About this protocol:' This protocol outlines the steps and materials involved creating nanoporous gold thin films from a gold/silver alloy with the use of heated nitric acid. This protocol typically gives small pore sizes in the range of 50-100 nm diameter, but it can be altered to give smaller/large pore sizes depending on the dellaoying time and temperatures used. Additionally, final silver content can be controlled through varying nitric acid concentration.
1. 70% Nitric Acid
- Purchased from Sigma Aldrich (258113). CAUTION: Nitric Acid is extremely corrosive and should be stored properly!
2. Ceramic Boat
- Purchased from Thomas Scientific (8542E40)
3. Hot Plate
4. Deionized Water Source
Important: Care must be taken to wear proper PPE during this protocol!
1. Remove gold/silver alloy samples from the deposition wafer and place into a ceramic boat.
- If using thin glass substrates take care not to chip the sample during the dismounting procedure.
2. Pour 125 mL of 70% nitric acid into a glass beaker and place (covered) onto a hot plate.
3. Set the hot plate to 95 °C and start a timer.
4. Check the temperature of the nitric acid every 10 minutes.
- Make sure to write down the temperature for your notes!
5. After approximately 30-40 minutes nitric acid will be at 55 °C.
6. When nitric acid reaches 55 °C place samples to be dealloyed into the acid for 15 minutes.
7. After 15 minutes remove samples and place directly into a beaker with deionized water.
8. Transfer the samples between two beakers with DI water five times to wash the samples (replacing water after each wash).
9. To store samples in water, cover the beaker with Parafilm and leave in a clean environment.
If you intend to work with cells on these samples see the next steps!
10. Store samples in DI water for seven days replacing the water every 24 hours.
11. After seven days dry samples under nitrogen flow in a clean environment and seal into a petri dish for storage.
12. Label with:
- Date deposited (or deposition number):
- Date dealloyed:
- Your name:
- Cell Culture Ready - 7 Days DI (This is very important so you can keep track of the proper samples to use during cell culture!)
1. Let nitric acid cool overnight.
- You MUST label this properly!
2. After nitric acid has cooled dispose of all acid into a neutralized sink or proper waste storage area.
3. Rinse all glassware with DI and dry under nitrogen flow before replacing.
4. If the nitric acid is finished, rinse out the glass bottle and top and leave overnight to dry. Throw away the top in the garbage and dispose of the glass bottle in the appropriate rinsed container disposal area.