An ultra-selective fluorescence method with enhanced sensitivity for the determination of manganese (VII) in food stuffs using carbon quantum dots as nanoprobe

Abstract A novel fluorescence method was for the first time established for the efficient determination of permanganate (Mn(VII)) based on sulfur, chlorine and nitrogen co-doped carbon quantum dots (S,Cl,N-CQDs). The S,Cl,N-CQDs was prepared via a fast and simple acid-base neutralization method. The fluorescence of S,Cl,N-CQDs could be dramatically quenched by Mn(VII) ascribed to a combination of inner filter effect (IFE) and dynamic quenching. Under the optimal working conditions, the S,Cl,N-CQDs-based nanoprobe exhibited high selectivity and sensitivity towards Mn(VII) sensing. A good linear Stern-Volmer equation was obtained for Mn(VII) in a wide concentration range of 0.05–110 μM with a detection limit as low as 12.8 nM. The proposed fluorescence method also exhibits additional advantages of great simplicity, fast in analysis and low cost. The as-fabricated fluorescent nanoprobe was successfully applied for the determination of Mn(VII) in vegetable, cereal and tea samples with high accuracy. It is anticipated that the S,Cl,N-CQDs-based nanoprobe could be further exploited to construct a nanoprobe device for Mn(VII) monitoring in complex food matrix.