Solvothermal hot injection metal nanoparticle synthesis


                                           Vít Vykoukal

                                      Ústav chemie, Př. F. MU

Nanomaterials and especially their preparation by chemical approach is a very attractive field of
materials research. The synthesis of nanoalloys is one integral part of nanoscience and development
of efficient methods is a challenging task due to their chemical, phase, and morphological
variability.

Nanoparticles of metal alloys exhibit many interesting properties, such as depression of melting
point, plasmon resonance, catalytic activity and phase separation. Nanoalloys can be prepared by
many routes, but the solvothermal synthesis, specifically in oleylamine is highly advantageous. Hot
injection technique should ensure homogeneous conditions for nanoparticles nucleation and growth.

AgNi nanoparticles were prepared by injection of an oleylamine solution of AgNO[3] and Ni(acac)[2]
(different molar ratios) and AgCu were prepared by injection of [Ag(DDA)[2]NO[3]] and
[Cu(PPh[3])[2]BeA] or [Cu(PPh[3])[3]Hphtal] (eutectic ratio = 60:40 mol%) to a mixture of
oleylamine and octadecene at 230 °C. After 10 minutes, the reaction mixture was cooled down to room
temperature in a water bath. Then 20 cm3 of acetone was added to precipitate nanoparticles and the
suspension was centrifuged. The precipitate was washed by a mixture of hexane and acetone. This
procedure was repeated twice and finally the precipitate was dispersed in hexane and characterized.

Dynamic light scattering (DLS), transmission electron microscopy (TEM), Scanning transmission
electron microscopy with energy dispersed spectroscopy (STEM-EDS), elemental analyses (ICP OES),
and small-angle x-ray scattering (SAXS) analyses were performed for determination of chemical
composition, average size, size distribution, and shape of the prepared nanoparticles. Plasmon
resonances were also observed. Phase separation was observed by high temperature x-ray diffraction
(HT-XRD) technique and was confirmed by scanning electron microscope (SEM) and by measuring of
magnetic properties during heating.