Graphene Modified With DNA On The Surface Used In Chemical Sensors

Graphene is a kind of carbon single layer which comes from graphite.It is the ever first two-dimensional material of single atom layer which had been made.Owing to its unique structure of two-dimension,graphene has ultra-high carrier mobility and exhibits high sensitivity to the external environment.The two-dimensional structure of graphene provides a detection area for sensing detection.The sensitivity of graphene to the environment makes it possible to get significant electrical signal changes.Based on the above theory,graphene sensors of the type of field effect transistor have been made and the detection system of graphene sensors has been founded.Characterizing graphene samples in this study,this kind of graphene was of one atomic thickness and was qualified to be used for the following sensing detection.The graphene sensors had been used to detect DNA and mercury ion respectively.In the detection of DNA,graphene sensors had specific response to the DNA of specific sequence.They could detect DNA solution of the concentration from 1 pM to 100 nM.The DNA imposed n-type dopping on graphene,so the Dirac point in transfer characteristics of graphene field effect transistors shifted to the left.Minimum conductance voltage corresponding to the Dirac point decreased and the change amount is 0.1 V.Meanwhile,the sheet resistance of graphene increased by 38% and the carrier density of graphene decreased by 38% because of DNA solution.Changing the way of combining DNA and graphene could decrease the measurable concentration to 1 fM.In the detection of mercury ion,graphene sensors could detect mercury ion of the concentration from 100 pM to 100 nM and the change of minimum conductance voltage was 0.073 V.To be a supplyment to the traditional PMMA transfer method,this study involved a transfer method by using gold nanolayer as the protecting layer of graphene in the transfer process and has proved that gold transferred graphene had cleaner surface.Detecting mercury ion by gold transferred graphene sensors,the measurable concentration of mercury ion was broader which was from 10 pM to 100 nM.In the meantime,the change of minimum conductance voltage increased to 0.115 V.At last,we got a kind of graphene sensor which could detect DNA and mercury ion.Moreover,a platform of graphene sensors for detection sensing has been provided which is hopeful to detect various determinands by different decoration methods for graphene sensors.