New chromogenic and fluorogenic symmetric Carbazole Schiff base-derivative: Synthesis, sensing performances and smartphone-assisted fluorometric assay for selective Al3+ detection in drinking water

• Published in: Journal of molecular structure 2025-02, Vol.1322, p.140548, Article 140548
• Main Authors: Bhiri, Fatma, Chemli, Mejed, Sakly, Nawfel, Bahrouni, Yahya, Wazzan, Nuha, Majdoub, Mustapha
• Format: Article
• Language: English
• Subjects: Al3+ detection; Fluorescence turn-On; Hydrolysis; Schiff base; Smartphone-assisted fluorescence analysis platform
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2024.140548

•Designed and synthetized of a new symmetric carbazole derived-Schiff base (Carb-Azo) by simple condensation between 2,7-bisformylecarbazole and 2-aminophenol.•Achievement of rapid and highly sensitive chromogenic and fluorometric optical probe for the selective detection of Al3+ in an optimal volume ratio (THF/H2O: 9/1) with limit of detections of 112 nM and 9.4 nM, respectively.•Confirmation of the Al3+ induced hydrolysis and turn on sensing mechanism by a correlation between MEP, 1H NMR titration, UV–visible and fluorescence spectroscopies.•Building of low cost and readily-use smartphone (SP) coupled fibre optic endoscope camera-assisted fluorescence sensing platform for practical on-site Al3+ detection.•Development of straightforward and reliable fluorescence assay for the control of the safety of drinking water against Al3+ contaminant by means of combination of a portable device with RGB (Red/Green/Blue) color analysis android application. The symmetric carbazole-derived Schiff base reported herein, Carb-Azo, has been synthesized as a chromogenic and fluorogenic probe for Al3+ ion detection in aqueous media. The compound Carb-Azo was synthesized by the condensation of 2,7-bisformylcarbazole and 2-aminophenol and subsequently characterized by means of NMR, FT-IR, Mass, UV-visible, and fluorescence spectroscopies. Besides, DFT calculations confirmed the most stable conformation. In an optimized mixture of THF/H2O (9:1), Carb-Azo exhibits excellent selectivity, rapid response time (∼2 min), and high sensitivity toward Al3+ cation with detection limits (LoD) of about 112 nM and 9.4 nM via, respectively, spectrophotometry and fluorescence spectroscopy. The probable sensing mechanisms were clarified based on the observed turn-On blue fluorescence emission and the irreversible induced hydrolysis process. Finally, for practicable on-site Al3+ detection, a smartphone-coupled fiber-optic endoscope camera platform was built. With the help of the extracted RGB values from the output fluorescence image, a LoD of 0.4 µM was obtained, making the proposed assay suitable for the control of drinking water safety against Al3+. [Display omitted]