Chirality of Graphene Oxide–Humic Acid Sandwich Complex Induced by a Twisted, Long-Range-Ordered Nanostructure

Graphene oxide (GO) with an extraordinary atomic and electronic structure has germinated into an attractive building block for the design and fabrication of new chiral nanomaterials. Herein, we have synthesized a GO–humic acid (HA) sandwich-type complex that can self-assemble into a twisted, long-range-ordered nanostructure in aqueous media. The GO–HA sandwich complex shows obvious chirality under circular dichroism (CD) measurement. By means of scanning electron microscopy, small-angle X-ray scattering, confocal microscopy, and polarized optical microscopy (POM), the morphology, size, fine texture, and orientation of the assembly nanostructure of GO–HA have been validated. The results of experiments and molecular dynamics simulations reveal that the interactions between GO and HA (via electrostatic repulsive, π–π stacking, hydrogen bond, and solvation) induce the enhanced formation of natural ripples in a single GO–HA sheet, cause interlayer and interdomain distortion, and generate a twisted conformation of the C═C double bond, which contributes to the induction of the macroscopic chirality of the GO–HA complex.