Impedimetric determination of Cs(I) using AuNPs@PoPD-DB24C8: A targeted molecular-scale perturbation

Most attributes of the bulk materials, especially in the solid-state, are directly dictated by a manner by which the molecules are ordered. Thus, it is expected that the possibility of controlling these structural orders would allow predominating some particular physical properties. The methodology used in this work follows the molecular scale perturbation occurred by Cs⁺ ion within a ternary composite of dibenzo-24-crown-8 (DB24C8), poly ortho-phenylenediamine (PoPD) and gold nanoparticles (AuNPs). Hypothetically, two former substances were respectively employed as recognition element and conductive platform to establish a monolithic structure that resembles supramolecular synthon in solid-state. The third precursor was Au(III) that carries out a dual role including vulcanization of the polymeric units via creating quinoid rings and solid signal amplification by deposition of AuNPs at the welded points. This strategy affords an intertwined ternary composite in which the electronical properties of the system can be directly affected by lowest agitation sensed by the recognition element, DB24C8, making the supported transducer capable of monitoring trace amount of Cs⁺ ion by Faradaic impedance spectroscopy (FIS) and single-frequency measurements (SFM). The fabricated sensor showed a signal change against Cs⁺ ion over the linear range of 0.6-25.0 nM with a detection limit of 0.37 nM (S/N = 3). Density functional theory (DFT) studies were used to explore the possible recognition mechanism, by which the incorporation of Cs⁺ ion meaningfully dispersed the structural order of the ternary system.