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

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 degrees 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 O-2 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 angstrom) 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 Eu3+ 5D0 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.

Automated summary

This study demonstrates the tuning of various properties of (Y,Eu)VO4 structures through colloidal conversion of rare earth hydroxycarbonates in water/ethylene glycol suspensions. By controlling the size and aggregation of hydroxycarbonate precursors, the amorphous to crystalline conversion can be directed at 1 atm/95 degrees C. Additionally, a template effect leads to the formation of solids with high oxygen defect densities and high-porosity (Y,Eu)VO4 nanoparticles with expanded unit cells.