Epitaxial Core/Shell Nanocrystals of (Europium-Doped) zirconia and hafnia

Abstract

A careful design of nanocrystal architecture can strongly enhance the nanocrystal function. So far, this strategy faced a synthetic bottleneck in the case of refractory oxides. Here, we demonstrate the epitaxial growth of hafnia shells onto zirconia cores, and pure zirconia shells onto europium doped zirconia cores. The core/shell structures are fully crystalline. Upon shelling, the optical properties of the europium dopant are dramatically improved (featuring a more uniform coordination and a longer photoluminescence lifetime), indicating the suppression of non-radiative pathways. These results launch the stable zirconium and hafnium oxide hosts as alternatives for the established NaYF4 systems.

Synthesis of zirconium(iv) and hafnium(iv) isopropoxide, sec-butoxide and tert-butoxide

“…19 In our laboratory, we have ample experience in producing oxide nanocrystals and oxo clusters from metal alkoxide precursors. 1,3,18,19,[24][25][26][27][28][29][30] While zirconium and hafnium isopropoxide and tert-butoxide compounds are commercially available, we experienced a high supplier-to-supplier and batch-tobatch variability in terms of color of the isopropoxide (from slightly yellow to brown instead of white) or purity of the tertbutoxide (e.g., turbid instead of transparent). Given that reagent purity directly affects the reproducibility of chemical reactions, this is cause for concern.…”