An Ultrasensitive Fluorescence Sensor with Simple Operation for Cu²⁺ Specific Detection in Drinking Water

Whether short-term or long-term, overexposure to an abnormal amount of copper ion does significant harm to human health. Considering its nonbiodegradability, it is critical to sensitively detect copper ion. Herein, a novel fluorescent strategy with a "turn-on" signal was developed for highly sensitive and specific detection of copper ion (Cu²⁺). In the present investigation, we found that Cu²⁺ exhibits excellent peroxidase-like catalytic activity toward oxidizing the nonfluorescent substrate of Amplex Red into the product of resofurin with outstanding fluorescence emission under the aid of H₂O₂. Thus, an enzyme-free and label-free sensing system was constructed for copper ion detection with quite simple operation. To ensure the detection sensitivity and reproducibility, the amount of H₂O₂ and incubation time were optimized. The limit of detection can reach as low as 1.0 nM. In addition, the developed assay demonstrated excellent specificity and could be utilized to detect copper ion in water samples including tap water and bottled purified water without standing recovery.