Cadmium-containing
quantum dot (QD) nanoparticles are integrated
into electronic displays because of their ability to efficiently convert
colors. There are conflicting accounts as to whether these particles
present a hazard to the environment, as they have been studied either
as (1) embedded QDs in display screen films or (2) as model QDs with
small, hydrophilic ligands. Both approaches have limitations that
we addressed by synthesizing QDs featuring the core–shell structure
and the thick polymer coating present in commercial devices to probe
the dissolution of QDs in response to two environmental factors (pH
and dissolved oxygen) over 1 day and 6 months. Results show that QDs
were chemically stable at circumneutral pH (0% Cd dissolution after
6 months), but low pH initiated rapid dissolution under both aerobic
and anaerobic conditions (up to 100% Cd dissolution after 6 months).
In addition to the presence of a capping polymer, the QD shell structure
led to more chemically stable nanoparticles compared to nonshelled
QDs, as the presence of ZnS shells decreased Cd dissolution by 75%.
The dense aggregation of QDs into structures of ∼100 nm diameter
over time was observed as well, which could lead to decreased bioavailability.
To test this, we used liver cells to compare the toxicity of pristine
QDs to those subjected to acid dissolution. Our results reveal that
low-pH-exposed QDs separated from dissolved ions are less toxic than
pristine QDs (half maximal inhibitory concentration, IC50, of 290 and 150 mg/L, respectively) and suggest a key role of dissolved
ions and capping polymers for QD toxicity. These findings highlight
the use of a commercially relevant nanoparticle structure to demonstrate
fate and toxicity.
Cadmium-containing quantum dot nanoparticles (QDs) are integrated into electronic displays because of their ability to efficiently convert colors. There are conflicting accounts as to whether these particles present a hazard to the environment, as they have been chloroform. Samples were run on Bruker AVIIIHD 500 MHz NMR spectrometer.
Cadmium-containing quantum dot nanoparticles (QDs) are integrated into electronic displays because of their ability to efficiently convert colors. There are conflicting accounts as to whether these particles present a hazard to the environment, as they have been studied either as (1) embedded QDs in display screen films or (2) as model QDs with small, hydrophilic ligands. We synthesized QDs featuring the core-shell structure and the thick polymer coating present in commercial devices, to probe their fate under low pH conditions. The role of dioxygen was also explored in this context. We also used liver cells to compare the toxicity of pristine QDs to those subjected to acid dissolution.
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