Preparations And Electrochemical/Fluorescence Sensing Of Nitrogen-Doped Graphene Nanosheets And Nitrogen-Doped Carbon Dots

Carbon materials have received much attention for many years.Graphene,a two-dimensional honeycomb lattice carbon material,has unique physical and chemical properties,such as excellent conductivity,large surface area,high mechanical strength,and good electrocatalytic activity.It has been shown that the electron property,chemical activity,and optical characteristics of graphene can be tailored by chemical doping with heteroatoms such as nitrogen for a variety of applications in sensors,supercapacitors,and fuel cell.Carbon dots are a kind of nanometer materials that mainly consist of carbon and are typically quasi-spherical nanoparticles comprising amorphous to nanocrystalline cores with diameters ranging from 1 to 10 nm.Because carbon dots possess excellent fluorescence properties,good biocompatibility,low toxicity,and easy modification,they show broad applications in cell imaging,biosensing,chemical sensing,and metal ions detection.This thesis of nitrogen-doped reduced graphene oxide and nitrogen-doped carbon dots research has the following aspects.(1)Nitrogen-doped reduced graphene oxide(NrGO)were prepared through a hydrothermal method,metal-free NrGO shows a good electrocatalytic activity toward oxidation of nitrite with the relatively low oxidation over potential of 0.68 V,thus,a facile electrochemical sensor based on metal-free NrGO was fabricated for sensitive detection of nitrite for the first time.The novel sensor showed a wide linear concentration response range from 0.5 to 5000?M and a low detection limit of 0.2?M at a signal-to-noise ratio of 3 with good selectivity,stability,and reproducibility.This fabricated sensor was further used for determination of nitrite in pickled garlic and river water.These results demonstrate that the facile metal-free NrGO modified sensor has promising applications for determination of nitrite in food and environment.(2)Nitrogen-doped carbon dots were synthesized using a solvothermal method with citric acid as the carbon source and formamide as the nitrogen source and as the solvent.The as-prepared nitrogen-doped carbon dots could emission red fluorescence,which was selectively quenched by Cu2+ions.The nitrogen-doped carbon dots were used as the fluorescent probes for the detection of Cu2+ ions with a wide linear range from 20 to 1000 ?M and a low detection limit of 4.3 ?M at a signal-to-noise ratio of 3.These results demonstrate that the nitrogen-doped carbon dots with red fluorescent emission have potential application in detection of Cu2+ ions.