Surface enhanced Raman scattering (SERS) is difficult to detect molecules with weak adsorption, like aldehydes. Herein, we fabricated core‐shell Au@Ag‐MOFs nanoparticles as SERS substrate. The shell can be controllably synthesized, with the thickness about 3 nm. After the morphology and SERS activity characterization, Au@Ag‐MOFs were employed to sensitive and label‐free detect p‐chlorobenzaldehyde (PCB) in water samples. The pore structure and large surface area of Ag‐MOFs shell results more adsorption of PCB, dragging more molecules to “hot spots” area. The abundant amino group in Ag‐MOFs allows the occurrence of Schiff base reaction with aldehyde group in PCB. Taking the synergistic effect of both physical and chemical enhancement, SERS signals of PCB were greatly boosted. The method showed good linearity between 5.0×10−12 M to 1.0×10−8 M for PCB with the limit of detection (LOD) down to 3.3×10−12 M. The proposed method has great potential to be a reliable analytical strategy for aldehydes in real samples.

17β-Estradiol (17β-E2) could accumulate in human by milk thus cause diseases by interfering the function of endocrine system. But its detection at trace level in milk is still a challenge...