User:Javier Vinals Camallonga/Notebook/Javier Vinals notebook/2013/09/02

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Objective

Synthesize two different sets of gold nanoparticles. In one set, Au3+ is reduced by a protein (bovine serum albumin, BSA) and the synthesized nanoparticle is also surrounded and stabilized by BSA. In the second set, Au3+ is reduced by citrate, and the AuNP is stabilized by citrate in solution. The BSA-AuNPs are purple in color and the citrate-AuNPs are more of a burgundy (reddish) color.

BSA-AuNP

This procedure was taken from the following reference and has been used by our previous two Experimental Biological Chemistry groups.

  1. Add 1mL of the (~2.5mM -note the exact concentration) gold (HAuCl4) solution to a 10mL volumetric flask
  2. Add an appropriate amount of BSA solution so that the final concentration of gold is 90X that of BSA
                   - Through calculation, we obtained that 0.001809 L was the necessary amount of BSA solution needed to add, so that the final concentration of gold is 90X that of BSA. Calculations done: First we find the amount of moles of BSA necessary for the reaction. [(2.54*10^-3 moles/L of HAuCL4)*(1L/1000mL)*1mL]/90=2.82 *10^-8 moles of BSA. Now we find the volume of BSA necessary to add to the reaction: (2.82 *10^-8 moles BSA) *(1L/15.6 *10^-6 moles)= 0.001809 L of BSA or 1.8 mL of BSA
  1. Add deionized water up to 10mL
  2. Transfer solution to a test tube and cap with aluminum foil
  3. Heat in oven at 80C for 3 hours
                  - After we took the solution out of the oven, we observed that some nanoparticles had formed, due to an error during the process fo the experiment. Thus it was discarded away.
  1. Transfer solution to a plastic falcon tube (with blue cap)

Stock solutions made Gold solution (HAuCl4·3H2O) 0.0100g in 0.0100mL water → 2.54mM BSA solution 0.0104g BSA (MW = 66776g/mol) in 0.0100mL water → 15.6μM


Citrate-AuNP

This procedure is used by Dr. Miller in her research lab - Allison Alix's notebook and is taken from this reference and can be analyzed according to this reference.

  1. Take 50mL of the HAuCl4 solution from the 250mL volumetric flask. Note the concentration
  2. Heat this solution to boiling while stirring
  3. Add 3mL 1.5mL of 1% (w/v) sodium citrate
       - It was observed that the solution turned purple at the beggining after adding the sodium citrate, and then it turned red after 4 minutes.
  1. Boil solution for another 40 minutes
       - During this part of the experiment at 30 minutes we have to add more water,5 mls of water, since a lot of the solution had evaporated.
  1. Cool to room temperature and measure the volume
      - After we let it cool for 10 minutes, we measured the new volume, which is 25 mls
  1. Determine the final concentration of gold and citrate
     - In order to determine the final concentration, we first found out the initial amount of moles of citrate and gold.
         Gold: 0.05 L* 2.49 *10^-4 M= 1.245 *10^-5 moles of Au.
         Citrate: (0.1010 g/0.01 L)*(1 mol/294 grams)= 0.034 M
                     0.034 M* 0.0015 L= 5.15 *10^-5 moles of citrate.
    - Final concentration
         Gold: 1.245 *10^-5 moles of Au/ 0.025 L= 4.98 *10^-4 M
         Citrate: 5.15*10^-5 moles of citrate/0.025 L= 2.06 *10^-3 M
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