TY - CONF A1 - Muhr, Verena A1 - Würth, Christian A1 - Kraft, Marco A1 - Resch-Genger, Ute A1 - Baeumner, A. J. A1 - Hirsch, Thomas T1 - Lifetime-based FRET Sensing Using Upconverting Nanoparticles T2 - 11th Internatinal Biosensor Conference BBMEC CY - Regensburg DA - 2015-09-28 PY - 2015 AN - OPUS4-34488 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Muhr, Verena A1 - Hermann, C. A1 - Wiesholler, L. M. A1 - Hirsch, Thomas A1 - Baeumner, A. J. A1 - Resch-Genger, Ute T1 - Surface Modification of Upconverting Luminescent Nanoparticles Suitable for Förster Resonance Energy Transfer T2 - Anakon 2015 CY - Graz, Austria DA - 2015-03-23 PY - 2015 AN - OPUS4-33665 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kraft, Marco A1 - Würth, Christian A1 - Muhr, Verena A1 - Hirsch, Thomas A1 - Resch-Genger, Ute T1 - Particle-size-dependent upconversion luminescence of NaYF4: Yb, Er nanoparticles in organic solvents and water at different excitation power densities N2 - A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12–43 nm is presented utilizing steady-state and time-resolved fluorometry. Special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by highenergy O–H and C–H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated Population pathways of the 4F9/2 energy level of Er3+ were examined. Our results Highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Er3+ emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. Because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the 4F9/2 energy level of Er3+, which correlate with the size-, environment-, and P-dependent quenching states of the higher Er3+ energy levels. KW - Quantum Yield KW - Nanoparticle KW - Quenching KW - Upconversion PY - 2018 DO - https://doi.org/10.1007/s12274-018-2159-9 VL - 11 IS - 12 SP - 6360 EP - 6374 PB - Tsinghua Univ. Press CY - Beijing AN - OPUS4-47172 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -