User:Floriane Briere/Notebook/CHEM-496/2011/09/07

Objective

Today, we are performing the same experiment we made on the 31th of August. However, we are going to synthetise NPs by using two different buffers: water and acetate. The goal is to determine which buffer works best; water has a pH of 7.0 and acetate has a pH of 9.0.

Moreover, on the 31st of August, the Gold NPs didn't work very well, we're going to try to improve the synthesis.

Protocol

• Experiment with water:

1. Add 8ml of water + 1ml BSA stock solution + 1ml HAuCl4 stock solution
2. Spectrum of the solution (T0)
3. Heat at 80°C
4. Spectrum of the solution at:
   1. T1 (after 30 minutes of heat)
   2. T2 (after 60 minutes of heat)
   3. T3 (after 90 minutes of heat)
   4. T4 (after 120 minutes of heat)
5. Spectrum of a pure water solution (blank)

• Experiment with acetate:

1. Add 8ml of acetate + 1ml BSA stock solution + 1ml HAuCl4 stock solution
2. Spectrum of the solution (T0)
3. Heat at 80°C
4. Spectrum of the solution at:
   1. T1 (after 30 minutes of heat)
   2. T2 (after 60 minutes of heat)
   3. T3 (after 90 minutes of heat)
   4. T4 (after 120 minutes of heat)
5. Spectrum of a pure acetate solution (blank)

Results for water

• Curve of the Absorbance (at 550nm) as a function of time (minutes)

• Curve of the Absorbance (between 0 and 4) as a function of the wavelength (nm)

• Curve of the Absorbance (between 1 and 0,20) as a function of the wavelength (nm)

Results for acetate

• Curve of the Absorbance (at 550nm) as a function of time (minutes)

• Curve of the Absorbance (between 0 and 4) as a function of the wavelength (nm)

• Curve of the Absorbance (between 1 and 0,20) as a function of the wavelength (nm)

Conclusion

In both experiments, we observe no real increase of the Absorbance at ~580nm which mean that no (or very few Gold NPs) have been synthesized (according to Absorbance versus wavelength curves).

For the water, between T0 and T2 there is a little increase of the Absorbance at 550nm and then between T2 and T4 there is a decrease of the Absorbance at 550nm. This result is similar to the one we obtained on the 31st of August, however, the Absorbance at 550nm reaches a lower maximum today. The Gold NPs worked better on the 31st of August.

For the acetate, the Absorbance at 550nm increases regularly between T0 and T4. However, the increase is really minimal. We can observe that the Absorbance at 550nm reached an upper maximum when we use water compare to the results we obtained by using acetate as a buffer. So the Gold NPs seems to work better in water (at a neutral pH).

As on the 31st of August, we obtained purple filaments after leaving the solution at room temperature overnight.

As a conlusion, using water or acetate as a buffer, a mole ratio (Au/BSA) equal to 166 and a discontinuous temperature, we obtained purple fibers into a clear solution.