A combination of picosecond and microsecond transient absorption dynamics reveals the involvement of two mechanisms by which substituted 1,4-benzoquinone derivatives (BQs) induce decay of the excited state of PbS quantum dots (QDs): (i) electron transfer to BQ molecules adsorbed to the surfaces of PbS QDs and (ii) collisionally gated electron transfer to freely diffusing BQ. Together, these two mechanisms quantitatively describe the quenching of photoluminescence upon addition of BQ to PbS QDs in solution. The fraction of the QD ensemble that participates in each mechanism depends on the number, size, and electron-donating character of the BQ substituents. This work represents the first quantitative study of QD-ligand systems that undergo both adsorbed and collisionally gated photoinduced charge transfer, and reveals the relative contributions of electronic driving force and steric factors to a molecule's ability to extract charge from a photoexcited QD and the mechanism by which this charge transfer occurs.

Dual-timescale photoinduced electron transfer from PbS quantum dots to molecular acceptors

245th National Meeting (2013)

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