Graphene And Its Composites Modified Electrodes For Electrochemical Sensing Of Antibiotics

In this thesis, graphene and graphene-gold nanoparticles were synthesized. Thesegraphene-based materials were employed to modify electrodes to construct highlysensitive electrochemical sensors for the detection of antibiotics. The main contents weredescribed as follows:1. Graphene modified glassy carbon electrode (G/GCE) was prepared. Theelectrochemical response of oxytetracycline on GCE was effectively enhanced by G.0.15M HCl solution,8μL of graphene modifier,-0.2V of accumulation potential, and120sof accumulation time were selected as the optimized conditions for studying theelectrochemical of oxytetracycline on G/GCE. Under optimized conditions, the peakcurrent increased linearly with the concentration of oxytetracycline from9.0×106mol·L1to2.0×104mol·L1and the linear equation was expressed as Ip(μA)=0.257C(μmol·L1)+4.88, with a detection limit (3S/N) of5.0×106mol·L1.2. A molecularly imprinted polymer/graphene-gold nanoparticles modifiedelectrode (MIP/G-AuNPs/GCE) was prepared for electrochemical sensing oflevofloxacin. Compared with bare glassy carbon electrodes (GCE), MIP/G-AuNPs/GCEdramatically promotes the electrochemical response of levofloxacin under the sameconditions. The anodic peak of levofloxacin on MIP/G-AuNPs/GCE was remarkablyenhanced, accompanied with negative shift of anodic peak potential. For preparing theMIP modified electrode,0.05M phosphate buffer solution (PBS, pH=6.8) containing1mM pyrrole and1mM levofloxacin was chosen as the electropolymerization solution.Cyclic voltammetry (CV) was performed for electrochemical polymerization of pyrrolefor six cycles and the modified electrode was overoxidized with three cycles of CV scanin0.2M Na2HPO4solution to remove temple molecules. In0.2M H2SO4, and underoptimized conditions such as7μL of graphene-gold nanoparticles modifier and4minuteof incubation time, the oxidation peak current increased linearly with the concentration of levofloxacin in the range from1.0×106mol·L1to1.0×104mol·L1with adetection limit (3S/N) of5.3×107mol·L1. The linear equation was expressed as Ip(μA)=1.40C (μmol·L1)+5.49.