Investigation Of Doped Carbon Dots And Nanocomposites For Small Molecule Detection By Nanoprobes

Based on unique optical and chemical properties,carbon dots are widely used in multiple disciplines and fields such as chemistry,environmental detection,biosensing,disease diagnosis,treatment,photocatalysis and optoelectronic devices.However carbon dots with a simple composition and structure have low quantum yields,poor optical properties and other shortcomings,so heteroatom doping and functionalization are often used as the effective means to improve its performance of carbon dots.Non-metal atoms adjust the chemical structure and properties of carbon dots thr ough the size effect,changing the surface functional groups and conjugate structure and molecular structure.Metal atoms are realized by adjusting the energy band structure of carbon dots.Functionalization mostly passes through the passivation of the sur face of the carbon dots to obtain carbon dots with specific fluorescent properties.In this paper,zinc/nitrogen doped and copper/iodine doped carbon dots and cyclodextrin functionality carbon dots were synthesized,their characterization and optical prope rties were studied,and they were used for detection of small molecule nanoprobes and the study of the activity of mimic enzymes.The main research contents of this paper are as follows:1.Synthesis of Zn,N-doped carbon dots as fluorescent probes for the detection of tetracyclineEthylenediamine and zinc sulfate as raw materials,synthesis of Zn,N-doped carbon dots(Zn,N-CDs)was the one-step hydrothermal method.The quantum yield of Zn,N-CDs was 14.26%.The characterization results showed that the surface of Zn,N-CDs is rich in carboxyl,hydroxyl and amino groups,and Zn N is doped.Studies have shown that the fluorescence intensity of Zn,N-CDs changes with the concentration of tetracycline(Tc).The fluorescence intensity at?ex=515nm decreases with the increase of Tc concentration,and the fluorescence intensity at?ex=515nm shows a completely opposite trend.Therefore,based on the proportional changes of the fluorescence intensity of F415 and F515 of N,Zn-CDs,respectively,the detection of Tc can be achieved.Tc showed a linear relationship in the concentration range of 2.5-75?M at F415 and 2.5-100?M at F515,the regression coefficient was R2 both were 0.99,and the limit of detection(LOD)was 1.25?M.Used for the detection of Tc for the actual sample milk,with a good recovery rate.2.Synthesis of cyclodextrin functionality Zn,N-doped carbon dots and their use in the detection of fluoroquinolone fluorescent probesZn,N-CDs as raw materials,and functionalization obtain?-cyclodextrin functionality Zn,N-doped carbon dots(?-CD-Zn,N-CDs).After characterization,it was found that the shape of?-CD-Zn,N-CDs is similar to that of Zn,N-CDs,but the size is larger than the Zn,N-CDs.Studies have found that fluoroquinolones(FQs)have an effect on?-CD-Zn,N-CDs.The fluorescence intensity has an influence.Not only enhance the fluorescence intensity of?-CD-Zn,N-CDs,but also has a red shift.Therefore,adding different concentrations of FQs to change the fluorescence intensity of?-CD-Zn,N-CDs,and the fluorescence detection of FQs.Due to the FQs has the same effect for the fluorescence of?-CD-Zn,N-CDs,so ofloxacin(OFL)was used to the representative of FQs.Under optimized detection conditions,the linear range is 0.075-3.75?M,and the LOD is 0.05?M(S/N=3).Detection of FQs in actual samples of milk and domestic water,and the recovery rate is satisfactory.3.Cyclodextrin functionality Zn,N-doped carbon dots for the detection of uric acid as a fluorescent probeFurther research of the?-CD-Zn,N-CDs.3,3',5,5'-tetramethylbenzidine(TMB)could enhance the fluorescence intensity of?-CD-Zn,N-CDs,but not has been red shift.Using the principle that urea(UA)competes with TMB of the surface groups of?-CD-Zn,N-CDs,the fluorescence d etection of UA was realized.This method was based on the?-CD-Zn,N-CDs-TMB system,in which TMB enhances the fluorescence of?-CD-Zn,N-CDs through electronic transfer,and at the same time,it competes with?-CD-Zn,N-CD by introducing UA and TMB.CDs surface functional groups to achieve fluorescence recovery.So as to realize the detection of UA concentration,the relative fluorescence intensity of?-CD-Zn,N-CDs-TMB decreases linearly with the linear increase of UA concentration from 0.2-17.5?M and 0.0125-0.2?M,and the LOD is 0.0086?M(S/N=3).This method is used for the analysis of UA in serum,with satisfactory accuracy and recovery rate.4.Cu,I-doped carbon dots/platinum nanocomposite for the colorimetric probe determination of hydrogen peroxi deCu,I-doped carbon dots(Cu,I-CDs)were synthesized by a one-step hydrothermal method using the precursors of CuCl2,3-iodo-L-t yrosine and ethylenediamine,and the quantum yield was 5.24%.Then,using Cu,I-CDs as reducing agent and polyethyleneimine(P EI)as stabilizer,the Cu,I-doped carbon dots and Pt nanoparticle composites(Cu,I-CDs/Pt NPs)are finally prepared by mixing..The characterization results showed that Cu,I and Pt NPs aggregated on PEI to form a stable cluster-like complex.Further research found that Cu,I not only enhanced Pt nanoparticles(Pt NPs)as peroxidase mimics to catalyze hydrogen peroxide(H ₂O₂)through a synergistic effect,but also enhanced the stability of PEI/Pt NPs.Based on the peroxidase-like activity of Cu,I-CDs/Pt NPs,H₂O₂ is detected by the colorimetric method,and it has a good linear relationship(0.025-0.5 m M)and LOD(0.012 m M S/N=3).