Ratiometric fluorescence sensing of Fe2+/3+ by carbon dots doped lanthanide coordination polymers

In this work, we proposed a ratiomatric fluorescent strategy for sensing Fe²⁺ by using the carbon dots (CDs) doped lanthanide coordination polymers (Ln-CPs). Herein, the Ln-CPs were prepared by self-assemble of adenosine monophosphate (AMP) with Tb³⁺ (AMP-Tb) through coordination reaction, and CDs were encapsulated during the assembly process as guest materials. A cofactor, phenanthroline (Phen), could incorporate into the CDs@AMP-Tb, and strongly sensitized the luminescence of Tb³⁺ through energy transfer. Therefore, the obtained CDs@AMP/Phen-Tb could emit dual fluorescence signals. One is the characteristic emission of Tb³⁺, which could be specifically quenched by Fe²⁺ due to the high affinity between Phen and Fe²⁺. Another is originated from CDs encapsulated in Ln-CPs, which did not change in the presence of Fe²⁺. Subsequently, CDs@AMP/Phen-Tb was chosen as the ratiomatric fluorescent probe for sensing Fe²⁺, where the fluorescence of Tb³⁺ was quenched serving as the reporter, while that of CDs remained constant serving as the internal control for self-calibration. In addition, with the help of a reducing agent, which can reduce Fe³⁺ to Fe²⁺ efficiently, the proposed method can also be applied in selective detection Fe³⁺. By taking advantage of the unique property of Ln-CPs, the proposed strategy promises flexibility for designing of a series of ratiometric fluorescent sensors and expanded in practical applications.