Natural organic matter-mediated phase transfer of quantum dots in the aquatic environment

Imminent commercialization of semiconductor quantum dots (QDs) has raised concerns regarding the potential environmental impact of these materials. Understanding the partitioning behavior and obtaining information on the mobility and persistence of QDs in water is key to evaluating potential ecological hazards posed by QDs in the environment The role of natural organic matter (NOM) in the phase transfer of trioctylphosphine oxide-capped CdSe QDs from an organic solvent to water has been investigated. Results show that humic and fulvic acids, which have been used as model NOM, facilitate the stabilization of organic-capped QDs in water in less than 24 h. Spectroscopic studies indicate that some or all of the organic ligands of QDs are conserved during the phase transfer. The displacement of organic ligands by NOM also appears to play a role in phase transfer. This NOM-mediated phase transfer has also been demonstrated using two natural surface water samples. This study presents the first evidence of the stabilization of QDs in water by humic substances in real environmental samples, illustrating that interactions with NOM will play a significant role in the fate and transport of QDs in natural aquatic systems.