Structural organization of water-based ferrofluids with sterical stabilization as revealed by SANS

Small-angle neutron scattering (SANS) with contrast variation is applied to reveal structural organization of a water-based ferrofluid where magnetite nanoparticles are sterically stabilized by the double layer of dodecylbenzenesulphonic acid (DBS). The contrast is changed by the use of different ratios between light and heavy water in the carrier. The modified basic functions are introduced and determined following the analysis of the shape scattering from the colloidal particles in the fluid. Three types of particles are detected, which are presumably initial particles (size ∼20 nm), secondary fractal aggregates (size >250 nm) and micelles of DBS (size ∼5 nm). The found effective match point (35% of D2O) gives the 26 vol% content of magnetite in the initial particles