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.
This procedure was taken from the following reference and has been used by our previous two Experimental Biological Chemistry groups.
- Add 1mL of the (~2.5mM -note the exact concentration) gold (HAuCl4) solution to a 10mL volumetric flask
* In this experiment the stock solution had a concentration of 2.54mM
- Add an appropriate amount of BSA solution so that the final concentration of gold is 90X that of BSA.
* In this experiment the appropriate volume of BSA needed was calculated and found to be 0.001809 L (1.809mL).
- Add deionized water up to 10mL
- Transfer solution to a test tube and cap with aluminum foil
- Heat in oven at 80C for 3 hours
* When the test tube was removed from the oven after 3 hours, it was observed that filaments had formed which is an indication that the BSA/Gold ratio was not correct. This was most likely due to an error when transferring the required volumes of both solution to the volumetric flask.
- 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
This procedure is used by Dr. Miller in her research lab - Allison Alix's notebook and is taken from this reference.
- Take 50mL of the HAuCl4 solution from the 250mL volumetric flask. Note the concentration
- 50.5mL of the 0.249 mM HAuCl4 solution
- Heat this solution to boiling while stirring
3mL 1.5mL of 1% (w/v) sodium citrate
- Almost instantly after adding the sodium citrate the solution turned purple and gradually changed to a red/burgundy
color after about 4 minutes.
- Boil solution for another 40 minutes
- After about 30 minutes of boiling, about 5mL of deionized H2O were added to the solution to replace the
H2O lost by evaporation.
- Cool to room temperature and measure the volume
- Once cooled, the volume of the solution was measured to be 25mL
- Determine the final concentration of gold and citrate
- Determining the final concentration of gold and citrate required us to calculate the initial amounts of gold and
citrate in the initial solution.
Gold: 0.05L * 2.49 *10^-4 M = 1.245*10-5 moles of Au.
Citrate: 0.0015L * (0.101g/0.01L) * 1mol citrate/294g = 5.15*10-5 moles of citrate
- Final Concentrations
Gold: 1.245*10-5 / 0.025L = 4.98*10-4 M
Citrate: 5.15*10-5 / 0.025L = 2.06*10-3 M
- Note: According to Allison, and Madeline will corroborate, we don't need to reflux the
solution (which would carry out the reaction in a closed system). We should be able to bring the solution to a boil on the
Stock solutions made
- Gold solution (HAuCl4·3H2O) 0.0245g in 0.2505mL water → 0.249mM
- Sodium Citrate (Na3C6H5O7·2H2O) 0.1010g in 10.0mL → 1.01%
- A sample was made up in order to run the UV-Vis, which was 1/10 ratio between the citrate sample and water. A cuvette was
filled with deionized water and was put in the UV-Vis before filling the same cuvette with our diluted sample in order to
subtract errors from the actual data.
The data was analyzed using thisthis reference
The maximum recorded was of 0.158 and this occured between 522nm and 525nm.
File:Citrate-AuNP-UV-Vis-DML 2013 28 08.pdf is a graph of the results of the UV-Vis of the sample.
Analyzing this maximum absorbency allowed us to
determine that the size of the gold nanoparticles was about 14nm.