Synthesize two different sets of gold nanoparticles. In one set, Au3+ is reduced by a protein (bovine serum albumin, BSA) and the synthesized nanoparticle is also surrounded and stabilized by BSA. In the second set, Au3+ is reduced by citrate, and the AuNP is stabilized by citrate in solution. The BSA-AuNPs are purple in color and the citrate-AuNPs are more of a burgundy (reddish) color.
BSA-Au Nanoparticles
Add 1mL of the (~2.5mM -note the exact concentration) gold (HAuCl4) solution to a 10mL volumetric flask
Add an appropriate amount of BSA solution so that the final concentration of gold is 90X that of BSA
Add deionized water up to 10mL
Transfer solution to a test tube and cap with aluminum foil
Heat in oven at 80C for 3 hours
Transfer solution to a plastic falcon tube (with blue cap)
Stock solutions made
Gold solution (HAuCl4·3H2O) 0.0100g in 0.0100mL water → 2.54mM
BSA solution 0.0104g BSA (MW = 66776g/mol) in 0.0100mL water → 15.6μM
Citrate-Au Nanoparticles
Take 50mL of the HAuCl4 solution from the 250mL volumetric flask. Note the concentration
Heat this solution to boiling while stirring
Add 3mL 1.5mL of 1% (w/v) sodium citrate
Boil solution for another 40 minutes
Cool to room temperature and measure the volume
Determine the final concentration of gold and citrate
Stock solutions made
Gold solution (HAuCl4·3H2O) 0.0245g in 0.2505mL water → 0.249mM
Sodium Citrate (Na3C6H5O7·2H2O) 0.1010g in 10.0mL → 1.01%