On the impact of surfactant type on the structure of aqueous ferrofluids

Abstract

The impact of surfactant type on the structure organization of aqueous ferrofluids was considered based on the data of small-angle neutron scattering (SANS). The aggregates of different sizes and types were observed for magnetite magnetic nanoparticles of in heavy water stabilized by sodium oleate (SO) or dodecylbenzene sulphonic acid (DBSA). According to the surface tension measurements it was shown the significant difference of the critical micelle concentrations for SO and DBSA solutions. The observed structural difference of the aggregates in the ferrofluids was related to the behaviour of surfactant molecules in aqueous solutions including the structure and interaction parameters of micelles (micelle aggregation number, fractional charge, charge per micelle and surface potential, etc.) derived from the SANS analysis.