Optical fiber fluorescence Cu²⁺ sensing technology based on CdSe/ZnS quantum dots: Large detection range, low detection limit

Copper ion (Cu²⁺), a crucial heavy metal ion, is closely associated with human health and the ecological environment. Imbalances in Cu²⁺ can result in health issues for humans and damage to the ecosystem. Therefore, it is essential to detect Cu²⁺ in the environment. However, current Cu²⁺ sensors still face challenges such as limited detection range, poor detection limits, high costs, and complex preparation processes. Clearly, there is a need for a Cu²⁺ sensor with an extensive detection range, low detection limit, cost-effectiveness, and simple preparation methods that enable online monitoring and real-time measurement of Cu²⁺.

In this paper, a high-performance optical fiber fluorescent Cu²⁺ sensor based on polyethylene glycol diacrylate (PEGDA) hydrogel encapsulated CdSe/ZnS quantum dots (QDs) is designed and fabricated. Due to the porous nature of PEGDA hydrogels, large-diameter CdSe/ZnS QDs are confined within the hydrogels, while small molecules Cu²⁺ are allowed to permeate them. Cu²⁺ reacts with QDs, resulting in the fluorescence quenching of QDs, which enables the detection of Cu²⁺. Experimental results show that the sensor can quantitatively analyze Cu²⁺ in the concentration range of 0.1-200 μM, with a limit of detection (LOD) of only 0.8 nM, and the fastest response time is only 5 s. Additionally, the sensor exhibits strong specificity, has been successfully applied to real water sample detection, demonstrates good stability, and shows great potential for real-time Cu²⁺ detection.

The sensor possesses a large detection range and low LOD, and the synthesis of its core fluorescent probe is straightforward and expedient. Specifically, the fluorescent probe can be synthesized by subjecting a solution of hydrogel precursors doped with CdSe/ZnS QDs to UV irradiation for approximately 2 min. This method is particularly suitable for monitoring confined environments and holds significant implications for the production of Cu²⁺ sensors capable of real-time detection.