Dual-response for Hg²⁺ and Ag⁺ ions based on biomimetic funnel-shaped alumina nanochannels

Biomimetic dual-ion-responsive nanochannels were developed by the principles of metal-ion-mediated base pairs of the responsive T-/C-rich single strand DNA (ssDNA). The responsive ssDNA was immobilized into the funnel-shaped alumina nanochannels, which were fabricated using the anodization technology and pore-widening process. In neutral solution, the conformation of the ssDNA changed from a loosely packed structure into a duplex structure by interacting with Hg²⁺ or Ag⁺ ions (T-Hg²⁺-T or C-Ag⁺-C complexes). The decreasing ionic currents through the nanochannels were utilized to detect concentrations of Hg²⁺ or Ag⁺ ions. The conversion of duplex-quadruplex of Ag⁺ ions and DNA could be triggered by changing the pH value of aqueous solutions to 4.5, whereas it did not happen in Hg²⁺ ions solution. Thus, the ssDNA-modified alumina nanochannels selectively responded to Hg²⁺ and Ag⁺ ions at pH 4.5 with different ionic transportation properties. The biomimetic dual-ion-responsive nanochannels promised great potential in multiplexed ion sensing.