Two-dimensional biomimetic potassium channels at an oil/water interface supported by graphene laminar membranes

In this work, a new strategy was proposed herein to mimic K+ channels embedded in biomembrane by using the graphene laminar membrane (GLM) composed of two-dimensional (2D) angstrom(Å)-scale channels to support a simple model of semi-biomembrane, namely oil/water (O/W) interface. Additionally, the ion-transfer voltammetry (ITV) was firstly employed to investigate the transmembrane behaviors of some small cations through GLM with comparison to the measurements of ionic conductivity (G). Amazingly, we found that K+ is completely preferred over Na+ and Li+ to transfer across the GLM-supported O/W interface although the monovalent ion selectivity of GLM in the W/GLM/W system is still low (K+/Na+~1.11 and K+/Li+~1.35). Moreover, the voltammetric responses for the ion transfer of NH4+ at the GLM-supported O/W interface are also observed as found that NH4+ can pass through the biological K+ channels. The underlying mechanism of as-observed K+-selective voltammetric responses is discussed and found to be consistent with the energy balance of cationic partial-dehydration (energetic cost) and hydrated cation-π interactions (energetic gain) as involved in biological K+ channels. This work provides a novel platform to not only understand the ion discrimination of graphene-based Å-scale channels from a new perspective by using ion-transfer voltammetry but also exploit the potential applications of 2D laminar membranes in the fields of biomimetic ion channel and electrochemical ion sensing or extraction. Fig. 3(d) and Fig.S3 a-c are the data of PXRD patterns of dry GLM/PET, PET, F-GLM (free-standing GLM) and the GLM/PET after immersion inside deionized water for 48 h. Fig.4. a-d, Fig. 5a,b, and Fig. S4 and Fig. S5a,b are the I-V characteristics and the corresponding Ionic conductance (G=ΔI/ΔV) values obtained by using GLM/PET or F-GLM under different conditions as described in every Figure. Fig.6a-d, Fig. 7b, c, and Fig. S6 and Fig. S7 are the CVs and the corresponding DPVs obtained by using GLM/PET or F-GLM under different conditions as described in every Figure.