Selective Detection of Cu²⁺ Ions by Immobilizing Thiacalix[4]arene on Graphene Field-Effect Transistors

Highly accurate quantitative detection of heavy metals is essential for environmental pollution monitoring and health safety. Here, for selective detection of Cu²⁺ ions with high sensitivity, thiacalix[4]arene (TCA) immobilized on graphene field-effect transistors (G-FETs) are developed. Our proposed TCA-immobilized G-FETs are successfully used to detect Cu²⁺ ions at concentrations ranging from 1 μM to 1 mM via changes in their transfer characteristics. Moreover, the measured transfer characteristics clearly shift only when Cu²⁺ ions are introduced in the buffer solution despite it containing other metal ions, including those of Na⁺, Mg²⁺, Ni²⁺, and Cd²⁺; this selective detection of Cu²⁺ ions is attributed to the planar arrangement of TCA on graphene. Therefore, TCA-immobilized G-FETs selectively detect Cu²⁺ with high sensitivity.