Photochemistry using Nanomaterials

Charge transfer (CT) is a process wherein the interfacial charge, electron or hole, relocates from a donor to an acceptor. The CT in quantum confined semiconductor nanomaterials have been recognized as a crucial process for light harvesting and solar energy conversion, especially photochemical reactions. Recently, we compared three inorganic surface capping ligands (ICLs) (SnS44–, SbS43– and AsS33–) for the CT process from QDs to metal oxide.(1) In the case of organic capping ligands, the size of ligand (e.g., alkyl chain length) critically governs the carrier dynamics. In contrast, the HOMO LUMO energy levels with respect to the QD bands become very important for ICL-QDs because ICLs can be exempt from the high energy barrier which is quite inherent for organic ligands. Finally, a very efficient charge transfer and collection that exceeds the performance attainable by organic capped QDs can be promised. 

1. J. Am. Chem. Soc. 137, 13827-13835 (2015).

In electrophotochemical reaction, electrochemistry generates reactive species or excited states whose reactivity is enhanced or enabled by light. Cooperatively acting electricity and light can facilitate previously thermodynamically inaccessible or kinetically inert transformations via electron/energy transfer processes. Recently, we demonstrated multistate modulation of QD's PL intensity or energy through the combination of two different quenching pathways of QD and three redox states of Prussian blue (PB).(1) By designing QD-PB composites, we leveraged PB’s electroswitchable properties, where applied voltages control the oxidation state of iron ions within PB. Fe3+ ions can accept electrons from the conduction band of CdSe QDs, whereas Fe2+ ions can accept holes from the valence band of CdSe QDs. Facilitating or impeding charge transfer pathways between QD and PB enables precise control over PL intensity in QDs, as the transfer of charge from QDs leads to PL quenching. This multistate PL modulation will provide a foundation for high-resolution displays and advanced optoelectronic devices.

1. Nano Lett. 25, 11391-11397 (2025).

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