Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 4: New Experimental Techniques
CPP 4.12: Vortrag
Montag, 27. März 2006, 17:15–17:30, ZEU Lich
Nanometer-sized temperature-sensors using the upconversion signal in single colloids of Lathanide-doped NaYF4 — •Stefan Schietinger1, Björn Lauritzen1, Stephan Heer2, Hans-Ulrich Güdel2, and Oliver Benson1 — 1AG Nano-Optik, Institut für Physik, Humboldt-Universität zu Berlin, Hausvogteiplatz 5-7, 10117 Berlin (Germany) — 2Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3000 Bern 9 (Switzerland)
Because of low absorption of biological tissue in the near-infrared (NIR), luminescent biolabels based on two-photon absorption processes in this spectral region are of great interest. NaYF4 colloids doped with Yb3+/Er3+ with a size of 10-30 nm can be excited by photon upconversion. The excitation is based on sequential absorption of one photon by the Yb3+ ions followed by the absorption of a second photon and the energy transfer to Er3+ ions emitting the upconversion signal. Due to the contribution of a real metastable level in the Yb3+, excitation rates are much higher than in two-photon absorption processes using a ”virtual” quantum mechanical state1.
Two states emitting around 540 nm are coupled thermally and therefore their intensity ratio is ∝ exp(−Δ E/ kB T). We were able to measure the temperature dependence in the biological interesting region around 300 K of a single nanocrystal. We therefore suggest not only the use of these colloids as stable and high efficient biomarkers, but also their employment as local temperature-sensors on a nanometer scale.
1 W. Krämer et al., Chem. Mater. 16, 1244, (2004)