Enhanced fluorescence of copper nanoclusters based on dual-ligand engineering for sensitive detection of vitamin B12 and diosmetin in food samples.

Employing a dual-ligand surface engineering strategy, red-fluorescent copper nanoclusters (Neu5Ac@5-MTU-CuNCs) was fabricated via an eco-friendly one-pot method with 5-methyl-2-thiouracil (5-MTU) and N-acetylneuraminic acid (Neu5Ac) as ligands. The incorporation of Neu5Ac can improve the coordination environment, restrict the vibration of 5-MTU on the CuNCs surface, and simultaneously create steric hindrance between its rigid sugar ring structure and the pyrimidine moiety of 5-MTU. Based on this, the fluorescence intensity of Neu5Ac@5-MTU-CuNCs at 680 nm was boosted, along with improved detection sensitivity for vitamin B12 (VB12) and diosmetin (Dio). Detection limits of 0.039 μM (VB12) and 0.160 μM (Dio) were received, with linear ranges of 0.10-52.25 μM and 0.50-62.25 μM. Meanwhile, synthesis conditions of Neu5Ac@5-MTU-CuNCs and corresponding quenching mechanisms were intensively studied. The CuNCs was successfully employed to monitor VB12/Dio in various foods with good recoveries, demonstrating high reliability. A compact and economical paper-based strip was formulated by leveraging Neu5Ac@5-MTU-CuNCs, enabling expeditious, equipment-free, and visual semi-quantitative determination of VB12/Dio for field deployment. Besides, the Neu5Ac@5-MTU-CuNCs also held promise for applications in multifunctional anti-forgery and dactyloscopic analysis.