This procedure separates CdSe quantum dot nanoparticles from the solvent in which they were prepared.
- Wear eye protection
- Chemical gloves required
Step 1. Transfer the octadecene CdSe quantum dot suspension to a micro centrifuge tube. Add 100% ethanol. Cap.
Step 2. Shake to get an emulsion.
Step 3. Add a matched tube and the freshly shaken sample tube to opposite sides of a centrifuge, or use an even number of sample tubes. Spin at 3000 rpm for 5 minutes.
Step 4. Carefully remove the ethanol layer. An oil often appears in the pipet tip. Option: obtain the infrared spectrum of the oil.
The removed ethanol solution is cloudy.
Step 5. Add a second ethanol wash.
Step 6. Shake to mix and immediately repeat the centrifuge step.
Step 7. Carefully remove the ethanol.
Step 8. Add a third ethanol wash.
Step 9. When shaking no longer gives a suspension then further centrifugation is not needed.
Step 10. Pour off the ethanol.
- Different size quantum dots isolated by the same procedure.
- The quantum dots can be resuspended in an organic solvent (chloroform was used here.)
- Suspensions of different size quantum dots in an organic solvent (chloroform was used here.)
Observe the resuspended quantum dots under long wave UV light (hexane was used as the solvent.)
- What is the identity of the oil that is removed from the quantum dots? How do you know?
- What is the absorption wavelength or color of the quantum dots you isolated?
- How can CdSe exhibit so many different colors?
CAUTION: Avoid physical contact with cadmium selenide since cadmium compounds are carcinogens. If chloroform is used avoid contact or inhalation since it is a likely human carcinogen
- CdSe quantum dots in octadecene (preparation)
- 100% Ethanol
- Hexane (or chloroform)
- microcentrifuge and tubes
- Pasteur pipets and bulbs
- UV light source