Rapid detection of trace Cu2+ using an l-cysteine based interdigitated electrode sensor integrated with AC electrokinetic enrichment

Abstract

Copper is an indispensable trace element for human health. Too much or too little intake of copper ion (Cu²⁺ ) can lead to its own adverse health conditions. Therefore, detection of Cu²⁺ is always of vital importance. In this work, a simple sensor was developed for rapid detection of trace Cu²⁺ in water, in which L-cysteine (Cys) as a molecular probe was self-assembled on a gold interdigital electrode to form a monolayer for specific capture of Cu²⁺ . The interfacial capacitance of interdigital electrode was detected to indicate the target adsorption level under an AC signal working as the excitation to induce directed movement and enrichment of Cu²⁺ to the electrode surface. This sensor reached a limit of detection of 4.14 fM and a satisfactory selectivity against eight other ions (Zn²⁺ , Hg²⁺ , Pb²⁺ , Cd²⁺ , Mg²⁺ , Fe²⁺ , As³⁺ , and As⁵⁺ ). Testing of spiked tap water was also performed, demonstrating the sensor's usability. This sensor as well as the detection method shows a great application potential in fields such as environmental monitoring and medical diagnosis.

Keywords: AC electrokinetics; Capacitive sensing; Cu2+ detection; l-cysteine.