Chemical	CAS #
Gold(III) chloride hydrate	[27988-77-8]
NaBH4	[16940-66-2];
Silver nitrate	[7761-88-8]
Cetrimonium bromide (CTAB)	[57-09-0];
Ascorbic acid	[50-81-7]
Ultrapure H2O > 18MΩ

balance	weighing boat / paper	graduated cylinder	teflon coated spatula	glass vials (20mL)
ice bath / refrigerator (4oC)	magnetic stir plate / bar	beaker /flask >250mL	pipettor / tips	sonication bath or oven

AuCl4 may be ordered as 49% or 52% purity. The procedure described here uses the 49% AuCl4. If the 52% AuCl4 is used, more AgNO3 is required in step 2

1. Make sure the collected glassware is clean. The solutions may be prepared in any order, but impurities will prevent the formation of rods
2. Label the glassware for your solutions. Silver nitrate, Ascorbic acid, Sodium borohydride, seed solution, gold solution, & CTAB
3. Transfer ~130 ml of ultrapure H2O to a flask. This will be for the CTAB solution
4. Weigh out 11.27g of CTAB into a weighing boat and slowly transfer to the CTAB solution flask.

   CTAB powder with water

   The CTAB will not readily dissolve in room temperature water.

   CTAB powder with water

   The dissolving process can be speeded up by placing the flask in a sonication bath or in an oven at 60^oC. It may require more than 1 hour to dissolve.
5. As the CTAB dissolves, it may form a cloudy gel on the bottom of the flask. If it appears that CTAB is not dissolving, manually break up the CTAB.

   The clear blob is partially dissolved CTAB at the bottom of the flask. Continue to heat or stir to dissolve. Manually breaking the precipitated CTAB into smaller clumps will speed up the process

6. Transfer ~152.5 mL of >18MΩ to a clean flask. This will be for gold solution
7. Weigh out 54.54 mg Au(III) chloride into a weighing boat or paper using the teflon coated spatula. Metal spatulas can oxidize the Au(III), making it less reactive, so if possible use a teflon coated or plastic spatula.

   CTAB powder with water

8. Using a clean pipette, transfer ~5mL of water from the gold solution flask to the weighing boat holding the Au(III)Cl4.  The gold will dissolve almost immediately. After all of the gold has dissolved, pour the solution back into the gold solution flask. Set aside for later

   Gold(III) chloride (54.54mg)

9. Weigh out 138.8 mg of ascorbic acid either on weighing paper or directly into a glass vial, transfer to a clean glass vial if necessary, and add 10 mL of ultra pure water. Cover and set aside
10. Weigh out the 13.7 mg of AgNO3 either on weighing paper or directly into a glass vial, transfer to a clean glass vial if necessary, and add 10 mL of ultra pure water. Cover and set aside
11. Weigh out the ~7.7 mg of NaBH4 either on weighing paper or directly into a glass vial, transfer to a clean glass vial if necessary, and add 10 mL of ultra pure water. Cover and place in an ice bath or in a freezer until ice cold.

    Image of seed solution, gold solution, silver nitrate, ascorbic acid solutions

12. Solution preparation is now complete, and when the CTAB is completely dissolved, proceed to the next step.

    dissolved CTAB solution