A self-assembled nanohelix for white circularly polarized luminescence via chirality and energy transfer

Abstract

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.