Effect of surfactant type on platinum nanoparticle size of composite Pt/α-Al₂O₃ catalysts synthesized by a microemulsion method.

A facile method for the generation of platinum-on-alumina hybrid materials with high-surface area is presented, employing a microemulsion-based synthesis of metal nanoparticles. Pt nanoparticles (NPs) supported on α-Al2O3 were prepared by the reduction of metal ions in water-in-oil microemulsion systems stabilized by a range of different surfactants with cationic, anionic and nonionic headgroups, namely AOT, CTAB, Tween80 and TX-100. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is demonstrated that choice of surfactant can be used to tailor the size of the generated Pt nanoparticles, and seen that surfactant charge has a determining role in this process. Pt NPs formed in microemulsion systems based on charged surfactants (AOT and CTAB) are smaller than those prepared in nonionic microemulsion systems (TX-100 and Tween80). A solvent-induced demixing process was used to cleanly obtain the hybrid materials from the reaction medium at low energy cost.