Luminescent behavior of pyrene-allied calix[4]arene for the highly pH-selective recognition and determination of Zn2+, Hg2+ and I−via the CHEF-PET mechanism: computational experiment and paper-based device

Abstract

In this article, for the first time, we have reported a novel CHEF-PET fluorescence sensor L based on calix[4]arene containing four pyrene groups as binding sites, which is highly selective and sensitive towards Zn²⁺, Hg²⁺ and I⁻. This fluorescence probe was synthesized and characterized using the emission study, UV-vis titration, ¹H NMR spectroscopy and ESI-MS investigation. The linear concentration range at pH 7 of L for Zn²⁺, Hg²⁺ and I⁻ is 0–135 nM, 0–140 nM and 0–120 nM, respectively, with the detection limit of 6.43 nM for Zn²⁺, 2.94 nM for Hg²⁺ and 20.93 nM for I⁻. The binding ability was determined through Benesi–Hildebrand equation, which was found to be 7.535 × 10⁸ M⁻¹ for Zn²⁺, 9.001 × 10⁸ M⁻¹ for Hg²⁺ and 8.139 × 10⁸ M⁻¹ for I⁻. Further, we reported an easy-to-use, low-cost and disposable paper-based sensing device for the rapid chemical screening of Zn²⁺, Hg²⁺ and I⁻. The device comprises luminescent sensing probes embedded into a cellulose matrix, where the resonance energy transfer phenomenon seems to be the sensing mechanism. It opens up new opportunities for simple and fast screening in remote settings, where sophisticated instrumentation is not always available. The MOPAC-2016 software package was used to optimize the L using the well-established PM7 method and calculate the HOMO–LUMO energy band gap for structure L and L with Zn²⁺, Hg²⁺ and I⁻ ion-based structures. The molecular docking study was carried out using HEX software.