Two-dimensional nanoconfined channels for a heavy metal sensor

Abstract

Two-dimensional (2D) metal oxide lamellar membranes provide high-aspect-ratio interlayer nanochannels and yield continuous interstitial space and a nanoconfined length scale comparable to the size of charged ions, which opens up the platform to fabricate channels at this dimension to study charge transport and storage for chemical sensing. Here, we demonstrate a versatile approach to construct the wafer-scale nanoconfined membrane from 2D metal oxide nanosheets through a layer-by-layer assembly process. Such a layered nanochannel by arranging 2D MoO3−x nanosheets into a dense network can be percolated by molecular conducting polyaniline and further protonic acid doping, and consequently, its conductivity shows improvements of 1797 and 354 times, respectively. The nanoconfined membrane further shows an electrochemical response to the presence of heavy metal ions (lead), enabling a successful demonstration of an electrochemical sensor. The nanoconfined 2D channels with light-tunable capacitance show a promising application in heavy metal detection with high sensitivities of 1.12 × 10−4 and 2.81 × 10−4 mA μM−1 cm−2 under dark and light conditions, respectively. Our results suggest that nanoconfined 2D metal oxide channels represent an efficient approach to study charge transport and storage for heavy metal sensing at this dimension.