Preparation And Application Of New Type Fluorescent Carbon Dots

Fluorescent carbon dots,one promising zero-dimensional carbon materials with a size of less than 10 nm,have many applications in sensors,catalysis,bioimaging and drug delivery due to their adjustable property in fluorescent and good biocompatibility.In this paper,two kinds of carbon dots,nitrogen and chlorineco-doped carbon quantum dots(N,Cl-CQDs)and polyethyleneimine-functionalized graphene quantum dots(GQDs-PEI),were prepared.Since fluorescent carbon dots generally have low quantum yield that may limit their applications in some fields,therefore,we proposed a method of dual-elemental doping to increase their quantum yield.N,Cl-CQDs were prepared using D-Glucosamine hydrochloride as the only precursor and the dopant of nitrogen and chlorine.After optimizing reaction time and temperature,blue fluorescent N,Cl-CQDs with 16.8%quantum yield were obtained.Experiments on detecting metallic ions suggest that N,Cl-CQDs are selective to detect Fe3+.Meanwhile,N,Cl-CQDs can still effectively detect the existence of Fe3+ with a low concentration(0?2?M)and the detection limit can reach 0.16?M(R2 = 0.997).As a result,N,Cl-CQDs have large potential in the field of sensor.Polyethyleneimine,as a non-viral gene vector with high transfection efficiency,is high toxicity that prevents its possibility of being a gene vector.In this thesis,using acylation reaction of carboxyl that comes from GQDs surface and amino of PEI,GQDs-PEI complex,as a novel gene delivery vector,was prepared with 1:1,1:3 and 1:5 mass ratio.Gene transfection experiments of COS7 cells and A549 cells were carried out and we found that when the mass ratio of GQDs and PEI-1800 was 1:3 the transfection efficiency was the highest and they were 51%and 43%,respectively,which were better than the gold standard for non-viral vector gene transfection PEI 25KDa(45%,35%).What's more,the toxicity of GQDs-PEI-1800 complex in COS7 cells was measured via MTT experiments and results suggested that when the concentration of GQDs-PEI-1800 complex was up to 30 ?g/mL their cell viability were more than 85%,which was higher than the PEI 25KDa(5%).Therefore,GQDs-PEI complex was able to act as a gene delivery vector with high efficiency and low toxicity.