SERS detection of Hg2+ and aflatoxin B1 through on–off strategy of oxidase-like Au@HgNPs/carbon dots

In this work, cerium-doped carbon dots (Ce-CDs) both as a reducing agent and template hybrid gold nanoparticles (AuNPs) with weak oxidase-like (OXD) activity was synthesized for the detection of Hg2+ and aflatoxin B1 (AFB1). The AuNPs can catalyze efficiently mercury ion (Hg2+) reduction to the metallic (Hg0) to form Au-Hg amalgam (Au@HgNPs). The obtained Au@HgNPs with strong OXD-like activity oxidize without Raman-active leucomalachite green (LMG) into the Raman-active malachite green (MG) and simultaneously as the SERS substrates by the formed Raman “hot spot” through MG-induced Au@HgNPs aggregation. While AFB1 was introduced resulting in the SERS intensity decreasing due to Hg2+ with AFB1 via carbonyl group to inhibit the aggregation of Au@HgNPs. The work paves a new path for the design of a nanozyme-based SERS protocol for tracing Hg2+ and AFB1 residues in foodstuff analysis.