Tuning of ion current rectification and ion current saturation of multiple nanochannels in polymeric membrane

Abstract

The present study gives an insight into ion flow dynamics of aqueous electrolytes via functionalized multiple nanochannels in polyethylene terephthalate (PET) membrane. The selectivity of certain ions (anions/cations) of various electrolyte combinations KCl- KClO4 (S1), KBr-KCl (S2), KBr-KClO4 (S3) over their counter-ions by the nanochannels (generated via swift heavy ion irradiation followed by chemical etching) has been studied. Tuning of the ion transport and ion current rectification has been done using different functionalized nanochannels (with charged carboxyl and protonated amino groups). The impact of ion selectivity of the nanochannels is reflected in the short circuit current and ion current saturation of different systems. The collection of counter ions outside the channels along with the in-built potential due to the flow of ions inside the channels play a crucial role in the ion transport behaviour of the collective system. The cation-selective channels (with charged carboxyl groups) show low rectification ratio compared to the anion-selective channels. The functionalized nanochannels with two -OH polar charge groups (generated through the amino-silane based reagent (3-aminopropyl) trimethoxysilane (APTMS)) exhibit higher current saturation values (S1AP∼31 μA, S2AP∼30 μA and S3AP ∼ 30.5 μA) and higher short circuit current values (S1AP ∼32.3μA, S2AP ∼ 29.6μA and S3AP ∼31.3μA) due to the overlapping of electric double layer (EDL). Systematic study of tuning of ion transport through nanochannels helps to understand the nanofluidic flow and has imminent application in the fabrication of nanoelectronic and bioinspired nanodevices.