Controllable Preparation of High Concentration Nitrogen-Doped Porous Graphene toward Enzyme-like Catalytic Properties

Graphene oxide (GO) was synthesized by modified Hummer's method. Nitrogen-doped reduced graphene oxide (N-RGO) meshes with enriched nano-pores were prepared through one-step and mild hydrothermal reaction, by using ammonium hydroxide as the nitrogen -dopant source. The N -RGO exhibited high enzyme-like catalytic activity and could catalyze the organic compounds to induce chromogenic reaction, such as 3,3',5,5'-tetramethylbenzidine (TMB), o-phenylenediamine (OPD) and 2,2'-azino-di(3-etliylbenzothiazoline sulfonic acid) (ABTS), etc. The N -RGO meshes were systematically characterized by transmission electron microscope (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Control experiments revealed that the catalytic oxidation of TMB by N-RGO was processed by an effective 4-electron transfer reaction involving oxygen. Catalytic performance indicated that the N-RGO meshes had stronger tolerance than horseradish peroxidase (HPR), which maintained catalytic activity in a wider range (temperature of 25 similar to 85 degrees C, pH value of 4-7, and NaCl concentration of 0 similar to 100 mmol.L-1). From the fitting calculation by using the Michaelis-Menten model, the N-RGO meshes generated in optimized GO concen- tration of 5 mg.mL(-1) possessed the lowest Michaelis constant (1(K-m approximate to 0.2 mmol.L-1) and the highest reaction velocity (v(max)approximate to 0.07 mu mol.L-1).