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User:Carly M. Montanero/Notebook/CHEM-571/2013/08/28

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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.

From Dr. Hartings


Part 1: BSA-AuNP Synthesis

  1. Add 1.00 ml of 2.54 mM gold solution (HAuCL4) to a 10 ml volumetric flask.
  2. Add 1.81 BSA (90x more gold than BSA) to the volumetric flask.
  3. Add 7.19 ml deionized water to the volumetric flask.
  4. Transfer the solution to a test tube and cap with aluminum foil.
  5. Heat in the oven at 80°C for three hours.
  6. Transfer the solution to a plastic falcon tube.

Part 2: Citrate-AuNP Synthesis

  1. Take 50 ml of 0.254 mM gold solution (HAuCL4) from the stock solution.
  2. Heat the solution to boiling while stirring and covered with a watch glass.
  3. Add 1.5 ml of 1.01% (w/v) sodium citrate.
  4. Boil the solution for another 40 minutes.
  5. Cool to room temperature and measure the final volume.
  6. Determine the final concentration of gold and citrate.


  • Spectrum from UV-VIS of 50x Diluted Citrate-AuNP Solution

UV-VIS Spectrum of UV-Vis of 50x Diluted Citrate-AuNP.png

Matt Hartings In the future, your spectra are going to be much easier to read if they only have lines (and no symbols).

Calculations from Part 2

  • The absorbance of the citrate-AuNP solution was determined by first determining the absorbance of a blank sample. The absorbance of the citrate-AuNP solution was correct by subtracting the absorbance of the blank sample.
  • In order to determine the molar absorptivity, ε, this reference was used. The peak appeared at 520 nm on the UV-VIS spectrum with a corresponding absorbance of 0.02. Using the ratio, Aspr/A450, it was determined that the nanoparticle diameter was 12 nm. This diameter is associated with a molar absorptivity of 1.09x108 M-1cm-1 as stated in the reference.
  • Using Beer's Law, A = εbc, the concentration of the diluted solution was calculated to be 1.83x10-10 M.
  • The concentration of gold in the original solution was calculated to be 1.97x10-9 M.


  • The final volume of Citrate-AuNP solution was 31.0 ml.

Matt Hartings based on this final volume (and initial concentration) what is your concentration of gold?

  • The progression of color change in Part 2 was light purple → dark purple → magenta → burgundy → deep red.
  • The final color of the BSA-AuNP solution was dark purple.