| Autor: |
Bastian, Philipp U., Nacak, Selma, Roddatis, Vladimir, Kumke, Michael U. |
| Zdroj: |
The Journal of Physical Chemistry - Part C; May 2020, Vol. 124 Issue: 20 p11229-11238, 10p |
| Abstrakt: |
Lanthanide resonance energy transfer (LRET) was used to investigate the motion of dopant ions during the synthesis of core–shell–shell nanocrystals (NCs) that are frequently used as frequency upconversion materials. Reaction conditions (temperature, solvent) as well as lattice composition and precursors were adapted from a typical hydrothermal synthesis approach used to obtain upconversion nanoparticles (UCNPs). Instead of adding the lanthanide ions Yb3+/Er3+as the sensitizer/activator couple, Eu3+/Nd3+as the donor/acceptor were added as the LRET pair to the outer shell (Eu3+) and the core (Nd3+). By tailoring the thickness of the insulation shell (“middle shell”), the expected distance between the donor and the acceptor was increased beyond 2 R0, a distance for which no LRET is expected. The successful synthesis of core–shell–shell NCs with different thicknesses of the insulation layer was demonstrated by high-resolution transmission electron microscopy measurement. The incorporation of the Eu3+ions into the NaYF4lattice was investigated by high-resolution time-resolved luminescence measurements. Two major Eu3+species (bulk and surface) were found. This was supported by steady-state as well as time-resolved luminescence data. Based on the luminescence decay kinetics, the intermixing of lanthanides during synthesis of core–shell UCNPs was evaluated. The energy transfer between Eu3+(donor) and Nd3+(acceptor) ions was exploited to quantify the motion of the dopant ions. This investigation reveals the migration of Ln3+ions between different compartments in core–shell NCs and affects the concept of using core–shell architectures to increase the efficiency of UCNPs. In order to obtain well-separated core and shell structures with different dopants, alternative concepts are needed. |
| Databáze: |
Supplemental Index |
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