Synthesis And Sensing Applications Of Fluorescent Carbon Quantum Dots

Photoluminescent nitrogen-doped carbon quantum dots?NCQDs?hold great promise for numerous applications because of their attractive attributes.However,the development of NCQDs with bright fluorescence and unique optical responsibility is still in its infancy.In the first paragraph demonstrated some fluorescent CQDs,because their excellent electroconductivity,magnetic,optical properties,easy available,nontoxic,and easy functionlization,with stable chemistry property and catalytic activity,had been attracting account of attention in recent years,with little size?¹0 nm?of nanoparticals,and was filled into 0D carbon structure,which different with polymer dots or graphite quantum dots.There are great of process in synthesis and apply of NCQDs recent years,and these contents make up vary develop direction.However,the synthesis ways were concluded with double pattern:“top-down”and“bottom-up”pattern.To this end,this thesis studies the low-cost preparation of CQDs for detection applications,which includes the following three parts:The second paragraph,herein,we present a facile and green approach to prepare versatile NCQDs via hydrothermal carbonization of watermelon juice.The resulted NCQDs with high fluorescence quantum yield?10.6%?showed superior water dispersibility,stable photoluminescence,and low cytotoxicity.In addition,the NCQDs exhibited selective and sensitive fluorescence quenching behavior towards Fe³⁺ions and the limit of detection?LOD?can reach 0.16?M.It was also demonstrated that the NCQDs/Fe³⁺system can be employed to selectively detect cysteine?LOD=0.27?M?based on the fluorescence turn on effect.On the other hand,NCQDs could detect tempture,with the tempture raise the fluorescent intensity down.The thired paragraph,one-pot fabricated dopamine fluorescent carbon quantum dots though ultrasonic ways,which can be used to detect Fe²⁺ions,bioimaging,and optical thermometry.It can detect Fe²⁺ions and would not be bothered by other metal ions,and the fluorescent intensity will be decreased with the temperature raise,opposite with watermelon juice NCQDs.To our knowledge,most of the reported CQDs focused on the detection of Fe³⁺ions,while the sensing of Fe²⁺ions by CQDs has rarely been studied.On the other hand,the Fe²⁺ions are also essential ions for human and animal healthy.For example,Fe²⁺ions are not only crucial to transport and storage of oxygen but also are key ions in energy and metabolism.Therefore,using dopamine and DMF to fabricate fluorescence NCQDs to sensitive and selective detect Fe²⁺ions.Since the fluorescence and surface properties of CQDs are highly dependent on the synthesis method and used precursor,it is highly desired to explore viable synthesis method associated with appropriate precursor to prepare CQDs with high sensitivity towards Fe²⁺ions.Moreover,the NCQDs also showed interesting temperature-dependent fluorescence behavior and can be utilized as a nanothermometer,as demonstrated by determining temperature in cells in this study.The use of natural biomass as a carbon source to prepare fluorescent CQDs has attracted intensive attention,which is due to the wide source of natural biomass,cheap raw materials,good biocompatibility and other characteristics.The last part is also NCQDs made by pitaya skin as carbon source,synthesis strong blue fluorescent material through one-pot hydrothermal and can selectively detect the concentration of Fe³⁺ions.The resulted CQDs with size in the range of 3-6 nm exhibited excellent water dispersibility and stability and strong fluorescence.Moreover,NCQDs also present priority optical thermometry function,and there are three kinds of CQDs with temperature behavior.