N'-(4-(diethylamino)-2-hydroxybenzylidene) isonicotinohydrazide based chemosensor for nanomolar detection of Ni(II) ion

A novel Schiff base, N'-(4-(diethylamino)-2-hydroxybenzylidene) isonicotinohydrazide (S1) was synthesised by the condensation reaction between isonicotinohydrazide and 4-(diethylamino)-2-hydroxybenzaldehyde. The chemo-sensing behaviour of S1 towards Ni2+ was investigated and confirmed that the S1 exhibited fair selectivity and sensitivity. Furthermore, it was noted that there was no significant effect of co-existing cations and anions on the detection of Ni2+. The complexation ratio of S1 and Ni2+ was confirmed as 1:1 with Jobs continuous variation method and two isosbestic points on absorption titration further supported by DFT calculations. The binding constant (Kb) for S1+Ni2+ was calculated as 22,769 M-1 and 22,134 M-1. Moreover, the obtained limit of detection (LOD) for Ni2+ was found to be 375 nM. Finally, chemosensing applications of S1 as a paper test strip kit in the environmental monitoring assessment laboratory for the recovery of Ni2+ from real water samples were successfully designed and evaluated.

Automated summary

A novel Schiff base, S1, was synthesized and found to exhibit fair selectivity and sensitivity towards Ni2+. It showed no significant interference from co-existing cations and anions. The complexation ratio of S1 and Ni2+ was confirmed as 1:1, and the binding constant (Kb) was calculated. A paper test strip kit using S1 was successfully designed for the recovery of Ni2+ from real water samples in the environmental monitoring assessment laboratory.