Potassium-induced ionic conduction through a single nanofluidic pore modified with acyclic polyether derivative

Abstract

Solid-state nanofluidic pores have been attracting considerable attention of scientific community because of their structural and chemical resemblance with biological ion channels for mimicking biological processes in living systems. Compared to ion channels, synthetic nanopores exhibit high stability, control over pore dimensions (size and geometry) and their surface chemical properties can be tuned on demand. Therefore, they are considered perfect candidates to design and develop nanofluidic sensory devices by introducing a variety of functional moieties on the inner pore surface. Here, we present a nanofluidic pore for the recognition of potassium cations using acyclic polyether derivative in confined environment. To this end, amine terminated acyclic polyether derivative (bis-podand–NH2) is synthesized and covalently coupled with the carboxylic acid groups on the single conical nanopore walls prepared in polymer membrane. The bis-podand moieties fixed on the pore walls in the presence of potassium cation yield recognition domain for the specific binding of K+ cation. Therefore, the changes in rectified ion flux are only noticed on exposure to potassium chloride solution due to formation of positively charged bis-podand–K+ complexes on the pore surface. In contrast, for the case of other alkali metal chloride solutions, only slight changes in the ion current rectification are noticed. We believe that the proposed device provides a strategy to develop and miniaturize different nanofluidic pore based sensors for the efficient detection of other cations/anions by simply changing the length of polyethylene glycol units.