Synthesis of Composite-Color Fluorescent Carbon Dots for Simultaneous Accurate Quantitative Detection of Cu2+ and Fe3+

Abstract Carbon dots (CDs) are suitable for metal ion detection owing to their distinct optical tunability, structural controllability, and varied fluorescence response mechanisms.This research produced blue-fluorescent carbon dots (B-CDs) and red-fluorescent carbon dots (R-CDs) by a one-step microwave-assisted technique.B-CDs specifically recognized Cu²⁺ in an aqueous system, while R-CDs exhibited a distinctly selective response to Fe³⁺.Composite carbon dots (B/R-CDs) were synthesized by integrating B-CDs and R-CDs, achieving superior dual-metal ion detection capabilities.The detection system, utilizing ratiometric fluorescence signal changes of B/R-CDs that emit purple fluorescence, was designed for the simultaneous detection of Cu²⁺ and Fe³⁺ in aqueous solutions.Dynamic quenching primarily influenced both detection processes, while the distinct coordination of the two metal ions with B/R-CDs' functional groups and their varied energy level alignment prevented mutual interference.The B/R-CDs synthesized in this study realized the quantitative detection of two trace metal ions by using a single material, which could also be made into test strips for visually detecting Cu²⁺ and Fe³⁺.