A chemosensing approach for the colorimetric and spectroscopic detection of Cr 3+ , Cu 2+ , Fe 3+ , and Gd 3+ metal ions.

Metal cations are present in domestic and industrial wastewater and have adverse effects on human and aqueous life. The present study describes the development of the molecular probe 9-anthracen-9-ylmethylene)hydrazineylidene)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol (AMHMPQ) to detect Cr ³⁺ , Cu ²⁺ , Fe ³⁺ , and Gd ³⁺ ions by using UV-visible, fluorescence, colorimetric and excitation-emission matrix (EEM) spectroscopy techniques. The interaction of Cr ³⁺ , Cu ²⁺ , Fe ³⁺ , and Gd ³⁺ can be observed by the absorption maxima shift, turn-off, colour changes, and EEM shifts. In addition, fluorescence limits of detection 17.66 × 10 ^-6 M, 6.44 × 10 ^-9 M, 28.87 × 10 ^-8 M, and 12.49 × 10 ^-6 M in wide linear ranges, low limits of quantifications, high values of Stern-Volmer constant, Job's plot and Benesi-Hildebrand plot justify the 1:1 association affinity with association constants of 1.46 × 10 ⁴ M ^-1 , 1.86 × 10 ⁷ M ^-1 , 2.69 × 10 ⁵ M ^-1 , 2.13 × 10 ⁴ M ^-1 for AMHMPQ-metal ions (Cr ³⁺ , Cu ²⁺ , Fe ³⁺ , and Gd ³⁺ ions), respectively. Paper- and mask-based kits are developed to explore the utility of the designed chemosensor. Additionally, AMHMPQ acts as a reusable sensor for two, seven, two, and zero cycles for Cr ³⁺ , Cu ²⁺ , Fe ³⁺ , and Gd ³⁺ ions, respectively, when checked with EDTA.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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