Electrochemical Sensing Of Phenolic Contaminants On Metal Oxide/Expanded Graphite Composite Films

Sensitive,selective and reproducible monitoring of multiple phenols simultaneously needs an electrochemical interface with a large surface area and a big amount of active sites.Herein,electrochemical methods were used to analyze phenolic contaminants.Metal oxide nanomaterials were prepared by different methods,and expanded graphite（EG）as the supporter was decorated with metal oxide nanoparticles.Phenolic contaminants were successfully detected by metal oxide/expanded graphite composite film modified electrode.The research work content mainly includes:（1）Rod,polyhedral,and cubic Ce O₂ were prepared by hydrothermal method,and above three different morphologies of nano-Ce O₂ were supported by EG with good conductivity and large surface area.The composite suspension was prepared by ultrasonic dispersion method and dropped onto the surface of bare glassy carbon electrode（GCE）to form different morphology Ce O₂/EG composite films modified electrodes.The electrochemical behavior of tetrabromobisphenol A（TBBPA）on Ce O₂/EG composite films with different morphologies of nano-Ce O₂ was studied.The results showed that the morphology of nano-Ce O₂ in composite films had an effect on the oxidation signal of TBBPA.Cubic Ce O₂/EG composite films showed better signal enhancement effects on the catalysis of TBBPA.The effects of p H,mass ratio of Ce O₂ to EG and accumlation time on the oxidation signal of TBBPA were discussed.A new method for detecting TBBPA was constructed with a linear range of 10-600 nmol/L,and the detection limit of 3.4 nmol/L（S/N=3）.（2）Carbon-coated palladium oxide（Pd O@C）nanoparticles were prepared by azeotropic distillation method,and Pd O@C/EG composite suspension was obtained by ultrasonic dispersion in a chitosan solution.The Pd O@C/EG/GCE composite suspension was modified to the surface of the bare glassy carbon electrode by drop coating.The electrochemical properties of the composite films and the electrochemical behavior of TBBPA on the composite films were studied by electrochemical technique.It was found that composite films had excellent electrical conductivity,small electron transfer resistance,and large active area,showing significant catalysis for the oxidation catalysis of TBBPA.This phenomenon was attributed to the synergistic effect of EG and Pd O@C nanoparticles.After further optimization of experimental conditions,high-sensitivity sensing of TBBPA was achieved.The concentration ranged from 5 to 1000 nmol/L,with a detection limit of 1.3 nmol/L（S/N=3）.（3）The electrochemical behaviors of hydroquinone（HQ）and catechol（CC）,and the sensitization mechanism of low concentration HQ and CC on Pd O@C/EG composite films modified electrode were studied.The results showed that the response signal of TBBPA on the surface of the composite membrane modified electrode appeared as two completely separated oxidation peaks with a peak potential difference of 121 m V when HQ and CC were simultaneously detected,compared with the EG modified electrode.Their peak currents were greatly enhanced,and the shape of the two oxidation peaks was better.This is due to the improved enrichment efficiency of HQ and CC on the surface of the composite membrane.Finally,simultaneous detection of HQ and CC was achieved.The detection rangers were 100 to 10000 nmol/L and 50-400 nmol/L for HQ and CC.The detection limits were 26 nmol/L and 17 nmol/L（S/N=3）,respectively.