From Light to Dark: Dancing with Electrons in Colloidal 2D MoS₂ Nanosheets

Extending the lifetime of photogenerated electrons in semiconductor systems is an important criterion for the conversion of light into storable energy. We have now succeeded in storing electrons in a photoirradiated colloidal molybdenum disulfide (MoS2) suspension, showcasing its unique reversible photoresponsive behavior. The dampened A and B excitonic peaks indicate the accumulation of photogenerated electrons and the minimization of interactions between MoS2 interlayers. The stored electrons were quantitatively extracted by titrating with a ferrocenium ion in the dark, giving ca. 0.2 electrons per MoS2 formula unit. The emergence of the photoinduced A1g* Raman mode and the decrease in zeta potential after irradiation suggest intercalation of counterions to maintain overall charge balance upon electron storage. These results provide insights into the mechanism of photogenerated electron storage in 2D materials and pave the way for the potential application of colloidal 2D materials in electron storage.