Preparation Of Carbon Dots-based Composite Nanomaterials And Their Applications In Analysis And Detection

Carbon dots,a kind of carbon nanomaterial with excellent fluorescence properties,are known for their water-soluble,low-toxicity,biocompatibility,stable luminescence,abundant surface groups,and easy functionalization,which lay the foundation for development in analytical sensing,bioimaging,and drug delivery,photoelectrocatalysis,photovoltaic devices.The application of carbon dots in sensors has attracted more attention in recent years,but it is still the difficulties and hotspots to build a novel analytical model and to explore the detection mechanisms.In this thesis,we have prepared highly fluorescent carbon dots by simple,efficient and green synthetic methods,and have explored their luminescence mechanism simply.Meanwhile,we designed multi-functional carbon dots-based composite nanomaterials by combining carbon dots with other materials to create new types of chemical sensors for the detection of small molecular substances.Firstly,this article introduces the structure and properties of carbon dots and their applications in analysis briefly,and we conduct our research from the following aspects:The carbon dots were prepared by hydrothermal method using aloe as carbon source,and the carbon dots were composited with Fe₃O₄ by solvothermal method to obtain carbon dots-based Fe₃O₄/CDs composite nanomaterials,which has excellent peroxidase-like properties.Fe₃O₄/CDs composite nanomaterials can effectively catalyze the coloration of 3,3’,5,5’-tetramethylbenzidine（TMB）in the presence of H₂O₂,and glutathione（GSH）can effectively inhibit the catalytic reaction.Based on this,we have established a sensitive and rapid method for detecting GSH.The absorbance difference was proportional to the concentration of GSH showed a linear range of 0.1²0μM,and the corresponding detection limit was 58 nM.The method has been successfully applied to the determination of commercial medicine and adult urine.Using urea as the N source and Fe Cl₃·6H₂O as the Cl source,the N,Cl codoped fluorescent carbon dots（N,Cl-FCDs）were synthesized by hydrothermal method,which the original carbon dots come from aloe.The quantum yields of N,Cl-FCDs is60.52%,which have good fluorescence properties,and N,Cl-FCDs have good acid,alkali and salt resistance.Based on the mechanism of fluorescence resonance energy transfer（FRET）between tartarzine and N,Cl-FCDs,a rapid,convenient,sensitive test method for tartrazine was designed.The fluorescence quenching efficiency was proportional to the concentration of tartarzine showed a linear range of0.1³0μM,and the corresponding detection limit was 48 nM.The method was applied to the determination of actual drinks with good recovery and precision.The fluorescence carbon dots（N,S-CDs）were synthesized by calcination method using fresh bamboo as carbon source.Characterized by TEM,XPS,FT-IR,UV-vis and FL,the mechanism of fluorescence emission was discussed.After analysis of the fluorescence properties,it was found that N,S-CDs is stable and has good photobleaching,acid,alkali and salt resistance.The relationship between nitrophenol compounds and N,S-CDs was studied based on the quenching effect of nitrophenol compounds on N,S-CDs.The detection limit of 4-NP,2,4-DNP,2,4,6-TNP are 0.32μM,0.33μM and 0.25μM,respectively.It is expected that N,S-CDs will be developed into fluorescent probes of corresponding nitrophenol compounds.