The Electrochemical Biosensor Research Based On Two-dimensional Functional Material Of Graphene And Its Compounds

The graphene has specific two-dimensional structure,leading to the covalent and non covalent bonding reaction with other nanometer materials or their derivativeseasily,because of self-assembly effect,nanometer scale effect,surface functionalization effect and surface effect.Graphene and its derivatives modified electrodes can catalytic specifically,increase specific surface area,accelerate the electron transfer and provide new ideas for substantial rapid quantitative detection,presentingwitha wide prospect in the field of biosensing.Hence,we proposing a very simple and facile method for immobilization of pyrroloquinoline quinone(PQQ)on GCE through graphene(Gr)adsorption effect,in this process chitosan(CTS)is applied to disperse Gr to form a stable robust film on GCE.The synergistic effect between Gr and PQQ in reducing the oxidation overpotential of NADH and their pH dependent electrochemical response are explored for the design of nicotinamide-adenine dinucleotide(NADH)biosensor.In addition,a simple synthetic method of dual metal oxide Fe3O4-Co3O4 anchored at reduced oxide graphene(rGO)nanocomposite has been explored for fabricating the high sensitive sensor,which is expected to apply in the rapid quantitative detection of dopamine(DA)and uric acid(UA).This dissertation fabricated several electrochemical sensors based on graphene nanometer compound,meanwhile investigated their specific role in accelerating electron transfer rate at the electrode surface,increasing the selectivity and improving sensitivity of detection:(1)We had presented a simple,facile,non-polluting and cost-efficient strategy to prepare self-assembled Gr-PQQ/CTS composites and fabricate NADH biosensor with highsensitivity.The results showed that Gr-PQQ/CTS film modified GCE exhibited fast electron transport ability and low surface resistance property.And it could inhibit the surface adsorption and passivation of intermediate and final reaction products in the NADH oxidation reaction process at GCE.Moreover,the synergic effect of Gr and PQQ made the oxidation overpotential of NADH reducedsignificantly,leading a negative potential shift of 260 mV for NADH oxidation.NADH electrochemical biosensor based on the Gr-PQQ/CTS film modified electrode illustrated with several advantages,such as rapid amperometric response,wide linear range(0.32-220 ?M),high stability,and high sensitivity(0.421 ?A·?M-1 cm-2)etc.Besides,the Gr-PQQ/CTS modified GCE revealed a robust capability of anti-interference,accompanying with acceptable recovery in serum samples.(2)A new nanocomposites of Fe3O4-Co3O4 bimetallic oxides hybrid with rGO had been designed and prepared to build a biosensor with high electrocatalytic activity.Both Fe3O4-Co3O4 and rGO endowed the superior properties of as-prepared electrochemical sensor,and a synergistic effect between Fe3O4-Co3O4 and rGO could provide a high conductivity and catalytic activity for DA and UA detection,eventually led to DA and UA peak currents increased by 271.7%and 590%respectively;supplied with a wide range from 5×10-7to 1.55×10-3 Mand a low detection limit(LOD)of 1.3 ×10-7 M(S/N=3)for DA detection;the linear range for UA detection was1.5×10-6-1.6×10-3 M and LOD was 1.8×10-7 M.The Fe3O4-Co3O4/rGO nanocomposites modified GCE displayed not only high detection sensitivity,but also prominent selectivity for DA,UA,AA and 5-HT by distinguishable oxidation peaks.Meanwhile,a robust capacity of anti-interference in practical assessment was exhibited on this modified GCE,resulting in acceptable recoveries in serum samples which for DA was 97.3%-99.0%and for UA was 99.2%-110.8%.The results showed that electrochemical biosensor based on Fe3O4-Co3O4/rGOcomposites could quickly respond to the analyte(-2s)and remain stable excellent electrochemical properties for a long time.Consequently,the as-prepared Fe3O4-Co3O4/rGO nanocomposites had a good application prospect in fabrication of relevant electrochemical sensors for real samples analysis and possessedpotential application value in the real-time dynamic detection of DA and UA.