Disposable paper-based PET fluorescence probe linked with calix[4]arene for lithium and phosphate ion detection

Abstract

As a part of our ongoing research, we have synthesized a new fluorescence probe, p-C4A, based on a calix[4]arene substituted with 4-aminoquinoline moieties with amide linkages. p-C4A can selectively recognize Li⁺ and PO₄³⁻ ions and has been characterized via an emission study, an absorption study, ESI-MS spectroscopy, a ¹H NMR study and cyclic voltammetry. The fluorescence sensor p-C4A can operate over a concentration range of 5–170 nM for Li⁺ sensing and 5–80 nM for PO₄³⁻ sensing. The R² values obtained for the sensing of Li⁺ and PO₄³⁻ ions are 0.9962 and 0.9911, respectively. p-C4A demonstrates a minimum detection limit of 6.15 nM for Li⁺ and 9.0 nM for PO₄³⁻. The quantum yields of p-C4A as its Li⁺ and PO₄³⁻ ion complexes were found to be 0.014 and 0.27, respectively. Herein, we report an easy-to-use, low-cost, disposable, paper-based, fluorescent, wax-printed device for the rapid chemical screening of Li⁺ and PO₄³⁻. This device can be used as a quick, portable, multiple-test panel that is simple, lightweight, and disposable. Moreover, in order to assess its analytical applicability, the prepared sensor was successfully used for the determination of Li⁺ and PO₄³⁻ from wastewater samples, validating the proposed ion recovery method with 96–99% recovery rates.