Luminescence sensing, DFT, extraction and monitoring of Cr3+ and Al3+via the application of first derivative fluorescence spectroscopy

Abstract

A novel anthracene containing Schiff base (L) has been developed as a turn-on chromofluorogenic sensor for chromium(III) (Cr³⁺) and aluminium(III) (Al³⁺) ions in an aqueous environment. It has been characterized by absorption, emission, FTIR, NMR and mass studies. The receptor shows a significant colour change from blue to green under UV light, in the presence of Al³⁺ and Cr³⁺ with limit of detection (LOD) and association constant (K_ass) values of 10⁻¹¹ M and 10⁵ M⁻¹, respectively. In the presence of monovalent and divalent ions (Na⁺, Hg²⁺, Pb²⁺, Cd²⁺, Ni²⁺, Co²⁺, Cu²⁺, Fe²⁺, Mn²⁺ and Zn²⁺), no significant changes are observed in their spectral patterns. Upon excitation, the ligand exhibits a turn-on emission in the presence of Al³⁺ and Cr³⁺, which may be due to chelation-enhanced fluorescence (CHEF), which is further supported by DFT/TDDFT studies. Herein, Al³⁺, Cr³⁺, Fe³⁺ and EDTA have been used to design an advanced level combinational INHIBIT gate. Moreover, this ligand is capable of selectively extracting Al³⁺ and Cr³⁺ from an aqueous mixture of other metal ions by the liquid–liquid extraction method. In order to estimate Al³⁺ and Cr³⁺ concentrations simultaneously in the mixture without prior separation, first derivative normal fluorescence spectroscopy has been applied.