Eu3+-Doped ZnB2O4 (B = Al3+, Ga3+) Nanospinels: An Efficient Red Phosphor

This paper describes the synthesis of Eu(III)-doped ZnB2O4 (B = Al(III) or Ga(III)) nanospinels with Eu(III) concentrations varying between 1% and 15.6%. The synthesis was achieved through a microwave (MW) synthetic methodology producing 3 nm particles by the thermal decomposition of zinc undecylenate (UND) and a metal 2,4-pentanedionate (B(acac)(3), B = Al3+ or Ga3+) in oleylamine (OAm). The nanospinels were then ligand exchanged with the beta-diketonate, 2-thenoyltrifluoroacetone (tta). Using tta as a ligand on the surface of the particles resulted in soluble materials that could be embedded in lens mimics, such as poly(methyl methacrylate) (PMMA). Through a Dexter energy transfer mechanism, tta efficiently sensitized the Eu(III) doped within the nanospinels, resulting in red phosphors with intrinsic quantum efficiencies (QEs) and QEs in PMMA as high as 50% when excited in the UV. Optical measurements on the out of batch and tta-passivated nanospinels were done to obtain absorption, emission, and lifetime data. The structural propertieS of the nanospinels were evaluated by ICP-MS, pXRD, TEM, FT-IF, EXAFS, and XANES.