Design and Development of Solvent-Sensitive Zn(II)/Al(III) Responsive Chemosensor: Extension to the Real-World Application.

In this work, we have synthesised and spectroscopically characterised an acyl hydrazone-based chemosensor, H2L, through two intermediate steps. Remarkably, this chemosensor exhibits selective recognition of Zn(II) and Al(III) ions in 9:1 EtOH-water and DMSO-water media, respectively, among competing cations. Followed by an optical colour change, the presence of Zn(II) and Al(III) ions enhances the luminescence property of the probe H2L. The limit of detection for both ions is within the nanomolar range. As a practical advantage, the sensor can also be employed in several applications for easy, on-site detection, such as paper strips, cotton buds, and fluorescent ink. The chelation-enhanced fluorescence emission in the presence of two target cations is the primary reason for the increased emission intensity when both analytes are present. The probe-analyte NMR titration confirms the deprotonation of H2L and its coordination to the target metal ions. The Job's plot and mass spectral data are used to assess the stoichiometric addition of the probe to the analyte. The high binding constants obtained for the probe-analyte interactions confirm strong affinity between H2L and the target ion, which is further supported by the successful isolation and characterisation of the corresponding solid Zn(II) complex (complex 1).