Nanowire-like phosphorus modulated carbon-based iron nanozyme with oxidase-like activity for sensitive detection of choline and dye degradation

Choline is mainly supplemented through food intake, lack of choline would result in diseases like liver cirrhosis, hardening of the arteries, or neurodegenerative disorders. The accurate detection of choline is important for human health. Herein, a novel nanowire-like phosphorus/nitrogen co-doped carbon-based iron nanozyme (FeNPC) with outstanding oxidase-like activity was synthesized, and the influence of phosphorus doping on oxidaselike activity was explored. Proper phosphorus doping was found to enhance the oxidase-like activity of Fe-NPC by increasing surface defects, promoting iron loading, and modulating chemical environment of central site. The oxidase-like activity of Fe-NPC was successfully applied to colorimetric-fluorescent dual mode detection of choline, and good linear relationship in the ranges of 3-200 mu M were achieved with LODs of 1.95 and 1.50 mu M, respectively. The fluorescent detection was constructed based on the fluorescence quenching of silicon quantum dots (Si QDs) by quinone-imine. The quenching mechanism was attributed to FRET due to the large spectra overlap, reduced fluorescence lifetime and proper donor-acceptor distance. The successful application to the detection of choline in milk proved the practicability of the proposed sensing method. The oxidase-like properties of Fe-NPC was further used in the degradation of cationic dye methyl blue, high degradation efficiency of 74 % was achieved within 5 min under optimal conditions, proving the enormous potential of Fe-NPC for application in environment protection.