Surfactant effects on the particle size and formation of iron oxides via a sol-gel process

This work illustrates the effects of adding a common surfactant, sodium dodecylbenzene sulfonate (NaDDBS), to the reaction mixture used in the formation of iron (III) oxide nanoparticles via a modified sol-gel process. In order to elucidate the role of the surfactant on the control of the resulting iron oxide particle size, experiments were conducted with two different metal salt precursors: Fe(NO₃)₃ 9H₂O and FeCl₃ 6H₂O. The average particle size of the dried iron oxide gels, in the absence of the surfactant, was 4.5 nm and 3.6 nm for Fe(NO₃) ₃ 9H₂O and FeCl₃ 6H₂O as precursors, respectively. The addition of a surfactant inhibited gel formation in the Fe(NO₃)₃ 9H₂O system, while in the FeCl ₃ 6H₂O system the gelation process was delayed. The resultant particle sizes were 3.2 nm and 4.9 nm, respectively. It appears that even though the Fe(NO₃)₃ 9H₂O system was unable to gel the surfactant was able to stabilize the nanoparticles to form even smaller particles than the gel counterpart.