remains challenging. Herein, we report the self-assembly of azobenzene-containing amphiphilic ternary alternating peptoids to construct photo-responsive ultrathin peptoids nanoribbons (UTPNRs) with a thickness of ~2.3 nm and the length in several micrometers. The pendants hydrophobic conjugate stacking mechanism explained the formation of one-dimensional ultrathin nanostructures, whose thickness was highly dependent on the length of side groups. The photo-isomerization of azobenzene moiety endowed the aggregates with a reversible morphology transformation from UTPNRs to spherical micelles (46.5 nm), upon the alternative irradiation with ultraviolet and visible light. Donor of 4-(2-hydroxyethylamino)-7-nitro-2,1,3-benzoxadiazole (NBD) and acceptor of rhodamine B (RB) were introduced onto the hydrophobic and hydrophilic regions, respectively, to generate photo-controllable artificial light-harvesting systems. Compared with the spheres-based systems, the obtained NBD-UTPNRs@RB composite proved a higher energy transfer efficiency (90.6%) and a lower requirement of RB acceptors in water. A proof-of-concept use as fluorescent writable ink demonstrated the potential of UTPNRs on information encryption.