Luminescent properties of lanthanide complexes possess unique characteristics that make them good candidates for possible bioimaging agents and have inspired research initiatives to further explore these materials. However, the toxicity of these metals limits their applications as in-vivo bioimaging agents. One solution that eliminates the toxic effects is to encase these lanthanide complexes in silica. This project was designed to probe the variation in the fluorescence properties of a highly luminescent europium (III) complex, utilizing a fluorinated â-diketonate ligand (thenoyltrifluoroacetone (tta)), upon the substitution of the solvent molecules by various functionalized dipyrido[3,2-a:2',3'-c]phenazine (DPPZ) ligands. A method for covalently attaching, or occluding complexes in silica nanoparticles were also included in the project design. The structure and properties of the functionalized DPPZ ligands and their respective complexes were determined by FT-IR, 1H-NMR, UV-Vis, and fluorescence spectroscopy techniques. UV excitation of the complexes resulted in red luminescence (~ 614 nm) characteristic of trivalent europium ions. The differences in luminescence properties of the complexes are rationalized in terms of the electronic features of the different functionalized DPPZ ligands. The higher overall quantum yield of the un-functionalized DPPZ complex, Eu(tta)3DPPZ (Q.Y.= 7.68 ± 0.06 %), and the low overall quantum yield observed for Eu(tta)3DPPZ-COOEt (Q.Y.= 1.08 ± 0.05%), Eu(tta) 3DPPZ-Si (Q.Y.= 0.65± 0.04%), Eu(tta)3DPPZ-COOH (Q.Y.= 0.61± 0.07 %), Eu(tta)3DPPZ-CH3 (Q.Y.= 0.59±0.02 %) are rationalized in terms of how electron donating or withdrawing groups affect their respective ligand-to-metal energy transfer efficiencies. Eu(tta) 3DPPZ was the only complex to show enhanced luminescent properties capable of potential applications in biomedical imaging.
|Commitee:||De Silva, Channa, Evanoff, David|
|School:||Western Carolina University|
|Department:||Chemistry and Physics|
|School Location:||United States -- North Carolina|
|Source:||MAI 54/02M(E), Masters Abstracts International|
|Subjects:||Inorganic chemistry, Biomedical engineering, Nanoscience|
|Keywords:||Dipyridophenazine, Europium, Quantum yield, Silica nanoparticle, Thenoyltrifluoracetone|
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