The Determination Of NADH And Fabrication Of Alcohol Biosensor Based On Graphene Modiifed Electrodes

Graphene(GR) and graphene oxide(GO), with their unique physical and chemicalproperties, structure of polycyclic aromatic hydrocarbons and oxygen functional groups,make them enable to react with various organic compounds containing oxygen and aromaticstructure and are also known as wide application prospects in the fields of sensors, energystorage and composite materials. In recent years, GR has played more and more role inelectroanalytical chemistry. This article researches for the detection response to NADH andethanol by the modified electrodes that are prepared with electrochemical reaction between avariety of organic compounds such as: quinone, small oxygenated molecules and dyes andGO and GR based on their properties. With the GR of larger surface area and strongadsorption capacity, GR(GO) modified electrodes can effectively improve the stability of theelectrode reaction, sensitivity and reduce electrode reaction potential, which further expandtheir application in electroanalytical chemistry.This major purpose studies with the GO electrochemically polymerizatedp-benzoquinone(PB), rutin(quinone) and dopamine(DA, small molecules) and GRpolymerizated toluidine blue(TB, dye) to form modified electrodes for the detection ofNADH and ethanol sensor with ADH based on modified electrodes. Preparation method ofmodified electrode uses the electrodeposition, cyclic voltammetry(CV) and amperometric aremeasured to the electrode nature, NADH and ethanol. Experiments find that quinone and GOcan combine each other effectively and stably with their aromatic hydrocarbon structure andshow higher sensitive for NADH, the methyl blue and GR also display good electriccatalytic activity to NADH which is obviously responded with dopamine and GO, all of themcan be constituted to ethanol sensor based on the ADH enzyme and have a good response.The details are as fallowed:1. At the different voltages, GO on GCE surface and rutin polymerize to be Rutin/GO/GCEmodified electrode. With the amperometric investigating the electrochemical behavior ofNADH and testing23points, the electrode has good linear coefficient of0.9991anddetection limit of0.82μM for NADH. The equation of I(-1μA)=2.82CNADH(mM)+0.0338is established at NADH range of2-44μM. Under same electrode for three determinationrecords of NADH, the relative standard deviation is less than1%.2. Modified solution that is the GR mixed with TB and then paint on GCE electrode is polymerized in empty PBS(pH=7) to be the TB/GO/GCE modified electrode. It emergesgood electrochemical behavior for NADH: detection limit is3.8μM, the linear regressionequation is I(-1μA)=7.20CNADH(mM)-0.0402and correlation coefficient R(N=17) is0.9989, linear range is8-127μM. The electrode relative standard deviation with0.671%for NADH is measured three times on one electrode.3. With cyclic voltammetry, GO and DA are reacted to be DA/GO/GCE modified electrode.The electrode reveals a linear relationship for NADH of25-291μM and correlationcoefficient R (N=12) to0.993. The detection limit that is calculated by linear equation ofI(-1μA)=0.01002CNADH(mM)+0.0283is1.44μM. Three measurements for NADH withsame electrode obtain relative standard deviation of6.38%.4. The PB/GO/GCE modified electrode is electrochemical polymerization with GR and PB.The amperometric currents of the electrode show the linear relationship with the NADHconsistency of8-40μM and the linear equations is I(-μA)=0.121+9.95CNADH(mM) withR(N=18)=0.9956. The detection limit is2.57μM. When one modified electrode tests theNADH three times in a row, the relative standard deviation of data is2.21%.Based on the above electrodes and ADH sol, alcohol sensors are composed and havegood catalytic activity for ethanol. ADH/Rutin/GO/GCE modified electrode measureseffectively the concentration of ethanol and ADH enzyme’s Michaelis constant for ethanol of42mM. The other electrodes can also display the catalytic reaction with ethanol.