Berlin 2015 – wissenschaftliches Programm
MM 28.13: Poster
Dienstag, 17. März 2015, 18:30–20:30, Poster E
Absolute Photoluminescence Quantum Yields and Lifetimes of in Toluene Dispersed Hexagonal β-NaYF4: x % Tm3+, 20 % Yb3+ Upconversion Nanoparticles — •Marco Kraft1, Martin Kaiser1, Christian Würth1, Tero Soukka2, and Ute Resch-Genger1 — 1BAM Bundesanstalt für Materialforschung und -prüfung, Richard-Willstaetter-Str. 11, 12489 Berlin — 2Department of Biotechnology, University of Turku, Tykistoekatu 6A, FI-20520 Turku, Finland
Hexagonal β-NaYF4 doped with Yb3+ and Tm3+ is an efficient upconversion (UC) phosphor for the conversion of 976 nm to 800 nm and 450 nm light. The emission behavior of this material is strongly influenced by the doping concentration, particle size, and surface chemistry. The design of nm-sized UC particles requires reliable spectroscopic tools for the characterization of the optical properties of these materials like the UC quantum yield (QYUC). This UC emission originates from multiphotonic absorption processes, rendering the QYUC excitation power density (P) dependent. The absolute measurement of QYUC presents a considerable challenge due to the low absorption coefficient and the P-dependence of these materials, which can introduce a dependence of QYUC on illumination geometry. Here, we present the P-dependent QYUC of 30 nm-sized NaYF4 UC particles with systematically varied dopant concentrations of 20 % Yb3+ and x % Tm3+ (x = 0.2, 0.5, 0.8, 1.1, 2). In addition to QYUC, the emission intensities and lifetimes of the different UC bands are studied as function of excitation power density to gain a better insight of their photonic nature.