Project Details
Projekt Print View

Nanoengineering of up- and down converting materials to enhance the quantum yield and investigating the effect of the density of photon states on the probability for Förster energy transfer

Applicant Dr. Stefan Fischer
Subject Area Experimental Condensed Matter Physics
Solid State and Surface Chemistry, Material Synthesis
Physical Chemistry of Solids and Surfaces, Material Characterisation
Term from 2014 to 2016
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 263646147
 
Final Report Year 2017

Final Report Abstract

Due to advances in the literature and the obstacles of highly efficient and narrow emitting NIR quantum dots, the focus of this previously proposed project was shifted to innovative synthesis and characterization of lanthanide-based nanocrystals to gain a better structural control of the nanocrystals as well as a deeper understanding of the photo physical properties. The expertise on shelling methods in the Alivisatos lab was used to explore an epitaxial shell growth method using liquid shell precursors. Tuning the injection rate of shell precursors allowed significant control over the growth rate on the different crystal facets which resulted in the fabrication of high quality and monodisperse nanocrystals. Now synthesis of highly luminescent complex anisotropic core/multishell structures are possible which promise interesting optical properties. The shelling method was also used to grow isotropic inert shells with different thicknesses around an optically active upconverting core nanocrystal. Carefully studying the photo physical properties of these core/shell by time-resolved and calibrated photoluminescence enabled the unraveling of the surface quenching rates of all relevant energy levels in Er 3+ and Yb3+. Besides the unprecedented high upconversion quantum yield for 980 nm to visible photons of 4% at 63 W/cm2, the study demonstrated a novel effect called surface quenching enhanced downshifting (SQAD) which results in conversion of 980 nm to roughly 1500 nm photons with quantum yields above 16%. These results will pioneer future studies on surface related quenching processes in lanthanide-based nanomaterials.

Publications

 
 

Additional Information

Textvergrößerung und Kontrastanpassung