Characterization of multifunctional β-NaEuF4/NaGdF4 core-shell nanoparticles with narrow size distribution

• Published in: Nanoscale 2016-02, Vol.8 (5), p.2832-2843
• Main Authors: Schneider, Lilli, Rinkel, Thorben, Voß, Benjamin, Chrobak, Artur, Klare, Johann P, Neethling, Jan, Olivier, Jaco, Schaniel, Dominik, Bendeif, El-Eulmi, Bondino, Federica, Magnano, Elena, Píš, Igor, Balinski, Kamil, Wollschläger, Joachim, Steinhoff, Heinz-Jürgen, Haase, Markus, Kuepper, Karsten
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Cristallography
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c5nr06915g

The properties of β-NaEuF4/NaGdF4 core-shell nanocrystals have been thoroughly investigated. Nanoparticles with narrow size distribution and an overall diameter of ∼22 nm have been produced with either small β-NaEuF4 cores (∼3 nm diameter) or large β-NaEuF4 cores (∼18 nm diameter). The structural properties and core-shell formation are investigated by X-ray diffraction, transmission electron microscopy and electron paramagnetic resonance, respectively. Optical luminescence measurements and X-ray photoelectron spectroscopy are employed to gain information about the optical emission bands and valence states of the rare earth constituents. Magnetic characterization is performed by SQUID and X-ray magnetic circular dichroism measurements at the rare earth M(4,5) edges. The characterization of the core-shell nanoparticles by means of these complementary techniques demonstrates that partial intermixing of core and shell materials takes place, and a significant fraction of europium is present in the divalent state which has significant influence on the magnetic properties. Hence, we obtained a combination of red emitting Eu(3+) ions and paramagnetic Gd(3+) ions, which may be highly valuable for potential future applications.