Fig. 2: Characterization of the synthesized Au@MPN.

A Hydrodynamic diameter and polydispersity index of the prepared Au@MPN with the indicated Fe/Au precursor concentration ratios. B TEM image of Au@MPN. C Zeta potentials of AuNPs and Au@MPN. D Normalized UV‒Vis absorbance spectra of the AuNPs and Au@MPN. E XPS spectra of Au@MPN. F High-resolution XPS spectra of Fe in Au@MPN.