User:Nicole Bonan/Notebook/Quantum Dots/2014/03/28

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Objective

  1. Analyze fluorescence of quantum dots in solutions made last week
  2. Synthesize Mn-doped ZnS quantum dots using a slightly modified version of the synthesis described here

Description

Synthesis Protocol for Mn-doped ZnS nanocrystals with an Mn:Zn ratio of 1:7.5 and a final (Zn+Mn) concentration of 0.4mM

  1. Add 176μL of 5mM Zn(CH3COO)2 to two separate test tubes
  2. Add 24μL of 5mM Mn((CH3COO)2) to each test tube
  3. Add 200μL of 40mM NH4CH3COO to each test tube
  4. Add 244μL of 1.00mg/mL protein to each test tube
  5. Add 250μL of 10mM NH4OH to each test tube
    1. This should bring the pH up to 8.2. Check on this with a pH strip
  6. Bring the volume in each test tube up to 2.5mL with water (Add 1606μL of water)
  7. Incubate at room temperature for 1 hour
  8. Add 200μL of 5mM Na2S to each test tube
    1. When you add this add it drop wise (as best as you can) while vigorously shaking the test tube.
  9. Incubate one test tube at 80C and the other at 37C for 4 hours.

Observations and Data

Figure 1: Quantum Dots Fluorescence Data

alt text

The chart above showed the observations made of last week's quantum dot solutions under a UV light. Each column is a different solution (labeled at the top) and each row is a different concentration of manganese in the quantum dot solution.

From the observations made of the quantum dots under the UV light, blue quantum dots were almost always in solution while orange quantum dots were almost always out of solution. Orange dots seemed to appear when the concentration of manganese was higher and blue quantum dots seemed to appear when the concentration was lower, but this was not always the case. There didn't seem to be a major pattern for the appearance of orange vs. blue dots, so more dots were synthesized this week in order to do further research. One hypothesis for the appearance of blue vs. orange dots was that the protein that was helping to bind the manganese to the ZnS core was denatured or detached from the dots in cases where the dots fluoresced blue, but we're not sure why.

Stock Solutions for This Week's Quantum Dot Synthesis

All solutions are made in 250mL volumetric flasks.

  1. 5mM Zn(CH3COO)2
    1. FW = 219.49 g/mol
    2. V = 250mL
    3. mass to be measured = 0.274g
    4. actual mass = 0.274g
    5. actual concentration = 5mM
  2. 5mM Mn(CH3COO)2
    1. FW = 173.02 g/mol
    2. V = 250mL
    3. mass to be measured = 0.216g
    4. actual mass = 0.220 g (slightly pinkish hue)
    5. actual concentration = 5.1mM
  3. 40mM NH4(CH3COO)2
    1. FW = 77.08 g/mol
    2. V = 250mL
    3. mass to be measured = 0.7708g
    4. actual mass = 0.780g
    5. actual concentration = 40.5mM
  4. 10mM NH4OH
    1. initial M = 14.5M
    2. final V = 250mL
    3. volume to be diluted = 172μL
    4. actual concentration =
  5. 5mM Na2S
    1. FW = 240.18 g/mol
    2. V = 250mL
    3. mass to be measured = 0.300g
    4. actual mass = 0.300g
    5. actual concentration = 5.00mM

Notes

First solution synthesized, labeled "NB 1", was incubated at 80C and contained:

  • 176µL Zn(CH3COO)2
  • 24µL Mn(CH3COO)2
  • 200µL NH4CH3COO
  • 244µL protein
  • 510µL NH4OH
  • 1346µL H2O
  • 200µL Na2S


Second solution synthesized, labeled "NB 2", was incubated at 37C and contained:

  • 176µL Zn(CH3COO)2
  • 24µL Mn(CH3COO)2
  • 200µL NH4CH3COO
  • 244µL protein
  • 550µL NH4OH
  • 1306µL H2O
  • 200µL Na2S