Designed Ionic Microchannels for Ultrasensitive Detection and Efficient Removal of Formaldehyde in an Aqueous Solution

Ultrasensitive and ultraprecise detection of toxic target molecules is highly desirable for monitoring water pollution and improving human safety. Herein, a novel formaldehyde (HCHO) responsive ionic microchannel was successfully fabricated through constructing ethylenediamine (EDA)-functionalized poly(ionic liquid)/polyacrylonitrile nanofibrous membrane (PIL/PAN NFM). By employing the reactivity of HCHO with EDA immobilized on the prepared ionic nanofibrous membrane, the resultant ionic current output can switch from low to high because of the electron affinity increase and zeta potential decrease of the microchannels when reacting with more HCHO. Meanwhile, benefiting from the poly(ionic liquid) backbones in the designed ionic microchannels, the ions in electrolyte were greatly enriched in the channels and facilitating more ion transport paths formed along with the ionic nanofibers, therefore amplifying the detected ionic current signals. On the basis of the ionic current amplification mechanism, it is further used to detect a trace of HCHO in an aqueous solution. Finally, the ionic microchannels exhibited high sensitivity for the determination of HCHO ranging from 360 ppm (3.6 x 10(2) mg/L) to 0.036 ppt (3.6 x 10(8) mg/L) (R-2 = 0.93) through an established linear correlation between responsive ionic current and HCHO concentrations. Furthermore, the ionic microchannels can remove a large number of HCHO molecules from an aqueous solution due to the abundant amino grafted on the membrane. In a sum, this work paves a promising way toward the design of artificial microchannels for various harmful compounds detection.