A new “off-on-off” sensor for sequential detection of Al3+ and Cu2+ with excellent sensitivity and selectivity based on different sensing mechanisms

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 391; p. 112372
• Main Authors: Xu, Yuankang, Yang, Lei, Wang, Hanyu, Zhang, Yanxia, Yang, Xiaofeng, Pei, Meishan, Zhang, Guangyou
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-03-2020
• Subjects: Different sensing mechanisms; Excellent detection limit; Real water sample; Schiff base; Theoretical calculation; Schiff base; Excellent detection limit; Theoretical calculation; Different sensing mechanisms; Real water sample
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/j.jphotochem.2020.112372

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•A new simple fluorescence sensor (X) was designed and synthesized based on salicylaldehyde and imidazo[2, 1-b]thiazole.•X could be used as “off-on-off” sensor for sequential detection of Al3+ and Cu2+ based on different sensing mechanisms•The detection limits of sensor for Al3+ and Cu2+ were calculated to be 3.1 × 10-10 M and 9.8 × 10-11 M, respectively.•The optimized structure and energy calculations of X, X[Al3+] and X[Cu2+] were obtained by Gaussian 09.•The sensor successfully detected Al3+ and Cu2+ in the real water sample with a satisfactory recovery and RSD values.
A new simple Schiff base, (E)-N'-(2-hydroxybenzylidene)imidazo[2,1-b]thiazole-6-carbohydrazide (X), was designed and synthesized based on salicylaldehyde and imidazo[2, 1-b]thiazole. X could be used as a sensor to identify Al3+ through a significant fluorescence enhancement because of CHEF and inhibition of PET process and then to detect Cu2+ through a highly efficient quenching behavior due to the paramagnetic quenching. The sensor showed a high selectivity for Al3+ and Cu2+ in methanol solution at pH = 5 and was not disturbed by other competing metal ions. Furthermore, based on the equation 3σ/slope, the detection limits of sensor for Al3+ and Cu2+ were calculated to be 3.1 × 10−10 M and 9.8 × 10-11 M, respectively. Additionally, the association constants of X[Al3+] and X[Cu2+] were also determined to be 2.3 × 104 M-1 and 6.1 × 104 M-1 on basis of Benesi-Hildebrand equation. In addition, the titration experiment of fluorescence and mass spectrometry showed that sensor was combined with Al3+ or Cu2+ both in 1:1 ratio. Moreover, the optimized structure and energy calculations of X, X[Al3+] and X[Cu2+] were obtained by Gaussian software based on the basis set of B3LYP/6−31 G(d) and B3LYP/LANL2DZ. And, the sensor successfully detected Al3+ and Cu2+ in the real water sample with a satisfactory recovery (91.4 % - 107.1 %) and RSD values (0.66 % - 1.91 %).