Structural properties of palladium nanoparticles embedded in inverse microemulsions

Pd nanoparticles were synthesized by reduction of palladium acetate by ethanol in systems containing tetrahydrofuran (THF) as dispersion medium and tetrado-decylammonium bromide (TDARr) surfactant as stabilizer. The polar phase (ethanol) acts at the same time as reducing agent. THF/TDABr/H2O inverse microemulsions containing micelles of various sizes were also prepared, and the structure of complex liquids was studied by density measurements. Sols containing nanosize Pd-0 particles were synthesized within the water droplets of this micellar system. The stabilized Pd-0/surfactant system was characterized by density measurements, absorption spectroscopy, and transmission electron microscopy. The stabilizing surfactant layer adsorbed on the liquid/liquid interface and on the surface of the nanoparticles (i.e., the liquid/solid interface) significantly reduced the excess volume for the palladium nanodispersion in organic solvent.