Probe integrated with laser-induced graphene electrode: application towards multimodal optoelectrochemical detection of Cu(ii) ions and their remediation

Abstract

Copper(II) is an essential trace mineral that plays a significant role in facilitating enzymatic processes for energy production. However, its excess intake from agricultural and industrial sources can result in toxicity. Therefore, a ferrocenyl-based chalcone probe FCN has been developed for the selective detection of Cu(II) ions in CH₃CN medium. The probe displayed an increase in absorbance, along with a redshift (∼17 nm) upon incremental addition of Cu(II) ions. Conversely, the presence of Cu(II) ions caused a significant quenching of fluorescence intensity of the probe, by approximately 32.5 times. The minimum detectable concentration was determined to be 0.25 ppm. Mechanistic investigations revealed the formation of a 1 : 1 complex between the probe and Cu(II) ions, which involves the coordination through the oxygen of the chalcone and nitrogen of the pyridine. The fluorescence quenching mechanism was attributed to chelation-enhanced fluorescence quenching (CHEQ) and energy transfer processes. Furthermore, the electrochemical response of the probe towards Cu(II) ions was evaluated by the surface modification of the laser-induced graphene (LIG) electrode FCN@LIG. LIG offers rapid, flexible electrodes on a multitude of recyclable and sustainable substrates for implementation within graphene-based electrochemical biosensors. As evidenced by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry analysis, the probe-modified LIG demonstrated excellent electrochemical sensing performance, along with increased sensitivity and selectivity towards Cu(II) ions. Such multimodal sensing broadens detection capabilities and offers a more comprehensive understanding of the system, advancing sensing technologies. Furthermore, the practicability of the probe was explored in the detection and effective removal of Cu(II) ions from aqueous environment, scavenging toxic ions from industrial wastes. Additionally, cost-affordable, pre-coated paper strips were developed for the rapid, onsite detection of Cu(II) ions. Therefore, such easily synthesizable probes for the highly efficient multimodal sensing of Cu(II) ions could offer potential applications in environmental monitoring and industrial remediation.