Synthesis of NiAu colloidal nanocrystals with kinetically tunable properties

NiAu colloidal nanocrystals were synthesized via the co-reduction of nickel 2,4-pentanedionate and gold acetate by 1,2-hexadecanediol. At temperatures below 200 °C, pure Ni nanocrystals could not be synthesized alone but Au nuclei might promote the reduction of nickel 2,4-pentanedionate to form NiAu nanocrystals. The resultant NiAu nanocrystals were superparamagnetic with a face-centered cubic (fcc) structure and exhibit the surface plasmon absorption at 520 nm, which increased with increasing Au content and reaction time. Their mean diameters decreased with increasing Au content in the feed solution because of the formation of more nuclei at the beginning of the reaction, while became larger first owing to the particle growth and then decreased due to the atom rearrangement with increasing reaction time. When reaction temperature was above 200 °C, the reduction of nickel 2,4-pentanedionate could occur without the assistance of Au nuclei. The particle size and surface plasmon absorption decreased due to the formation of nuclei at the beginning of the reaction and the participation of more Ni atoms. This work revealed that the properties of NiAu nanocrystals could be tuned kinetically.