Electrochemical impedance spectroscopy (EIS) is a rapid and powerful method for evaluating the pore structure of membranes. However, the application is limited due to the lack of appropriate training of engineers in electrochemistry and materials engineering. The introduction of laboratory practices can effectively improve the understanding of electrochemistry and the theory behind the various applications. In this paper, we suggest a laboratory experiment on the characterization of the pore structure in a membrane by EIS. The membrane resistance was obtained from the impedance spectrum, and the correlation between the membrane resistance and water flux of the membrane is discussed. Moreover, the influence of the electrolyte concentration on the EIS result was also investigated in the designed experiment. Students are trained to collect the impedance spectra of the membrane under different conditions and learn to understand the effects of the operating parameters (electrolyte concentration and pore size) on the impedance spectrum. This laboratory class allows undergraduate students to better understand the principle of impedance spectroscopy on membrane characterization.
Two-dimensional nanomaterials could be potentially applied in the field of brain-computer interface due to their significant inductive effect during ion permeation. In order to tune the inductive signal through the microstructure, a membrane based on MXene-grafted β-cyclodextrin (β-CD) was prepared, and its electrochemical performance was recorded. The experimental results confirmed that β-CD has been successfully intercalated into the gallery between the MXene sheets, and the intercalation induced a weaker inductive effect of MXene in the ion diffusion process. Moreover, the results indicated that easier ion diffusion through the membrane could result in weaker inductance. Besides, the experimental results were roughly analyzed by the backpropagation (BP) neural network to compare the contribution of the influence factors. The results suggested that tunable inductance can be achieved by constructing a certain interlay spacing of MXene, which could be potentially used to design microsized inductors in biological applications.
The inductive effect of 2D material in an aqueous solution can be potentially applied in biological implantable electronic devices. In this paper, graphene oxide (GO) membranes were prepared via the vacuum filtration method and then treated under different heat temperatures. X-ray diffraction and scanning electron microscopy results showed the shrinkage of the interlayer spacing in the GO membrane, while Fourier transform infrared results indicated the loss of oxygen-containing polar groups during the heat treatment. EIS results confirmed the inductive signal of the GO membrane appeared during the ion diffusion process. And the inductive effect can be controlled by the polar groups and the interlayer spacing in the GO membrane. Moreover, at lower electrolyte concentrations (0.0100 mol/L), more polar groups lead to a stronger inductive signal, while at higher electrolyte concentrations (0.10 mol/L), narrower interlayer spacing results in a stronger inductive signal. The investigation may provide a key clue to tune the inductance of the biological electronic device based on GO.
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