Fabrication Of Two Dimensional Nano-materials Based Field-Effect Transistor Biosensors And Their Applications

Although the detection equipments in clinical laboratory have the advantages like integration,automation,and intelligent level,they still face the challenge including complicated operation,expensive reagents and timeconsuming analysis,low sensitivity and un-applicability for point of care test.Therefore,there is a significant need for the development of a simple,inexpensive,rapid and accurate tool for point of care test.The biosensors have numerous of advantages,such as simple operation,cheap cost,fast detection,high sensitivity and so on,so it has been widely used in disease diagnosis and life science.The nanomaterials based field effect transistor?FET?biosensor hold particular advantages for detecting biological molecules,like high sensitivity and specificity,rapid analysis,label-free detection,easy operation.Moreover,the FET bisoensor can also be compatible with integrated circuit,capable of achieving high-throughput detection.These superior advantages are ascribed to unique physical and chemical properties of nanomaterials.For instance,graphene has the merits including high electron mobility,high surface-to-volume ratio,low intrinsic noise,good biocompatibility and stability.Besides these amazing unique properties of graphene,Molybdenum disulfide?MoS₂?'s band gap characteristics can improve the detection performance of the sensor.Interestingly,MoS₂ also holds the good catalytic properties.In this work,the nanomaterials of graphene and MoS₂,respectively,were applied to construct nanomaterials based FET biosensors.The single layer chemical vapor deposition?CVD?graphene FET was constructed by directional transfer method.The method is simple,rapid and inexpensive,and it can realize the highly sensitive and highly specific detection of DNA.The MoS₂ was prepared by liquid phase exfoliation of ultrasonication,and drop casting method was employed to layer by layer assemble reduced graphene oxide?RGO?and MoS₂ to construct RGO-MoS₂ FET biosensor.The hydrogen peroxide?H2O2?released from cells was detected by using RGO-MoS₂ FET biosensor.More details are described in the following:? Fabrication of Field Effect Transistor DNA Biosensors by A Directional Transfer Technique Based on CVD-Grown GrapheneThe FET sensor chip was fabricated by standard conventional miro fabrication technique.Graphene was prepared by CVD method.The graphene was cut into small fragments,and then directly transferred to the prefabricated FET sensor array in solution.The method realized is simple,fast and cheap for preparing high quality of graphene FET.The electrically neutral PNA was immobilized on the surface of graphene via a link molecule PASE.By detecting the change of Dirac point before and after PNA-DNA hybridization,DNA detection was realized.The limit of detection of the biosensor was found to be 10 fM,which is 1 magnitude lower than that reported.The high sensitivity is mainly attributed to usage of monolayer graphene as the channel material,as well as PNA as the probe.In addition,the CVD-grown FET biosensor could discriminate complementary DNA from noncomplementary DNA and one-base-mismatched DNA with high specificity.Moreover,the biosensor could also be used repeatedly.To sum up,the CVD FET DNA biosensor prepared by the directional transfer is not only simple,fast,cheap,but also sensitive and specific.The developed method can provide help for the development of ultrasensitive and highly specific nanobiosensors.? The MoS₂-RGO based field effect transistor biosensor for detection of hydrogen peroxide released from living cellsThe RGO was prepared by chemical reduction of graphene oxide,and liquid phase exfoliation of ultrasonication method was used for preparing MoS₂ nanoflakes.First of all,the well-prepared RGO was drop-casted onto the sensor array of the prefabricated devices to form the RGO based FET,after which MoS₂ was assembled onto the RGO surface by using the same drop-casting method.By such,a MoS₂-RGO based FET sensor was built.H2O2 released from the cells was able to be detected by utilizing the catalytic properties of MoS₂ nanoflakes.The real-time response to H2O2 of the FET biosensors based on MoS₂-RGO was particularly rapid?< 1s?.With the increase of the H2O2 concentration,the response signal also increased.The limit of detection was found to be approximately 100 fmol/L,which is lower than that obtained by other detection methods.In addition,the sensor showed high specificity.It is believed that the developed detection platform can provide a support for the clinical detection of hydrogen peroxide-related diseases.