  A one-pot simple procedure for the synthesis of uniform, ellipsoidal
Eu3+-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)2, X = W, Mo)
nanophosphors, functionalized with carboxylate groups, is described. The method
is based on a homogeneous precipitation process at 120 C from appropriate Na+,
Ln3+ and tungstate or molybdate precursors dissolved in ethylene glycol/water
mixtures containing polyacrylic acid. A comparative study of the luminescent
properties of both luminescent materials as a function of the Eu3+ doping level
has been performed to find the optimum nanophosphor, whose efficiency as X-ray
computed tomography contrast agent is also evaluated and compared with that of
a commercial probe. Finally, the cell viability and colloidal stability in
physiological pH medium of the optimum samples have also been studied to assess
their suitability for biomedical applications.
