I have CdSe/ZnS quantum dots with oleic acid ligand in hexane solvent. As synthesized quantum dots were purified with excess of methanol and acetone in a centrifuge. I wish to isolate the quantum dots in powder form to re-disperse in hexane at a concentration of 10 mg/ml.
I tried to evaporate the solvent by heating the quantum dot dispersions above the boiling point of hexane, but I ended up with a sticky precipitate of quantum dots.
You should do with the reduced pressure machine when you let your QDs precipitate with acetone.
If you don't want to spoil the dispersibility of your QDs, you better think about exchanging the solvent without going through the dry state. If hexane is not miscible with the solvents you have in the beginning, try to go through some intermediate by centrigugation, decantation of supernatant liquid and adding the solvent of choice several times.
Try to suck the solvent of this sticky material using vacuum suction pump
@Kubrin: Thank you. I believe most of the solvent (Octadecene) that I used during synthesis is removed during purification steps. Currently the nanocrystals are fully dispersed in Hexane (Hopefully free of by products and unreacted precursors). How do I extract and re disperse the nanocrystals in hexane to get a final QD concentration of 10 mg/ml in hexane?
Weigh a clean vial, add a few millilitres of the QD solution in hexane, remove the hexane by drying with nitrogen (insert two needles into the vial lid and have nitrogen flowing in via one, solvent vapour will come out the other). When all the solvent is gone re-weigh the vial and calculate the mass of QDs by difference, and disperse in the appropriate volume of hexane.
Try with rota vapor pump to concentrate your sample, because you can concentrate your liquid samples at low temperature by increasing the vacuum.
You can use from reduse of SeO2 with NaBH4 on the glovbox of Ar gas and SILAR procces
The paper below is about cleaning alloy CdSe/S nanocrystals, however they are capped with oleic acid, and they are precipitated as a pellet. You need to use a mixture of butanol and ethanol for the precipitation, and then collect with centrifguation. The procedure is described on page 3 of the paper. I hope this helps.
Read this article you can know how we were able to synthesize high quality CdSe Nanocrystals and then prepared pn junctions using them.
Article Enhanced photocurrent in solution processed electronically c...
Dear Dr.Vasan, could I ask what was the solution for your case? Until the end, could you get the powder form of QDs from OA ligands? Ramesh Vasan
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