- 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.
- Today I'm also synthesizing cysteine-ZnmMnn-mSn quantum dots using the procedure described here.
1. BSA-ZnmMnn-mSn quantum dot prep
Solutions to be made
- Dissolve 4.14g of BSA in 60mL of water (That's 69 mg/mL BSA)
- Add 0.4g NaBH4 (That's 6.7 mg/mL NaBH4)
- Stir until no more bubbles (H2) are generated.
- Note NaBH4 can be dangerous to work with see here and here.
- I will be doing all of the handling of this material until researchers add it to their reactions.
- 100mM Zn(CH3COO)2
- FW = 219.49 g/mol
- V = 50mL
- mass to be measured = 1.0975g
- actual mass = 1.0970g
- actual concentration = 100 mM
- 10mM Mn(CH3COO)2
- FW = 173.02 g/mol
- V = 50mL
- mass to be measured = 0.0865g
- actual mass = 0.0870
- actual concentration = 10.1mM
- 100mM Na2S (Note: paper uses 0.25M)
- FW = 240.18 g/mol
- V = 50mL
- mass to be measured = 1.201g
- actual mass = 1.2060g
- actual concentration = 100mM
- Start preparing a 70C water bath
- Add a stir bar to a 100mL round bottom flask
- Add 1 mL of BSA/NaBH4 to the flask
- Add 2.25mL of Zn stock solution
- Note: Solution will form a white precipitate upon addition of Zn2+
- Add 2.5mL of Mn stock solution
- Adjust the volume to 19mL using 13.25mL of water
- Stir mixture
- Adjust pH of solution to 9 with 1M NaOH
- Note how much NaOH you ultimately use
- Adding NaOH will help dispel the precipitate
- Seal container with a rubber septum
- Bubble N2 through the sample for 20 minutes
- Use the protocol we previously developed
- Add 2.5mL of Na2S solution
- Put the reaction vessel in the water bath and stir for three hours
- 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.
- To a 250mL round bottom is added a stir bar and
- 50mL of 20mM L-cysteine
- 5mL of 100mM ZnSO4 (0.5 mmol)
- 5.437mL of 10.3mM MnCl2 (0.056 mmol)
- This is where the white ppt is observed
- The pH of this mixture is adjusted to 11 with ~1M NaOH
- The solution was added drop wise, and I used between 1.5 and 2.0mL before the ppt disappeared
- After the ppt went back into solution, the pH was close to 11 and I stopped adding NaOH
- This mixture is stirred N2 for 30 minutes (started at 8:46am)
- 5.505mL of 101mM Na2S is quickly added. (started at 9:20)
- The solution is stirred for 20 minutes
- The solution is then aged at 50C under air for 2 hours. (Started at 9:47)
- The nano particles are purified through precipitation by ethanol and centrifuging at 5000rpm for 5 minutes
- That's all they really say about this. I'm assuming it means:
- The reaction mixture is cooled in an ice bath.
- I performed this step for 1 hour as I was busy with other things in lab/office
- At least 200mL of chilled ethanol is added to the reaction mixture to precipitate the solid
- I began chilling this in the freezer as soon as I put the reaction in the 50C water bath.
- I stopped at this point because my QDs did not precipitate out of solution. Will need to contact author. I tried ethanol as well as acetone (as I had seen in other reports)
- I placed the tubes in the freezer
- After about 10 minutes I did notice some precipitate. I'm going to let them ppt longer (overnight and collect them tomorrow).
- The solid is collected by centrifugation (5 minutes at 5000 rpm)
- The solid is re-dissolved in a minimum amount of cold water
- The nanoparticles are precipitated through the addition of cold ethanol
- Steps 4 and 5 are repeated once
- The product is dried under vacuum and the product is stored in an inert environment.
- 0.60mL NaOH and 0.10mL HCL were added in step 8 of the protocol in order to adjust the pH to 9.
Note: Only the protocol for the BSA-ZnmMnn-mSn quantum dot prep was carried out today.
- Once the solution had been adjusted to a pH of 9, the solution was cloudy and had a pale yellow/peach hue.
- Some protein was lost when bubbling N2 through the solution in step 10 because the bubbles of protein came out of the vent.
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