Preparation Of Functionalized Carbon Quantum Dots Doped With Metal And Non-metal And Its Application In Many Fields

Carbon-based fluorescent nanomaterials have unique chemical stability and light stability,low biological toxicity,and good biocompatibility,making them more effective than organic fluorescent dyes,semiconductor quantum dots,fluorescent proteins,etc.Better potential and room for development.Among the many types of carbon-based nanomaterials,Carbon Quantum Dots(CDs)is a new star of carbon-based nanomaterials with a particle size of less than 10 nm.Due to its low preparation cost,simple synthesis method and easy surface modification,The advantages of adjustable excitation and emission have attracted the attention of many scholars.At present,researchers have done a lot of research on improving luminescence performance and exploring luminescence mechanism.Experiments show that the doping of heteroatoms can impart more groups to the surface of carbon quantum dots,which can effectively improve the optical properties of carbon quantum dots.In addition,doping of metal elements on this basis can give carbon quantum dots more characteristics Functionalize carbon quantum dots.This dissertation is based on previous studies,with the potential of carbon quantum dots in various fields as the research object,mainly using a variety of organic small molecules and natural substances as raw materials,using hydrothermal methods,microwave methods,etc.The above synthesis method prepares metal-doped and non-metal-doped carbon quantum dots,and characterizes the structural composition and optical properties of the synthesized carbon quantum dots through a variety of methods.Specific applications in catalytic degradation.The main research contents and results are as follows:(1)Using p-aminobenzene sulfonic acid(p-ASA)and tetrahydroxymethyl phosphorous chloride(THPC)as the carbon source,manganese chloride(MnCl₂·4H₂O)as the manganese metal doping source,the one-step hydrothermal method has Superparamagnetic manganese-doped carbon quantum dots(Mn-CDs).The structure of Mn-CDs was characterized by TEM,XRD,XPS,and FT-IR,and the superparamagnetic properties of Mn-CDs were characterized by VSM.Due to the fluorescence internal filter effect(IFE),the fluorescence of Mn-CDs can be quenched by Mn(?),and due to the redox effect,ascorbic acid(L-AA)can reduce colored Mn(?)to nearly colorless Mn(?),which can realize"on-off-on"detection of Mn(?)and ascorbic acid.Cytotoxicity and cell imaging experiments have proved the low toxicity of Mn-CDs,can successfully enter the cell to emit green fluorescence,and can be used for intracellular visual detection of Mn(?)and L-AA.In addition,due to the superparamagnetic properties of Mn-CDs,Mn-CDs have been successfully applied to in vitro magnetic resonance imaging(MRI).(2)Sucrose solution and sulfuric acid(H₂SO₄)are used as carbon sources,diethylene glycol(DEG)is used as the solvent,and dysprosium chloride(DyCl₂·6H₂O)and ytterbium chloride(YbCl₂·6H₂O)are respectively doped with rare earth elements.For miscellaneous sources,rare earth element dysprosium doped carbon quantum dots(Dy-CDs)and rare earth element ytterbium doped carbon quantum dots(Yb-CDs)are prepared by simple microwave heating.Compared with undoped CDs,Dy/Yb-CDs red-shifted the excitation wavelength of carbon quantum dots from 360 nm to 368 nm,while the emission wavelength remained unchanged at 515 nm.The structure of the three carbon dots was characterized by TEM,XPS and FT-IR,and the successful doping of Dy and Yb was also proved by EDS.Cytotoxicity and cell imaging experiments have proved the low toxicity of Dy-CDs and Yb-CDs,which can successfully enter the cell and emit green fluorescence,which can realize fluorescence imaging(FI).In the medical imaging applications of Dy-CDs and Yb-CDs,it is found that Dy-CDs are more suitable for T₁-weighted imaging in the field of magnetic resonance imaging(MRI),while Yb-CDs are more suitable for T₂-weighted imaging.In the field of CT imaging,experiments have shown that both Dy-CDs and Yb-CDs have good CT imaging effects and meet the conditions of in vivo imaging.Dy-CDs have a larger HU value because Dy is more likely to be doped on the surface of CDs.It was successfully applied to CT imaging of mouse leg tumors.The Dy-CDs and Yb-CDs prepared by this system successfully achieved single element doping to meet the three-mode imaging of fluorescence,nuclear magnetic and CT.(3)Using natural material peanut shell powder,urea and sulfuric acid as raw materials,a one-step hydrothermal method is used to prepare carbon quantum dots.Carbon quantum dots such as TEM,XRD,XPS and FT-IR were used for structural characterization.The best excitation wavelength of N,S-CDs is 320nm,and the best emission wavelength is 395nm.The band gap of N,S-CDs calculated by solid ultraviolet is 2.76eV.Using N,S-CDs as a photocatalyst and methyl orange(MO)as a model dye,the dye degradation experiment was carried out under a xenon lamp simulating sunlight.The photocatalytic degradation rate was measured by ultraviolet spectroscopy,and the influence of catalyst concentration,dye concentration,light time and p H environment on catalytic degradation was investigated.It is determined that the main active substance of catalytic degradation is superoxide radical(O₂^-).Cytotoxicity experiments and cell fluorescence imaging show that N,S-CDs can enter the cell and emit blue fluorescence.This also proves that carbon quantum dots have the potential for chemocatalytic treatment in cells.