Quantum Dot Behavior In The Environment

Non-water-soluble quantum dots (QDs) migrate from an organic phase to an aqueous phase containing natural organic matter, a new study shows (Environ. Sci. Technol., DOI: 10.1021/es8017623). The finding could help researchers better understand how the semiconducting nanoparticles might behave in the environment. QDs feature metal-based semiconductor cores coated with organic ligands and are used in electronics and as imaging agents. But little is understood about the mobility of QDs in waterways. The concern, according to the study’s authors, is that the coatings on the QDs may degrade in water and expose the cores, which are known to harm aquatic organisms at relatively low levels. Diana S. Aga, Sarbajit Banerjee, and colleagues of the State University of New York, Buffalo, dissolved QDs made up of CdSe cores and trioctylphosphine oxide coatings in hexane. They then mixed the solution with creek water or deionized water spiked with humic acid or fulvic acid, which are organic components of soils. Spectroscopy and microscopy results demonstrated that QD migration into water occurred in less than 24 hours—despite the QDs’ hydrophobic coating—and that some metal-ion leaching occurred. Aga says the results indicate a need for more robust QD coatings, which may help to maintain the particles’ structural integrity.