Highly selective and sensitive colorimetric chemosensor using PVA/chitosan ion-imprinted nanofibers for copper ion...

Herein, a highly efficient colorimetric chemosensor incorporating ion-imprinted electrospun nanofiber was developed for the removal and detection of Cu²⁺ ions. In this regard, PVA/chitosan composites were used as the polymeric matrix, and 1-(2-pyridylazo)-2-naphthol was employed for complex formation. The prepared naked-eye sensor was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, atomic force microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction analysis, revealing the morphological, structural, and molecular properties of the sensor. The results showed that the colorimetric chemosensor based on copper-imprinted nanofiber (Cu-INF) possesses higher selectivity for Cu²⁺ compared to interference ions. The selectivity coefficient (k) and relative selectivity coefficient (K') indicated the selective behavior of Cu-INF in the adsorption of Cu²⁺ in binary systems including Cu²⁺/Co²⁺, Cu²⁺/Ni²⁺, and Cu²⁺/Zn²⁺. Furthermore, the ion-imprinted nanofiber was used for the preconcentration of copper ions, demonstrating a high adsorption capacity of 128.205 mg g^-1 for Cu²⁺. The equilibrium adsorption isotherm and adsorption kinetics of Cu²⁺ on Cu-INF followed the Freundlich adsorption isotherm and a pseudo-second-order model, respectively. The developed sensor exhibited a linear detection range of 5 × 10^-8 - 2 × 10^-7 M with a limit of detection (LOD) of 1.07 × 10^-8 M for copper ions. The results indicated satisfactory adsorption and successful detection of Cu²⁺ at trace concentrations.