A highly selective, colorimetric, and environment-sensitive optical potassium ion sensor

Abstract

Potassium ions (K⁺) play vital roles in many biological processes and thus highly selective sensors for K⁺ are critical for disease diagnosis and health monitoring. Herein, we report a colorimetric K⁺ sensor (KS7) in which a hemicyanine dye was used as a fluorophore and phenylaza-[18]crown-6 lariat ether (ACLE) was utilized as a K⁺ ligand. The maximum absorption peak of KS7 shifted hypsochromically by 77 nm (from 515 to 438 nm) with an isosbestic point at 452 nm upon the addition of K⁺ to its aqueous solution accompanied by a color change from red to yellow. This sensor exhibited a linear response range to K⁺ from 1 to 200 mM, indicating its wide detection range for cellular, urinary, and environmental potassium ions. Further, this sensor is solvent-sensitive, implying its environmental sensitivity. For the demonstration of its applications, we prepared filter paper-based K⁺ test strips, which were used to detect K⁺ in urine conveniently.