Outer-surface Covering of Nanochannels with Hydrogel for Highly Sensitive and Specific Cr(VI) Detection Through Analyte-caused Charge Change in Hydrogel

Nanochannels have made great progress and are a promising platform for detecting a series of targets. However, most nanochannels are modified on the inner wall, while ignoring the outer surface. Here, we modified the outer surface of nanochannels with hydrogel. Different from other reported outer-surface modification methods, we directly cover nanochannels with hydrogel to form heterogeneous membrane. The selected hydrogel hardly adsorbs other ions and shows specific adsorption for Cr(VI). The adsorption sites in hydrogel are homogeneous, and Cr(VI) adsorption onto hydrogel is endothermic and spontaneous. The charge in hydrogel changes after Cr(VI) adsorption, and the resulting current changes can be used for the detection of Cr(VI) with the detection limit of 10 −11 mol/L. Our platform is expected to be used for Cr(VI) detection in living organisms, especially within cells. This work provides a new approach for outer-surface modification of nanochannels and offers a new choice for nanochannel detection platforms.