A DNA-Stabilized Ag1812+ Cluster with Excitation-Intensity-Dependent Dual Emission |
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Authors: | Vanessa Rück Mikkel B Liisberg Christian Brinch Mollerup Yanmei He Junsheng Chen Cecilia Cerretani Tom Vosch |
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Institution: | 1. Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark;2. Department of Forensic Medicine, University of Copenhagen, Frederik V's Vej 11, 2100 Copenhagen, Denmark;3. Division of Chemical Physics and NanoLund, Lund University P.O. Box 124, 22100 Lund, Sweden |
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Abstract: | DNA-stabilized silver nanoclusters (DNA-AgNCs) are easily tunable emitters with intriguing photophysical properties. Here, a DNA-AgNC with dual emission in the red and near-infrared (NIR) regions is presented. Mass spectrometry data showed that two DNA strands stabilize 18 silver atoms with a nanocluster charge of 12+. Besides determining the composition and charge of DNA2Ag18]12+, steady-state and time-resolved methods were applied to characterize the picosecond red fluorescence and the relatively intense microsecond-lived NIR luminescence. During this process, the luminescence-to-fluorescence ratio was found to be excitation-intensity-dependent. This peculiar feature is very rare for molecular emitters and allows the use of DNA2Ag18]12+ as a nanoscale excitation intensity probe. For this purpose, calibration curves were constructed using three different approaches based either on steady-state or time-resolved emission measurements. The results showed that processes like thermally activated delayed fluorescence (TADF) or photon upconversion through triplet-triplet annihilation (TTA) could be excluded for DNA2Ag18]12+. We, therefore, speculate that the ratiometric excitation intensity response could be the result of optically activated delayed fluorescence. |
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Keywords: | Excitation Intensity Probe Fluorescence Luminescence Optically Activated Delayed Fluorescence Silver Nanocluster |
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