Facile visual colorimetric sensor based on iron carbide nanoparticles encapsulated in porous nitrogen-rich graphene

Herein, via one-step pyrolysis of glucose, dicyandiamide (DCDA) and Fe containing metal-organic framework (Fe-MOF), small Fe₃C nanoparticles were in-situ decorated in 3D porous network of N-rich graphene (NGr). The Fe-MOF served as size regulating precursor, layered g-C₃N₄ (derived from pyrolysis of DCDA) acted as not only a template to guide the growth of small Fe₃C nanoparticles, but also the carbon source for 3D porous NGr network. The intrinsic peroxidase-like catalytic activity of Fe₃C/NGr was unpredictably discovered, by taking the oxidation reaction of 3,3',5,5'-tetramethylbenzidine (TMB) with H₂O₂ as a protocol. Fast and distinguished color change, improved stability in exposure to extreme H₂O₂ concentration and high temperature were obtained. The Michaelis-Menten kinetics was investigated. The detection of glucose was accomplished over a wide concentration range of 2.0~500.0μM with a detection limit lower than most of other similar systems. The reliability of the present sensor was further evaluated by practical monitoring glucose in diluted serum samples. Low cost and simple preparation, fast and distinguished color change, high tolerance to extreme H₂O₂ concentration and high temperature, endow Fe₃C/NGr as one of the promising materials for fast visual colorimetry.