User:James C. Schwabacher/Notebook/CHEM-571/2013/08/28

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Objective

Synthesize two different sets of gold nanoparticles:

  1. Au3+ is reduced by a protein (bovine serum albumin, BSA) and the synthesized nanoparticle is also surrounded and stabilized by BSA.
  2. Au3+ is reduced by citrate, and the AuNP is stabilized by citrate in solution.

Adapted from Prof. Hartings

Procedure

Part I: Synthesizing BSA-AuNP

The procedure followed was taken from this reference. Note: Instead of adding distilled water to the 10 mL mark on the volumetric flask, a pipette was used to measure out the exact volume of water required to make the total soultion 10 mL.

The gold stock solution had a concentration of 2.54 mM. Thus, in a 10 mL solution, the concentration of gold particles was calculated to be .254 mM. A BSA concentration of 90 times less than the concentration of gold particles in the final solution was calculated to be 2.82 μM. To achieve a final BSA concentration of 2.82 μM in 10 mL, a 1.81 mL volume of the 15.6 [math]\displaystyle{ mu }[/math]M BSA stock solution was used.

Part II: Synthesizing Citrate-AuNP

The procedure followed was taken from this reference. Note: A reflux condenser was not used. Instead, a beaker filled with the boiling solution was covered with a watch glass.

The gold (HAuCl4) stock solution had a concentration of 0.249 mM and only 1.5 mL of the 1.01% (w/v) citrate stock solution was added to the solution.

After the synthesi was completed and the solution was cooled and transferred into a falcon tube, a 50x diluted sample was made by adding 20 μL of the solution to 980 μL of water. This 1 mL diluted sample was tested using the UV-Vis.

Data: Citrate-AuNP

  • Absorbance Spectrum from UV-Vis of 50x Diluted Citrate-AuNP

Calculations

  1. The absorbance was found by subtracting the data for the water-filled cuvette from the data gathered from the diluted Citrate-AuNP sample.
  2. To determine the molar absorptivity, ε, this reference was consulted. Given that the peak appeared at the 520 nm wavelength with an absorbance of 0.02, the nanoparticle diameter was estimated to be 12 nm using the reference's ratio of Aspr/A450. The molar absoptivity at 450 nm for nanoparticles of 12 nm in diameter was 1.09E+08 M-1cm-1 stated in the reference.
  3. The concentration of the diluted solution was found to be 1.83E-10 M using Beer's Law, simplified to c=A/ε
  4. With the diluted sample's concentration determined, the stock solution's gold concentration was found to be 9.17E-9 M

Notes

  • The resulting BSA-AuNP solution was dark purple
  • The resulting 30 mL of 9.17*10E-09 M Citrate-AuNP was burgundy
  • Later, the final concentration of gold in the citrate-AuNP sample was found to be 6.815μg/mL

Matt Hartings What was the final concentration of gold in your citrate-AuNP sample (not the same as concentration of AuNP)?




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