Pt3Co alloy nanoparticles were prepared by the reduction of H2PtCl6 and Co(OOCCH3)2 using NaBH4 as a reducing agent. The Pt3Co core-Pt shell nanoparticles (Pt3Co@Pt) were synthesized using hydrogen absorption reduction and characterized by plasma-atomic emission spectrometry (ICP), transmission electron microscopy (TEM), X-ray diffraction (XRD) and SQUID magnetometer. The results show that average size of Pt3Co@Pt nanoparticles is 3.6 nm with a standard deviation of 0.9 nm. Heating Pt3Co nanoparticles in air at 700 ℃ for 1 h, Co in Pt3Co nanoparticles was oxidized to Co3O4 and CoO; while no oxidation tendency was detected for Pt3Co@Pt nanoparticles. The crystallize structure of Pt3Co@Pt changed from the face centered cube (fcc) to the face centered tetragonal (fct) after the heating treatment. The coercivity of the heated Pt3Co@Pt reached to 276 Oe at room temperature.
A new washing device was used to separate hydrophobic trimetal nanoparticles with particle size less than 10 nm monodispersed in organic solvent. The washing device and method is not only easy to control but also very efficient. Quantum dots with different sizes such as 4.5 nm, 5.1 nm, 6.4 nm were obtained. The UV-Vis spectra of those nanoparticles were at 522 nm, 529 nm, 538 nm indicating very good separation. Particularly, the absorbent peak of the particles with size of 4.5 nm is very narrow distributed.
