Self-assembly of acridine orange dye at a mica/solution interface: Formation of nanostripe supramolecular architectures

Optical waveguide spectroscopy and atomic force microscopy (AFM) have been used to characterize the supramolecular architectures of acridine orange (AO) dye self-assembled at a mica/aqueous solution interface. Under the saturated adsorption conditions, optical waveguide spectroscopy revealed that the dye formed H  -type aggregates at the interface. In situ AFM visualized interesting morphology of the dye aggregates showing nanosized meandering stripes with the width of ∼1.5 nm∼1.5 nm (or brightness periodicity of ∼3 nm∼3 nm). Electrostatic adsorption of the dye cations onto a mica surface as well as the intermolecular π–ππ–π stacking brought about the ordered nanostructures. We propose an interfacial aggregation model that shows a meandering staircase structure with the intermolecular slip angle of 60°. According to the model, the AO molecule occupies a surface area of about 1.0 nm2.

Graphical abstractMeandering nanostripe morphology of self-assembled AO dye at a mica/solution interface.Figure optionsDownload full-size imageDownload as PowerPoint slide