Fig. 1. (a)—(d) High-magnification TEM images of Au@AgNPs with Ag shell thicknesses of 1, 3, 5, 7 nm respectively^[18];(e) TEM images of Au@AgNR^[16]; (f) SEM of B-g-PAMDAC^[20]

Fig. 2. Schematic diagram of bacterial aptamer-AgNPs formation in situ^[23]

Fig. 3. (a) Agglutinin (Con A) functionalized silver-plated magnetic nanoparticles (Ag@MNPs) are combined with bacteria, and the bacteria are separated from the sample matrix in the presence of a magnet; (b) Antibody and SERS tag addition; (c) 3 AgNP conjugates are added together with 3 bacterial pathogens and Con A (combined with all three bacteria), and analyzed by 532 nm laser^[25]; (d) AMP modified and The sample matrix (including bacteria, blood cells or other interfering substances) are cultured together; (e) Fe₃O₄NPs@bacterial complex is magnetically separated from the sample matrix; (f) 4-MPBA modified Au@Ag-GO is cultured with Fe₃O₄NPs@bacterial complex to form a sandwich structure^[26]

Fig. 4. (a) Schematic diagram of the microfluidic system and device^[27]; (b) Optical microscope image taken under 4X magnification showing the microfluidic channel and the active square at the center^[28]; (c) The symmetrical arrangement of four electrodes with polynomial boundaries and the graphs of electric potential field distribution and electrophoretic force^[30] ; (d) Schematic diagram of DEP-SERS device^[29]

Fig. 5. (a) SEM image of S.aureus mixed with AgNPs^- (left), AgNPs⁺ (right); (b) SERS spectra of S.aureus using AgNPs^- or AgNPs^+[32]