User:Matthew R Skorski/Notebook/Gold Nanoparticles Summer 2014/2014/05/21
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Purpose: To synthesize gold nano particles using a citrate reduction method. Then run the gold nano particles though a UV-Vis to determine the size and concentration of the gold nanoparticles.
Reference: Allison Alix's "Analysis of Telomeric-DNA through Fluorescence Correlation Spectroscopy" and Supporting Information from Haiss, Thanh, Aveyard, and Fernig "Determination of Size and Concentration of Gold Nanoparticles from UV/Vis Spectra."
Safety: Working with HAuCL4 and sodium citrate.
1)Bring 100 mL of 0.001g HAuCL4*3H2O to boil while stirring continuously
2)While stirring, add 3 mL of 1% sodium citrate
3)Boil for an additional 40 minutes and then remove to cool under the hood to room temperature
32.9 mL of 0.001g HAuCL4*3H2O was added to a 125 mL erlenmeyer flask . The original color was a very light yellow-gold. 1 mL of 1% sodium citrate was added once bubbles formed on the stir bar in the flask and condensation formed on the side. The sodium citrate was added at 9:38 am. The solution turned a red-purple color within two minutes after mixing. The flask was taken off the heat at 9:49 am and allowed to cool to room temperature.
Several dilutions of the gold nanoparticles, along with several blanks, were made in order to run the sample though a UV-Vis spectrophotometers from 200-800 nm.
PBS and H2O proved to be the best solution to dilute the gold nanoparticles with as they did not create a 800 nm bump due to aggregation. For this reason their data will be used to determine the size and concentration of the gold nanoparticles.
From the PBS graph, the max peak of 0.92 A was seen at 526 nm. From the H2O graph the max peak of 0.793 A was observed at 528 nm.
From table S-1 in the supporting information page cited, the H2O wavelength of 528 nm means the nanoparticles were estimated to be between 40 and 42 nm wide. The PBS wavelength of 526 nm means the nanoparticles were estimated to be between 34-36 nm wide.
While Table S-2 can be used to estimate the length of the gold nanoparticles, because the gold nanoparticles appear to be bigger than 35 nm Table S-2 does not apply. From the previously recorded diameters, 36 nm will be the used as the width of the gold nanoparticles.
The concentration of gold nanoparticles synthesized could be determined by C = A450/ε450. From Table S-3 ε450 for a 36 nm nanoparticle is 3.52 x 109 M-1 cm-1. Using PBA's A450 of 0.504 A, the calculated concentration was C = 0.504 A /3.52 x 109 M-1 cm-1 = 1.4318 x 10-10 M. Using H2O's A450 of 0.445 A, the calculated concentration was C = 0.445 A /3.52 x 109 M-1 cm-1 = 1.2642 x 10-10 M.
As these were the concentrations of the gold nanoparticles at the 1/3 ratio, they must be multiplied by 4 to get the original concentration. This gives 4(1.4318 x 10-10 M) = 5.7272 x 10-10 M and 4(1.2642 x 10-10 M) = 5.0568 x 10-10 M. The concentration for the gold nanoparticles made on this day is assumed to be the average of these two values C = (5.7272 x 10-10 M + 5.0568 x 10-10 M) / 2 = 5.392 x 10-10 M.