Synthesis of Ligand-Free Colloidally Stable Water Dispersible Brightly Luminescent Lanthanide-Doped Upconverting Nanoparticles
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- 9 February 2011
- journal article
- research article
- Published by American Chemical Society (ACS) in Nano Letters
- Vol. 11 (2), 835-840
- https://doi.org/10.1021/nl1041929
Abstract
The synthesis using the thermal decomposition of metal trifluoroacetates is being widely used to prepare oleate-capped lanthanide-doped upconverting NaYF4:Er3+/Yb3+ nanoparticles (Ln-UCNPs). These nanoparticles have no inherent aqueous dispersibility and inconvenient postsynthesis treatments are required to render them water dispersible. Here, we have developed a novel and facile approach to obtain water-dispersible, ligand-free, brightly upconverting Ln-UCNPs. We show that the upconversion luminescence is affected by the local environment of the lanthanide ions at the surface of the Ln-UCNPs We observe a dramatic difference of the integrated upconverted red green emission ratio for Ln-UCNPs dispersed in toluene compared to Ln-UCNPs dispersed in water. We can enhance or deactivate the upconversion luminescence by pH and H/D isotope vibronic control over the competitive radiative and nonradiative relaxation pathways for the red and green excited states. Direct biofunctionalization of the ligand-free, water dispersible Ln-UCNPs will enable myriad new opportunities in targeting and drug delivery applications.Keywords
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