User:Moira M. Esson/Notebook/CHEM-571/2013/08/28

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  1. Prepare a bovine serum albumin (referred to as BSA) and gold nanoparticle (referred to as AuNP) solution for later testing.
  2. Prepare a sodium citrate- AuNP solution.
  3. Determine the concentration of the prepared sodium citrate-AuNP solution using UV/vis.

BSA-AuNP Preparation

General Protocol:

  1. Add 1mL 2.54mM HAuCl4 solution prepared by Dr. Hartings to an 10mL volumetric flask.
  2. Add 1.80mL 15.6μM BSA solution to the 10mL volumetric flask.(The concentration of gold in the solution is 90x that of the BSA)
  3. Add 7.2mL deionized H2O to the 10mL volumetric flask.
  4. Transfer the solution into a test tube. Cap the test tube with aluminum foil
  5. Heat in oven at 80°C for 3hrs.
  6. Store the solution in a blue falcon tube.

Note:Use caution when removing the test tube from oven. The test tube will be hot.

Sodium citrate-AuNP solution Preparation

General Protocol:

  1. Add 50mL of the prepared 0.295mM HAuCl4 solution to a clean 150mL beaker.
  2. Heat this solution to a boil while stirring the solution with a magnetic stir bar. Keep the beaker covered with a watch glass while the solution is heating.
  3. After the solution comes to a boil, add 1.5mL of 1%(w/v) sodium citrate(prepared by Dr. Harting's).
  4. Cover the beaker with a watch glass and allow to boil and stir for another 40 minutes.
  5. Remove the beaker from the hot plate and allow to cool to room temperature. Keep the watch glass on the top of the beaker until solution is cooled.
  6. Measure the volume of the solution.

Table 1. Prepared citrate-AuNP particle solution

Final volume(mL) 9.5
  • Added 0.01475mmol gold. With final volume of 9.5mL. concentration of gold is 1.55mM.

UV/vis analysis

  • In order to determine the concentration of the solution, the solution was diluted using a 1/10 dilution. 1mL was used for the UV/vis sample.
  • To analyze the solution this reference was used.

Figure 1.
Absorbance 10dilution CHEM571 08282013.png

  • The maximum absorbance of the citrate-AuNP was 0.405 at 518-521nm.
  • The absorbance at 450nm was 0.259.
  • According to this reference, the Au nano-particles have a diameter of 12nm.
  • The molar absorptivity coefficent for the Au-Citrate solution is 1.09E08 M-1cm-1
  • Using Beer's law, concentration of the 1/10 dilution was 2.38E-9M.

Matt Hartings Moira, keep reading in this reference. There are notes on what to do if the size is less than 32nm. Please complete this analysis. You need to determine the size AND concentration of the nanoparticles along with the concentration of gold (based on your initial concentration and final volume)


  • After the addition of the citrate to the HAuCl4 solution, the solution turned a light purple color. This color darkened during the 40min boiling process. Half way through the boiling process the solution turned a deep reddish purple color for approximately 5 min and then changed back to a dark purple color.
  • After the BSA-AuNP solution was heated for 3 hours, the solution turned into a dark purple color.