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, th e construction of two surfactant monolayers of the soap film is nearly inde pendent 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 p arallel to the plane of the film in the form of a J-aggregate with a concen tration approximately 190 times higher than that in the film-forming soluti on.