Figure 4.

(a) Sensitivity and specificity comparison between K⁺ and Na⁺ ions; (b) Schematic illustration of the interaction between K⁺ ions and guanine-quadruplexes; (c) High selectivity for K⁺ ion detection over other interfering cations (added concentrations: K⁺ 1 nM; Others 10 nM).