2.3 AuNPs-SS synthesis.
HAuCl4 was solubilized in deionized water to obtain a 1.0 × 10-3 stock solution. 1.5 mL of this solution were mixed with 2 mL of water and 500 µL of the received SS. The mixture was moderately stirred at room temperature. The UV–Vis spectra of this solution were carried out soon after the preparation and at 4, 6, 24, 48 and 72 h after, to monitor the AuNPs-SS formation. The induced AuNPs-SS were purified at each acquisition time, and the excess SS and unreacted HAuCl4 were removed by washing in fresh water and centrifuging (7000 g, for 10 minutes). Before the spectra acquisition, the obtained solutions were properly diluted if necessary.