AI Article Synopsis
- During photon upconversion, quantum dots transfer energy to molecules but their long ligand shells create a barrier that affects efficiency.
- Experimental measurements reveal that shorter ligands (less than 8 carbons) significantly enhance energy transfer, achieving a 6.9% upconversion quantum yield, while longer ligands yield only 0.01%.
- This research highlights the importance of ligand length in optimizing quantum dot-based photosensitizers for improved performance in catalysis and energy conversion.
Article Abstract
During photon upconversion, quantum dots (QDs) transfer energy to molecules in solution through a long ligand shell. This insulating ligand shell imparts colloidal stability at the expense of efficient photosensitization. For the first time, we quantify the barrier these aliphatic ligands pose for triplet energy transfer in solution. Using transient absorption spectroscopy, we experimentally measure a small damping coefficient of 0.027 Å for a ligand exceeding 10 carbons in length. The dynamic nature of ligands in solution lowers the barrier to charge or energy transfer compared to organic thin films. In addition, we show that surface ligands shorter than 8 carbons in length allow direct energy transfer from the QD, bypassing the need for a transmitter ligand to mediate energy transfer, leading to a 6.9% upconversion quantum yield compared with 0.01% for ligands with 18 carbons. This experimentally derived insight will enable the design of efficient QD-based photosensitizers for catalysis and energy conversion.
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| http://dx.doi.org/10.1021/acs.jpclett.2c00514 | DOI Listing |
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