Heterostructures of semiconductors can fulfill a wide variety of applications, such as photoelectrochemical (PEC) water splitting. Specifically, heterostructures comprised of quantum dots (QDs) and molybdenum disulfide (MoS2) nanoplatelets have demonstrated potential as architectures for PEC water splitting and hydrogen generation. Linker-assisted assembly (LAA) is a promising alternative to other synthetic methods, such as successive ionic layer adsorption and reaction (SILAR), as LAA allows the charge transport properties of the heterostructures to be tuned based on the ligand used. Previous work on QD/MoS2 heterostructures using cysteine as the linker exhibited rapid electron transfer from the QDs to MoS2 due to the type-II energetics. This work focuses on probing the effects of different linker lengths on the rates of charge transfer, photocurrent production, and PEC H2 generation. The QD/MoS2 heterostructures produced oxidative photocurrent, demonstrated PEC and photocatalytic hydrogen generation, and exhibited dynamic quenching in time-resolved emission experiments compared to the QD controls. Mercaptoalkanoic acid ligands, ranging from 3 to 16 carbon atoms, were used to attach the QDs to MoS2. We hypothesized that as the alkyl chain length of the ligand increases, the rate of electron transfer will decrease due to the increased spatial separation between the components. The electron transfer rate constants for the heterostructures with increasing alkyl chain length exhibited a 10- to 1000-fold decrease, within the band edge and trap state emission bands, respectively. Increasing the length of the ligand also corresponded to an approximate 4-fold decrease in the net amount of oxidative photocurrent produced for the heterostructures. These results highlight the ability to tune the rate of charge transfer in semiconductor heterostructures by changing the ligand used to attach the components providing insight with moving forward to create architectures for PEC water splitting.

Heterostructures of cadmium chalcogenide quantum dots and MoS2 nanoplatelets prepared by linker-assisted assembly: Influence of ligand properties on excited-state charge transfer and photocatalysis

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.