No Enzyme Electrochemical Sensor And Its Application Built On DVD Discs

In the early1980s, it has been discovered that the physical properties of somematerials would greatly change when their size was in a mesoscopic state, especiallyin a nanometer level. The study on nanometerials has then attracted a lot of attention.Within different kinds of nanometerials, metallic nanomaterial is one of the mostattractive materials and has been applied in different application areas. While, theapplication of metallic nanomaterials in constructing non-enzymatic electrochemicalbiosensors has been becoming one of the most promising research areas. The keymotivation derives from the important properties of metallic nanomaterials, includingits much larger specific surface areas, higher surface reactivity and catalytic efficiency,and stronger adsorption capacity than that of bulk materials.Typically, metallic nanomaterial was used as the reinforcing material to constructelectrochemical sensors. It not only provided the unique electrochemical catalysis tobiomolecules, but also improved the performance of the sensors, including reducingthe overpotential, enhancing the selectivity, and improving the sensitivity ofelectrodes, etc. It is not surprising that constructing non-enzymatic sensors base onmetallic nanomaterials have been becoming a hot research topic.By considering the above advantages of metallic nanomaterials, the motivationof this thesis was to make use of the silver reflecting layer and the gold anti-oxidatinglayer that built on the Digital Video Disk （DVD） and develop the high performancenon-enzymatic sensors. The DVD-based electrodes have been prepared with differentchemical and electrochemical methods, and the research has been mainly focusing onthe detection of hydrogen peroxide, paracetamol and cupric ions using theDVD-based non-enzymatic sensors.1Construction of Au-Ag alloy DVD electrode for hydrogen peroxide detectionThe pristine Au-Ag alloy DVD electrode was electrochemically treated in thesolution of NaOH using the technique of cyclic voltammetry. And the various Au-Ag surfaces with different microstructures have been achieved. The microstructure hasbeen approved to enhance the electrocatalytic performance of the hydrogen peroxidereduction, especially decrease the reduction overpotential. The experimental resultsillustrated that the sensor possessed many advantages including simple preparation,high sensitivity and selectivity, low detection limit and wide detection linear range.The sensor has been employed to determine the hydrogen peroxide in practicalsamples.2Construction of reticular gold nanostructure on DVD electrode and itsenhanced electrocatalytic activity toward the oxidation of paracetamolReticular gold nanostructure has been fabricated homogeneously on DVDsubstrate by directly treating the Au-Ag DVD electrode in the concentrated nitric acidand getting rid of the silver layer. The results showed that the reticular goldnanostructure exhibits the good continuity and conductivity. The electrocatalytic studyof the as fabricated Au electrode toward the oxidation of paracetamol has beenperformed and the results indicated the excellent electrocatalytic reactivity of Auelectrode toward the oxidation of paracetamol. The good linear range has beenobtained from6.0×10^-61.29×10^-3M. It should be pointed out that the sensor basedon the as-fabricated Au electrode possessed the good reproducibility and stability,high selectivity for the determination of paracetamol. The sensor has been used todetect the paracetamol in febrifuge tablets.3Fabrication of porous gold nanostructure on DVD substrate and itselectrochemical property toward the reduction of H₂O₂Porous Au nanostructure has been fabricated on a DVD substrate after treatingthe DVD in concentrated nitric acid and following by an electrochemical treatment inthe solution of HAuCl₄. The electrochemical study showed that the porous Aunanostructure made contribution to the higher performance of electrocatalytic reduction of H₂O₂. The further study also showed that the electrochemical sensorbased on porous Au nanostructure shows good reproducibility, high sensitivity andhigh stability as well as anti-interference capability. The sensor has been used todetermine H₂O₂in practical application.4Determination of copper ions with a L-cysteine modified gold DVDelectrodeL-cysteine has been widely used in preparation of modified electrodes andbiosensors because it contains the functional groups such as amino and carboxyl. Byusing the self-assembly method, L-cysteine monolayer has been modified on goldDVD electrode owing to the formation of Au-S bond between Au and L-cysteine. Theelectrochemical behavior of the copper ions on the as-modified electrode has beeninvestigated. The study showed that the copper ions tend to accumulate on theelectrode surface through coordination with L-cysteine and the copper ions were thendetected by the electrochemical reduction. The detection limit of2×10^-8M has beenachieved.