Study Of Carbon Dots Prepared By Electrochemical Method And Their Application

Carbon dots attract more and more researchers’ attention owing to low toxicity,good biocompatibility and specially optical properties.In recent years,carbon dots already have preliminary applications in bioimaging,biochemical,biosensing and optoelectronic devices.This thesis investigates the structure and optical properties of carbon dots by electrochemical method from 15V to 120V,and the application of carbon dots in microbial fuel cells is also explored.The details are as follows:Carbon dots are synthesized by electrochemical method under different voltages,in which graphite rod is as carbon source,and distilled water is as electrolyte.The operating of electrochemical method is simple and the prepared carbon dots exhibit high purity,controlled particle size,and excellent luminescence characteristics.This thesis focuses on study of the structure and properties of carbon dots prepared by electrochemical method under different voltages.The prepared carbon dots are spherical or quasi-spherical.Carbon dots randomly distribute and their particle size range between 1.5nm and 5nm.Carbon dots consist of mainly C and O elements,and functional groups such as C = C,C-O,O-H and C = O are found.Carbon dots have a significant absorption peak at 300 nm in the absorption spectra,which is related to n-π*the transition of C=O.The fluorescence spectra of carbon dots prepared under different voltages,excited by 320nm,exhibite three peaks,including a sharp peak at 361nm,a wide peak at about 450nm and a broad peak at about 550nm.With the increase of the excitation wavelength,the center of the sharp peak at 361nm moves from the ultraviolet region to the visible region,while the intensity of the peak decreases and the full width at half maximum of the peak remain about 10nm.Specially,for the carbon dots prepared under 60V voltage,only one sharp peak at 361nm is observed with excellent monochromaticity,which can be used as a new type of ultraviolet light source in medical and biological fields.The investigation of the time-resolved fluorescence decay curve of carbon dots prepared under 15V indicates that carbon dots have three kinds of lifetimes,which are 1.4ns,7.8ns and 0.03ns.The average lifetime of carbon dots is 7.2ns.Catalytic performance of carbon dots prepared under 60V is comparable with that of Pt/C.We also explore the application of carbon dots in microbial fuel cells,using carbon dots prepared at 60V as cathode catalyst in mini microbial fuel cells,it was found that the voltage of microbial fuel cells is 420mV and the maximum output power is 21.9mV/m2.The catalytic performance of carbon dots prepared at 60 V is lower than the catalytic performance of Pt/C,but the difference between them is not so much.And carbon dots prepared at 60V have potential application in microbial fuel cells.