Rational Design of Multiple-Stimulus-Responsive Materials via Supramolecular Self-Assembly

In this report, multiple-stimulus-responsive materials were synthesized via supramolecular self-assembly. One-dimensional nanorods were constructed by the self-aggregation of 4-(phenyl-azo)­benzoic acid (PBA) molecules in aqueous solution at pH 3.2. As the pH of the solution was increased to 6.5, these nanorods transformed into two-dimensional polygons. Upon UV irradiation, the as-prepared nanorods disappeared completely, and nanospheres were subsequently obtained. On the basis of the weak interactions between PBA and additive molecules, for example, N-alkyl-N′-carboxymethyl imidazolium bromide, β-cyclodextrin, and cetyltrimethylammonium bromide, materials with various morphologies were also fabricated by a surfactant-assistant self-assembly strategy. Noteworthy is that Salvia officinalis-shaped material is among them. To the best of our knowledge, this type of microstructured material has been rarely reported. In addition, slender fibers, sphere-like particles, and aggregates of spheres were also observed. These results suggest that the rational fabrication of materials with desired shapes and sizes can be achieved by changing external environments during the self-aggregation of PBA molecules. Both cyclic voltammogram experiments and density functional theory calculations exhibit the optoelectronic behavior of these materials, which is expected to have potential applications in the fabrication of photoelectronic nanodevices.