Highly Sensitive SERS Detection of Hg²⁺ Ions in Aqueous Media Using Gold Nanoparticles/Graphene Heterojunctions

Gold nanoparticles (AuNPs)/reduced graphene oxide (rGO) heterojunctions were synthesized directly on SiO₂/Si substrates via a seed-assisted growth process. The in situ chemical fabrication strategy has been proven to be quite simple and efficient for generating highly active surface-enhanced Raman scattering (SERS) substrates due to synergistic enhanced protocol from rGO and AuNPs. The SERS substrates with AuNPs/rGO heterojunctions have been utilized for trace analysis of mercury­(II) ions via thymine–Hg²⁺–thymine coordination. Thereby, very low limits of detection, i.e., 0.1 nM or 20 ppt for Hg²⁺, can be achieved in contrast with some other SERS subsrtates, which suggests that the heterojunctions are appropriate as versatile surface-enhanced substrates applied in chemical sensing or biosensing