Preparation of an ordered array of cyanine complex microdomes by a simple dewetting method

Abstract

We demonstrate a simple method for fabricating a two-dimensional array of microdomes that consist of cyanine dye complexes. Investigation of the morphology and the fluorescence emission of microdomes was carried out before/after annealing. The principal of microdome formation is “dewetting,” which is a self-organization phenomena. Generally, one can observe dewetting when a liquid film breaks spontaneously on a nonwettable substrate, leaving droplets or patterns on the substrate. A cyanine dye complex was prepared from a cationic cyanine dye and an anionic amphiphile, or vice versa, an anionic dye and a cationic amphiphile. When a chloroform solution of the cyanine complex was spread on a glass substrate by a roller, microdomes of the cyanine dye complex formed in dewetted films. The roller draws the three-phase line (the air–solid–liquid boundary of the droplet of the chloroform solution) with a constant rate. Thus dewetting can be controlled and leads to a two-dimensional ordered array of uniform sized microdomes. The diameter and height of microdomes decrease with increasing roller speed. Fluorescence microscopy shows that the cyanine dye complex formed J-aggregates. Annealing caused transformation of the dome morphology and a change of the fluorescence spectra. The microdome transformed into anisotropic crystals or became amorphous depending on the molecular structure of the cyanine dye.