High Selectivity and Sensitivity in Chemiresistive Sensing of Co(II) Ions with Liquid‐Phase Exfoliated Functionalized MoS2: A Supramolecular Approach

Abstract

AbstractChemical sensing of water contamination by heavy metal ions is key as it represents a most severe environmental problem. Liquid‐phase exfoliated two‐dimensional (2D) transition metal dichalcogenides (TMDs) are suitable candidates for chemical sensing thanks to their high surface‐to‐volume ratio, sensitivity, unique electrical characteristics, and scalability. However, TMDs lack selectivity due to nonspecific analyte‐nanosheet interactions. To overcome this drawback, defect engineering enables controlled functionalization of 2D TMDs. Here, ultrasensitive and selective sensors of cobalt(II) ions via the covalent functionalization of defect‐rich MoS2 flakes with a specific receptor, 2,2′:6′,2″‐terpyridine‐4′‐thiol is developed. A continuous network is assembled by healing of MoS2 sulfur vacancies in a tailored microfluidic approach, enabling high control over the assembly of thin and large hybrid films. The Co2+ cations complexation represents a powerful gauge for low concentrations of cationic species which can be best monitored in a chemiresisitive ion sensor, featuring a 1 pm limit of detection, sensing in a broad concentration range (1 pm ‐ 1 µm) and sensitivity as high as 0.308 ± 0.010 lg([Co2+])−1 combined with a high selectivity towards Co2+ over K+, Ca2+, Mn2+, Cu2+, Cr3+, and Fe3+ cations. This supramolecular approach based on highly specific recognition can be adapted for sensing other analytes through specific ad‐hoc receptors.