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Au NR synthesis step 3: Purification
The Au NR are prepared in a large excess of CTAB that is removed by
repeated centrifugation / decantation, resulting in Au NR coated with a
double layer of CTAB. The time required for centrifuging depends on
capabilities of the centrifuge. We employ a bench top unit with a swing arm
of 20 cm @ 6000 rpm for ~80 minutes
Materials List
centrifuge |
hot plate |
centrifuge tubes |
collection flask |
storage vial glass or plastic |
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Step 3: Purifications
- Make sure the collected glassware is clean. The solutions may be prepared in any order,
but impurities will prevent the formation of rods
- Label the glassware for your solutions.
- Transfer ~130 ml of ultrapure H2O to a flask. This will be for the
CTAB solution
- Weigh out 11.27g of CTAB into a weighing boat and slowly transfer to the
CTAB solution flask. The CTAB will not readily dissolve in room
temperature water. The dissolving process can be speeded up by placing
the flask in a sonication bath or in an oven at 60oC. It may
require more than 1 hour to dissolve.
- 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.
- Transfer ~152.5 mL of >18MΩ to a clean
flask. This will be for gold solution
- 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 unreactive
- 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
- 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
- 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
- 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.
- Solution preparation is now complete
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