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Llombart, Pablo Alcolea Palafox, Mauricio González Mac-Dowell, Luis Noya, Eva G. 2024-12-05T12:12:33Z 2024-12-05T12:12:33Z 2019 Pablo Llombart, Mauricio Alcolea Palafox, Luis G. MacDowell, Eva G. Noya, Structural transitions and bilayer formation of CTAB aggregates, Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580, 2019, 123730, ISSN 0927-7757, https://doi.org/10.1016/j.colsurfa.2019.123730. (https://www.sciencedirect.com/science/article/pii/S0927775719307186) 10.1016/j.colsurfa.2019.123730 https://hdl.handle.net/20.500.14352/112147 https://doi.org/10.1016/j.colsurfa.2019.123730 https://www.sciencedirect.com/science/article/pii/S0927775719307186 Controlled CTAB self-assembly is an essential prerequisite for the formation of gold nanorods with tailored shape and monodispersity. In this paper, we exploit the use of salt concentration and co-surfactant decanol for the preparation of CTAB aggregates with different morphologies. To this end we use a model of CTAB recently developed by ourselves, and perform electronic structure calculations in order to improve current point charge parametrization of decanol. Using molecular dynamics simulations with the new models, we find a sequence of structural transitions of CTAB aggregates induced by salt concentration and added cosurfactant. In pure solutions, CTAB aggregates form spherical micelles with a compact ionic shell and a diffuse double layer that can be qualitatively described with Poisson–Boltzmann theory. Addition of decanol as a cosurfactant induces a sequence of dramatic structural transitions at low surfactant concentration and allows the stabilization of compact ordered bilayers in a well defined range of intermediate decanol/CTAB ratios. At low and high decanol/CTAB ratios spherical micelles are transformed into wormlike cylindrical micelles. At intermediate decanol/CTAB ratios, fully formed bilayers are observed, with surfactants exhibiting a compact structure with strong positional and orientational order. We discuss how the controlled self-assembly of compact CTAB bilayers at low global CTAB concentration can pave the way for the selective passivation of gold facets and the controlled formation of monodisperse gold nanorods. eng restricted access Structural transitions and bilayer formation of CTAB aggregates journal article