Spectroscopic study of the self-assembly behavior of a vertical soap film stabilized with cetyltrimethylammonium bromide and Thiazole Yellow

FTIR and UV-vis spectroscopy were used to investigate the thinning process and self-assembly behavior of a stable black soap film (BSF) prepared from the cationic surfactant cetyltrimethylammonium bromide and the anionic dye Thiazole Yellow (TY) in a micellar phase. During the course of thinning, the construction of two surfactant monolayers of the soap film is nearly independent of the aqueous core thickness, indicating the self-assembly feature of the BSF. At equilibrium, the thickness of the aqueous core is estimated to be approximately 1.7 nm, and the TY molecules in the film are aligned parallel to the plane of the film in the form of a J-aggregate with a concentration approximately 190 times higher than that in the film-forming solution.