Free Chlorine Ultra-Sensitive Detection in Tap Water Via an Enrichment-Sensing Process by an Interdigitated Microelectrode Sensor

Electrochemical free chlorine sensor is considered to be a feasible device for on-line monitoring of free chlorine in tap water due to their reagent-free and short-response-time etc. However, the low sensitivity and the difficulty of to mass-production of the sensor always are the stubborn issues for reliable detection and application in ultra low concentration range. In this paper, we design an interdigitated microelectrode structured electrochemical sensor chip for free chlorine sensing in tap water and fabricate by MEMS. The batch-fabricated sensor demonstrates an acceptable limit of detection (< 0.05 mg/L), a desirable linearity (R2 = 0.991). What's more, a novel detection method (TSAM) is proposed/applied to improve the sensitivity for free chlorine sensing though an enrichment-sensing process. A small and positive potential (0.1 V) is applied to the interdigital electrode to form a ClO-enrichment region near WE before the operating bias voltage (-1.65 V). Fortunately, about 30 times increase (46.334 mu A/mgL-1) in sensitivity of sensor by TSAM is witnessed, comparing with the amperometric method. Far greater than the sensitivity of other researches on free chlorine sensor. Beside, by employing the MEMS technique, favorable response consistency and high reproducibility (RSD < 3.85%) is witnessed, offering the opportunity of mass-producing the proposed sensor in future. It is anticipated that the proposed sensor and sensing method will provide a competitive strategy to design high sensitivity, reliable and mini sensor for water contaminants detection.