Label-Free Simultaneous Analysis of Fe(III) and Ascorbic Acid Using Fluorescence Switching of Ultrathin Graphitic Carbon Nitride Nanosheets

Abstract

A simple chemical oxidation and ultrasound exfoliation method has been developed to synthesize the two-dimensional and ultrathin-layer materials-graphitic carbon nitride nanosheets (g-C₃N₄ NNs). The prepared ultrathin g-C₃N₄ NNs display strong fluorescence and stability, including good photostability and excellent antisalt ability. Herein, a new "on-off-on" fluorescent switching sensor is designed. The iron ion (Fe³⁺) has an ultrasensitive response to quench the fluorescence of g-C₃N₄ NNs based on the synergistic effect between inner filter effect and photoinduced electron transfer. The linear limit for Fe³⁺ was from 0.05 to 30 μmol L^-1 with a detection limit of 0.018 μmol L^-1. Meanwhile, the fluorescence of g-C₃N₄ NNs can recover through the redox reaction between Fe³⁺ and ascorbic acid (AA). In addition, the linear range for AA was from 0.2 to 112.5 μmol L^-1 with a 0.086 μmol L^-1 detection limit. The proposed method exhibited rapid response, excellent selectivity, wide detection range, and low detection limit for simultaneous analysis of Fe³⁺ and AA, and it was applied for the determination of Fe³⁺ and AA in water sample and human serum with satisfactory results.