User:Trisha I. Ibeh/Notebook/Trisha Notebook/2013/08/28

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Template for this lab is taken from Dr. Hartings. Values are altered to accurately describe the lab that was conducted on this day. The template can be found here


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 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. Using the class data, a calibration curve will be created to find the molar absorbtivity. A Grubbb's test will be done in order to determine the outliers.


Start by placing all of the materials into a volumetric flask so that you know the exact volumes and exact amounts of what you have added. I will have prepared the initial protein and gold solutions for you (this one time only). In the future, you will be expected to make most of the starting solutions.

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

  1. Add 1.2mL of the (~2.54mM -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
  3. Add deionized water up to 10.2mL
  4. Transfer solution to a test tube and cap with aluminum foil
  5. Heat in oven at 80C for 3 hours
  6. Transfer solution to a plastic falcon tube (with blue cap)

Stock solutions made

  1. Gold solution (HAuCl4·3H2O) 0.0100g in 0.0100mL water → 2.54mM
  2. 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 and can be analyzed according to this reference.

  1. Take 50mL of the .249mM of HAuCl4 solution from the 250mL volumetric flask.
  2. Heat this solution to boiling while stirring
  3. Add 3mL 1.5mL of 1% (w/v) sodium citrate
  4. Boil solution for another 40 minutes
  5. Cool to room temperature and measure the volume
  6. Determine the final concentration of gold and citrate
    • 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 bench top.

Stock solutions made

  1. Gold solution (HAuCl4·3H2O) 0.0245g in 0.2505mL water → 0.249mM
  2. Sodium Citrate (Na3C6H5O7·2H2O) 0.1010g in 10.0mL → 1.01%


As a result of the citrate being discarded, the citrate from Moira's group was used for the purposes of this lab.

Peak Wavelength: 518 nm

Absorbance at Peak: .612

In order to determine the concentration, the Absorbance at 450 is known.

Abs (450): .389

Abs (518)/ Abs (450)= .612/ .389= 1.57

Using the data found here the value of 1.57 resulted in 12 d/nm. Again, using the link, this led to a molar absorptivity of 1*10^8.

Using Beer's law and the newly found value for molar absorptivity, the concentration was determined to be 3.57*10^-9M.


The citrate- AuNPs were discarded as a result of it being spilled on the lab bench therefore it will be synthesized again in a future lab.