Colloidal gold nanoparticles on anodic alumina oxide substrates for surface-enhanced Raman scattering

A method to synthesize colloidal gold nanoparticles on Anodic Alumina Oxide substrates for Surface-enhanced Raman Scattering comprising:

• soaking a 250 mL Erlenmeyer flask in a base bath solution overnight;
• thoroughly rinsing said flask with purified water and creating a solution by adding 200-300 mL of purified water and 0.05 to 0.06 grams HAuCl4;
• turning off any lights to prevent any interaction with gold salt;
• bringing said solution to a boil with moderate magnetic stirring on a hot plate;
• once boiling, the stirring is increased until a vortex is achieved in said solution;
• then rapidly adding 0.05 to 0.06 grams sodium citrate to said solution, and continue boiling with rapid stirring for 14 minutes;
• removing said flask from the hot plate and cooling said solution to room temperature;
• cooling said resulting solution containing colloidal gold nanoparticles in a refrigerator;
• once cooled, measuring said colloidal gold nanoparticles solution with absorption spectroscopy to confirm the presence of a surface plasmon peak;
• centrifuging said colloidal gold nanoparticles solution in plastic centrifuge tubes at 4000 rpm for 25 minutes for a batch comprising 6 plastic centrifuge tubes;
• and,
• forming colloidal gold nanoparticle films on nanoporous anodic alumina oxide substrates using a wet-chemical, three-phase ligand-exchange procedure carried out at room temperature.