Electrochemical Detection Based On Several Electrodes Modified With Polymer/Amino-Functionalized Quantum Dots

In this thesis,the principle,preparation and classification of electrochemical sensor as well as the polymer-modified electrode are introduced.Three types of glassy carbon electrodes modified with polymer and amino-functionalized graphene quantum dots（af-GQDs）were prepared,respectively.The simultaneous determination of Cd（II）and Pb（II）,vitamin B2(V_B2)and dopamine（DA）,uric acid（UA）and folic acid（FA）were successfully realized.The main contents are listed as follows:1.The glass carbon electrode（GCE）modified with the poly（thionine）（PTH）and af-GQDs（PTH-（af-GQDs）/GCE）was prepared via cyclic voltammetric scan and it was characterized with scanning electron microscopy（SEM）and infrared spectroscopy（IR）.The determination of Cd（II）and Pb（II）was achieved by using the differential pulse voltammetry（DPV）based on the deposition of bismuth film in situ.The good conductivity of af-GQDs and the larger surface area of the composites promoted the deposition of Cd（II）and Pb（II）on the electrode surface.Under the optimum experimental conditions,the peak current in the DPV curve was linearly related to the concentration of Cd（II）and Pb（II）.The detection range was obtained from 20 nM to 20mM.The limit of detection（LOD）for Cd（II）and Pb（II）was measured to be 4 nM and 6nM,respectively,at the signal-to-noise ratio of 3.The currents of the two kinds of heavy metal ions in water samples were analyzed via this method.2.The composite film composed of poly(glyoxalbis（2-hydroxyanil）,manganese dioxide nanoparticles and af-GQDs（PGBHA-（af-GQDs）-MnO₂）was fabricated on GCE by using a one-step method.The electrode surface was characterized by SEM,IR,X-ray photoelectron spectroscopy（XPS）and electrochemical techniques.The modified electrode played on excellent catalytic function for the electrochemical reaction of V_B2 and DA.Under the optimum conditions,the relationship between the current peak in the DPV curve and the concentration of V_B2 and DA in the range of 0.1μM-100μM was obtained.The LOD for V_B2 and DA was calculated to be 0.04μM and 0.05μM（S/N=3）,respectively.The developed sensor was applied for the determination of V_B2 and DA in tablet and injection samples.3.The GCE modified with poly melamine（PMA）,sulfosalicylic acid（SSA）and af-GQDs was prepared and it was characterized by SEM and electrochemical techniques.The good electrochemical response of uric acid（UA）and folic acid（FA）on the modified electrode was found.The simultaneous detection of UA and FA was realized based on the DPV measurement.Under the optimum conditions,the peak current in the DPV curve was proportional to the concentration of UA and FA from0.1μM to 100μM.The LOD for UA and FA arrived at 0.02μM and 0.09μM,respectively.The two analytes in human urine were measured by using the proposed sensor.