Fluorophores functionalized with heavy elements show enhanced intersystem crossing due to increased spin-orbit coupling, which in turn shortens the fluorescence decay lifetime (τPL). This phenomenon is known as the heavy-atom effect (HAE). Here, we report the observation of increased τPL upon functionalisation of near-infrared photoluminescent gold nanoclusters with iodine. The heavy atom-mediated increase in τPL is in striking contrast with the HAE and referred to as inverse HAE. Femtosecond and nanosecond transient absorption spectroscopy revealed overcompensation of a slight decrease in lifetime of the transition associated with the Au core (ps) by a large increase in the long-lived triplet state lifetime associated with the Au shell, which contributed to the observed inverse HAE. This unique observation of inverse HAE in gold nanoclusters provides the means to enhance the triplet excited state lifetime.

EMAT University of Antwerp Groenenborgerlaan 171 B 2020 Antwerp Belgium

Faculty of Mathematics and Physics Charles University Ke Karlovu 3 121 16 Prague 2 Czechia

Institute of Macromolecular Chemistry of the CAS Heyrovsky Sq 2 162 06 Prague 6 Czechia

Institute of Macromolecular Chemistry of the CAS Heyrovsky Sq 2 162 06 Prague 6 Czechia and Faculty of Mathematics and Physics Charles University Ke Karlovu 3 121 16 Prague 2 Czechia

Institute of Organic Chemistry and Biochemistry of the CAS Flemingovo nam 2 166 10 Prague 6 Czechia

Nanoscale. 2021 Jul 8;13(26):11576. doi: 10.1039/d1nr90138a. PubMed

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