The Construction Of Electrochemical Sensor Based On Graphene Nanocomposites And Its Application For Chlorophenols

Graphene is the two-dimensional nanomaterials which consisit ofsp2-hybridized carbon. Due to its novel properties, such as large specific surface area,excellent conductivity and good biocompatibility, the electrochemical sensorsfabricated by using of the graphene modified electrode exhibit excellentperformance.Chlorophenols (CPs) are well-known to be pollutants of environment and aremainly found in effluent discharges from industries, such as those producinginsecticides, pesticides and pharmaceutical intermediates. CPs can cause serioushealth hazards due to their inherent toxicity and relative persistence in theenvironment. As a consequence, European Unites (EU) has listed chlorophenols assensitivity and selectivity priority pollutants and regulated the maximum admissibleconcentration of CPs in drinking water at0.5ng mL-1. It is significant to establishhigh sensitive electrochemical sensors for the determination of CPs. However, thedetection limits of CPs of the reported electrochemical methods are too high to meetthe requirements of regulation tolerance. It is aim to fabricated high sensitive andhigh selective electrochemical sensors for the determination of CPs.This result constructs four electrochemical sensors based on ZnSe-CTAB,GO-ZnSe, rGO-AgNPs, GO-MIP nanocomposites, respectively. Besides, weinvestigated the electrocatalytic property of the modified electrodes to thechlorophenols, which were used for the analysis of real samples. Relative to thereported methods, the established sensors significantly improve the sensitivity andselectivity for the determination of CPs. The study contents as follows:1. Determination of cholorphenols based on ZnSe-CTAB composite filmmodified glassy carbon electrodeIn this section, the PVP/ZnSe-CTAB/GCE electrochemical sensor wasfabricated based on ZnSe-CTAB nanocomposites which were obtained ZnSequantum dots and cetyltrimethyl ammonium bromide (CTAB) by hrough electrostatic self-assembly technology. Since the long hydrophobic chain of CTABpossessed a great ability of accumulation for chlorophenols, the sensitivity ofmodified electrode fabricated based on ZnSe-CTAB nanocomposites was improvedsignificantly. Besides, the ZnSe-CTAB modified electrode was covered withpolyvinylpyrrolidone film to improve its stability. The ZnSe-CTAB composites andmodified electrode were characterized by using atomic force microscope (AFM) andAC impedance (AC). Under the optimum conditions, the peak current ofchlorophenols were proportional to their concentration at the range from0.02to10.0μM for2-CP,0.006to9.0μM for2,4-DCP and0.06to8.0μM for PCP. Thedetection limits were0.008μM for2-CP,0.002μM for2,4-DCP and0.01μM forPCP respectively. The method was successfully applied for the determination of CPsin the waste water with satisfactory recoveries.2. Determination of TCP based on GO-ZnSe composite film modified glassycarbon electrodeIn this work, we fabricated the GO-ZnSe/GCE electrochemical sensor based ongraphene oxide-ZnSe QDs (GO-ZnSe) composites. CTAB was used as bridge toconnect GO and ZnSe. The composites and the interface of electrochemical sensorwere characterized by transmission electron microscopy (TEM), fluorescencespectrum and AC impedance. The results demonstrated that this electrochemicalsensor possessed excellent electrochemical catalytic activities for TCP. Under theoptimized experimental conditions, the oxidation of TCP at GO-ZnSe/GCE was alinear range from0.002to10.0μM with a detection limit of0.0009μM. The sensorwas successfully applied for the determination of TCP in the real sample of textile.This method was validated by high-performance liquid chromatography (HPLC).3. Determination of PCP based on rGO-AgNPs composite film modified glassycarbon electrodeIn this section, we investigated one green and simply method to synthesizereduced graphite oxide-silver nanocomposites (rGO-AgNPs). rGO-AgNPscomposites were successfully obtained using ascorbic acid (AA) as reducing agent,which were characterized by UV–vis spectrum, TEM, AC impedance.As-synthesized rGO-AgNPs has been used to modify the glass carbon electrode (GCE) and exhibited excellent electrocatalytic activity for oxidition of PCP. Underthe optimum conditions, the linear range for PCP is from0.008to10.0μM with thedetection limit of0.002μM. The sensor was successfully applied for thedetermination of PCP in vegetable and this method was validated by HPLC.4. Determination of2,4-DCP based on GO-MIP composite film modified glassycarbon electrodeIn this section, molecularly imprinted polymer (MIP) was synthesized andutilized as a recognition element for2,4-dichlorophenol (2,4-DCP). We build theGO-MIP/GCE electrochemical sensor based on excelent electrocatalytic GO andhigh selective MIP. This electrochemical sensor showed high sensitivity andselectivity to2,4-DCP. Scanning electron microscope (SEM) was used to observemorphology of MIP. Under optimized conditions, the sensor showed a linearresponse in the range of0.004–10.0μM with a detection limit of0.001μM. Theproposed sensor could be used for the determination of2,4-DCP in lake and thismethod was validated by HPLC.