Synthesis Of The Chiroptically Active Carbon Dots And Its Applications In The Analysis

Chirality can be defined in such a way that the structure is asymmetrical and has a non-superimposable mirror image,which is critical for molecular recognition and disease diagnosis,and has attracted extensive attention in many fields of chemistry and materials science,especially in pharmaceutical science.Chirality in nanoscale has recently attracted experimental and theoretical research efforts towards chiral nanomaterials such as chiral metal nanoparticles,chiral nanorods and chiral inorganic semiconductor quantum dots.Fluorescent carbon dots?CDs?have garnered much interest due to their ease of preparation,excellent stability,low toxicity and environment-friendly.However,to the best of our knowledge,a very limited number of cases as to the efforts towards the development of chiral carbon materials,especially chiral light emitting carbon dots have been made.Endowed with chirality,CDs will exhibit more marvelous properties and bridge the fields of material chemistry and life sciences tightly.In this thesis,we demonstrate the facile and general method to synthesis chiral CDs rationally.Here the method,two-step pyrolytic route,which designed to meet the requirements of specific tasks through surface modification performed by conjugating functional molecules such as chiral ligand?penicillamine,Pen?onto the surface of CDs.Furthermore,we discuss the mechanism of chirality and apply chiral CDs as a fluorescent probe in Golgi apparatus targeting and antibiotic drug detection.The detail research contents consist of the following three parts:1 Two-step pyrolytic route:a general strategy for preparation of chiral carbon dots.Herein,two pairs of chiroptical carbon dots?Pen-CA CDs and Pen-TA CDs?were prepared though a simple two-step pyrolytic route.Firstly,Pen-CA CDs were attempted to synthesize using citric acid?CA?as carbon sources,though a first pyrolytic process to form achiral carbon nucleus.The second pyrolytic process is using L/D-penicillamine?L/D-Pen?as chiral ligand to passivate the surface of the carbon nucleus,and then the final product L-Pen-CA CDs and D-Pen-CA CDs are obtained.The CDs not only have strong chiroptical activity but also have high fluorescence quantum yield?quantum yield,QY?,which are 49.2%and 52.7%,respectively.As for the mechanism that chirality is bestowed on the Pen-CA CDs through optically active surface passivation,the plausible explanation is the vicinal effect model.For a purpose of investigating the generality of two-step pyrolytic route,L-Pen-D-TA CDs and D-Pen-L-TA CDs were prepared by the same way,which using tartaric acid?TA?as a substitute for CA.Finally,we investigate the optical properties and chiroptical origin of L-Pen-D-TA CDs and D-Pen-L-TA CDs.2 Application of Pen-CA CDs in biological effect and cellular imaging.Biological effect and cellular imaging of Pen-CA CDs were investigated to discriminate the chiral effect of L-Pen-CA CDs and D-Pen-CA CDs.The related experiments show that the CDs capped with different chiral forms of the Pen have chirality-dependent cytotoxicity,with D-Pen-CA CDs being less cytotoxic than L-Pen-CA CDs for a given concentration,however,the cytotoxicity of L-Pen-CA CDs and D-Pen-CA CDs are generally very low.It is found that both the L-Pen-CA CDs and D-Pen-CA CDs could specifically target the Golgi apparatus,and D-Pen-CA CDs has relatively high target effect than L-Pen-CA CDs,although no sharp differences between them.Furthermore,the rac-Pen-CA CDs,L/D-Ala-CA CDs and competitive inhibition experiment show no Golgi targeting ability,indicating that the Pen and thiol of Pen play an important role in the specific targeting of Golgi apparatus.The discovery could provide a new avenue to trace the cell state by real-time monitoring the morphology of the Golgi apparatus,and may be also significant for the design of new drug carriers for Golgi-related diseases.3 Application of Pen-TA CDs in Doxycycline detection.The optical properties of L-Pen-D-TA CDs were discussed,indicating that as-obtained CDs have property of excellent photostability,salt stability and oxidation resistance,making it possible to act as a fluorescent probe to analyze drugs.Doxycycline?Dox?,a class of broad-spectrum antibiotics,have been extensively used in the therapy of human and animal infections such as respiratory tract infection,urinary tract.There is a quite precise overlap between the UV absorption band of Dox and excitation band of L-Pen-D-TA CDs,suggesting that the sensitive and selective sensing of Dox could be established via IFE effect.A good linear relationship between the fluorescence emission ratio?ln?F₀/F??at 440 nm and the Dox concentration is obtained over a range of 2.0–200?M,with a limit of detection of 0.86?M?3??.Due to the high stability of CDs,the detection of Dox in milk samples was successfully implemented.In summary,two pairs of chiroptical CDs are synthesized through two-step pyrolysis route.The origin of chirality could be explained by studying the various properties of chiral CDs.Moreover,the high QY CDs could be a fluorescent probe for Golgi apparatus targeting and detection of Dox.These discoveries can bring some reference values for studying the preparation and properties of chiroptical carbon materials,broadening application in biological imaging and drug molecular detection.