Multi-Functional Ratiometric Detection Based on Dual-Emitting N-Doped Carbon Dots

Abstract

Ratiometric fluorescence probes based on multi-emission carbon dots (CDs) improve accuracy and sensitivity on detecting various environment issues. Herein, a novel dual-emitting N-doped carbon dots (N-CDs) was synthesized from citric acid and urea via a solvothermal method in N,N-dimethylformamide (DMF). The blue and orange emissions of the N-CDs in water were modulated, and pure white light-emitting with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.33) was achieved. The two PL centers behaved differently for Fe3+, Cu2+ and Ag+ ions, with the limit of detection (LOD) of ppm as fluorescence probes. Additionally, the N-CDs displayed unique solvatochromism phenomenon. A new green emission appeared in organic solvents and gradually quenched with the increase of solvent polarity. The ratiometric PL displayed an excellent linear response in a wide range for detecting water, and the LOD was between 0.003% and 0.3% in DMF, ethanol, isopropanol and N-methylpyrrolidone. Furthermore, the as-prepared N-CDs exhibited pH-sensitive response in the range of 4.0–7.0 and temperature-dependent response during heating-cooling cycles between 15 and 70℃. Therefore, a simple, efficient and reliable multi-functional ratiometric probe for detecting metal ions, trace water content in organic solvents, pH and temperature simultaneously was realized based on the dual-emitting N-CDs.

Keywords: N-doped carbon dots, Solvatochromism, Water detection in organic solvents, Ions sensing, Temperature sensing, pH sensing