Microelectrode-Based MoS₂-Aptamer Functionalized Electrochemical Sensor for Trace Cadmium (II) Detection in Water

Prolonged exposure to elevated levels of cadmium ions in water can lead to serious health problems, and efficient detection of these ions is vital for preventing severe consequences. This letter presents an electrochemical detection technique realized via surface modification of working electrodes with metal sulfide and aptamer adaptation, offering a versatile platform for developing a robust, portable, and cost-effective sensor for environmental monitoring and in situ detections. A novel, compact, and miniaturized design of μ-dimensional working electrode along with on-chip counter and reference electrode (RE) fabricated on a silicon wafer has been used as the transducer to subdue the lack of portability of conventional carbon electrode. The electrodeposition technique is employed in this work to obtain superior control, better adhesion, and uniformity in electrode modification, leading to efficient sensor design. Molybdenum disulfide (MoS2) material is electrodeposited on the working electrode using chronoamperometric technique and functionalized with cross-linkers to bind to amine-terminated aptamers. Cd (II) specific aptamers immobilized on a μ-electrode sensor surface via a covalent surface modifier on electrodeposited MoS2 exhibit high specificity and a detection limit as low as 1.3 ng/L. The Si wafer-based integrated electrodes with μ-scale dimensions, combined with the electrodeposition technique, are a promising alternative to glassy carbon electrodes with compact design, and harbor the possibility of multiplexing for detecting different heavy metal ions in water.