Bifunctional magnetic carbon dots for the rapid fluorescent detection and the efficient adsorptive removal of copper ion

Abstract

Developing a bifunctional material capable of both sensing and removing heavy metal ions is crucial but remains a significant challenge. Herein, magnetic carbon dots (M/CDs) were developed using ferroferric oxide (Fe3O4) and riboflavin (C17H20N4O6). M/CDs with optimal fluorescence properties were obtained under the specific preparation conditions of a molar ratio of riboflavin / Fe3O4 of 6:5, at a temperature of 200 °C and following a reaction time of 24 h. The structure of M/CDs was characterized using TEM, XRD, FTIR and VSM, which exhibited the prepared M/CDs contained high-affinity groups (–CN, C=O) and excellent magnetic separation properties (83.87 emu/g), offering selective detection and higher separation capacity for copper ion (Cu2+). The fluorescence intensity of the M/CDs progressively decreased with increasing concentrations of Cu2+, and the calculated detection limit was determined to be 0.096 mg/L, which was below the permissible limit. Moreover, the M/CDs demonstrated a removal efficiency of 89 % for 5 mg/L of Cu2+ across a broad pH range. The adsorption data were well described by the pseudo-second-order kinetic and Freundlich isotherm models. Notably, the reusability could be achieved by recycling at least five turns by using an external magnet. All of these indicate magnetic carbon dots hold great promise for simultaneous detection and removal of Cu2+, offering a feasible solution for assessing water quality and treating wastewater.