The Preparation Of Modified Electrodes Based On Carbon Nanotubes And Its Application In The Determination Of Chlorophenols

Due to the unique structure of small diameter,large surface area as well as excellent electric conductivity,carbon nanotubes can enhance sensitization and catalysis of certain chemicals,which have been further widely applied in the field of chemical modified electrodes.In order to improve the electrocatalytic activity of modified electrodes,carbon nanotubes are frequently employed as a carrier to combine with other catalytic materials.Currently,it has been a hot spot to develop more sensitive carbon nanotubes modified electrodes via physical,chemical and electrochemical methods.The chlorophenols is a sort of persistent organic chemicals with high toxicity in the aquatic environment.Therefore,it is essential to develop a quick and sensitive analytical method to determine the concentration of chlorophenols.Thus,the current study is aimed to prepare for the carbon nanotubes modified electrodes via combination of carbon nanotubes and dye molecule as well as metal nanoparticles by electropolymerization and potentiostatic reduction for the detection of chlorophenols.The main results are listed as follows:(1)The poly(rhodamine B)/multiwalled carbon nanotubes composite modified glass carbon electrode(PRhB/MWCNTs/GCE)was prepared by dispensing and electropolymerization via the ?-? noncovalent interactions between the heterocyclic conjugate structure of rhodamine B and MWCNTs.The PPRhB/MWCNTs composite was characterized by scanning electron microscopy(SEM)and electrochemical impedance spectroscopy(EIS).It was demonstrated that the modification of PRhB/MWCNTs on the surface of GCE had been successfully completed.The PRhB/MWCNTs/GCE displayed an extraordinarily electrocatalytic activity in the oxidation of 2-chlorophenol(2-CP)enhancing the sensitivity of its determination.Under optimum condition(accumulation potential: 0.2 V,accumulation time: 150 s,the pH of PBS: 3.0,the scan range of LSV(Linear sweep voltammetry): from 0.5 V to 0.9 V,the scan rate: 50 mV/s),a linear range was obtained from 0.05 to 125 ?mol/L with the detection limit of 0.028 ?mol/L.Thus,the modified electrode exhibited broader detection range,lower detection limit and higher sensitivity.The recovery experiment suggested that it can be applied to determine 2-CP in the aquatic environment.(2)Combined Eosin Y(EY)with MWCNTs,the poly(eosin Y)/MWCNTs composite modified electrode(PEY/MWCNTs/GCE)was prepared via the methods of dispensing and electropolymerization.The results implied that it had advantages of high sensitivity and low detection limit for the determination of 2,4-dichlorophenol(2,4-DCP).The electrochemical behavior of 2,4-DCP on the PEY/MWCNTs/GCE was investigated by cyclic voltammetry.The results indicated that the oxidation of 2,4-DCP at the modified electrode was irreversible,diffusional-controlled and two electrons were involved.Under optimum condition(accumulation potential:-0.3 V,accumulation time: 250 s,the pH of PBS: 3.0,the scan range of DPV: from 0.3 V to 0.9 V,potential increment: 0.01 V,pulse amplitude: 0.05 V,pulse period: 0.2 s,pulse width: 0.05 s),a linear relationship was obtained in a range between 0.005 and 0.1 ?mol/L as well as 0.2 and 40 ?mol/L and the detection limit achieved 0.0035 ?mol/L.The high selectivity and stability of modified electrode suggested that it could be applied in the practical analysis of 2,4-DCP in aquatic environment.(3)Platinum nanoparticles were dispersed uniformly in the structure of MWCNTs by potentiostatic reduction.RhB was combined with MWCNTs by electropolymerization to prepare for the poly(rhodamine B)/platinum nanoparticles/ MWCNTs composite modified glass carbon electrode(PRhB/PtNPs/MWCNTs/GCE).Its composite was characterized by SEM.The results demonstrated that PtNPs was uniformly dispersed in the MWCNTs,and RhB was covered on the MWCNTs.The PRhB/PtNPs/MWCNTs displayed an extraordinary electrocatalytic activity in the oxidation of 2,4,6-trichlorophenol(2,4,6-TCP)and 4-chlorophenol(4-CP).The oxidation peaks of 2,4,6-TCP and 4-CP were well separated and showed a potential difference(E)of 0.091 V,which provided an adequately large window for simultaneously determining the concentrations of 2,4,6-TCP and 4-CP.Under optimum condition(accumulation potential: 0 V,accumulation time: 100 s,the pH of PBS: 6.0,the scan range of DPV: from 0.3 V to 0.9 V,potential increment: 0.01 V,pulse amplitude: 0.05 V,pulse period: 0.2 s,pulse width: 0.05 s),2,4,6-TCP and 4-CP were simultaneously detected by DPV at the PRhB/PtNPs/MWCNTs.The oxidation peak current displayed a significant linear relationship to concentration in a range from 5 to 175 ?mol/L for 2,4,6-TCP and 10 to 300 ?mol/L for 4-CP,with detection limit of 1.55 and 3.69 ?mol/L,respectively.Moreover,the results of recovery experiment implied that PRhB/PtNPs/MWCNTs/GCE can provide a new and practical approach to determine 2,4,6-TCP and 4-CP simultaneously.