Synthesis and luminescent properties of REVO₄-REPO₄ (RE = Y, Eu, Gd, Er, Tm, or Yb) heteronanostructures: A promising class of phosphors for excitation from NIR to VUV

Despite presenting very similar structural properties, rare earth (RE) phosphate and vanadate solids display different spectroscopic behaviors, which makes the elaboration of REVO₄-REPO₄ mixed structures an interesting prospect for the design of luminescent materials with improved activity. This work describes the application of a two-step colloidal precipitation approach for the formation of REVO₄-REPO₄ heteronanostructures and an investigation of their luminescent properties. The growth of the phosphate phase over REVO₄ particles was kinetically evaluated through spectroscopic methodologies comprising the observation of the VO₄^3- → Eu³⁺ energy transfer and the absorption of vanadium(V) peroxocomplexes in solution. This confirmed an effective coating of the precursor nanoparticles. In order to obtain materials with enhanced properties, a protected annealing methodology in SiO₂ was applied, leading to highly crystalline nanorods with low degree of aggregation. The final materials display efficient emissions in the red, green, and blue (RGB) regions under VUV, UV, or NIR excitation according to their composition. The described structures are promising for light generation in several different systems and can be tuned to provide RGB emissions as VUV-excited phosphors and as NIR or UV colloidal luminescent biomarkers.