Fabricated Based On Three Types Of Sensing Interface And Its Application In Electrocatalysis Research Of Biomolecules

Chemically modified electrode, is the research focus on electrochemistry andelectroanalytical chemistry, which has been widely applied in analytical science,1ifescience, environmental science, material science and neurophysiology. The existingresearch indicates that constructing high sensitive and selective sensing interface is akey for the preparation of novel chemically modified eleetrode and eleetrochemiealbiosensor. In this thesis, novel chemically modified electrodes were fabricated based onthree types of sensing interface and applied into the electrochemical study onbiomolecules. These researches may provide new thought for the construction of highsensitive and selective electrochemical biosensing interface and has a certain scientificsignificance for extending its application of bioanalysis. The main points of our thesisare presented as follows:1. LaPO₄nanowires were synthesized by a simple hydrothermal method andcharacterized using transmission electron microscope （TEM）, energy dispersive X-rayspectroscopy （EDS）, and scanning electron microscopy （SEM）. A novel electrochemicalsensor has been fabricated by use of a carbon paste electrode （CPE） coated with theprepared LaPO₄nanowires. Electrochemical characterization of the sensor wasinvestigated by electrochemical impedance spectroscopy （EIS）, cyclic voltammetry （CV）and differential pulse voltammetry （DPV）. The nanowires-LaPO₄showed excellentelectrocatalytic activity towards the oxidation of dopamine （DA） and uric acid （UA）.Moreover, the sensor exhibits good selectivity toward selective determination of DAand UA. By using DPV method, low detection limits of0.13μM and0.9μM for DA and UA were obtained, with the linear calibration curves over the concentration range0.4～11.4μM and2.7～24.8μM, respectively. In addition, the sensor was successfullyapplied for the determination of analytes in injection samples using the standard addingmethod with satisfactory results.2. A sensitive and selective electrochemical sensor based on poly （beryllonⅡ）/nanowires-LaPO₄composite film modified carbon paste electrodes （CPE） wassuccessfully constructed and used to study the catalytic oxidation of dopamine （DA）and uric acid （UA）. Scanning electron microscope （SEM） and electrochemicaltechniques were used to characterize the properties of the modified electrode. Thesensor exhibits strong electrochemical catalytic activity towards the oxidation of DAand UA thanks to synergic effect of poly （beryllon Ⅱ）/nanowires-LaPO₄in0.1Mphosphate buffer solution （pH7.0）. By using of differential pulse voltammetry （DPV）,linear calibration curves are obtained as0.10～31.60μM and39.38～403.28μM forDA and0.82to682.94μM for UA. The detection limits are0.03μM and0.23μM forDA and UA, respectively. Moreover, this electrochemical sensor was applied to theselective detection of DA and UA with high sensitivity and selectivity. Furthermore, themodified electrode displayed high reproducibility and stability for these speciesdetermination. Thus, the proposed sensor could be advantageously employed for thedetermination of DA in real pharmaceutical formulations.3. A novel hydrogen peroxide （H₂O₂） biosensor was successfully constructed,based on the immobilization of hemoglobin （Hb） on polypyrrole （PPy）-Fe₃O₄anddodecyltrimethylammonium bromide （DTAB） composite film modified carbon pasteelectrodes （CPE）. The PPy-Fe₃O₄composites were synthesized in the suspensionsolution of Fe₃O₄nanoparticles via in situ chemical oxidative polymerization under thedirection of cationic surfactant cetyl trimethyl ammonium bromide. Spectroscopic andelectrochemical examinations illustrated that the PPy-Fe₃O₄/DTAB composites werebiocompatible matrix for immobilizing Hb, which revealed high chemical stability andexcellent biocompatibility. The thermodynamic, dynamic and catalytic performances ofthe biosensor were discussed by cyclic voltammetry （CV）. The results indicated that thePPy-Fe₃O₄/Hb/DTAB/CPE exhibited excellent electrocatalytic activity to the reductionof H₂O₂with a high sensitivity （104μA mM1）. The catalytic reduction currents of H₂O₂were linearly related to H₂O₂concentration in the range from2.5μM to60μMwith the detection limit of0.8μM （S/N=3）. These results indicated thatPPy-Fe₃O₄/DTAB composites are proved to be a promising matrix for bioactivemolecules immobilization, suggesting it has the potential use in the fields of H₂O₂.