Fe³⁺-selective and sensitive "on-off" fluorescence probe based on the graphitic carbon nitride nanosheets

An effective and facile "on-off" fluorescence sensing approach for the determination of Fe³⁺ ion using a large area and relatively uniform size graphitic carbon nitride nanosheets (GCNS) was developed. The prepared GCNS have blue and stable emission, as well as excellent water dispersion, and were applied as an effective fluorescent probe that based on the quenched fluorescence for selective and sensitive detection of Fe³⁺ ion. Herein, we explain the ambiguous fluorescence quenching mechanism between the GCNS and Fe³⁺, which mainly springs from the redox potential and empty d orbital of Fe³⁺. The redox potential and unfilled d orbit of Fe³⁺ endow it excellent binding force with GCNS, which generates most obvious fluorescence quenching effect with respect to other metal ions. The limit of detection (LOD) for Fe³⁺ was found to be about 2.06 μM. Therefore, the prepared GCNS has the potential to be used as a fluorescent probe for detection.