Preparation Of Novel Fluorescent Carbon Dots And Their Applications In Sensor Analysis And Cell Imaging

Iron and copper,as common transition metals,play an important role in many physiological and pathological processes of human body.Abnormal metabolism of both in the human body can lead to a range of diseases,including cardiovascular disease,kidney metabolic disease,cancer,Alzheimer’s disease and Parkinson’s disease.Glutathione（GSH）,as an essential endogenous antioxidant,plays an indispensable role in maintaining cell homeostasis and balance,and protecting cells from oxidative stress.Therefore,it was of great significance to realize selective and sensitive the detection of Fe²⁺,Cu²⁺and GSH.Fluorescent probes have attracted great attention owing to their high sensitivity,excellent selectivity,fast response and clear imaging.At present,the existing fluorescent probes for detecting Fe²⁺,Cu²⁺and GSH were mainly organic fluorescent molecular probes and chemically modified quantum dots.However,most of the organic molecular probes and chemically modified quantum dots restrict their further applications in sensing owing to their high toxicity,environmental pollution,and difficulty in modification.Carbon dots（CDs）have fascinated widespread attention thanks to its small size,good water solubility,high biocompatibility,wide emission spectrum,good optical stability and low preparation cost.Based on the above content,the main research work of this paper is as follows:Using PEI as raw material and DMF as solvent,fluorescent CDs with bright blue emission were successfully prepared by a simple one-step solvothermal method.The morphology and structure of CDs were characterized by a variety of characterization methods.The experimental results shown that the CDs were spherical shaped with a clear lattice structure and there were carboxyl,Hydroxyl,Amino and other functional groups on the surface.Thus,the CDs exhibited excellent luminescence properties,good optical stability and outstanding water solubility.After optimizing the experimental conditions,the probe showed high selectivity and sensitivity to Fe²⁺,and its limit of detection（LOD）was51 n M.Moreover,the mechanism of Fe²⁺quenching CDs autofluorescence was deduced based on the construction of orbital energy levels.Preliminary biological experiments showed that CDs had good biocompatibility and could monitor the changes of different concentrations of Fe²⁺in living cells.Using L-cysteine and PEI as carbon sources,a kind of nitrogen and sulfur co-doped carbon dots（N,S-CDs）were prepared by a one-step solvothermal method,which acted as a selective fluorescent probe that could detect Cu²⁺and GSH in aqueous solution in“on-off-on”mode.The fluorescent probe had the characteristics of fast response,high sensitivity and excellent selectivity,which could not only detect Cu²⁺in tap water and lake water,but also detected GSH in BSA solution.And the detection limits（LOD）for Cu²⁺and GSH were 38 n M and 41 n M,respectively.Furthermore,owing to the stable optical properties and good biocompatibility of N,S-CDs,Cu²⁺and GSH in living cells could be successfully detected.Therefore,the fluorescent probe has potential application value in environmental monitoring and biosensing.