Multifunctional dual emissive fluorescent probe based on europium-doped carbon dots (Eu-TCA/NCDs) for highly selective detection of chloramphenicol, Hg2+ and Fe3+

Abstract

Lanthanide functionalized N-doped carbon dots have potential applications in the development of innovative photoluminescent probes for environmental and biological analytes. In this study, a novel multifunctional dual-emissive fluorescent probe based on a europium complex with 4,6′-dihydroxy-1,3,5′-triazine-2-carboxylic acid and N-doped carbon dots (Eu-TCA/NCDs) is reported for the selective detection of chloramphenicol (CAP), Hg²⁺ and Fe³⁺ in real samples. At an excitation wavelength λ_ex = 275 nm, an aqueous solution of the Eu-TCA/NCD probe exhibited strong fluorescence emission at two different wavelengths (445 and 617 nm). Under the same conditions, the addition of CAP to the probe resulted in significant fluorescence quenching at both emission wavelengths. An excellent linear relationship (R² = 0.9963) between the concentration of CAP (0.01–50 μM) and fluorescence quenching was observed with a detection limit of 12 nM. Furthermore, the probe demonstrated a ratiometric response in the presence of Hg²⁺ and Fe³⁺ ions. The addition of Hg²⁺ causes substantial quenching at 445 nm while the intensity at 617 nm almost remains unchanged. However, upon addition of Fe³⁺, the fluorescence intensity at 617 nm decreases sharply while the intensity at 445 nm remains the same. Furthermore, the practical applicability of the probe was authenticated by the detection of CAP, Hg²⁺ and Fe³⁺ in real samples (with RSD ≤ 2.35%) with a recovery percentage of 95.2–103. These results open a new avenue for developing lanthanide-doped nanocomposites that display white-light-based dual-emissive fluorescence recognition of biological and environmental pollutants.