Haitian Scientific Society 2021 Seminar Series

Photo-induced Charge Transfer from Colloidal Quantum Dots to Molecular Acceptors, Applications in Photocatalysis

Kedy Edmé, PhD
(Cours Privés Edmé Port-au-Prince Haïti)


Colloidal Quantum dots (QDs) are nanocrystals consisting of an inorganic semiconductor core functionalized with organic ligands. Through simple size modifications, we can tune their light absorption properties, as well as their ability to accommodate multiple molecular substrates on their surfaces. These combined properties have inspired several research efforts to investigate the light-induced transfer of electrons from QDs to molecular catalysts to generate solar fuels. Chemical generation of solar fuels, such as the production of hydrogen gas (H2) from water, employ small molecules that require multiple electrons to catalyze the transformation of interest. My research has fundamentally elucidated the light-induced transfer of multiple electrons to small molecules adsorbed on the surface of QDs. I have shown that sequentially accumulating electrons onto a molecular acceptor can be hindered by the first electron transfer process as it generates trapping sites, which prevent the second electron from reaching the acceptor. In a collaboration, we have shown that it was possible to carry out the accumulation of two electrons from photoexcited QDs to a surface-bound molecule within a single photoexcitation event. We demonstrated that the dimeric structure of the molecule was instrumental in allowing the electron to hop between the two fragments of the molecule thereby generating a long-lived singly-reduced species. This feature provided enough time for the second electron to further reduce the molecule. Furthermore, the dimeric structure allowed for a reduction in the charge repulsion associated with accepting two electrons, which also led to a long-lived doubly reduced species. This talk will first introduce the required components to build an artificial photosynthetic system, and will explore how QDs are an important class of photosensitizers, and understanding their photophysical properties is essential to conceive efficient solar-energy conversion apparatus.

Biographical Sketch:


Date and time:

Saturday, May 29, 2021
12:45 PM—2:30 PM

Zoom Meeting Link: