Chiral nanostructures and their optical activity have been attracting great interest. Here, we designed an enantiomer bolaamphiphile containing a naphthalene moiety (bola-1) and an alkyl spacer, and investigated its self-assembly as well as optical activity. It was found that the compound could form gels in various organic or mixed organic/water mixtures. In mixed DMSO/water, it formed a nanohelix. Due to the fluorescent nature of the naphthyl group, the nanohelix showed both CD and circularly polarized luminescence (CPL). When three achiral fluorescent molecules, pyrene-1-carboxylic acid (D2), rhodamine 110 (D3) and rhodamine B (D4), were incorporated into the helical structures formed by bola-1, the nanohelix could be retained and the CPL from the dye molecules could be induced. In addition, an energy transfer occurred between the bola-1 nanohelix and the dyes. By mixing the different emission dyes with the bola-1 in an appropriate ratio, white CPL was obtained. It was found that the dissymmetry factor of the white CPL could be increased through energy transfer. This work provided a new convenient and efficient way for obtaining white CPL.

A bolaamphiphile with diacteylene mesogen unit and L-glutamic acid as the terminal group was newly designed and its self-assembly was investigated. The compound formed hydrogels with water upon heating and cooling. The as-formed gel could be switched to a dispersion upon mechanical shaking. Both the gel and the water dispersion undergo polymerization upon UV irradiation. However, the gel turned to blue and then purple red color, while the dispersion turned red directly. Using AFM and SEM observations, it was found that nanohelix was formed in the as-prepared gel and polymerized blue gels, while nanobelt was formed from the water dispersion. The blue nanohelix was stable but showed selective response to certain amino acids and nucleobases. It was found that the blue gel underwent shrinkage when reacting with charged amino acids such as Glu, Asp, Lys, Arg and His. In the shrunk gel, the solution phase further turned pink in the case of His and Arg. In addition, the blue gel showed also shrinkage and color change when reacting with cytosine.

Two isomeric naphthalene appended glucono derivatives substituted at the 1 or 2-naphthyl positions (Nap-1 and Nap-2) were designed and their self-assembly behaviors and optical properties were investigated. Nap-1 and Nap-2 were found to self-assemble into nanofibers and nanotwists, respectively. While the molecular chirality of the glucono moiety could not be effectively transferred to the naphthalene moiety in the Nap-1 system, this was achieved in the Nap-2 assembly. Thus, the Nap-2 assembly showed obvious circular dichroism (CD) and circularly polarized luminescence (CPL) signals. From the XRD patterns and IR spectra of the supramolecular assemblies, it was found that Nap-2 packed in a more orderly fashion than Nap-1, leading to a hierarchical assembly forming nanotwist structures. Moreover, a light-harvesting system based on Nap-2 supramolecular gels and dyes was established, in which an efficient energy transfer was demonstrated from Nap-2 to an acceptor Eosin Y. It was further found that both chirality and energy transfer enhanced the dissymmetry factor of Eosin Y CPL emission.

Alkyl-substituted L/D-glutamide derivatives (L/D-SG) were designed as gelators to fabricate host gel matrices. Pyrene-appended L/D-glutamide derivatives (Py-LG/Py-DG) were employed as guest luminophores to investigate chiral packing and emission behavior in gel matrices. It was found that Py-LG and Py-DG are prone to form P- and M-chirally packed assemblies in DMSO gels, respectively. However, the chiral packing was inversed, and CPL was boosted after Py-LG/Py-DG was embedded in the L/D-SG gel matrix. M-chiral packing together with left-handed excimer emission ((−)-CPL) was observed in the Py-LG immobilized L-SG gel matrix, while P-chiral packing together with right-handed excimer emission ((+)-CPL) was found in the Py-DG immobilized L-SG gel matrix. It is more interesting to find that the molecular chirality of the matrix gelator did not affect the supramolecular chirality of pyrene assemblies. Either L or a D-matrix gelator can inverse the supramolecular chirality of the pure gel, but did not follow the chirality of the matrix. It was found that the gel matrix converts intralayer pyrene–pyrene (Py–Py) packing in the pure pyrene gel to interlayer Py–Py packing, thus giving an opposite chirality. The study not only deepened our understanding of the supramolecular chirality transfer but also unveiled the effects of an inert gel matrix in regulating the chiroptical properties.

Pyrene-appended glucono gelators with different spacer lengths (two and four methylene units) were designed and found to form supramolecular gels in organic aqueous solvents. The shorter spacer gelator 1 was prone to self-assemble into nanotubes due to well stacking multi-bilayer unit, while gelator 2 with the longer spacer formed nanofibers due to the relatively disordered packing structure. Both of the gels showed supramolecular chirality as well as circularly polarized luminescence (CPL) due to the chirality transfer from the glucose moiety to the assembly. Interestingly, the CD and CPL signals were opposite for the two gels. It was suggested that the packing of the pyrene unit in the gels were different due to the spacer and resulted in the inversed chiroptical properties. The work provided a deeper understanding of the origin of the supramolecular chirality and furthers the design of the CPL materials.