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
Solid State and Surface Chemistry, Material Synthesis
Physical Chemistry of Solids and Surfaces, Material Characterisation
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
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(2017) Optical nanoprobes for biomedical applications: shining a light on upconverting and near-infrared emitting nanoparticles for imaging, thermal sensing, and photodynamic therapy. Journal of materials chemistry. B 5 (23) 4365–4392
Hemmer, E.; Acosta-Mora, P.; Méndez-Ramos, J.; Fischer, S.
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Enhanced Upconversion Quantum Yield near Spherical Gold Nanoparticles – a Comprehensive Simulation Based Analysis. Opt. Express 2016, 24, A460–A475
Fischer, S.; Kumar, D.; Hallermann, F.; von Plessen, G.; Goldschmidt, J. C.; Plessen, G. Von; Goldschmidt, J. C.
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Enhancing Quantum Yield via Local Symmetry Distortion in Lanthanide-Based Upconverting Nanoparticles. ACS Photonics 2016, 3, 1523–1530
Wisser, M. D.; Fischer, S.; Maurer, P. C.; Bronstein, N. D.; Chu, S.; Alivisatos, A. P.; Salleo, A.; Dionne, J. A.
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Precise Tuning of Surface Quenching for Luminescence Enhancement in Core–Shell Lanthanide-Doped Nanocrystals. Nano Lett. 2016, 16, 7241–7247
Fischer, S.; Bronstein, N. D.; Swabeck, J. K.; Chan, E. M.; Alivisatos, A. P.
