An “Off-On-Off” type fluorescent chemosensor for the relay detection of Zn2+ and H2PO4− in aqueous environment

• Published in: Inorganica Chimica Acta 2020-03, Vol.502, p.119348, Article 119348
• Main Authors: Saravana Kumar, S., Selva Kumar, R., Ashok Kumar, S.K.
• Format: Article
• Language: English
• Subjects: Aqueous environments; CHEF; Chelation; Chemical sensors; Chemical synthesis; Chemoreceptors; Chemosensors; DFT; Fluorescence; Logic circuits; Phosphate; Qualitative analysis; Zinc
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2019.119348

[Display omitted] •Sensors HL and HL-Zn2+ detects Zn2+ and H2PO4− by fluorescence.•Binding mechanism of HL and HL-Zn2+ towards Zn2+ and H2PO4− studied by NMR, mass and DFT analysis.•HL and HL-Zn2+ detect Zn2+ and H2PO4− down to 8.8 nM and 55 nM respectively. A new fluorescence receptor 2-(diethylamino)-N-(quinolin-8-yl) acetamide (L) was synthesized by simple reaction condition. The ligand HL is highly selective and sensitive towards Zn2+ ions over other tested metal ions. Upon interaction HL with Zn2+, the receptor HL showed a distinct fluorescence enhancement at 496 nm due to chelation enhanced fluorescence (CHEF) leading to visible fluorescence color change from blue to cyan. Subsequently, an in-situ generated L-Zn2+ when interacted with various anions, only with H2PO4− showed fluorescence quenching while other ions did not respond. Accordingly, the receptor HL was developed for the highly selective determination of Zn2+ and H2PO4− with the lowest detection limit (LOD) of 8 nM and 55 nM respectively. The binding mechanism of HL with Zn2+ and L-Zn2+ with H2PO4− were studied by both experimental and theoretical studies. The off-on-off sequential of HL with Zn2+ and H2PO4− were successfully employed for the INHIBIT logic gate response and cellulose assisted test strips proved, the practical application for qualitative analysis of Zn2+ and H2PO4− ions. Finally, the receptor HL was applied for the detection of Zn2+ in different water and pharmaceutical samples.