Synthesis of Aqueous Sols of Nanocrystalline Hafnium Dioxide Doped with Europium or Gadolinium

A method for the synthesis of stable aqueous HfO2 colloids doped with Eu3+ or Gd3+ cations is proposed. It is shown that the introduction of a lanthanide cation into the hafnium oxide structure leads to the stabilization of the metastable tetragonal modification of HfO2. Dynamic light scattering showed that sols of HfO2 doped with rare-earth element cations are characterized by a narrow monomodal particle size distribution and possess high aggregative stability (ζ-potential less than −17 mV). The Eu3+-doped HfO2 colloid exhibits luminescent properties, making it a promising bifunctional theranostic material.