A simple method to control the size of Au nanoparticles via heat treatment. The Au nanoparticles grew to between 3 and 10 nm in size at 150 to 250 degrees C.
Teranishi T, Hasegawa S, Shimizu T
Prepare DT-Au following Brust two-phase reaction procedure.
Add HAuCl4.4H20 (0.6 mmol) aqueous solution (60mL) to tetraoctylammonium bromide (TOAB, 1.2 mmol) in toluene (160 mL) and stir vigorously for 10 minutes at room temperature. The HAuCl4.4H20 is transferred into the organic layer turning orange and the yellow aqueous solution becomes colorless. Add to the mixed solution DT (0.6mmol) in toulene (20 mL) and stir for another 10 minutes at room temperature.
Separate the organic phase via rotary evaporation at 40 degrees C and dry in vacuo at 30 degrees C for one day.
Heat-treat crude solid at 150, 190, and 230 degree C at the heating rate of 2 degrees C/min, and hold at this temperature for 30 minutes.
Dissolve heat-treated product in 30 mL toluene and mix with 300 mL methanol to remove excess DT and TOAB.
Filter off precipitate; wash with methanol; and redisperse in toluene.
For 250 degrees C anneal, replace dodecanethiol (DT) with octadecanethiol (ODT).