AU Biomaterials Design Lab:Notebook/Quantum Dots/2014/02/07

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Objective

  1. To prepare for the synthesis BSA-ZnmMnn-mSn quantum dots using the protocol described here. We do not have a subscription to this journal. So ask me for a copy of the paper if you want one.
  2. Today I'm also synthesizing cysteine-ZnmMnn-mSn quantum dots using the procedure described here.

Description

1. BSA-ZnmMnn-mSn quantum dot prep Solutions to be made

  1. BSA/NaBH4
    1. Dissolve 4.14g of BSA in 60mL of water (That's 69 mg/mL BSA)
    2. Add 0.4g NaBH4 (That's 6.7 mg/mL NaBH4)
    3. Stir until no more bubbles (H2) are generated.
      1. Note NaBH4 can be dangerous to work with see here and here.
      2. I will be doing all of the handling of this material until researchers add it to their reactions.
  2. 100mM Zn(CH3COO)2
    1. FW = 219.49 g/mol
    2. V = 50mL
    3. mass to be measured = 1.0975g
    4. actual mass = 1.0970g
    5. actual concentration = 100 mM
  3. 10mM Mn(CH3COO)2
    1. FW = 173.02 g/mol
    2. V = 50mL
    3. mass to be measured = 0.0865g
    4. actual mass = 0.0870
    5. actual concentration = 10.1mM
  4. 100mM Na2S (Note: paper uses 0.25M)
    1. FW = 240.18 g/mol
    2. V = 50mL
    3. mass to be measured = 1.201g
    4. actual mass = 1.2060g
    5. actual concentration = 100mM

Protocol

  1. Start preparing a 70C water bath
  2. Add a stir bar to a 100mL round bottom flask
  3. Add 1 mL of BSA/NaBH4 to the flask
  4. Add 2.25mL of Zn stock solution
    1. Note: Solution will form a white precipitate upon addition of Zn2+
  5. Add 2.5mL of Mn stock solution
  6. Adjust the volume to 19mL using 13.25mL of water
  7. Stir mixture
  8. Adjust pH of solution to 9 with 1M NaOH
    1. Note how much NaOH you ultimately use
    2. Adding NaOH will help dispel the precipitate
  9. Seal container with a rubber septum
  10. Bubble N2 through the sample for 20 minutes
    1. Use the protocol we previously developed
  11. Add 2.5mL of Na2S solution
  12. Put the reaction vessel in the water bath and stir for three hours
  13. Store reaction mixture at 4C until later use.

2. cysteine-ZnmMnn-mSn quantum dot synthesis

Note: Eleni, James, and Andrew ran this procedure yesterday. It took more than 60uL to bring the pH up to 11. While they were changing the pH, a clear precipitate formed in solution. Upon addition of 2 more mL of 1M NaOH, the precipitate dissolved back into solution, and the solution turned an orange'ish color. I also observed the presence of a black precipitate suspended in solution. When I run this today, I'm going to add NaOH drop wise until the original ppt goes away and then check the pH. THESE NOTES PRODUCED BY PROFESSOR HARTINGS

  1. To a 250mL round bottom is added a stir bar and
    1. 50mL of 20mM L-cysteine
    2. 5mL of 100mM ZnSO4 (0.5 mmol)
    3. 5.437mL of 10.3mM MnCl2 (0.056 mmol)
      1. This is where the white ppt is observed
    4. The pH of this mixture is adjusted to 11 with ~1M NaOH
      1. The solution was added drop wise, and I used between 1.5 and 2.0mL before the ppt disappeared
      2. After the ppt went back into solution, the pH was close to 11 and I stopped adding NaOH
  2. This mixture is stirred N2 for 30 minutes (started at 8:46am)
  3. 5.505mL of 101mM Na2S is quickly added. (started at 9:20)
  4. The solution is stirred for 20 minutes
  5. The solution is then aged at 50C under air for 2 hours. (Started at 9:47)
  6. The nano particles are purified through precipitation by ethanol and centrifuging at 5000rpm for 5 minutes
    1. That's all they really say about this. I'm assuming it means:
      1. The reaction mixture is cooled in an ice bath.
        1. I performed this step for 1 hour as I was busy with other things in lab/office
      2. At least 200mL of chilled ethanol is added to the reaction mixture to precipitate the solid
        1. I began chilling this in the freezer as soon as I put the reaction in the 50C water bath.
      3. The solid is collected by centrifugation (5 minutes at 5000 rpm)
      4. The solid is re-dissolved in a minimum amount of cold water
      5. The nanoparticles are precipitated through the addition of cold ethanol
      6. Steps 4 and 5 are repeated once
      7. The product is dried under vacuum and the product is stored in an inert environment.

Data

  • Add data and results here...

Notes

This area is for any observations or conclusions that you would like to note.


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