Synthesis And Application Of Nitrogen,Sulfur And Iron Doped Carbon Nano-materials

In this paper,the catalytic kinetics and catalytic mechanism of iron-doped carbon nanomaterials as peroxidase mimetics were investigated.These materials were respectively applied in the colorimetric detection of hydrogen peroxide,xanthine,glucose and L-cysteine with high selectivity.The main contents are as follows:（1）Sulfur-iron co-doped carbon dots（S/Fe-CDs）were successfully prepared by simple solvothermal method using citric acid monohydrate,L-cysteine and ferric chloride hexahydrate as precursors,The obtained S/Fe-CDs were characterized by transmitted electron microscope（TEM）,high-resolution TEM,X-ray photoelectron spectroscopy（XPS）and X-ray diffraction（XRD）.The characterization results show that the product has a uniform size.It is interesting to find that this product exhibits peroxidase-like activity even higher than HRP,following Michaelis-Menten kinetics.S/Fe-CDs catalyze the oxidation of TMB by H₂O₂ to produce a blue change in aqueous solution.A highly sensitive and selective detection method for H₂O₂ has then been developed.Based on the high catalytic activity of S/Fe-CDs combined with the property of xanthine oxidase,a rapid,sensitive and convenient colorimetry method for the detection of xanthine was developed with a detection limit of 47.37 nM.Taking advantage of this superiority,S/Fe-CDs represent an enzyme mimetics that can be potentially used in diagnostics and biotechnology.（2）Iron-doped carbon nitride nanoparticles（Fe-CNNPs）were prepared from citric acid,urea and ferric chloride through a convenient one-pot solvothermal method.Oleic acid was used as the reaction medium.The morphology and chemical composition of the obtained Fe-CNNPs were characterized by multiple methods including transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）and Fourier transform infrared spectroscopy（FT-IR）.The obtained Fe-CNNPs showed higher catalytic activity than horseradish peroxidase（HRP）,and tetramethylbenzidine（TMB）can be catalytically oxidized in the presence of H₂O₂ to produce a color change in aqueous solution.As H₂O₂ can be generated in the oxidation process of glucose catalyzed by glucose oxidase（GOD）,a novel sensitive method for the detection of glucose with a of detection（LOD）of 0.29μM has been developed combined with the catalytic properties of GOD and Fe-CNNPs.The Fe-CNNPs with peroxidase mimetics activity may have potential applications in biotechnology field.（3）Nitrogen-iron co-doped carbon dots（N/Fe-CDs）were synthesized by one-step solvothermal method using citric acid monohydrate,ethylenediamine and ferric chloride hexahydrate as precursors,which were characterized by transmission electron microscopy（TEM）,high-resolution TEM,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）and Fourier transform infrared（FT-IR）.The characterization results show that N/Fe-CDs have a uniform particle size distribution.It is also found that the N/Fe-CDs have the catalytic activity which is similar to peroxidase.In the presence of H₂O₂,N/Fe-CDs can rapidly catalyze the substrate TMB and the solution turn into blue.In addition,the steady-state kinetics experiments indicate that the catalytic behavior of N/Fe-CDs conforms to the classical Michaelis-Menten mode.In addition,the presence of L-cysteine would lead to blue color fading.Then a highly sensitive,label-free,fast and specific colorimetric assay of L-cysteine has been developed with a detection limit of 15.8 pM,indicating that the N/Fe-CDs have the potential to build portable field test sensors.