User:Sarah Burkhard/Notebook/471 Nano Notebook/2016/08/31

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UV Vis

Objective

Observe a change in concentration of gold nanoparticles in solutions which vary in pH and Fructose concentration. The change in gold nanoparticle concentration can be seen from a change of relevant light absorbance, measured with a spectrophotometer

Description

Compare absorption of UV-Vis of solutions containing 0.25 mM Gold with

  1. different pH
  2. different fructose concentration

Composition of solutions:

0 mM Fructose
pH μL of 1 mM HClstock μL of 1 mM NaOHstock μL of 1 M NaOHstock μL of AuCl3stock μL of Fructosestock μL of BSAstock μL of Water Change in absorbance Color
4 500 0 0 374 0 460 3666 ~ 0.55 purple
5 50 0 0 374 0 460 4116 increased purple
6 5 0 0 374 0 460 4161 no change purple
7 0 0 0 374 0 460 4166 increased purple
8 0 5 0 374 0 460 4161 increased purple
9 0 50 0 374 0 460 4116 no change purple
10 0 500 0 374 0 460 3666 increased slightly purple
11 0 0 5 374 0 460 4161 no peak transparent
12 0 0 50 374 0 460 4116 no peak transparent


0.0625 mM Fructose
pH μL of 1 mM HClstock μL of 1 mM NaOHstock μL of 1 M NaOHstock μL of AuCl3stock μL of Fructosestock μL of BSAstock μL of Water Change in absorbance Color
4 500 0 0 374 24 460 3642 ~ 0.6 purple
5 50 0 0 374 24 460 4092 increased purple
6 5 0 0 374 24 460 4137 no change purple
7 0 0 0 374 24 460 4142 N/A transparent
8 0 5 0 374 24 460 4137 increased purple
9 0 50 0 374 24 460 4092 no change purple
10 0 500 0 374 24 460 3642 decreased purple
11 0 0 5 374 24 460 4137 no peak transparent
12 0 0 50 374 24 460 4092 no peak transparent

pH 7 is not applicable because the gold solution had produced fibers. We discarded it and did not collect data with it.

Solutions were prepared by Dr Hartings

Data analysis

Gold nanoparticles are of purple color. The spectrophotometer can therefore detect the presence of gold nanoparticles when it measures absorbance of light in the UV and visible wavelengths. Gold nanoparticles absorb light with a wavelength of around 530 nm. The general trend, independent of Fructose presence, shows that absorbance at the relevant wavelength (around 530 nm) increases slightly with increasing pH, which means the concentration of nano particles increased slightly. For high pH values, starting at pH = 11, there seem to be no gold nano particles at all. The solutions are transparent, and show no peak in absorption. The difference between 0 mM Fructose and 0.0625 mM Fructose seems to be that latter has higher absorbance for pH 4 and pH 9. For all other pH values, the Fructose does not seem to affect the Au nano concentration significantly. One thing to be careful with when analyzing the peak values is to take into account potential shifts in the base line. The graphs below show both original results, and baseline-corrected results of absorption. The highest concentration of gold nano particles was for 0.0625 and pH 10.

Figure 1

Figure 2

Figure 7

Figure 8

Figure 9

Figure 3

Figure 6

Figure 4

Notes

Cuvette can be cleaned with DI water, 10 percent HCl (because we are using Gold) and soap. Water has to come last.

It should be dried with blowing air. Be cautious with air, can shoot off glass pipette at tip of tube if air comes out too strong.

for SILVER use nitric acid for cleaning !



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