Study Of Biosensor Based On Graphene Field Effect Transistor

A biosensor is a device capable of detecting the concentration or activity of various biochemicals and has the potential to be widely used in medicine,environmental monitoring,food safety and other fields to achieve the protection of human health and ecological environment.Graphene,as a two-dimensional nanomaterial with a single-layer sheet structure composed of carbon atoms,has unique physicochemical properties such as high specific surface area,mechanical strength,thermoelectric conductivity,and electron mobility.These properties can be used to improve the detection sensitivity and selectivity of biosensors,and therefore graphene is often used in biosensors.Compared with other conventional sensors,field effect transistor biosensors using graphene as the channel material have the advantages of higher sensitivity,selectivity,label-free,fast analysis,less reagent consumption,and simple operation.In this thesis,graphene field effect transistor is prepared by chemical vapor deposition of graphene and wet transfer to a metal electrode patterned by UV lithography,and the change of electrical properties of graphene under external action is used to achieve highly sensitive detection of the biomolecules to be measured.The detailed research work and innovations in this thesis are as follows:First,nitrate anion is the main form of nitrogen in the environment and threatens ecosystems and human health when its concentration exceeds 0.3 mg/L.In this work,a novel nitrate sensor based on graphene field effect transistor was proposed to be designed and fabricated using triethylamine（TEA）as a probe molecule.The sensor used graphene grown by chemical vapor deposition as the channel material and modified TEA on the graphene surface to detect nitrate anions.The limit of detection of the sensor is as low as 1.3 n M（0.111μg/L）,which is better than mainstream sensors.This low-cost and easily fabricated sensor also showed high specificity for other anions,such as Cl^-,CO₃^2-and SO₄^2-.This study provides a good technical tool for rapid,accurate and real-time monitoring of water pollution caused by nitrate anions.Second,interleukin-6（IL-6）is a multifunctional cytokine that plays a key role in the inflammatory response.When individuals have physiological levels of IL-6 up to 200 f M they may suffer from a disease,and its rapid and accurate detection can prevent and save patients.In this work,an array-shaped pleated graphene field effect transistor electronic biosensor was designed and fabricated.The sensor used gold nanoparticles formed by thermal annealing as a substrate and graphene grown by chemical vapor deposition was wet transferred on it to form an array-shaped deformation structure.In this structure,the nanoscale deformation can generate high potentials in the sensing channel,which increases the size of the electrical double layer and reduces the Debye shielding effect of the ionic solution,resulting in a limit of detection of 1.6×10^-15 M,significantly better than that of the planar graphene field effect transistor sensor(4.7×10^-14 M)and other mainstream sensors.This work provides an excellent technical tool for label-free,accurate and rapid monitoring of IL-6 and various biomolecules of human diseases.