Intensive research effort devoted to the preparation of nanomaterials has resulted in impressive progress in their synthesis, in order to access their unique properties. One of the remaining challenges is to develop large scale synthetic methods. The molten salt synthesis (MSS) is one of these methodologies in which a molten salt is used as the reaction medium for reactant dissolution and product precipitation. The characteristics of the products by MSS are generally affected by the synthesis temperatures, the type of salts used, the precursor compositions and the solubilities of the reactive constituents in the molten salts.

As energy becomes a scarce commodity, common low efficiency lighting device must be replaced with more efficient alternatives, such as light emitting diodes, where metal oxides are well suited. Since the crystallite size, composition and presence of dopants greatly affect the optical performance of these materials, in this work, we report the synthesis and characterization of luminescent rare-earth doped oxide nanoparticles (NPs) with a focus on controlling the spatial distribution of the dopants in metal oxide hosts and assessing its effect on the device performance.

In this talk, we present our recent work on the large scale synthesis of RE doped oxide NPs, including Er:Y₂O₃ and Er:La₂(Zr_xHf_1-x)₂O₇, by MSS. The formation of these NPs was probed in-situ by time-resolved synchrotron x-ray diffraction and absorption spectroscopy to delineate the process-structure-property relations. The as-synthesized NPs were further characterized by electron microscopy and various spectroscopy to be single crystalline, with well controlled size distributions. The erbium coordination number and local bonding environment were shown to dictate the measured photoluminescent characteristics, including photoluminescence (PL) and cathodoluminescence (CL). Specifically, these erbium-doped oxide NPs have sharp and well-resolved PL behavior in the near-infrared region, outstanding green and red upconversion emissions, and excellent CL properties. These properties make these NPs promising for applications in display, bioanalysis and telecommunications.