User:Floriane Briere/Notebook/CHEM-496/2011/08/31

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Objective

Today's experiment consist on performing a Gold NPs synthesis, using the artcle "Protein Films of Bovine Serum Albumen Conjugated Gold Nanoparticles: A Synthetic Route from Bioconjugated Nanoparticles to Biodegradable Protein Films" as an example for the protocol.

Each group is using a different buffer, each buffer is characterized by a specific pH. Depending on the value of the pH, proteins unfold more or less easily. This experiment is going to allow us to determine the best pH we've to use to create NPs.

Our group (#5) is using water as a buffer (pH = 7.0)

Protocol

  1. Add 0,0010g of BSA (0,0015mM;66,776g/mol) + 0,00085g of HAuCl4 (0,25mM;339,985g/mol) + 10ml of water
  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 105 minutes of heat)
  5. Spectrum of the buffer (blank)

Results

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

Image:31aout - Abs550, t.png

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

Image:31aout - Abs, w.png

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

Image:31aout - Abs, w - zoom.png

Conclusion

At the beginning of the experiment, the solution was yellow (due to the Gold); at the end of the experiment the solution was uncolored. We left the solution at ambient temperature overnight and observed the apparition of purple filaments.

Between T0 and T2, we observe an increase of the Absorbance for a wavelength equal to ~580nm. This increase is provoked by the Gold NPs synthesis. Then, between T2 and T4 we observe a decrease of the Absorbance at ~580nm. This decrease can be explained by the formation of the purple filaments, all proteins and Gold which absorb at ~580nm are stucked together; the rest of the solution is so only composed of buffer.

In the original experiment, the solution turned purple at the end of the experiment and no filaments were created. Fibers' formation can be explained by the fact that we removed the solution from the oven every 30minutes and left it at room temperature for about 10minutes each time. So, the solution didn't stay at 80°C during the entire experiment.*

As a conclusion, with a discontinuous temperature and a mole ratio (of Au/BSA) equal to 1176, we observe formation of purple filaments.

Notes

  1. We added 0,006g of HAuCl4 (instead of 0,00085g as written in the protocol) because the scales wasn't precised enough.
  2. HAuCl4 is sensible to light and moisturing.




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