Things You Need0.32g Cadmium Myristate0.06g Selenium Dioxide

10 mL OctadeceneRound Bottom Flask

Heating Mantle and a Variac400oC Thermometer8 Small Test Tubes

Pasteur PipetteGoggles and Gloves

Step 1: The Reactants

•gloves and goggles on

•0.32 g Cadmium Myristate

•0.06 g Selenium Dioxide

•10 mL OctadeceneIn here!

In fume hood

Step 2: Fume Cupboard• place flask in mantle but do not turn the

mantle on

• Connect the mantle to the variac and plug the variac in and make sure the variac is turned off

• place flask into the mantle in the fume hood

• set up test tubes and pasteur pipette next to the mantle

Step 3: Ready Set Go!• Turn on the variac and turn the dial to HI or MAX and PAY ATTENTION

• Once the temperature gets to about 140oC reduce the power to the mantle by turning down the variac so that the temperature rises slowly (say 2oC/min)

• Try to let the highest temperature be 200oC

• NEVER LET THE TEMPERATURE EXCEED 210oC - if it starts getting to that temperature turn off the variac and remove the flask from the mantle to prevent charring of the reaction mixture

• When the reaction mixture starts changing color withdraw some of the mixture with the pipette (1/2 mL is enough) into one of the test tubes

• Collect 6-8 samples of varying color from white to red (see below)

• When color goes as dark as the last test tube on the right turn off the mantle, remove the thermometer and raise the flask out of the mantle

Things You Need for Getting Spectra

•Hot Plate

•400 mL Beaker

•8 small test tubes

•Plastic Pipettes

•50 mL Hexane or Toluene

•PC / UV-Vis Spectrometer

Step 4: Solubilize QDs

• Take 1/2 mL of your QD solution

• Add 3-4 mL hexane or toluene

• Place test tube in hot water bath at 75oC

• QD should dissolve and make a clear solution

• If it doesn’t take 1mL of the solution and place it in a new test tube and add more of toluene and reheat

Step 5: Record Spectra• Connect the USB Vernier UV/VIS

spectrometer

• Start LoggerPro

• Calibrate the Spectrometer with the solvent (toluene or hexane) in a small test tube NOT THE PLASTIC CUVETTES THAT COME WITH THE SPECTROMETER

• Record the Absorbance vs. wavelength spectra for the solubilized samples, by placing these samples in their test tubes into the spectrometer

Step 5: Interpret SpectraFor absorption the energy of the photon has to equal the difference in energy between the ground state and the conduction state

In a quantum dot an electron is excited into one of the confinement states in the conduction band leaving a hole in the valence band where it started. The difference in energy between the hole and the excited electron is equal to the photon that is absorbed

Many transitions are possible ….

Step 5: Interpret Spectra

Many transitions are possible and so we end up with a complicated spectrum

electron starts here

ends up here

Transition seen here

Step 5: Interpret Spectra

While it is hard to identify every transition we can identify the lowest energy transition (highest wavelength) and this depends on the radius R of the QD

Step 5: Interpret Spectra

By identifying the highest wavelength transition we can use the equation to estimate the radius R of the dot

Step 6: Model the Spectra