Preparation Of Graphene And Metal Oxide/graphene Composite Materials And Their Applications In Biosensors

Graphene,as the newest form of carbon material followed by the discovery of fullerenes and carbon nanotubes,is considered to be the basic unit to constitute other forms of carbon materiaL Graphene has been drawn great public attention since it was firstly discovered by Geim et al.in 2004.Graphene is applied in electrochemical biosensors due to its desirable physical and chemical properties.A number of methods such as micromechanical cleavage,chemical vapor deposition,liquid-phase exfoliation and chemical method have been developed to produce this remarkable materiaL In the laboratory,the most commonly used methods are chemical method and liquid-phase exfoliation Although massive water-processable graphene oxide(GO)can be obtained via chemical method,the chemical processes definitely cause the irre versible structure destruction of GO and result in a decline in its conductivity.In the thesis,high quality pristine graphene(PG)dispersion is prepared conveniently via the method of liquid-phase exfoliation in ethanol and used to fabricate hydrogen peroxide(H2O2)electrochemical sensor.In addition,manganese oxide nanosheets/graphene(MnO2/PG)composites is also obtained via the liquid-phase exfoliation and displays enhanced performance.Based on the previous research results of our group,a new water-processable material composed of GO and PG is prepared.Decorating Fe3O4 nanoparticles on GO/PG composites is performed via a facile one-step chemical reaction strategy and applied in biosensor.The contents of the thesis are given as follows:1.High-quality PG is prepared by sonicating graphite powder in ethanol with aid ofpotassium sodium tartrate.A electrochemical biosensor based on PG is successfully febricated to detect H2O2.Compared to other biosensor based on chemical converted graphene,the nonenzymatic H2O2 sensor based on PG shows better performance for detection towards H2O2.The liner range for H2O2 is 2-437 μM with a detection limit of 0.19 μM at a signal-to-noise ratio(S/N)of 3.2.The MnO2/PG is prepared by sonicating the mixture of graphite powder and flower-like nanostructures of manganese oxide in isopropyl alcohol.A electrochemical biosensor based on MnO2/PG is successfully febricated to detect H2O2.The liner range for H2O2 is 0.5-237 μM with a detection limit of 0.07 μM at a signal-to-noise ratio(S/N)of 3.3.An easy technique is proposed to prepare a new water-processable material composed of GO and PG.GO is prepared by a modified Hummer’s method.Fe3O4 nanoparticles are well dispersed and loaded on GO/PG composites by eoprecipitation technique.We fabricated a novel biosensor based on highly exposed Fe3O4 nanoparticles decorated water-processable GO/PG composites for the reliable detection of dopamine(DA),uric acid(UA),and H2O2-.The linear detection ranges for DA,UA,and H202 are 0.2-30,0.5-90 and 0.5-267μM,respectively,with detection limits of 0.18、0.43 and 0.09 μM at a signal-to-noise ratio(S/N)of3.