The Optical Properties Of Carbon Dots And Their Applications In Recognizing And Labeling HepG2 Cells

As a kind of fluorescent nanomaterials,carbon dots(CDs)are focused due to their excellent luminescent properties,which make them applied to bioimaging,drug delivery,light-emitting devices and biosensor.CDs show good biocompatibility,low toxicity,excellent photostability and versatile surface modification.However,CDs have lower quantum yield compared to conventional semiconductor quantum dots.Therefore,improving the fluorescence quantum yield of CDs is the challenge for bio-application.In addition,CDs have low drug loading due to their size less than 10 nm.Most CDs havn't the ability to recognize cancer cells,which makes CDs unable to detect and label cancer cells.Based on the above questions,this thesis focuses on improving the fluorescence quantum yield of CDs and establishing a detection system which can recognize and label cancer cells.The main works of this thesis are as follows:(1)CDs were synthesized through hydrothermal method.The fluorescence of CDs is directly related to their surface states.The surface states of CDs were oxidized to different degrees by using the strong oxidation of hydrogen peroxide.The CDs were characterized by a series of instruments to investigate the relationship between the surface states and the photoluminescence of the CDs.On the other hand,the fluorescence quantum yield can be improved by oxidizing the surface defect states due to increasing of the number of luminescence center.(3)Liposomes are used to loading CDs.Hydrophilic CDs can be encapsulated in the hydrophilic region of the liposomes.Liposomes can passivate the surface states of CDs,which enhances the fluorescence quantum yield of CDs.D-Mannose is modified on liposome surface through aldehyde-amide condensation reaction.The specific recognition of carbohydrate and glycoproteins on cancer cells surface is used to achieve the purpose of recognizing HepG2 cells and labeling them.