| dc.description.abstract | This study is on the preparation and application of zirconia/acrylate nanocomposite and lanthanide doped nano-zirconia as up-conversion phosphor.
Cubic zirconia nanoparticles (~6nm) have been prepared at high concentration under strong alkaline (pH: ~12) and low temperature (110oC) conditions. Their surface was subsequently modified with acetic acid and β-carboxyethyl acrylate to enable the dispersion in solvents comparable to acrylic resin. Accordant to TGA and 1H NMR analysis, there were 1.3 and 2.5 molecules of acetic acid and β-carboxyethyl acrylate, respectively, bonded on each nm2 of zirconia surface. The dual ligand modified zirconia nanoparticle could be dispersed into ester ether or similar hydrophobic solvents. The clear sol obtained can then be blended with a high refractive index acrylic monomer (OPPA), and coated onto a substrate. A transparent and non-crack film, with ~1.74 index and above 95% transmittance, could be prepared. This would be useful in the manufacture of brightness enhancement film or optical lens.
The same synthesis process could be extended to the preparation of lanthanide doped zirconia. A nano-size up-conversion phosphor was obtained after proper rinsing and calcination. ICP, XRD, TEM and PL were employed to characterize its composition, crystalline phase and size, as well as its up-conversion efficiency. It was found that the addition of lanthanide helped to stabilize the cubic crystalline phase. The highest up-conversion efficiency achieved was the one doped with 1.2/5.8/3.7 mol% of Er2O3/Yb2O3/Y2O3 and subjected to 900oC calcination. It emitted red (650nm) and green (544nm) lights under the excitation of 980nm NIR. A broad emission range from 350 to 650nm could be observed when pumped by 354nm UV light. Finally, we tried to incorporate it into the scattering layer of a DSSC with the hope to extend the effective wavelength range of solar conversion. The phosphor included scattering layer did show a better reflectivity than the virgin one, but there was no improvement in the equivalent quantum efficiency. The overall efficiency of solar conversion actually decreased with the amount of phosphor incorporated. Therefore, our proposal on the use of nano-size up-conversion phosphor in DSSC was disproved.
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