Electrochemical Detection of Multiple Heavy Metal Ions Using a Hybrid Nanocomposite of a Metal–Organic Framework and Cellulose Nanocrystal-PEDOT:PSS

A novel hybrid nanocomposite based on a metal-organic framework (MOF) and electroconductive cellulose nanocrystals (CNCs) was developed for the individual and simultaneous detection of heavy metal ions Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺. The reported modified electrode was based on a thin layer of the hybrid nanocomposite formed on a glassy carbon electrode via a drop-casting method. The MOF, DUT-67, provided binding sites for heavy metal ions due to putative interactions between organic linkers and metal cation analytes. The electroconductive matrix was composed of PEDOT:PSS and CNC, which not only served as an effective template for the DUT-67 MOF but also enhanced electron transfer of the hybrid nanocomposites through the interconnected network of conductive CNC/PEDOT:PSS. Following optimization of the solution pH, accumulation time, and accumulation potential, the developed hybrid nanocomposite-based electrochemical sensor was successfully applied for individual and simultaneous detection of target heavy metal ions in aqueous solutions with high sensitivity and selectivity. Under the optimized conditions, linear detection ranges of simultaneous detection of Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ were found to be 20-163, 20-163, 20-84, and 20-112 μg L^-1, respectively, with detection limits of 2.5, 1.78, 0.226, and 0.294 μg L^-1, respectively. No major interference effects were found from possible coexisting, interfering ions. This allows the practical use of the sensor to examine a variety of different aqueous environments. This study demonstrates the feasibility of our hybrid nanocomposite as a novel sensing platform for the electrochemical detection of multiple heavy metal ions.