Construction Of Fluorescent Probes Based On Doped Carbon Quantum Dots And Their Application In Drug Sensing

Carbon quantum dots（CQDs）are a new type of fluorescent carbon nanomaterials in recent years,which are widely used in sensing fields due to their low production cost,small size,good biocompatibility,strong hydrophilicity,abundant surface functional groups,and strong and stable photoluminescence.Due to their unique photoluminescent properties,carbon quantum dots have intense and tunable fluorescence in the visible range.The synthesis of long-wavelength carbon quantum dots by hydrothermal method through the selection of different precursors has expanded their applications in biology and medicine.Hydrothermal preparation of carbon quantum dots is a simple,efficient,environmentally friendly and highly controllable method and is therefore widely used in the preparation of carbon quantum dots.The morphology,size and fluorescence properties can be controlled by adjusting the reaction temperature,time,mixing ratio and other parameters.With the advantages of high selectivity,high sensitivity,non-destructive and real-time detection of multiple information,fluorescent probes have become an important detection tool in chemical analysis and other fields.In this paper,three doped carbon quantum dots were prepared by one-step hydrothermal method by selecting different carbon sources and dopants as precursors for application in drug sensing,and the following work was carried out:Part one:Tazettine（TZ）is an alkaloid with antitumor activity.It can be used clinically to treat cough,toothache,sore throat,and bruises.TZ has certain toxic side effects,and rapid and sensitive determination of TZ is of great importance.In this paper,double-emitting nitrogen-phosphorus co-doped carbon quantum dots（N,P-CQDs）were prepared by a simple hydrothermal method using maleic acid,p-phenylenediamine and phosphoric acid as precursors.The fluorescence intensity of N,P-CQDs at 331 nm decreased with the increase of TZ concentration,while the fluorescence intensity of the emission peak at 481 nm was basically unchanged.After the optimization of the experimental conditions,the fluorescence ratio F₃₃₁/F₄₈₁of N,P-CQDs shows good linearity in the concentration range of 0.01-30μmol/L TZ,and the limit of detection（LOD）for TZ is 0.002μmol/L.The method demonstrated the superiority of N,P-CQDs for the detection of TZ,and was successfully applied to the detection of TZ in human serum.Part two:Vitamin B12(VB₁₂)is the only vitamin containing metal ions among vitamin drugs,which can be widely used for the treatment of various neurological diseases and also for the treatment of anemia.In this paper,nitrogen and sulfur co-doped carbon quantum dots（N,S-CQDs）were prepared by a one-step hydrothermal method using alizarin and thiourea as precursors.It was found that the absorption peaks of VB₁₂and the emission peaks of N,S-CQDs overlapped,which produced an internal filtering effect and caused the fluorescence of N,S-CQDs to quench.Based on this,an analytical method for the detection of VB₁₂based on N,S-CQDs was established.This method was successfully applied to the determination of VB₁₂in milk with good linearity in the range of 0.01～50μmol/L and a limit of detection（LOD）of 0.003μmol/L.Compared with other methods,this method is simple,rapid,stable and has low detection limits.Part three:6-mercaptopurine（6-MP）is a purine antimetabolite and antitumor drug,and insufficient dose of 6-MP can be detrimental to the therapeutic process.In this paper,yellow fluorescent nitrogen-doped carbon quantum dots（N-CQDs）were prepared by a one-step hydrothermal method using riboflavin,o-phenylenediamine as precursors.Due to the presence of hydroxyl,carboxyl and amino groups on the surface of the synthesized N-CQDs,they can complex with Fe³⁺,which makes the fluorescence of N-CQDs quenching.When 6-MP is added to the N-CQDs/Fe³⁺system,the fluorescence of the system is restored due to the formation of a more stable complex with 6-MP and with Fe³⁺.N-CQDs can be used as“off-on”fluorescent probes to detect 6-MP.The 6-MP concentration showed a linear relationship with the fluorescence recovery efficiency of N-CQDs in the range of 0.05～100μmol/L with a detection limit of 0.01μmol/L.The method was successfully applied to the detection of 6-MP in serum samples.