Fabrication Of Several Novel Nanomateirals For The Study Of Biosensors And Biofuel Cells

Electrochemical biosensors combine the high sensitivity, as indicated by low detection limits, of electrochemical transducers with the high specificity of biological recognition processes. Because of their simplicity of construction, short response time, good reproducibility precision of the response and operational reuse, they are extensively applied for agricultural, clinical, food, environmental, and national defense applications. The process that glucose as fuel and O2as oxidizer are converted into harmless gluconolactone and H2O is ’green’ and friendly environment, in the fabrication of enzymatic biofuel cell (EBFC). However, EBFC has still not become the new generation power device so far. Main problem lies in the electron transfer barrier between enzymes and electrodes, which is the rate-limiting step to hinder the improvement of EBFC power output. The nanoparticles with the high electrochemical stability and good conductivity can be selected as ideal conducting channels to promote efficient direct electron transfer between enzyme and electrodes. This dissertation focuses on the studies on the functional nanomaterials with the combination of nanotechnology, analytical chemistry, biotechnology, and material science:1. Fabrication of a dispersible graphene/gold nanoclusters hybrid and its potential application in electrogenerated chemiluminescence The dispersible graphene/AuNCs hybrid was synthesized in situ based on the bilayer graphene template, and the hybrid was more accessible to near-infrared emission than other aqueous AuNCs. The ECL intensity of the hybrid was larger than that of the BSA-stabilized AuNCs. The model of the H2O2ECL biosensor based on the hybrid showed acceptable detection to target molecules. The graphene/AuNCs hybrid could become a potential material for constructing H2O2biosensors in practical clinical analysis.2. Fabrication of gold nanoparticles on bilayer graphene for glucose electrochemical biosensingThe hydrophilic and carboxyl group functionalized graphene-gold nanoparticles (AuNPs) hybrid has been synthesized in situ. AuNPs can be scattered well on the graphene bilayer, and the loading amount of AuNPs can be controlled. Glucose oxidase (GOD) was successfully bound to the surface of the hybrid through a condensation reaction between terminal amino groups on the lysine residues of GOD and carboxyl groups on the AuNPs. The hybrid provided a suitable microenvironment for GOD to retain its biological activity. The direct and reversible electron transfer process between GOD and the hybrid electrode was realized without any supporting film or electron mediator. A novel model of the glucose biosensor based on the hybrid electrode was fabricated. Blood sugar concentrations measured in human serum samples by the glucose biosensor were in good agreement with the values provided by the Nanjing University hospital, and the average relative standard deviation was3.2%for six successive measurements. Three constructed biosensors showed good stability, and all of them retained80%of their initial signals after they were stored at4℃for four months. It is promising that the model of the glucose biosensor can be used as an effective candidate for the detection of blood sugar concentration in clinical diagnoses.3. Root-whiskery PEDOT nanoparticles as bridges for the connection of the active center of hemoglobinThe root-whiskery PEDOT nanoparticles were fabricated, and the single molecular thickness PEDOT nanowire was observed. It was successfully used as the electron transfer channels between the active center of Hb and the underlying electrode. The PEDOT nanowhiskers can keep Hb structure stable. The root-whiskery PEDOT nanoparticles can provide new opportunities for the design of electrochemical device.4. Design of the enzymatic biofuel cell with large power outputRenewable power source plays an important role to counter the ascending global energy crisis. The process that glucose as fuel and O2as oxidizer are converted into harmless gluconolactone and H2O is’green’ and friendly environment, in the fabrication of enzymatic biofuel cell (EBFC). However, EBFC has still not become the new generation power device so far. Main problem lies in the electron transfer barrier between enzymes and electrodes, which is the rate-limiting step to hinder the improvement of EBFC power output. In this study, the hydrophilic and carboxyl group functionalized graphene-gold nanoparticle hybrid can break the barrier of electron transfer in the EBFC. The open circuit voltage (Ecellocv,) can reach to the optimal value of1.20V, and the maximal power density (Pmax) is as high as1.96±0.13mW cm-2. Based on the two as-prepared EBFC units in series, the red and yellow light-emitting diodes (LEDs) were successfully lighted, respectively. Because the Ecellocv of the EBFC can keep stable for over70days, the fabricated EBFC is expected to be applied in the bioenergy fields.5. Enzymatic biofuel cell controlled by temperature signal for switchable "ON-OFF" state based on poly (N-isopropylacrylamide)The enzymatic biofuel cell controlled by temperature signal for switchable "ON-OFF" state was designed based on poly (N-isopropylacrylamide)(PNIPAm). The electrochemical-induced polymerization was performed at the Au electrode, and the radical NIPAm monomer was converted to PNIPAm. During the polymerization, the AuNPs-GOD and AuNPs-laccase were entrapped into the PNIPAm matrix, acting as the bioanode and biocathode, respectively. The "ON-OFF" state was observed when the temperature was switched from20℃to45℃. It demonstrated that when in the "ON" state, the Ecellocv and Pmax of the EBFC could reach to0.70V and20.52μW/cm2, respectively, while in the "OFF" state, the Ecellocv and Pmax of the EBFC were only0.28V and3.28μW/cm2, respectively. The switchable process was reproducible, and the response time was only several seconds.