Construction Andapplications Of Electrochemical Sensors Based On Nanomaterials

Because of its high sensitivity, good stability, easy operation, low cost and monitoringon-line in a complex environment, Electrochemical sensors have been widely applied in thefield of environmental protection, clinical, industrial and agricultural production. Due togood load capacity, biocompatibility and catalytic properties, application of carbon-basedmaterials and gold-platinum composite nanomaterials in the field of electrochemical sensorhave provided the foundation for the further development of electrochemical sensors.This paper is manily composed of three parts including literature review, experimentalstudies and conclusions. The main work of the experimental studies is to obtain series ofelectrochemical sensors with good performance of high sensitivity, good selectivity andstability by the combination of nanotechnology and electrochemical sensing technology. Toachieve this purpose, the suitable nanomaterials with good properties were selected bystudy of electrochemical catalytic activity of new nanomaterials including carbon-basedmaterials and composite nanomaterials. The main contents are as follows：1. Combination with good biocompatibility of gold (Au) and strong catalytic activityof platinum (Pt), the sensor interface based on Au-Pt composite nanoparticles wasconstructed and the electrocatalytic capability of Au-Pt composite nanoparticles to theoxidation of H2O2was optimized. Further combined with the advantage of good selectivityof polymer film, two kinds of glucose sensors of PPR-GOD-Au1Pt3NPs/GCE andNafion/GOD/CS/Au1Pt3NPs/GCE were constructed by relatively simple electrochemicalembedding technique and physical embedding technique respectivity. The performance oftwo glucose sensors to glucose detection were investigated and compared, the resultsshowed that two kinds of glucose sensors possessed quick response to glucose, highsensitivity, the low detection limit and the wide linear range. However,PPR-GOD-Au1Pt3NPs/GCE sensor prepared by electrochemical embedding technique haswider linear range, better anti-interference ability and more good reproducibility thanNafion/GOD/CS/Au1Pt3NPs/GCE sensor prepared by physical embedding technique.2. Direct electrochemistry of glucose oxidase (GOD) on three-dimensionalinterpenetrating porous graphene electrodes has been reported, which have been fabricatedby one-step electrochemical reduction of graphene oxide from its aqueous suspension. The electrochemically reduced GO (ERGO) modified electrodes exhibited excellent electrontransfer properties for GOD and enhanced the enzyme activity and stability by theassistance of chitosan. The immobilized GOD shows a fast electron transfer with the rateconstant (ks) of6.05s-1. It’s worth mentioning that in the air-saturated phosphate buffersolution without any mediator, the resultant modified electrodes exhibited low detectionlimit of1.7μM with wide linear range of0.02–3.2mM and high sensitivity and highselectivity for glucose detection.3. The electrochemical sensing interface based on Pt-electrochemical reduction ofgraphene oxide composite nanoparticles(Pt-ERGO) were prepared by one-stepelectrodeposition technique. Due to the positive synergistic effect of the two materials of Ptand ERGO, Pt-ERGO shows good electrical catalytic ability to H2O2and the promotedelectron transfer. When H2O2was detected by amperometry technique at applying potential-0.3V, it showd two linear range,0.5μM－600μM and0.6mM－57mM, sensitivity,8.70μAmM-1cm-2and0.549μA mM-1cm-2, respectivity. The detection limit is0.16μM (S/N=3).Because of large load capacity of Pt-ERGO, more GOD was successfully immobilized onthe surface of Pt-ERGO/GCE and maintained its activity to achieve the direct electrontransfer between the active center of GOD and electrode. Moreover, the heterogeneouselectron transfer rate constant (ks) is4.61s-1.4. Highly nitrogen-doped carbon capsules (hN-CCs) have been successfully preparedby using inexpensive melamine and glyoxal as precursors via solvothermal reaction andcarbonization. The hN-CCs with large surface area and high-level nitrogen content (N/Catomic ration of ca.13%) has high electrocatalytic activity and selective activity towardH2O2reduction reaction and dopamine oxidation reaction. The hN-CCs modified glassycarbon electrode (hN-CCs/GCE) not only had realized simultaneous detection of dopamine,ascorbic acid, uric acid in pH2.0phosphate buffer solution, but also had achieved selectivedetection of dopamine with the coexistence of ascorbic acid, uric acid in pH7.0phosphatebuffer solution by differential pulse voltammetry (DPV). The sensitivity and the detectionlimit of electrochemical sensors for dopamine detection in pH2.0PBS are40.46μA μM-1cm-2and18nM, erespectively, which is more sensitive than that for the detection of AAandUA. While the sensitivity and the detection limit of hN-CCs/GCE for dopamine detectionin pH7.0PBS is24.06μAμM-1cm-2,1.28μM and5.46μAμM-1cm-2,6.26μM, respectively. The linear range of the electrochemical sensor for the detection of dopamine in pH7.0PBSby the flow injection analysis technique (FIA) is wider than that by DPV. Due to the largesurface area and the high load capacity of hN-CCs, glucose oxidase sensing interface basedon hN-CCs was constructed and achieved the direct electron transfer of glucose oxidase.