Synthesis Of Functional Carbon Dots And Its Application In The Detection Of Drug And Small Molecule Isomers

Carbon nanomaterials have attracted much attention because of their unique photoelectric properties and extensive applications.Generaly,carbon nanomaterials refer to carbon elements consist of zero-dimensional,one-dimensional and two-dimensional carbon nanomaterials and carbon pore materials,whose sizes range from 1-100 nm.As a new type of fluorescent carbon nanomaterials,carbon dots has attracted researchers’ attention due to its excellent photoelectric properties,smaller size(≤ 10 nm),adjustable luminous wavelength and wide application.In the past ten years,the synthetical methods of carbon dots have become diversified and increasingly mature.Various functional carbon dots have been obtained through different preparation methods,and they have been widely used in biological imaging,environmental monitoring,energy conversion,analytical sensing,photocatalysis,information encryption,drug loading and other fields.Therefore,for the research on the preparation method and application of fluorescent carbon dots,combining the advantages of carbon dots as fluorescent probes for analysis and detection,building a bridge for applying carbon dots to the field of drug analysis,and ultimately achieving the analysis and detection of drugs has a very good Significance.Based on this,this work focuses on the construction of simple and effective synthetic methods to prepare specific functional carbon dots,and realize their application in the analysis and detection of drugs and small molecules.In this work,two kinds of fluorescent carbon dots were prepared by hydrothermal and microwave methods,and their elemental composition,luminescence mechanism and stability were explored.A dual-signal detection strategy for tetracycline drugs and a fluorescence analysis method for hydroquinone homologues were established,and the mechanism of detection was also explored.Specific research contents are as following:(1)Luminescence mechanism of long lifetime phosphorescent carbon dots,p H sensing and construction of dual signal detection of tetracycline:Conventional room temperature phosphorescent(RTP)materials are usually metal complexes and organic compounds doped with rare earth elements or heavy atoms.In fact,most current RTP materials have a relatively short phosphorescence lifetime(microseconds to milliseconds),so the shorter phosphorescence lifetime greatly limits the appliations of RTP materials.Actually,RTP materials are rarely used in the analysis and detection of drugs,but they have attracted much attention because of their excellent optical properties and unique physical and chemical properties.At present,researchers are focusing on room temperature phosphorescent materials based on carbon dots.Therefore,in this study,n-aminoethyl-p-aminopropyl trimethoxylsilane was applied as raw material to prepare an ultra-long phosphorescent carbon dots(p-CDs)by microwave method.Compared with ordinary fluorescent carbon dots,P-CDs exhibitted yellow-green phosphorescence as long as 9 s at room temperature,and the emission peaks of fluorescence and phosphorescence P-CDs were located at 418 nm and 525 nm.Meanwhile,the structural characterization of P-CDs,including particle size distribution,infrared and XPS element analysis,showed that P-CDs particles was uniform and have excellent optical properties,mainly composed of C,N and O elements.This study focuses on the mechanism of RTP generation of P-CDs,indicating that RTP generation is mainly determined by n-π* transition and steady-state hydrogen bond.In addition,the stability of P-CDs was investigated in this study,and it was found that the RTP intensity of P-CDs depended on the change of p H.Specifically,with the increase of p H value,the phosphorescent signal gradually decreased and had a good linear relationship between p H=2.1-12.8.Importantly,it was found that the introduction of tetracycline drugs could promote the fluorescence and phosphorescent double signal quenching of P-CDs.Therefore,the strategy of double signal analysis to detect tetracycline drugs was established based on this,and the quenching mechanism was studied.There findings showed that tetracyclines possessed have excellent selectivity to detect for P-CDs,and through the two-signal analysis strategy,more accurate analysis results for tetracyclines are finally obtained.(2)Blue fluorescent carbon dots based on Cryptococcus as carbon source for discrimination and detection of catechol compoundsCurrently,It is difficult to distinguish and detect the large number of small molecule isomers due to their highly similar structures and the same physical and chemical properties through a simple and fast method.Constructs are still full of challenges.it is still challenging for researchers to use simple and fast methods to simultaneously distinguish and detect small molecule isomers.Therefore,it is urgent to construct a strategy for distinguishing and detecting small molecule isomers.Here,Cryptococcus was used as the carbon source,and blue fluorescent carbon dots(CDs)were obtained by hydrothermal method.Through a series of characterization of the carbon dots,the uniform particle size distribution and surface of the prepared CDs were clarified.Rich in hydroxyl,carbonyl and carboxyl functional groups.This study further explored the stability and interference of CDs,and found that CDs have very different fluorescence changes in hydroquinone compounds.Specifically,the addition of resorcinol will enhance the fluorescence of CDs,and The introduction of phenol can cause CDs fluorescence quenching.Therefore,based on the above experimental results,a strategy to distinguish and detect two types of resorcinol through CDs as fluorescent probes was established.The method simultaneously established two linear relationships for the detection of two types of hydroquinones,with linear ranges of 2×10-3 to 1×10-7 mol/L and 2×10-5 to 2×10-9 mol/L,respectively.Mechanistically,the addition of resorcinol leads to the formation of hydrogen bonds between CDs,resulting in enhanced fluorescence.In contrast,when hydroquinone was added,electron-rich CDs promoted the oxidation of hydroquinone to paraquinone,which led to the transfer of electrons between the two,and induced fluorescence quenching.Currently,although high-performance liquid chromatography and other chemical methods for the determination of hydroquinone already exist,strategies based on CDs fluorescent probes for distinguishing and detecting hydroquinone isomers provide detection of small molecule isomers.This work has explored the preparation and characterization of room-temperature phosphorescent and fluorescent carbon dots,the exploration of the mechanism of luminescence,and their applications in drug analysis and identification.It provides new ideas for deep-level cognition and research of fluorescent carbon dots.It provides a richer theoretical basis for expanding the application of carbon dots in analysis and detection,drug identification and other aspects.