Enhanced solid-state fluorescence emitting of carbon nanodots by nafion matrix for sensitive and reusable detection...

Although carbon dots (C-dots) exhibit excellent optical properties in aqueous solutions, their practical application in solid-state devices is severely hindered by aggregation-induced quenching (ACQ). Herein, we report a solid-state fluorescence sensor fabricated by embedding C-dots into a Nafion matrix, which simultaneously addresses the ACQ issue and enhances sensing sensitivity. The Nafion matrix acts as an effective physical spacer, significantly improving the dispersion of C-dots and resulting in a remarkable enhancement of solid-state fluorescence compared to pristine C-dots. More importantly, we demonstrate that the sulfonate groups (-SO₃^-) within the Nafion framework serve as cation-exchange sites, facilitating the pre-concentration of copper ions (Cu²⁺) from the bulk solution to the membrane interface via electrostatic attraction. This enrichment effect, combined with the efficient fluorescence quenching of C-dots by Cu²⁺, endows the sensor with high sensitivity. The fabricated membrane sensor exhibits a linear response to Cu²⁺ in the range of 10 nM to 600 nM with a low detection limit (LOD) of 6.7 nM. Furthermore, the sensor demonstrates excellent selectivity against interfering metal ions and can be easily regenerated by washing with EDTA, maintaining stable performance over multiple detection cycles. The practical applicability of the sensor was validated by successful recovery tests in real water samples. This work provides a facile inter-facial engineering strategy to construct high-performance solid-state optical sensors for environmental monitoring.