Synthesis and Optical Properties of KYF4/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF4

✍ Scribed by Helmut Schäfer; Pavel Ptacek; Otmane Zerzouf; Markus Haase

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 283 KB
• Volume: 18
• Category: Article
• ISSN: 1616-301X
• DOI: 10.1002/adfm.200800368

✦ Synopsis

Abstract

KYF~4~/Yb^3+^, Er^3+^ nanocrystals with a mean diameter of approximately 13 nm were synthesized at 200 °C in the high boiling organic solvent N‐(2‐hydroxyethyl)ethylenediamine (HEEDA). The particles crystallize in the cubic phase known from α‐NaYF~4~ and form transparent colloidal solutions in tetraethylene glycol (TEG) or propanol. Solutions containing 1 wt % of the nanocrystals in TEG display visible upconversion emission upon continuous wave (CW) excitation at 978 nm. Growing undoped KYF~4~ on the surface of the KYF~4~/Yb^3+^, Er^3+^ nanocrystals increases the upconversion efficiency by more than a factor of 20. The XRD data of these particles, display a slight increase in the mean particle size from 13 to 15.5 nm, indicating that only a part of the subsequently added KYF~4~ shell material is deposited onto the particle surface. Nevertheless the performed surface modification obviously leads to core/shell structured particles.