Fig. 2. The basic constituents of SERS tags and the synthesis of PB-based nanomaterials. (A) The representation of the basic elements of SERS tags. Adapted with permission from ref. 51. Copyright 2019 American Chemical Society. (B) The synthesis and characterization of Au@PB NPs: (B.1) A schematic illustrating the synthesis of Au@PB NPs; (B.2) TEM images, the inset is the corresponding high-angle annular darkfield scanning TEM image; (B.3–B.6) EDX mapping of Au, Fe, O and the overlay images. Reproduced with permission from ref. 61. Copyright 2021 American Chemical Society. (C) The synthesis and characterization of Au@PBA NPs: (C.1) Schematic illustrating the synthesis procedure of Au@PBA NPs; (C.2) SEM image of Au@PBA (Cu) NPs, the inset is the TEM image of a single Au@PBA (Cu) NP; (C.3) SEM image of Au@PBA (Pb) NPs, the inset is the TEM image of a single Au@PBA (Pb) NP. Reproduced with permission from ref. 62. Copyright 2021 Elsevier. (D) The synthesis and characterization of p-Au@PB NPs: (D.1–D.7) TEM images of the formed process of p-Au@PB NPs, the inset is the magnified image of p-Au@PB NPs. Adapted with permission from ref. 63. Copyright 2019 John Wiley & Sons, Inc.