Controlling the Hierarchical Structures of Molybdenum Disulfide Nanomaterials via Self-Assembly of Supramolecular Polymers in Water

Programmed exfoliation of highly crystalline molybdenum disulfide (MoS2) into water-dispersible exfoliated nanosheets with well-tunable structural characteristics was successfully developed using an environmentally benign solvent (water) and a water-soluble cytosine-functionalized supramolecular polymer (Cy-PPG). Herein, we show that MoS2 can be directly dispersed in aqueous solution using ultrasound to obtain dozen-layered MoS2 nanosheets; this process is termed first exfoliation. When Cy-PPG is subsequently incorporated into the MoS2 solution (i.e., second exfoliation), ordered hierarchical lamellar nanostructures form through self-assembly of Cy-PPG on the surface of the metallic 1T and semiconducting 2H phases of the exfoliated MoS2 nanosheets due to the high-affinity interaction between Cy-PPG and MoS2. Furthermore, after second exfoliation, the resulting MoS2/Cy-PPG composites exhibit long-term dispersion stability in water. Broad, tunable MoS2 exfoliation can be achieved by systematically adjusting the content of Cy-PPG within the composites to obtain the desired structural, physical, and conductive performance; these exceedingly rare features offered by programmed exfoliation hold great potential for achievement of high-quality, custom-made MoS2 nanomaterials. Thus, this newly developed system offers a myriad of potential uses for fabrication of fully aqueous solution-processed MoS2-based thin films for optoelectronic and biomedical applications.