In-situ preparation of Ferrero® chocolate-like Cu2O@Ag microsphere as SERS substrate for detection of thiram

It is a challenging and valuable work to synthesize surface enhanced Raman scattering (SERS) substrate with low cost and high performance by simple methods, and use it to detect pesticide residues in food. Here, Ferrero® chocolate-like Cu2[email protected] microspheres (FRC-Cu2[email protected]) were fabricated by a facile in-situ redox reaction. Cu2O directly acted as templates and reducing agents to induce the nucleation and growth of Ag nanoparticles on the microspheres surfaces. The prepared semiconductor-noble metal hybrids of Cu2[email protected] were utilized as SERS substrates to detect 4-mercaptobenzoic acid (4-MBA) and thiram molecules. The distinguished SERS effect was achieved when target molecules absorbed on the FRC-Cu2[email protected] composite. The substrate presented excellent sensitivity and reproducibility for the detection of 4-MBA and thiram with the limit of 10−10 and 10−9 M, respectively. Due to combining both advantages of electromagnetic enhancement of Ag metals and chemical enhancement of Cu2O semiconductors, the obtained FRC-Cu2[email protected] microspheres provided a SERS platform to conveniently detect molecules with thiol groups. When it was applied to detect thiram residues on apple peel and the detection limit was 1.2 × 10−7 M, low than maximal residue limit (MRL) of 7 × 10−6 M in fruit prescribed by the U.S. Environmental Protection Agency (EPA).