Fig. 1: Preparation and characterization of the MLM-EDTA.
From: Two-dimensional MXene membranes with biomimetic sub-nanochannels for enhanced cation sieving
a The ion selectivity filter in KcsA K+ channel is a 5.6 Å channel composed of eight negatively charged oxygen atoms (PDB code 1K4C), which inspired us to design an MLM-EDTA with numerous negatively charged oxygen atoms and 6.0 Å two-dimensional channel. b TEM image and selected area electron diffraction (SAED) pattern of the Ti3C2Tx nanosheets. Scale bar, 1 μm. c SEM image of the cross-section for MLM-EDTA-1.0. Scale bar, 1 μm. d TEM image of the cross-section of the MLM-EDTA-1.0 membrane, insert: the computerized TEM image obtained from the inverse Fast Fourier-Transform (IFFT) and FFT patterns after removing background noise. Scale bar, 10 nm. e Schematic diagram of the cross-linking mechanism between Ti3C2Tx nanosheets and EDTA molecule. f Comparison of anti-swelling properties between MLM and MLM-EDTA-1.0 membranes obtained from XRD patterns. The XRD patterns of the wet samples were measured immediately after being immersed in different solutions (DI water, 0.2 M KCl, NaCl, LiCl, CaCl2, MgCl2 single salt solutions and mixed salts solution) for 3 h. g The free-spacings (see Supplementary Fig. 12 for details) of MLM and MLM-EDTA-1.0 in the dry state and various solutions obtained from the XRD patterns in (f). Error bars represent the standard deviation of three measurements of a sample.
