TY - JOUR A1 - Radunz, Sebastian A1 - Schavkan, A. A1 - Wahl, Sebastian A1 - Würth, Christian A1 - Tschiche, H. R. A1 - Krumrey, M. A1 - Resch-Genger, Ute T1 - Evolution of Size and Optical Properties of Upconverting Nanoparticles during High-Temperature Synthesis T2 - Journal of physical chemistry C N2 - We investigated the growth of β-phase NaYF4:Yb3+,Er3+ upconversion nanoparticles synthesized by the thermal decomposition method using a combination of in situ and offline analytical methods for determining the application-relevant optical properties, size, crystal phase, and chemical composition. This included in situ steady state luminescence in combination with offline time-resolved luminescence spectroscopy as well as small-angle X-ray scattering (SAXS) transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and inductively coupled Plasma optical emission spectrometry (ICP-OES). For assessing the suitability of our optical monitoring approach, the in situ-collected spectroscopic data, which reveal the luminescence evolution during nanocrystal synthesis, were compared to measurements done after cooling of the reaction mixture of the as-synthesized particles. The excellent correlation of the in situ and time-resolved upconversion luminescence with the nanoparticle sizes determined during the course of the reaction provides important insights into the various stages of nanoparticle growth. This study highlights the capability of in situ luminescence monitoring to control the efficiency of UCNP synthesis, particularly the reaction times at elevated temperatures and the particle quality in terms of size, shape, and crystal structure, as well as luminescence lifetime and upconversion quantum yield. PB - American Chemical Society CY - Washington, DC KW - Rare earth nanoparticles KW - Upconversion KW - TEM KW - SAXS PY - 2018 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/47169 AN - OPUS4-47169 UR - https://pubs.acs.org/doi/pdf/10.1021/acs.jpcc.8b09819 VL - 50 IS - 122 SP - 28958 EP - 28967 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany