Day 2
Goals
- Run a UV-Vis on the 14 AuNP + BSA solutions from the previous day.
- Prepare a Tris base buffer at a pH of 8 and 10
Procedure
- A UV-Vis was run at a wavelength of 200-700nm for all 14 samples. The baseline sample was that of water. This data was collected and charted.
- Two tris buffers were prepared. One with a pH of 8.04 and one with a pH of 9.99.
- The Tris base buffer had a concentration of .1 M.
.1Μ/L Tris × .1L = .01 mols
.01 mols × 121.14 g/M (mw tris) = 1.21 grams of tris
- Sample 1 was calibrated for a pH of 8 and contained 1.213 grams of Tris and 9mL of HCl.
- Sample 2 was calibrated for a pH of 10 and contained 1.2125 grams of Tris and 2 mL of HCl.
- The Tris was first dissolved in 85mL of H2O. Next the pH meter was inserted into the solution and measurements were continuously taken as HCl was mixed into the solution drop-wise in order to lower the pH appropriately. Once the desired pH was reached, H2O was added to bring the total volume to 100mL of buffer solution.
Conclusions/Results
- The AuNP/BSA fiber solutions that were tested were not the same samples made the previous week. Due to contamination from the spatula on the gold, the AuNP fibers were not visible in the solutions. Therefore, the samples used for the UV-Vis were made by Dr. Miller.
- Specific concentrations needed to be retested due to the observation of a significant peak drop between concentrations 128 and 130. As a result, new stock solutions of the AuNP and BSA were made with the intent of being mixed together and placed in the oven the next day.
- The pH of 8 was chosen because the optimal pH range for Tris is between 7-9. The tris buffer was also made at a pH of 10 because that was the pH at which the samples had been previously tested by others. And since this portion of the experiment is based on the work of the previous class and our desire is to repeat and build upon, it seemed appropriate.
- prior to the changing of the pH, the original pH of the tris buffer was slightly above pH 10 for each solution.
- The UV-Vis showed that several of the concentration samples had a similar peak at approximated 550nm. The spike is related to the how the light is passing through the AuNP- how the light responds to the NP. The peak position is related to the concentration of the AuNP fibers in the BSA solution. Thus, based on the data presented in the graph, it would seem that at the concentrations where the major peaks are similar, the NP in those samples are the same size.
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