Ultra-stable fluorescent film sensor based on quantum dots for the real-time detection of Cu²

Fluorescent films have recently gained attention as chemo-sensors for real-time detection in view of their high sensitivity and rapid response. However, these sensors are usually sensitive to UV irradiation, high temperature, etc., which seriously affects sensing accuracy and limits practical use. Here, an ultra-stable fluorescent film sensor based on CdSe/Cd_xZn_1-xS QDs and polyamide-6 nanofibrous membranes has been developed for the detection of Cu²⁺. To achieve high fluorescence stability, QDs with high colloidal stability are evenly immobilized on the surface of electrospun nanofibres by a dip-coating method, which can avoid fluorescence quenching caused by aggregation in the electrospinning process. As a result, the film sensor exhibits nearly constant PL intensity under the following conditions: pH values from 5.0 to 13.0, high temperature of 100 °C, 365 nm UV light for 60 min and long preservation time of 90 days. Under optimized conditions, a linear relationship was observed between the fluorescence quenching of the film and the concentration of Cu²⁺ in the range of 0-100 μM. In addition, the film sensor responds visually with a detection limit of 10 μM and response time of 10 s, which enabled it to be used as test strips in real-time detection and may provide new insights for the detection of other substances.