Synthesis Of Carbon Quantum Dots And Their Applications In Fluorescence Analysis

Carbon quantum dot is a supernova in carbon materials,it has nanosize particle diameter,superior electron transfer ability and strong fluorescence like traditional semiconductor quantum dots,and it has more biocompatibility,easier functionalization,more simple to synthesis.Carbon quantum dot is widely used in biological imaging,photocatalysis,solar cell and fluorometric analysis,it has a enormous development potential.At present,the research on carbon quantum dots mainly focused on N,S singly doped or co-doped carbon dots.Research on other dopant elements and ternary co-doped carbon dots was insufficient.Research on coated carbon quantum dots synthesis and application were nadequate,too.There was also a lack of simple and efficient synthesis of turnable fluorescent carbon quantum dots.Most of the target of fluorescence analysis was Fe3+ or Hg2+,the research about other detection target(especially negative ion and neutral molecule)was not enough,the investigate on fluorescence analysis mechanism was not profound enough.In this research background,the third chapter reported N,S,P co-doped carbon dots synthesized by hydrothermal method.The co-doped carbon dots can be used as fluorescence probe to detect Eu3+ ions The significance of this chapter was filling the gap that there was little study of ternary co-doped carbon dots in the related fields and the Eu3+ fluorescence analysis using carbon dots was established creatively.In the fourth chapter,N doped carbon dots were prepared,then coated with p-tosylation ?-cyclodextrin.The fluorescence intensity of coated carbon quantum dots can be enhanced by F-ions and based on this principle,a new fluorescence analysis method for F-ions detection was developed.This chapter provided a new idea of coated carbon dots preparation and expanded the application in detecting negative ion.That was meaningful because most carbon quantum dots can only detected positive ion.In the fifth chapter,yellow fluorescence carbon quantum dots were synthesized using o-phenylenediamine and n-propanol;based on the inner filter effect between carbon quantum dots and gold nanoparticles,a new detection method for melamine was established.The significance of this chapter was preparing the yellow fluorescence quantum dots,which is rare.That was an exploratory step for the preparation of turnable fluorescence carbon quantum dots.This method achieved the flexible use of inner filter effect,and the detection range was same with national standard HPLC method,but was easier operation and lower cost.The obtained conclusions are listed as follows:(1)The average particle size of N,S,P co-doped carbon dots is 20 nm;The UV-visible absorption spectra had absorption peaks at 209 nm and 342 nm,corresponding to ?-?*transitions in conjugated systems and surface state energy levels;X-ray photoelectron spectroscopy confirmed that N,S and P formed chemical bonds with C;The infrared absorption spectra showed that the surface of carbon quantum dots was rich in hydroxyl,amino and C=O,C-N,P-O and C-S structure.The maximum excitation wavelength of carbon quantum dots was 350 nm,the maximum emission wavelength was 443 nm,the emission light was blue,the half width was 77 nm,and the emission light was independent on excitation light.The Eu3+ detection range was from 4.878 ?mol·L-1 to 33.33?mol·L-1,the linear equation was ?F=10.2C-19.2 and the correlation coefficient is 0.998,the detection limit was 0.367 ?mol·L-1.The detection method had good selectivity,average recovery in simulated wastewater was 103.6%.(2)The average particle size of coated carbon dots is 50 nm,and the UV-Vis absorption peaks at 215 nm indicate that they contain large ?-?*bonds.X-ray photoelectron spectroscopy shows ?-cyclodextrin connected to carbon skeleton via C-N-C bond.The infrared absorption spectra shown that the surface of carbon quantum dots was rich in hydroxyl groups,amino groups and C=O?C=C,C-N,C-O-C structure.The maximum excitation wavelength of the coated carbon dots was 348 nm,the maximum emission wavelength was 462 nm,the emission light was blue and the half width was 92 nm,and the emission light could be changed depend on the excitation light.The F-detection range was from 27.62 ?mol·L-1 to 544.6 ?mol·L-1,the linear equation was ?F=0.383C-1.69 and the correlation coefficient is 0.998,the detection limit was 15.89 ?mol·L-1.The detection method had good selectivity and had 5.8%error while detect the F-in toothpaste.(3)The average particle size of yellow fluorescence carbon dots was 30 nm and the UV-visible absorption peaks shown that the carbon quantum dots contain ?-?*and surface energy absorption;X-ray photoelectron spectroscopy indicated the carbon quantum dots contain C,N,O element;infrared absorption spectroscopy testified the surface of carbon quantum dots was rich in hydroxyl,amino and C=O,C=C,C-N,C-O-C structure.The maximum excitation wavelength of yellow fluorescence carbon dots was 415 nm,the maximum emission wavelength was 556 nm,the half width was 78 nm,and the emission light was yellow.The melamine detection range of was from 50.0 ?mol·L-1 to 700.0 ?mol·L-1,the linear equation was ?F=0.421C-22.3,the linear correlation coefficient was 0.991 and the detection limit was 5.808 ?mol·L-1.