Multifunctional SERS Substrate for Simultaneous Detection of Multiple Contaminants and Photothermal Removal of Pathogenic Bacteria

In this work, a boric-acid-modified Fe₃O₄@Au@BA-MOF composite material as a multifunctional SERS substrate was ingeniously constructed for detecting both pathogens and antibiotics as well as photothermally inactivating the pathogens. Through improving the dispersity and stability of gold nanoparticles (Au NPs), leveraging the specificity of boric acid (BA) groups in recognizing cis-diol structures, and the ability of SERS technology to provide unique fingerprint spectra of targets, the sensitive and stable detection of pathogens and antibiotics was achieved. Compared with Au NPs and Fe₃O₄@Au, the SERS enhancement factor of Fe₃O₄@Au@BA-MOF was 4.31 × 10⁶, which was about 400 times and 16 times higher than the former two, respectively. Among the existing work, the limit of detection for pathogens was lower or comparable, and it exhibited good stability, maintaining consistent performance for 23 days. Additionally, this substrate achieved efficient photothermal inactivation of pathogens under both near-infrared light and natural light excitation. Within 8 min of near-infrared light irradiation, the bactericidal rates for <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> reach 100% and 99.3%, respectively.