Specific discrimination of zinc and manganese ions by label free dual emissive carbon dots by ratio-metric mode.

Due to the worldwide ecological and environmental issues induced by heavy metal pollution, including zinc and manganese, the ratio-metric discrimination of Zn and Mn based on CDs is urgently required. In this work, reduced CDs (re-CDs) with the intrinsic dual emissive peaks are obtained, and specific discrimination of Zn and Mn is realized by re-CDs with ratio-metric mode. With the addition of Zn, the fluorescent (FL) intensity at 650 nm increases obviously, while that at 680 nm progressively decreases. However, the presence of Mn would induce the quenching of FL intensity at 680 nm while that at 650 nm remains constant. Then the Zn and Mn can be separately determined with the ratio of FL intensity at 650 nm to that at 680 mm (F/F). Under optimal conditions, the limit of detection (LOD) of Zn is determined to be 9.09 nmol/L, and that for Mn is estimated to be 0.93 nmol/L, which is much lower than previously reported work and standard level of Zn and Mn permitted in drinking water by WHO. Moreover, the specific recognition of Mn and Zn can be realized via the addition of different masking agents (ethylenediamine for Zn and triethanolamine for Mn). Furthermore, our results reveal that the structural changes from -NH-CO to -NC-OH induced by Zn contribute to the shift of FL peak from 680 to 650 nm while both static and dynamic quenching processes are involved in the detection of Mn. The ratio-metric probe was successfully applied to Zn and Mn determination in human serum samples and Sandy Lake water.