Fabrication of Poly(styrene‐co‐maleic anhydride)@Ag Spheres with High Surface Charge Intensity and their Self‐Assembly into Photonic Crystal Films

Herein, we developed a method to prepare monodisperse poly(styrene‐co‐maleic anhydride)@Ag (PSMA@Ag) core–shell microspheres with high surface charge intensity by using an in situ reduction method. In this method, ethylenediamine tetraacetic acid tetrasodium salt (Na(4)EDTA) was used as a reducing agent to promote the growth of Ag, and at the same time endowed the PSMA@Ag spheres with a surface charge. The monodispersity of PSMA and PSMA@Ag and the ordered array of the photonic crystal films were characterized by using SEM. The formation of Ag nanoparticles was confirmed by using TEM, HR‐TEM, and XRD characterizations. Due to the existence of surface charges, the obtained PSMA@Ag microspheres easily self‐assembled to form photonic crystal structures. In addition, the surface‐enhanced Raman scattering (SERS) activity of the PSMA@Ag photonic crystal films was evaluated by detecting the signal from Raman probe molecules, 4‐aminothiophenol (4‐ATP). The PSMA@Ag photonic crystal films exhibited a high SERS effect, a low detection limit of up to 10(−8) for 4‐ATP, good uniformity, and reproducibility.