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May 26 2015: Au Nanoparticle Synthesis
A 1%(w/v) stock solution of sodium citrate was prepared for this experiment. 1.053 g of sodium citrate was weighed in a plastic wayboat on a scale and transferred into a 50 mL beaker. The wayboat was rinsed with water and emptied into the 50 mL beaker to ensure maximum sodium citrate transfer. Water was added to the 50 mL beaker and was stirred to dilute the solvent. The solution was then transferred into a 100 mL volumetric flask. The remaining space in the flask was filled with water and stirred. This solution was emptied from the volumetric flask into a sealed container and labeled.
This .001 mM stock solution was modified to use HAuCl4 in place of HAuClr*3H2O (see calculations 1). 0.17 g of HAuCl4 was weighed in a plastic wayboat on a scale and transferred into a 50 mL beaker. The wayboat was rinsed with water and emptied into the 50 mL beaked to ensure maximum transfer. Water was added to the 50 mL beaker and was stirred to dilute the solvent. The solution was then transferred into a 500 mL volumetric flask. The remaining space in the flask was filled with water and stirred. This solution was emptied from the volumetric flask into a sealed container and labeled.
1) A hot plate was obtained and placed under the fume hood, with heat set to level 4 and stirring set to level 2.
2) A 50 mL beaker and stirring rod were obtained. After placing stirring rod in beaker, 22 mL of water was measured using a graduated cylinder and transferred into the beaker. The water line was then marked, and the water was disposed. Using a graduated cylinder, 20 mL of the stock gold solution was measured and transferred into the beaker containing the stirring rod. This beaker was then placed on the hot plate in the fume hood and a timer was set.
3) When the solution in the beaker began to boil, the time since placement was recorded. Using a P1000 micro-pipette, 2 mL of the stock sodium citrate solution was added into the beaker. The time of color change from light yellow to purple was then recorded.
4) Water was added to the solution using a transfer pipette to keep water line at marked level.
5) Solution was left to change into a dark red color, which it was then removed and the time recorded.
The results show that the average time to which the solution came to a boil was after 6 minutes and 50 seconds. The average time it took for color to change following the addition of sodium citrate was approximately 52 seconds. The average time of which the beaker was removed from the hot plate was 12 minutes and 23 seconds. This procedure was repeated for 20 trials to reduce standard error and ensure more accurate results.
The purpose of this experiment was to synthesize gold nanoparticles using sodium citrate as a reducing agent. Citrate anions are absorbed to the surface of the gold nanoparticles, which creates an electrostatic repulsion. This prevents the nanoparticles from aggregating. Our procedure was modified from a lab performed at the Department of Chemistry of Northwestern University. Instead of using 38.8 mM sodium citrate, we substituted our 1%w/v stock solution. We did not perform trials with NaCl or sucrose, as was done in the original.
McFarland, Adam D., Christy L. Haynes, Chad A. Mirkin, Richard P. Van Duyne, and Hilary A. Godwin. "Color My Nanoworld." JCE Classroom Activities (n.d.): n. pag. ACSeBooks. Web. 27 May 2015