Fabrication Of Carbon Quantum Dots And Their Application In Fluorescence Sensing

Carbon quantum dots(CQDs)have great application potential in bioimaging,chemical sensors and many other fields and have attract tremendous attention due to their good optoelectronic properties,solubility and biocompatibility and simple preparation method.In this thesis,the preparation of CQDs was studied with an attempt to obtain CQDs with different performance through impurity atoms doping method with different precursors.Therefore,we have investigated the applications in fluorescence sensing and cellular imaging.The following research was carried out:(1)In this thesis,we have synthesized nitrogen doped carbon quantum dots(NCQDs)via microwave method.Results of Transmission electron microscope(TEM),Energy dispersive spctrometer(EDS),Photoelectro spectrograph(XPS)and Fourier trans form infrared spectrometer(FTIR)showed that the synthesized NCQDs were spherical with uniform average diameter about 4.0 nm.There are abundance of oxygen and nitrogen-containing groups on the surface of NCQDs,so it is demonstrated that it is nitrogen doped carbon nanomaterial.Results of The ultraviolet spectrophotometer and fluorescence spectrophotometer showed that absorption peak of NCQDs at 245 nm and 339 nm,fluorescent emission peak of The NCQDs had wavelength dependence properties with maximum excitation wavelength at 383 nm and maximum emission wavelength at 457 nm.In addition,the fluorescence emission peak have the properties of pH dependence and environmental stability.3,5-dinitrosalicylic acid can quench fluorescence of NCQDs.Therefore,detection method for 3,5-dinitrosalicylic acid base on NCQDs were developed.The linear relationships were obtanied from 1 ?mol/L~100 ?mol/L(R2=0.9976)and detection limit estimated to be 0.68 ?mol/L(S/N=3).Meanwhile,we preliminarily research quenching mechanism of NCQDs fluorescence for 3,5-dinitrosalicylic acid.(2)Baced on the previous exeriment,we have synthesized nitrogen and sulfur co-doped carbon quantum dots(NSCQDs)via microwave method with citric acid and cysteine.Meanwhile,we can enhance fluorescence quantum yield of NSCQDs.Results of TEM showed that the NSCQDs were spherical with uniform average diameter about 2.2 nm.Results of FTIR showed that There are abundance of oxygen,nitrogen and sulfur-containing groups on the surface of NSCQDs,so it is demonstrated that it is nitrogen and sulfur co-doped carbon quantum dots.Absorption peak of NSCQDs at 212 nm,244 nm and 348 nm,The NSCQDs had good photoluminesce properties with maximum excitation wavelength at 356 nm and maximum emission wavelength at 423 nm.Fluorescence quantum yield is 61.41%.Fluorescent emission peak of The NSCQDs have wavelength independence properties,concentration and pH dependence properties.Furthermore,the NSCQDs have the properties of good environmental stability and biocompatibility,we have researched application of NSCQDs on cellular imaging and Fluorescent ink pen.