User:Puja Mody/Notebook/Chem 571: Gold Nanoparticles/2012/11/28

UV-Vis Everything

Goals

• Run UV-Vis on Dialysis Au/ADA solutions
• Dissolve/ resuspend fibers in solutions using tris buffer
• Make new Au/ADA solutions

Procedure

• The Au/ADA solutions made yesterday produced fibers at most mole ratios except for mole ratio 25. We ran a UV-Vis of 1mL of each of the samples in plastic cuvettes After running the samples through the instrument, each sample was then repipetted back into it's test tube.
• We then took 1mL of .1M tris buffer at pH 9.99 made on 2012/09/04. We chose this pH because a quick search of the literature showed that the optimum pH for Tris and ADA was between pH 8-9. Therefore, in order to destabilize the ADA and cause it to unfold once again and get nanoparticles in solution, we chose the higher pH with the hopes that it would do what we were hoping for.
• The Au/ADA solutions had 2 mL of solutions to which we added 1mL of tris buffer into each solution. We shook the test tubes a little to mix the Tris in and let the samples sit for 10 minutes.
• After 10 minutes, fibers had not resuspended and there was no visual difference in the solutions, As a result, 1mL more of the tris buffer was added to the samples. and 10 more minutes were allowed to pass.
• Though not much visual difference was still noted, a UV-Vis spectra of the 'resuspended' fibers were taken. Some of the sample solutions looked resuspended and others did not. those that did not were mole ratios 75, 100, 125.

• The Au/ADA solutions had not shown fibers at mole ratio 25 but did show fibers at mole ratio 50. in order to better pinpoint a mole ratio that gave gold nanoparticles in solution, we remade Au/ADA solutions at mole ratios 10-45 (going up by intervals of 5 making a total of 8 solutions), using the same gold stock and the same ADA (Frac #8).
• These samples were then capped with aluminum foil and placed in an oven for 4 hours at 80°C.

Conclusions

• For images of the UV-VIs spectras for all runs, please see Mary's notebook.
• In the Au/ADA spectra, no peaks were seen in the λ500nm range, instead, a slight peak was seen around λ250-325. What this peak represents, we are not sure.
• For the newly made Au/ADA solutions at mole ratios 10-45, some of the samples produces a slight purple tinge prior to its placement in the oven. As a result, a UV-Vis spectrum of these samples ( mole ratios 10, 15, 40, 45) was taken. For full details on the makings of these samples and the data collected, please see Michaels Notebook. His results showed that in the 25-33 mole ratio range, purple solutions were present without fibers. Further zeroing in on this range needs to be done in the fugure in order to more specifically determine the mole ratio of Au to ADA that leads to the formation of nanoparticles in solution.