Journal
NANOMATERIALS
Volume 13, Issue 14, Pages -Publisher
MDPI
DOI: 10.3390/nano13142075
Keywords
quantum dots; transition metal dichalcogenide; quantum confinement; photoluminescence; optical property
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This study demonstrates that oxidation effect prevails over quantum confinement in metallic-phase transition metal dichalcogenide quantum dots when their size is larger than the exciton Bohr radius.
Metallic-phase transition metal dichalcogenide quantum dots (TMDs-mQDs) have been reported in recent years. However, a dominant mechanism for modulating their intrinsic exciton behaviors has not been determined yet as their size is close to the Bohr radius. Herein, we demonstrate that the oxidation effect prevails over quantum confinement on metallic-phase tungsten dichalcogenide QDs (WX2-mQDs; X = S, Se) when the QD size becomes larger than the exciton Bohr radius. WX2-mQDs with a diameter of similar to 12 nm show an obvious change in their photophysical properties when the pH of the solution changes from 2 to 11 compared to changing the size from similar to 3 nm. Meanwhile, we found that quantum confinement is the dominant function for the optical spectroscopic results in the WX2-mQDs with a size of similar to 3 nm. This is because the oxidation of the larger WX2-mQDs induces sub-energy states, thus enabling excitons to migrate into the lower defect energy states, whereas in WX2-mQDs with a size comparable to the exciton Bohr radius, protonation enhances the quantum confinement.
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