<p>As a typical non-ferrous metal, copper is heavily used in the manufacturing and chemical industries. Copper pollution has been demonstrated to have a significant detrimental impact on the natural environment, as well as causing irreparable damage to the human body, such as elevated Cu²⁺ levels have been identified as a factor in the pathogenesis of AD (Alzheimer’s disease). In this study, novel nanoscale carbon dots Blue-CDs (B-CDs) were obtained by the solvothermal approach in formamide solution utilizing citric acid as the carbon source and ethylenediamine as the nitrogen dopant. The particle size of B-CD was assessed to be 2.17&#xa0;nm, with a quantum yield (QY) of 10.28%. The B-CDs were found to be extinguished upon exposure to Cu²⁺, which exhibited a good fluorescence detection linear relationship within the concentration range of 0.25-10.0 µM Cu²⁺, showing a limit of detection (LOD) is 0.18 µM. B-CDs have been effectively used for the measurement of Cu²⁺ in actual aqueous systems. It is due to the chemical reactions that take place among the B-CDs and the Cu²⁺ that make the sensor highly sensitivities and highly selectivities. The results of the experiment demonstrate that the fluorescence quenching process is a consequence of Cu²⁺ binding to the amino groups of carbon dots, forming complexes via a non-radiative photoinduced electron transfer process. In conclusion, the described simple sensing techniques could be effectively utilized as monitoring tools for Cu²⁺ in environmental waters.</p> Graphical Abstract <p></p>