The goal of this experiment is to synthesize citrate protected gold nano particles and determine their size using this reference.
The aim is to find a ratio of gold to citrate that will yield nano particles approximately 50nm in diameter.
- Prepare stock solutions
- Dissolve HAuCl4 in water to have a solution of 10mM
- Dissolve 250mg of the citrate sodium salt into 25mL of water
- In a beaker mix 50mL of water and a volume of the gold stock solution
- Bring solution to a boil
- Add a volume of the citrate sodium solution and reflux for 30 minutes
- Note color change from dark blue to red
- 1.236mL gold and 0.509mL citrate
- 2.5mL gold and 0.509mL citrate
- 2mL gold and 0.509mL citrate
- 2mL gold and 1.5mL citrate
- 2mL gold and 2.5mL citrate
- 6mL gold and 1.5mL citrate
- 2mL gold and 4mL citrate
- Place 1/10 dilution of the nano particle solution with water in an Eppendorf tube
- Take UV-Vis spectra
- Measure the size of the nano particles using this reference.
The UV-Vis spectra of the solutions were obtained and the following graph represents the spectra:
The UV-Vis data allowed to calculate particle size using this reference.
The following table summarizes those results and the calculated size of the particles for each solution.
| Size (nm)||20-25||40-45||25-30||14-16||10||14-16||12.0-14.0
Solutions 1 and 5 were the only two not to form gold precipitate during nano particle synthesis.
From the results, solution yields the best nano particle size and that ratio will be used throughout the semester for nano particle synthesis.