Excitation wavelength-tuned dual-color carbon dots as a dual-channel sensing system for fluorescent and visual detection of Mn (VII) and Al (III)

Abstract

Heavy metal pollution is posing a serious threat to the environment. However, the multichannel fluorescence sensor simultaneously detecting multiple metals is promising but challenging. In this work, excitation-dependent red and blue carbon dots (RBCDs) were synthesized through carbonization and amide reaction. RBCDs emitted red and blue fluorescence under different excitation wavelengths. Interestingly, the fluorescence of RBCDs embedded in PVA films and various paper matrics was highly stable. The fluorescence emission of RBCDs at 590 nm was effectively quenched by MnO₄^- via the oxidation of RBCDs and the inner filter effect. Instead, the fluorescence at 485 nm could be effectively quenched by morin, whereas Al³⁺ can reverse the quenching. Based on the interaction between RBCDs, MnO₄^-, morin, and Al³⁺, dual-channel sensing systems for the analysis of MnO₄^- and Al³⁺ were successfully constructed. The established sensing systems exhibited excellent selectivity and practical applicability for detecting MnO₄^- and Al³⁺ in river water. These sensing systems offer several merits, such as low limits of detection (LOD), wide linear range, good anti-interference, and satisfactory detection reliability. These findings help to understand the behavior and distribution of these metal ions in the eco-environment, contributing to reinforcing resource management and strengthening environmental protection.