Bare conical nanopore embedded in polymer membrane for Cr(III) sensing.

In this article, we propose a nanopore-based approach to detect metal ions without any external functionalization. In detection of the biologically and environmentally relevant Cr(3+) ion as a prototypical example to prove our strategy, both selectivity and sensitivity were individually achieved. In contrast to mainstream research based on receptor-functionalized nanopores, we report a method for easy regeneration of the nanopore surface that allows elimination of the tedious functionalization steps. Besides, with the assistance of a strong chelator (EDTA), the asymmetric nanopore becomes highly resistant to the interference of the metal-ions matrix, and shows significant specificity towards Cr(3+). The detection limit of this sensor was 16 nM (signal-to-noise ratio=3), which was comparable to reported values. By virtue of the reusability of the polymer surface, metal ion sensors based on asymmetric nanopores can be applied universally in combination with chelators sensitive to specific metal ions.