Interplay between a heptamethine cyanine dye sensitizer (IR806) and lanthanide upconversion nanoparticles

This folder contains all raw data underlying the results presented in a manuscript, submitted to Angewandte Chemie, and entitled:Interplay between a heptamethine cyanine dye sensitizer (IR806) and lanthanide upconversion nanoparticlesAuthored by:Haichun Liu1, Abhilash Kulkarni1, Uliana Kostiv1, Elin Sandberg1, Anbharasi Lakshmanan1, Georgios A. Sotiriou2, Jerker Widengren1,*1 Department of Applied Physics, KTH Royal Institute of Technology, Roslagstullsbacken 21, SE-106 91, Stockholm, Sweden2Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77, Stockholm, SwedenCorresponding author:*[email protected] data files containing raw data and results of the analysis are grouped according to the different figures in the manuscript where the extracted results are presented.ABSTRACTLanthanide-doped upconversion nanoparticles (UCNPs) have attractive emission properties but suffer from weak light-absorbing capacities and thereby relatively low brightnesses. This motivates using strongly absorbing dye molecules as antennas and sensitizers. However, despite much effort, understanding of this dye-UCNP interplay is still limited. Major sensitization mechanisms are still under discussion, largely because there is a lack of effective means to observe key factors such as dark state transitions within the dyes. Here, we established a combined spectroscopic procedure to systematically investigate the photophysics behind the dye-UCNP interaction, embracing fluorescence-based transient-state excitation-modulation, lifetime and correlation spectroscopy, and spectrofluorometry/spectrophotometry. With this procedure we studied the heptamethine cyanine dye IR806, a typical UCNP sensitizer, established its photophysical model, deciphered its photophysics in UCL-sensitization-related environments and could identify energy transfer from the IR806 singlet excited state to Yb3+ (UCNP sensitizer ion) as the dominant sensitization mechanism. Our studies suggest that IR806 can form non-emissive H-aggregates at the nanoparticle surfaces, which can be dissociated after certain light excitation duration (typically>100µs). Moreover, buildup of a non-fluorescent, photo-redox state of IR806 after longer irradiation times (10–100ms) can deleteriously affect its UCL sensitization, inferring an optimal excitation duration for dye-sensitized UCNPs, relevant for e.g. optical imaging applications.