Metallochromic Hydrazone‐Based Chemosensor with Application in a Colorimetric Paper Strip for Selective Detection of Cu <sup>2+</sup>
Walid Sharmoukh, Meram S. Abdelrahman, Elkhabiry Shaban, Tawfik A. Khattab
Abstract
Abstract A new tricyanofuranhydrazone‐based colorimetric chemosensor (TCFH) was synthesized and immobilized onto paper strips for selective detection of Cu 2+ in aqueous environments. The synthesis strategy of TCFH involved an azo‐coupling process between the diazonium salt of 8‐aminoquinoline and an active methyl‐bearing tricyanofuran (TCF) heterocyclic moiety. Due to intramolecular charge transfer, TCFH chromophore demonstrated pronounced solvatochromism depending on the solvent polarity. Changes in both color and UV‐Vis absorption spectra demonstrated by the developed chemosensor proved that TCFH can be utilized to detect Cu 2+ in the presence of other competing metallic cations and anions. The synthesized TCFH probe, which contains a hydrazone recognition moiety, demonstrates dramatic solvatochromic activity and high selectivity at the microlevel of copper ions with a color shift from yellow to purple. Moreover, test strips of TCFH were successfully developed and applied for the detection of copper ions at different concentrations in aqueous media. The colorimetric properties of the prepared TCFH‐immobilized paper strips were investigated by CIE Lab chromogenic parameters, colorimetric strength ( K/S ) and UV‐Vis absorbance spectra. The best detection of Cu 2+ was achieved in the pH range of 6.6–7.4 demonstrating an immediate color switch relying on the total content of Cu 2+ . SEM was applied to characterize the deposition of tricyanofuranhydrazone onto the surface of the paper strip.