Selective detection of manganese(II) ions based on the fluorescence turn-on response via histidine functionalized carbon quantum dots

• Synthesis of a stable carbon quantum dot-based fluorescent probe with aqueous dispersibility. • High selectivity and sensing ability of the probe for Mn(II) ions. • Successful application of the probe for the determination of trace Mn(II) in whole blood quality control material. • Study of the sensing mechanism of the probe for the detection of Mn(II). Herein, water-soluble emissive carbon quantum dots (His-CQDs) were synthesized from pyrolysis of sodium citrate in the presence of histidine under hydrothermal conditions. The as-synthesized His-CQDs were characterized using Fourier transform infrared (FT–IR), fluorescence spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques. The obtained His-CQDs display a strong emission peak at 534 nm when excited at 476 nm with a high quantum yield (61.8 %). The as-synthesized His-CQDs were applied as a new platform for highly selective determination of Mn(II) based on the fluorescence “turn-on” response with a limit of detection of 1.85 µg L −1 (at 3σ) and a linear range of 3.50–35.5 µg L −1 in aqueous solution. The sensing mechanism of the His-CQDs probe for the detection of Mn(II) was studied via density functional theory (DFT), FT-IR, and EDTA complexation methodology. In addition, His-CQDs were successfully applied to determine the accurate amounts of Mn(II) in whole blood control material. More importantly, the integrating such an efficient sensor with point-of-care technology can enable portable, easy-to-use, and rapid sensing systems for better biological and clinical applications.