Effect of dye molecules on black film stability and property of aqueous core phase

The black soap films of cationic surfactant cetyltrimethylammonium bromide with three kinds of dye molecules have been investigated using UV-Vis spectroscopy. The film stability is greatly improved with the addition of anionic dye and is relevant to the number of negative charges of the dye molecule and the distance between the negatively charged groups in the molecular system. The neutral and anionic dye molecules increase the monolayer cohesion to promote film stability. The aqueous core phases in the black soap films show a specific microenvironment different from that on the corresponding micellar surfaces.