FIG. 2.

Construction of 4-MBA functionalized core-shell magnetic nanoparticles: (a) schematic diagram of the magnetic core-shell nanoparticles, which are composed of (i) an iron core (17 nm), (ii) an SiO₂ layer (110 nm), (iii) a gold shell (48 nm), and (iv) a Raman reporter dye molecule (4-MBA); (b) the structure of Raman reporter 4-MBA, (c) TEM images of silica coated iron before gold coating; and (d) SEM images of the core-shell magnetic nanoparticles after coating with gold and functionalization with 4-MBA.