Synthesis of GdPO4 Nanoparticles. It is well known that
uniform particles can be formed in solution by homogeneous
precipitation, which can be achieved, for example, through slow
and controlled release of the precipitating anions or cations in
the reaction medium.18 In this work, we selected the latter
strategy using Gd(acac)3 as Gd3+ reservoir, since these
compounds can be dissolved in polyol media and further
decomposed on heating such solutions, thus liberating the Ln3+
cations required for precipitation of LnPO4 in the presence of
phosphate anions.19 It has been also documented that another
requirement for precipitation of uniform particles is the
separation of the nucleation and growth processes, which
only occurs under a precise set of experimental conditions
(reagents concentration, temperature, and aging time).18 To
establish such conditions for synthesis of our nanophosphors,
we first addressed the undoped GdPO4 system for simplicity.