Research And Development Of Graphene Biosensor

Since 2004,when British scientists obtained graphene by mechanical stripping method for the first time,it has sparked an upsurge of research on structure,properties and applications of graphene.In graphene,six sp2-hybridized carbon atoms are connected to each other to form a ring structure.This hexagonal ring structure forms a honeycomb lattice material through the close binding of carbon atoms.Because graphene is made up of carbon atoms,a single layer of graphene is about the thickness of a carbon atom,but it is extremely strength and toughness.Due to its lattice structure,graphene has more biometric sites in a limited area.In addition,graphene also has excellent performance such as high carrier mobility,high conductivity and thermal conductivity,which also make graphene have great development potential in the field of biosensors.Biosensor is an electronic device that can specifically identify the target molecules by the biometrics,and then convert the generated biological signals into electrical and optical signals that can be detected,so as to analyze the composition and concentration of the measured objects.Biosensors with efficient detection process and accurate detection results have a wide range of applications.At present,they can not only detect nucleic acids,proteins,enzymes,microorganisms and metal ions,but also analyze them at the level of single molecule.With the in-depth study of graphene by researchers,graphene's excellent electrical properties and biocompatibility are conducive to its applications in the field of biosensing,which can improve the sensitivity,fastness and integration of biosensor.In this paper,copper foil and nickel foam were selected as growth substrates by chemical vapor deposition(CVD)to prepare nanometer graphene materials.Based on the nanomaterials,graphene field effect tube(G-FET)and three-dimensional graphene field effect tube(3D-G FET)biosensors were prepared to implements the trace detection of E.coli and microRNAs.In this experiment,nucleic acid aptamers were fixed on the surface of graphene as a molecular probe,and the relationship between G-FET transfer curve changes and E.coli concentration was established.By adding E.coli solution in the sensor,electrical signal changes were generated,thus realizing the detection of E.coli.In addition,DNA was selected as a detection probe,which was fixed on the three-dimensional graphene(3D-G)surface,and microRNAs molecules were analyzed and detected.The relationship between the transfer curve of 3D-G FET biosensor and the concentration of microRNAs was established to realize trace detection of microRNAs at different concentrations.This article consists of six parts.First of all,the first chapter is the introduction,which briefly introduces the development and application background of biosensors and graphene,and summarizes the main research contents of this paper.The second chapter mainly introduces the preparation of graphene nanomaterials by chemical vapor deposition(CVD),the transfer process and structure characterization of graphene,and the preparation of graphene field effect tube(FET)biosensors.The third chapter is the detection of E.coli based on the G-FET aptamer biosensor.In this experiment,the aptamer was selected for functionalization of the device through specific binding with E.coli,and the detection limit of E.coli by biosensor was reduced to 8.8 cfu/mL.In addition,the G-FET biosensors can distinguish E.coli from other strains,showing high selectivity in detection of E.coli.In the fourth chapter,a 3D-G FET biosensor was prepared.Using DNA as a probe,the micro-label-free detection of microRNAs was realized,saving the cost and time of detection.It provides a new detection method for the detection of microRNAs.Finally,the fifth chapter is the summary and prospect,which summarizes the main contents of this research topic,and prospects the improvement of the deficiencies of this research direction.