Synthesis and application of Schiff base as a dual-mode chemosensor for optical determination of aluminium ion content in water samples

Aluminium is highly abundant in the earth's crust and has played a pivotal role in various industries for centuries. Its versatility and abundance have led to its widespread use in everything from food packaging to construction materials. However, this extensive use has also raised concerns about its potential impact on human health and the environment. This study aimed to synthesize and apply a Schiff base molecule, N-(2-hydroxy-1-naphthylmethylidene)-o-aminoacetophenone (N-HyNA), as an optical sensor for aluminium ion (Al³⁺) determination. The synthesis of N-HyNA was achieved with a high yield of 85 % through the reaction of 2-Hydroxy-1-naphthaldehyde and 2-aminoacetonephenone. N-HyNA showed a maximum absorption wavelength at 465.0 nm, and fluorescence emission at 357.0 nm with the excitation wavelength of 278.0 nm. Both absorption and fluorescence signals of N-HyNA were selectively quenched in the presence of aluminium ion. Under optimal conditions for Al³⁺ detection, the absorption mode of N-HyNA with DMSO as a solvent had the limit of detection (LOD) of 0.005 ppm and detection range of 0.01–2.0 ppm, while the fluorescence mode with EtOH as a solvent had the LOD of 0.013 ppm and detection range of 0.05–0.40 ppm. The developed approach demonstrated good agreement in Al³⁺ determination with the conventional atomic absorption spectroscopic technique when using natural water samples and their standard-spiked samples with recovery ranging from 84.0 to 114.0 %. Additionally, analytical characterization was conducted to investigate the quenching mechanism between Al³⁺ and N-HyNA, and a computational study was performed to elucidate the binding position of Al³⁺ in the N-HyNA complex. This developed chemosensor offered a simple and fast, yet accurate and selective detection of Al³⁺ in water samples.