User:Puja Mody/Notebook/Chem 571: Gold Nanoparticles/2012/09/12

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Day 5 Goals Centrifuge the 7 samples of AuNP/BSA in order to separate out the fibers. Look to yesterday's entry for concentrations Run UV-Vis spectra's for the samples every 1 hour to test absorbency rates of the AuNP into the buffer. begin making solutions to replicate experiment. The experiment attempting to be retested is in testing the ionic strength of the refolding buffer. A [previous class] had tested the effect of different concentrations of tris buffer on the AuNP fibers. We are attempting to replicate this and see how our results compare. Procedure The samples from yesterday were centrifuged in order to separate out the fibers They were then combined with 7 different concentrations of the pH 10 Tris buffer. Just as was similarly done the previous week. a serial dilution was done. prepare tris buffer and AuNP/BSA solution at a concentration of 70 for next weeks lab. This stock solution will be used to run UV-Vis based on variations in tris buffer as previous students had done. Calculations/ Data Solution was made with a mole ratio of 70 2.4268M BSA solution was used m1v1=m2v2 24.266μM * (volume) = 1μM * 6mL .247mL BSA solution 2150μM HAuCl4 solution was used 2150μM * (volume) = 6mL *(1μM*70) .195mL HAuCl4 solution 6-.195mL BSA -.247mL HAuCl4 = 5.558mL H2O was added Solutions went in oven at 85oC from 2:32-6:32 Stock solution was made by Dr. Miller Tris Buffer MW= 121.14 g/mol per 1 Liter make 100mL of solutions so..... 12.11grams of tris /100mL were mixed. For further breakdown by run and concentration see attached spreadsheet Link to spreadsheet for Tris buffer pH 10 UV-Vis. http://openwetware.org/wiki/Image:AuNP_in_tris_buffer_pH_10.xlsx Conclusions pH 10 AuNP fibers + Tris buffer UV-Vis data showed that: A. The results were fairly consistent with there not being an increase in the concentration of the gold nano particles. For all 7 samples, the peak stayed at generally the same wavelength for all three tests and therefore the entire length of experimentation time. Thus it seems that changes in the pH of the tris buffer did not result in a noticeable change in abs. However, it is important to note the drop in absorbency for some of the concentration samples. For example, the 1x10-4 concentration shows the most obvious drop between The first time the were measured after the addition of tris (immediately) and two hours later when the third run of UV-Vis was taken. Whether or not this is simply a result of noise or actually because an increase in the amount of AuNP dissolved in the buffer solution is unknown because a blank of water was not measured during these tests.