Doped Zirconia Luminescent Nanoparticles
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Doped Zirconia Luminescent Nanoparticles Jennifer Sample1,2, and Dajie Zhang2 1 Research and Technology Development Center, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD, 20723 2 Johns Hopkins University, Baltimore, MD, 21218 ABSTRACT Nanoparticles that fluoresce or absorb light in the visible and near-IR wavelengths are desirable for a variety of applications including biological tagging for medical imaging purposes and for solar control glazing in the automobile industry. Semiconductor quantum dots are commercially available and dyed polymer nanoparticles as well as organic dye/silica core shell nanoparticles have also been demonstrated. We report the synthesis, characterization, and optical properties of another luminescent nanoparticle: doped zirconia. The zirconia nanoparticles reported in this study are doped with up to 10% of the lanthanide dopants Er, Gd, Nd and Eu. These materials emit in the visible and near-IR wavelengths depending on the dopant and are refractory, making them useful for high temperature applications. These cations were found to stabilize the cubic phase over the monoclinic phase of zirconia, at approximately 10% dopant, as characterized by X-ray diffraction. We report the luminescence spectra of these nanoparticles at various wavelengths which reveal emissions from the matrix as well as from the dopants. INTRODUCTION Nanoparticles can be synthesized via a variety of techniques including chemical synthesis, chemical or physical vapor deposition, grinding, ball milling, etc. Chemical synthesis with or without a template affords the most control over nanoparticle size and homogeneity and in fact is the only technique which affords control of nanoparticle shape. This technique is also amenable to scale up. Luminescent nanoparticles useful for biomedical imaging such as semiconductor quantum dots and more recently dye-doped organic nanoparticles1 have been prepared by chemical synthesis. Various reactions have been used to produce nanoscale zirconia particles including microwave irradiation of precursors,2 hydrolysis/condensation,3 and hydrothermal reactions.4 In this work, we report a novel synthesis exploiting the nanoscale size of carbon black as a template for the growth of zirconia and doped zirconia, followed by removal of the carbon black in air at 600 oC to leave pure metal oxide particles. This procedure has the advantage of being very straightforward, aqueous, and scalable to industrial quantities, readily allows incorporation of the dopant in various quantities as an additional salt without interfering with the reaction, as well as the significant advantage of producing crystalline or polycrystalline material as evidenced by XRD. Nanoparticles with tunable fluorescence emission can thus be produced by varying the dopant as outlined below. EXPERIMENT
Nanoparticle Synthesis Zirconia and doped-zirconia nanoparticles were produced using a novel reaction exploiting carbon black as a template. Briefly, a zirconium-containing prec
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