Preparation Of Graphene Guantum Dots Composites And Their Applications In Electrochemical Sensors

Graphene quantum dots（GQDs）as graphene nanoscale derivatives,are less than30 nm in size.GQDs has physical properties such as large diameter,high surface area and surfaceπ-πconjugate.These properties give it great advantages:high catalysis,excellent biocompatibility and good tolerance.It has become an attractive material and been widely used in imaging,sensors,phototransistors and photovoltaic devices.In this thesis,graphene quantum dots and their composites were synthesized based on graphene,and the material modified glassy carbon electrode was applied to electrochemical sensors.The main contents are as follows:（1）Graphene quantum dots and nafion composite film modified glassy carbon electrode（GQDs/nafion/GCE）was prepared.The morphology of GQDs was characterized by Transmission electron microscope（TEM）,Zeta potential analyzer（Zeta）,UV-vis absorption spectra and fluorescence spectra.The electrodes were characterized by cyclic voltammetry（CV）and differential pulse voltammetry（DPV）.Then the GQDs/nafion/GCE was applied to determine the Fe（Ⅲ）.Under the optimal conditions,the GQDs/nafion/GCE showed that it was better electrochemical response for the detection of Fe（Ⅲ）than that of the glassy carbon electrode（GCE）.Furthermore,GQDs/nafion/GCE exhibited good ability to suppress the background current from Fe（Ⅲ）,Cu（Ⅱ）,Pb（Ⅱ）,Cd（Ⅱ）,Zn（Ⅱ）,Ni（Ⅱ）,Cr（Ⅲ）.The oxidation peak current(I_pa)of Fe（Ⅲ）was linear with concentration of Fe（Ⅲ）in the range from 1μM to 200.0μM.The GQDs/nafion/GCE was applied to the detection of Fe（Ⅲ）content in lake of Fe（Ⅲ）with satisfactory results,and the biosensor could keep its activity for at least one month.（2）One-step method synthesis of zinc oxide（ZnO）/graphene quantum dot（GQDs）nanocomposites by hydrothermal method,and the SEM,TEM,XRD and UV-vis were utilized to characterize the obtained nanomaterials.The as-prepared nanomaterials were employed to modified electrodes,and the electrochemical behavior of dopamine at the electrode was investigated by cyclic voltammetry and differential pulse voltammetry.The experimental results show the hybrid modified electrode for detecting the dopamine with excellent redox ability compared with single materials of zinc oxide and graphene quantum dots,and in the range of 0.3～100μmol/L for dopamine concentration have a good liner relationship,the detection limit was 0.19μmol/L（S/N=3）.Moreover,the biosensor was employed to detect practical sampled with satisfactory results.（3）In this study,a convenient,novel and sensitive electrochemical sensor was designed to detect p-nitrophenol based on Graphene Quantum Dots/Multi-wall carbon nanotubes（GQDs/MWCNTs）composite modified the glassy carbon electrode（GCE）.GQDs/MWCNTs composite has been obtained by a facile,efficient and rapid reaction.Then,UV-vis,Zeta,XRD,Raman and TEM were carried out to characterize the surface morphology and surface composition analysis.Furthermore,the proposed sensor displayed excellent electrochemical property and exhibited a wide linear range of 0.1～400.0μM with a lower detection limit of 0.21μM in detecting p-nitrophenol using differential pulse voltammetry（DPV）.At the same time,the sensor was applied to detect p-nitrophenol with great results.