Abstract
Lead selenide quantum dots (QDs) are low-bandgap IV-VI semiconducting nanomaterials that have been studied for a variety of applications. Their preparation using colloidal methods can create small spherical to larger cubic nanocrystals, with an upper limit of ~17 nm reported to date. Here we describe methods for preparing cubic PbSe nanocrystals over a 20–40 nm size range using a twostep procedure. Specifically, ~10 nm PbSe QDs are generated using the rapid injection method, the products from which are overcoated with additional lead and selenium precursors. The use of two lead reagents were studied; lead oleate resulted in a maximum of 20 nm cubes, while more reactive lead hexyldecanoate resulted in much larger nanomaterials with bulk bandgaps. However, PbSe samples prepared with lead hexyldecanoate also contained agglomerates. Special care must be taken when characterizing larger strained nanomaterials with X-ray powder diffraction, for which the Scherrer equation is inadequate. A more rigorous approach using the Williamson–Hall method provides characterizations that are consistent with electron microscopy analysis.
Highlights
Quantum dots (QDs) are nanoscale particles that have size-tunable optoelectronic properties that may differ substantially from their bulk counterparts
We explored the use of lead acid precursors of varying reactivity, which resulted in the development of two protocols to produce cubic PbSe QDs over a 20–40 nm in size range
Large 20–40 nm cubic-shaped PbSe colloidal nanocrystals were synthesized from “core” PbSe QDs that were overcoated with additional lead and selenium precursors
Summary
Quantum dots (QDs) are nanoscale particles that have size-tunable optoelectronic properties that may differ substantially from their bulk counterparts. Method (2) Excess Ligand Condition Another set of PbSe QDs were prepared following the same procedure above with excess ligand present in the lead precursor/ODE solution. The preparation of magic-sized PbSe QDs was attempted using lead hexyldecanoate as above, with the exception that the solution was maintained at room temperature for a 24 h growth period.
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