Statistical analysis of photoluminescence decay kinetics in quantum dot ensembles: Effects of inorganic shell composition and environment

Discerning the kinetics of photoluminescence (PL) decay of packed quantum dots (QDs) and QD-based hybrid materials is of crucial importance for achieving their promising potential. However, the interpretation of the decay kinetics of QD-based systems, which usually are not single-exponential, remains challenging. Here, we present a method for analyzing photoluminescence (PL) decay curves of fluorophores by studying their statistical moments. A certain combination of such moments, named as the n-th order moments’ ratio, Rn, is studied for several theoretical decay curves and experimental PL kinetics of CdSe quantum dots (QDs) acquired by time-correlated single photon counting (TCSPC). For the latter, three different case studies using the Rn ratio analysis are presented, namely, (i) the effect of the inorganic shell composition and thickness of the core–shell QDs, (ii) QD systems with Förster resonance energy transfer (FRET) decay channels, and (iii) system of QDs near a layer of plasmonic nanoparticles. The proposed method is shown to be efficient for the detection of slight changes in the PL kinetics, being time-efficient and requiring low computing power for performing the analysis. It can also be a powerful tool to identify the most appropriate physically meaningful theoretical decay function, which best describes the systems under study.
Funding from the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Financing UID/FIS/04650/2020 is acknowledged. V.K. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement 101025664 (QESPEM). Y.P.R. acknowledges funding from the Basque Government for Consolidated groups of the Basque University (Grant IT 1526-22) and Basic and/or Applied Research Projects (Grant PIBA-2021-0026). Part of this work dealing with the synthesis of CdSe/ZnS and CdSe/ZnS/CdS/ZnS quantum dots was supported by the Russian Science Foundation (Grant 18-19-00588).