Photocatalytic carbon disulfide production via charge transfer quenching of quantum dots

Carbon disulfide, a potentially therapeutic small molecule, is generated via oxidative cleavage of 1,1-dithiooxalate (DTO) photosensitized by CdSe quantum dots (QDs). Irradiation of DTO-QD conjugates leads to λ(irr) independent photooxidation with a quantum yield of ~4% in aerated pH 9 buffer solution that drops sharply in deaerated solution. Excess DTO is similarly decomposed, indicating labile exchange at the QD surfaces and a photocatalytic cycle. Analogous photoreaction occurs with the O-tert-butyl ester (t)BuDTO in nonaqueous media. We propose that oxidation is initiated by hole transfer from photoexcited QD to surface DTO and that these substrates are a promising class of photocleavable ligands for modifying QD surface coordination.