Reversible photo- and thermal-effects on the luminescence of gold nanoclusters: implications for nanothermometry

0543095 - ÚOCHB 2022 RIV GB eng J - Journal Article
Valenta, J. - Greben, M. - Pramanik, Goutam - Kvaková, Klaudia - Cígler, Petr
Reversible photo- and thermal-effects on the luminescence of gold nanoclusters: implications for nanothermometry.
Physical Chemistry Chemical Physics. Roč. 23, č. 20 (2021), s. 11954-11960. ISSN 1463-9076. E-ISSN 1463-9084
R&D Projects: GA ČR(CZ) GA18-12533S
Institutional support: RVO:61388963
Keywords : state quantum yields * nanocrystals * fluorescence
OECD category: Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect)
Impact factor: 3.945, year: 2021
Method of publishing: Limited access
https://doi.org/10.1039/D0CP06467J

The optical properties of colloidal near-infrared (NIR) emitting gold nanoclusters (AuNCs) are thoroughly investigated at variable temperatures and excitation powers. Both absorption and photoluminescence (PL) excitation spectra reveal optical transitions expected from literature models of thiolated AuNCs – with the exception of the lowest energy transition which has the form of a featureless absorption tail partially overlapping with the PL band. The absorption cross section is determined via the PL saturation and PL modulation techniques to be in the range of 2–3 × 10−14 cm2 for excitation at 405 nm (relatively large value for such small clusters) and decreases ∼20 times toward 633 nm. Slow transient quenching (perfectly reversible) of PL is observed when the excitation power exceeds the saturation threshold, i.e. when the probability of achieving the second absorption in an excited AuNC before its relaxation is significant. A stable PL quenched level is reached within a fraction of a minute or a few minutes after the start of the excitation. Similar time intervals are needed for AuNCs to relax back to the original state in the dark. By comparing thermally-induced and light-induced PL decreases and PL kinetics speed up, we conclude that the transient quenching is due to heating caused by the dissipated excitation power. The light-induced PL amplitude reduction is much stronger (up to ∼80% under 405 nm, 60 W cm−2 excitation) than changes in PL decay time (∼20%), which is due to PL blinking and PL switching-off in a fraction of the AuNC ensemble. The potential application of these AuNCs in nanothermometry is discussed.
Permanent Link: http://hdl.handle.net/11104/0320383