▎ 摘　　要

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.