  At the nanometric scale, the synthesis of a random alloy (i.e. without phase
segregation, whatever the composition) by chemical synthesis remains a not easy
task, even for simple binary type systems. In this context, a unique approach
based on the colloidal route is proposed enabling the synthesis of face-centred
cubic and monodisperse bimetallic, trimetallic, tetrametallic and pentametallic
nanoparticles with diameters around 5 nm as solid solutions. The Fe-Co-Ni-Pt-Ru
alloy and its subsets are considered which is a challenging task as each
element has fairly different physico-chemical properties. Nanoparticles are
prepared by temperature-assisted co-reduction of metal acetylacetonate
precursors in the presence of surfactants. It is highlighted how the
correlation between precursors' degradation temperatures and reduction
potentials values of the metal cations is the driving force to achieve a
homogenous distribution of all elements within the nanoparticles.
