Surfactant effects on the particle size of iron (III) oxides formed by sol-gel synthesis

In this work, we probed the effects of a common surfactant, sodium dodecylbenzene sulfonate (NaDDBS), on the particle size of iron (III) oxides formed via a modified sol-gel synthesis. The goal was to create tunable nanosized particles via a method that combines the efficiency and advantages of the sol-gel process, but inhibits the formation of a gel. Two different metal salt precursors were used, ferric nitrate nonahydrate, Fe(NO₃)₃ · 9H₂O, and ferric chlorate hexahydrate, FeCl₃ · 6H₂O. The particle size of the dried gel was 4.5 nm for Fe(NO₃)₃ · 9H₂O and 3.6 nm for FeCl₃ · 6H₂O. In the presence of the surfactant FeCl₃ · 6H₂O formed a gel and Fe(NO₃)₃ · 9H₂O was unable to gel, but the new particle sizes were 4.9 nm and 3.2 nm, respectively. The addition of the surfactant in the later stages of the process afforded the stabilization of independent nanoparticles of the same size as those obtained in the systems that gelled.