Wide spread usage of engineered metallic nanoparticles within consumer products has evoked a need to assess their fate within environmental systems. Quantum dots (QDs) are mixed-metal semiconductor nanocrystals with unique and tunable optical properties that readily leach heavy metal cations in water. QDs distinctive properties including bright fluorescence, wide absorbance range, narrow emission spectrum and size dependent emission may lead to unique reactivity when released into the environment, compared to the more homogeneous lattice structures of naturally-occurring bulk metal sulfide or selenide minerals. The goal of this work is to examine dissolution kinetics and mechanisms of QDs relevant to natural surface waters. This work uses a systematic approach to understand dissolution mechanism of mercaptopropionic acid capped CdSe/ZnS QDs in an aqueous environment in both dark and the light conditions. QD suspensions were prepared in different water conditions and release of Zn and Cd cations as well as production of reactive oxygen species in light were monitored over a time. Results from dark experiments show that detachment of capping ligand as well as shell and core solubility in the environment play important roles in QD dissolution. Preliminary results from light experiments show that super oxide and hydrogen peroxide to be involved in the QD dissolution. Presence of other compounds like nitrate, iron, and NOM was observed to change dissolution kinetics. QD properties (e.g., size, band gap) were investigated and it was shown that smaller QDs leach heavy core metals faster than larger QDs. Results obtained from this study benefits the understanding of fate and transformation of QDs in environmentally relevant low concentrations.

Factors influencing quantum dot dissolution kinetics and mechanism

254th National Meeting (2017)

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