Reverse Microemulsion Synthesis, Structure, and Luminescence of Nanosized REPO₄:Ln³⁺ (RE = La, Y, Gd, or Yb, and Ln = Eu, Tm, or Er)

Abstract

A surfactant-mediated solution route for the obtainment of nanosized rare-earth orthophosphates of different compositions (LaPO4:Eu3+, (Y,Gd)PO4:Eu3+, LaPO4:Tm3+, YPO4:Tm3+, and YbPO4:Er3+) is presented, and the implications of the morphology control on the solids properties are discussed. The solids are prepared in water-in-heptane microemulsions, using cetyltrimethylammonium bromide and 1-butanol as the surfactant and cosurfactant; the alteration of the starting microemulsion composition allows the obtainment of ∼30 nm thick nanorods with variable length. The morphology and the structure of the solids were evaluated through scanning electron microscopy and through powder X-ray diffractometry; dynamic light scattering and thermal analyses were also performed. The obtained materials were also characterized through vibrational (FTIR) and luminescence spectroscopy (emission/excitation, luminescence lifetimes, chromaticity, and quantum efficiency), where the red, blue, and upconversion emissions of the prepared phosphors were evaluated.