Coating with Zinc Sulfide Shell
APPARATUS
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Weighing Scale
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Magnetic Stirrer
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Heating Mantle
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3-Neck Flask
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Micropipette
MATERIALS
PROCEDURE
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2ml of Sulfur Precursor solution was prepared by dissolving Sulfur in a solution of Octadecene and Oleylamine (in a 10/1 ratio) to form a 0.1 M solution.
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3 mL of Zinc Precursor solution was prepared by dissolving Zinc Stearate in 3 ml of Octadecene to form a 0.1 M solution.
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The two precursor solutions were injected into the reaction chamber in three batches with a time interval of 15 min at 150 degrees Celsius. This was to ensure even coating of the Copper Indium Sulfide Cores with a Zinc Sulfide shell.
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The temperature was then increased to 220 degrees Celsius.
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Thereafter, the reaction was allowed to proceed for another 60 minutes.
VIDEO
This video depicts the addition of one batch of the Precursors into the reaction mixture. The white suspension is the Zinc Precursor while the yellow one is the Sulfur Precursor.
The next two batches of Precursors are then added in at an interval of 15 minutes before the temperature is increased to 220 degrees Celsius for an hour.
***Note: At this point, the quantum dots are not just coated with zinc sulfide, but are covered in a hydrophobic layer of trioctylphosphine oxide (TOPO).