Sensitive Detection of Copper(II) Ions in Water Using Nitrogen-Doped Carbon Quantum Dots Synthesized from Pine Cone...

The accurate and rapid determination of trace copper Cu-(II) ions in environmental water is of great significance for both ecological safety and human health. In this work, a novel, eco-friendly, and highly sensitive fluorescence sensor was developed using carbon dots synthesized from pine cone deep eutectic solvent (DES) lignin and doped with lysine for the selective detection of Cu-(II) ions. The synthesized carbon dots exhibited excellent optical properties. They demonstrated a strong, concentration-dependent fluorescence response to Cu-(II) with a wide linear range of 2.81 × 10^-7-5.87 × 10^-5 and a remarkably low limit of detection (LOD) of 2.8 × 10^-8 mol L^-1. To validate the practical applicability and reliability of the proposed sensor, it was successfully employed for Cu-(II) determination in highly complex matrices, including various certified reference materials (primary drinking water, NASS-5 seawater, SM-WW1, and SM-WW2 wastewater) and real environmental samples (ground, lake, and tap water). The standard addition method yielded excellent recovery rates ranging from 98.9 to 104.4%, with relative standard deviations (RSDs) strictly below 4.3%. Furthermore, the analytical results were statistically compared with the standard flame atomic absorption spectrometry (FAAS) method at a 95% confidence level, showing exceptional agreement and no significant differences. The proposed lysine-doped carbon dot sensor offers a highly accurate, cost-effective, and highly selective alternative for the routine monitoring of Cu-(II) in diverse and complex environmental water samples, effectively overcoming significant matrix interference.