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

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.