User:Michaela Harper/Notebook/Biological Chemistry Lab/2011/09/07

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Objective

To determine the effect of pH on the synthesis of gold nanoparticles, and to repeat the experiment from 08/31/11, which has been optimized.

Description

  • Add 1.5 uM BSA and 0.25 mM of HAuCl4 to 10 mL of 50mM acetate buffer (pH 5.46) at room temperature. Repeat with water in place of buffer solution. The ratio of Au to BSA is 167 for optimum results.
    • Note: Properly concentrated solutions pre-prepared by Dr. Hartings.
    • 1mL of BSA solution and 1mL HAuCl4 solution combined. Buffer used to create a total volume of 10mL. Repeat with water in place of buffer solution.
  • Heat mixture at 80°C for four hours (actual temperature varies closer to 70°C).
  • Using a UV-Vis Spectrophotometer, obtain spectra for each solution every 30 minutes, starting at t=0 minutes.
  • The solution is covered in aluminum foil and stored at room temperature overnight.

Data

This graph shows the absorbance for each spectrum taken every 30 minutes in buffer. First, a blank spectrum of the buffer solution was taken and subracted from each of the following spectra to create a corrected absorbance. Series 1 represents the spectra taken at t=0, series 2 represents the spectra taken at t=30 minutes, etc up to series 6 representing t=150 minutes.

Image:Absorbance_in_buffer.png

This graph shows the zoomed in features at 550nm in buffer. The changes at 550nm are due to an increase in the baseline, not a new feature.

Image:550nm_zoom_buffer.png

This graph shows the corrected absorbance at 550nm over time in buffer. This represents the concentration of gold nanoparticles that were formed. However, from the zoomed in graph, it is apparent that the changes are due to an increase in the baseline.

Image:Absorbance_at_550-buffer.png

This graph shows the absorbance for each spectrum taken every 30 minutes in water. First, a blank spectrum of the water was taken and subracted from each of the following spectra to create a corrected absorbance. Series 1 represents the spectra taken at t=0, series 2 represents the spectra taken at t=30 minutes, etc up to series 6 representing t=150 minutes.

Image:Absorbance_in_water.png

This graph shows the zoomed in features at 550nm in water. The changes at 550nm are due to an increase in the baseline, not a new feature.

Image:550nm_zoom_in_water.png

This graph shows the corrected absorbance at 550nm over time in water. This represents the concentration of gold nanoparticles that were formed. However, from the zoomed in graph, it is apparent that the changes are due to an increase in the baseline.

Image:Absorbance_at_550nm-water.png

Notes

These observations may indicate that the experiment did not proceed correctly, as these results were not reported by Bashki, et al.

BSA and HAuCl4 solutions were concentrated to be 10x as much as last week. Also, both solutions initially appeared clear with a slight yellowish color. The slight yellow color disappeared with time and solutions became clear. A pocket of cloudy material appeared in the center of the acetate mixture part way through the experiment.



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