Tuning morphology, surface, and nanocrystallinity of rare earth vanadates by one-pot colloidal conversion of hydroxycarbonates

Abstract

We show that particle size, morphology, nanocrystallinity, surface area, and defect density of (Y,Eu)VO₄ structures can be tuned by one-pot colloidal conversion of rare earth hydroxycarbonates in water/ethylene glycol (EG) suspensions. Using small angle X-ray scattering, transmission electron microscopy and dynamic light scattering, we show how volume fractions of EG direct the amorphous to crystalline conversion at 1 atm/95 °C by controlling size and aggregation of hydroxycarbonate precursors. A template effect due to a Kirkendall-type conversion occurs for low EG contents, yielding solids with high densities of oxygen defects, as demonstrated by O₂ uptakes in thermogravimetry and X-ray photoelectron spectroscopy profiles. Starting from small and aggregated hydroxycarbonates high-porosity (Y,Eu)VO₄ nanoparticles were produced with expanded unit cells and short-range (<100 Å) crystalline ordering. We explored the effects of synthesis on the textural, microstructure, and defects of (Y,Eu)VO₄ solids, which were further correlated to the spectroscopic profiles of Eu³⁺-activated samples. We show that the ratios between Eu^{3+ 5}D₀ internal quantum yields and particle diameters can be directly correlated to the particle surface areas, opening new perspectives for theoretical detailing of f–f luminescence in YVO₄ solids, and enabling accurate tuning of structure and applicability of colloidal vanadate nanoparticles for sensing and catalysis applications.