An ultrasensitive surface-enhanced Raman scattering sensor for the detection of hydrazine via the Schiff base...

The development of convenient assays for the determination of hydrazine (N₂H₄) has drawn significant attention due to the high toxicity of this substance. Herein, we developed a concise, rapid and ultrasensitive surface-enhanced Raman scattering (SERS) sensor for N₂H₄ detection based on alpha-cyclodextrin-silver nanoparticles (α-CD-AgNPs) modified by 4-mercaptobenzaldehyde (4-MBA). The 4-MBA molecules can specifically capture the N₂H₄ molecules and undergo a Schiff base reaction. As a result, this induces the aggregation of nanoparticles and generates a new characteristic peak at 1529 cm^-1 that is attributed to CN and CC vibrations. Compared with noble metal nanoparticles, 4-MBA not only formed AgS bonds but could also be fixed in the cavity of cyclodextrin to produce a more stable and stronger SERS signal. The SERS intensity at 1529 cm^-1 and the logarithm of the concentration of N₂H₄ presented a good linear relationship from 10^-9 to 10^-7 M with an unprecedented limit of detection (LOD) of 38 pM. The proposed SERS sensor exhibited satisfactory selectivity and reproducibility and was applied to detect N₂H₄ in real and complex water samples. We expect this assay to be a promising alternative tool for the on-site detection of N₂H₄.