Stacked-overlapped graphdiyne nano-iontronics enabling enhanced monovalent/divalent cation selectivity for single-cell pH detection

ABSTRACT Developing nano-iontronic devices that minimize ionic interference is essential for precise measurements in complex physiological systems. Graphdiyne (GDY), a novel carbon allotrope featuring sub-nanometer pores, enables effective regulation of ionic transport and is therefore a promising material for high-performance iontronic applications. Here, we report a pH-responsive nano-iontronic device fabricated by stacking and overlapping graphdiyne (so-GDY) layers onto the tip of the nanopipette. This so-GDY-based pH nano-iontronic sensor exhibits a linear decrease in ionic current under negative potential as the pH decreases from 8.00 to 5.50. This response is attributed to protonation of the oxygen-containing functional groups on the so-GDY surface and edges, which diminishes the negative surface charge and thereby reduces ionic conductivity. A key advantage of this nano-iontronic device is its excellent selectivity, demonstrating robust resistance to interference from divalent cations (Mg2+, Ca2+) and small molecules within the pH range of 8.00–5.50, while maintaining stable detection currents. The so-GDY-based pH nano-iontronic device transports monovalent cations up to 5 times more rapidly than divalent cations, alongside excellent repeatability, reversibility, and stability. This combination of features yields a biocompatible, high-resolution tool for minimally invasive, real-time pH measurements at the single-cell and even at a single-organelle level, opening new avenues for investigating cellular dynamics and disease pathogenesis with enhanced clarity.