Study on the Biological Behaviors of Graphene Film and Graphene Derivatives
Supervisor:liu xuan yong
The properties of graphene are closely related to the number of layers,surface defects and dopants.Graphene based materials have shown great advantages in the field of antibacterial,anticancer and tissue engineering.However,lacking attention is payed to biologic behaviors of monolayer graphene and nano-sized graphene materials.Based on this issue,different methods were used to prepare monolayer graphene and graphene quantum dots.And then the effects of the structural defects as well as dopants on their biological properties were investigated.The main content of the paper are summarized as follows:(1)Controllable preparation of monolayer graphene film and its biological propertiesThe monolayer graphene film was deposited on semiconductor germanium(Ge)substrate by chemical vapor deposition(CVD).By adjusting the growth time,continuous and discontinuous graphene films were obtained.The discontinuous graphene film with abundant edge structure caused higher defects density,leading to its decreased conductivity.Continuous graphene film improved the corrosion resistance of Ge substrate significantly.The stronger antibacterial ability against S.aureus and E.coli of the prepared Graphene-Ge film than that bare Ge was observed.A plausible antibacterial mechanism of the graphene-Ge system based on phospholipid perturbation induced membrane damage as well as the electron extraction caused by schottky barrier structure was reported.In addition,the conformation change of blood protein based on the electron extraction process may lead to the aggregation and activation of platelets on graphene film.Compared to traditional physical injury mechanism,we focus on the interaction between organisms and graphene from the perspective of the interfacial physical and chemical process.(2)Controllable fluorination of graphene film and its biological propertiesIn order to further explore the effect of fluorine doping on the biological behavior of monolayer graphene film,the continuous graphene film was deposited on Ge substrate by CVD,and fluorinated by plasma etching.The experimental results showed that with the increase of fluorination duration,the graphene transited from partially fluorinated graphene to fluorographene.The combined actions of interfacial force and fluorine contributed to the favorable antibacterial ability against E.coli of partially fluorinated graphene.Owing to the C-F bonds existed in fluorinated graphene,the fluorinated graphene behaved good biological response to rBMSCs including low cytotoxity and facilitation to cell adhesion at early stage.Besides,the attenuate π-π interaction between the surface of fluorinated graphene and blood protein lead to reduction of the adherent blood platelet.After fluorination,graphene gradually transformed into semiconductor or insulator,thus weakening electron extraction function of schottky barrier structure of graphene-Ge system,resulting of the reducement of the probability of platelet activation.The distinct biological response between partially fluorinated graphene and fully fluorinated graphene was observed which may relate to the different structures of C-F bonds in the both fluorids which may provide valuable insights for the study of biological application of fluorinated graphene.(3)Nitrogen doped graphene quantum dots preparation and their stem cell imaging and osteogenic differentiation propertiesIn order to prepare nitrogen doped graphene quantum dot(N-GQDs),the prepared graphene oxide and ammonia were adopted as carbon source and nitrogen source respectively.The experimental results showed that N-GQDs possess typical crystal structure.Except the stable optical properties,N-GQDs also possessed favorable cytocompatibility.The N-GQDs with intrinsic photoluminescence characteristics could be used to label cells with high uniformity and light stability in absence of chemical dyes under the concentration of 50 μg/ml.In addition,the enhanced osteogenic differentiation of rBMSCs was observed after incubating with N-GQDs at a suitable concentration of 10 μg/ml.A potential possibility of application in the field of tissue engineering of graphene quantum dots has been pointed out.