Fig. 2. Transmitted signals tuned by the size of ions.

a The V_b⁰-V_t dependence in monolayer graphene obtained using various cations in the top reservoir. The bottom reservoir was filled with KCl. All solutions used were 0.01 M. The solid line is a guide to the eye, indicating the relationship of V_b⁰ = V_t. Error bars are S. T. D. Inset shows statistic results from 4 monolayer devices, where each bar represents one device. The grey bars are the ratio of V_b⁰ between using Li⁺ and K⁺ ions in the top reservoir, taken at V_t = −0.6 V. The red bars are the same ratio, but taken at V_t = +0.6 V. b The variation of V_b⁰ as a function of cations’ hydration sizes 1/d_H, taken from (a) at V_t as indicated. The dashed lines are the predictions using V_b⁰ = V_t d_H^K+/d_H, with d_H^K+ = 6.6 Å.