Frequency-domain method for characterization of upconversion luminescence kinetics

<p><strong>This folder contains all raw data underlying the results presented in a manuscript, submitted to </strong><strong><em>The Journal of Physical Chemistry Letters</em></strong><strong>, and entitled:</strong></p> <p><strong>Frequency-domain method </strong><strong>for </strong><strong>characterization of upconversion luminescence kinetics</strong></p> <p><strong>Authored by:</strong></p> <p>Luc&iacute;a Labrador-P&aacute;ez,^a Jouko Kankare,^b Iko Hypp&auml;nen,^b Tero Soukka,^b,* Elina Andresen,^c Ute Resch-Genger,^c Jerker Widengren,^a Haichun Liu^a,*</p> <p><em>^a</em><em>Department of Applied Physics, KTH Royal Institute of Technology, Stockholm, Sweden. </em></p> <p><em>^b&nbsp;</em><em>University of Turku, Turku, Finland.</em></p> <p><em>^c</em> <em>Federal Institute for Materials Research and Testing (BAM), Berlin, Germany. </em></p> <p>*Corresponding authors: <a href="mailto:haichun@kth.se"><em>haichun@kth.se</em></a><em>; tejoso@utu.fi.</em></p> <p>&nbsp;</p> <p><strong>The data files are grouped according to the different figures in the manuscript where the extracted results are presented.</strong></p> <p>&nbsp;</p> <p><strong>ABSTRACT</strong></p> <p>The frequency-domain (FD) method provides an alternative to the commonly used time-domain (TD) approach in characterizing the luminescence kinetics of luminophores. This method has its own strengths compared to the TD approach, e.g., the capability to decouple multiple lifetime components with higher reliability and accuracy. While extensively explored for characterizing luminophores with a linear emission, the FD method has not been investigated for studying nonlinear luminescent materials such as lanthanide-doped upconversion nanoparticles (UCNPs), featuring more complicated luminescence kinetics. In this work, employing a simplified rate-equation model representing a standard two-photon energy-transfer upconversion process, we thoroughly analysed the response of the upconversion luminescence (UCL) of UCNPs in the FD method in theory. We found that the application of this method can potentially obtain the effective decay rates of three critical energy states of the sensitizer and activator ions involved in the upconversion process, from a single experiment. The validity of the FD method is further demonstrated by experimental data, agreeing reasonably well with the results obtained by TD methods.</p>