Application Of Electrochemical Sensors Based On Carbon Nanotube Composite Materials In Food And Drug Detection

At present,the development of new electrochemical sensors based on nano materials,especially carbon nanotubes and their composite materials is still one of the research hot spots in analytical chemistry.It is of great significance to improve the selectivity and sensitivity of the detection methods.In this paper,five novel electrochemical sensors based on carbon nanotube composite materials were fabricated by the dropwise-coating method and self-assembly method.The modified materials of the electrodes were characterized using the scanning electron microscope and energy spectrum.The sensitivity,selectivity,and stability of the modified electrodes were also investigated in detail.Then the proposed electrochemical sensors were successfully applied to sensitive detection of heavy metals,pesticide residues and drugs in food and medicine.This article concludes five parts,and the details are listed as follows:Part 1.Determination of mercury in food using a glassy carbon electrode modified with nano Ti02 and multi-walled carbon nanotube composites dispersed in a novel cationic surfactantA glassy carbon electrode modified with nano TiO2 and multi-walled carbon nanotube composites dispersed in a novel cationic surfactant was described for the determination of trace mercury(II)in food.The scanning electron microscopy was used to characterize the electrode modification materials.The electrochemical behavior of Hg(II)on the electrode was studied by cyclic voltammetry(CV).The effects of potential scanning rate,pH value,deposition potential and deposition time were investigated to probe the mechanism of electron transfer process.Under the optimal experimental conditions,the analytical performance was studied by linear sweep anodic stripping voltammetry(LSASV).The experimental results showed that the LSASV peak current was linear with the concentration of Hg(II)in the range of 0.1-100 ?mol L-1 with a detection limit of 0.025 ?mol L-1 on signal-to noise of 3.The sensitivity was found to be 3.7014 A/mol L-1.The proposed electrode also showed a high selectivity for mercury in the presence of common potential interfering metal ions.Moreover,the proposed electrode revealed good reproducibility and stability.The proposed method was successfully applied to the determination of Hg(?)in food samples.Part 2.Fabrication of electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan-copper complex by self-assembly techniqueAn electrochemical sensor for paracetamol based on multi-walled carbon nanotubes and chitosan-copper complex(MWCNTs/CTS-Cu)was fabricated by self-assembly technique.The scanning electron microscopy was used to characterize the electrode modification materials.The electrochemical behavior of paracetamol on the the electrode was studied by cyclic voltammetry(CV).The effects of potential scanning rate,pH value,deposition potential and deposition time were investigated to probe the mechanism of electron transfer process.The MWCNTs/CTS-Cu modified GCE showed an excellent electrocatalytic activity for the oxidation of paracetamol,and accelerated electron transfer between the electrode and paracetamol.Under optimal experimental conditions,the differential pulse peak current was linear with the concentration of paracetamol in the range of 0.1 to 200 ?mol L-1 with a detection limit of 0.024 ?mol L-1 on signal-to noise of 3.The sensitivity was found to be 0.603 A/mol L-1.The proposed sensor also showed a high selectivity for paracetamol in the presence of ascorbic acid and dopamine.Moreover,the proposed electrode revealed good reproducibility and stability.The proposed method was successfully applied to the determination of paracetamol in tablet and human serum samples.Part 3.Electrochemical sensor based on multi-walled carbon nanotubes and chitosan-cobalt complex for o-phenylphenol determination in fruits and vegetablesA simple,sensitive and selective method for the determination of o-phenylphenol in fruits and vegetables was developed in this work.This method was based on an electrochemical sensor fabricated with multi-walled carbon nanotubes(MWCNTs)and chitosan-cobalt complex(CTS-Co)by self-assembly technology.The scanning electron microscopy was used to characterize the electrode modification materials.The electrochemical behavior of o-phenylphenol on the the electrode was studied by cyclic voltammetry(CV).The effects of potential scanning rate and pH value were investigated to probe the mechanism of the electron transfer process.The experimental results indicated that MWCNTs/CTS-Co modified electrode remarkably enhanced the electrocatalytic activity towards the oxidation of o-phenylphenol.The electrocatalytic behavior was further exploited as a sensitive detection scheme for o-phenylphenol by differential pulse voltammetry(DPV).The results revealed that the proposed sensor exhibited linear response to o-phenylphenol in the concentration range of 0.1 to 100 ?mol L-1,with a detection limit of 0.024 ?mol L-1 on signal-to noise of 3.Moreover,the sensor also showed good selectivity,reproducibility and stability.The proposed method was successfully applied to the efficient determination of o-phenylphenol in fruit and vegetable samples.Part 4.Electrochemical sensor based on multi-walled carbon nanotubes and chitosan-nickel complex for sensitive determination of metronidazoleAn electrochemical sensor based on multi-walled carbon nanotubes and chitosan-nickel complex(MW CNTs/CTS-Ni)was fabricated by self-assembly technique for sensitive determination of metronidazole.The scanning electron microscopy was used to characterize the electrode modification materials.The electrochemical behavior of metronidazole on the electrode was studied by cyclic voltammetry(CV).The effects of potential scanning rate and pH value were investigated to probe the mechanism of the electron transfer process.The electroanalytical performance of the proposed MWCNTs/CTS-Ni modified electrode was intensively evaluated.The experimental results indicated that the MWCNTs/CTS-Ni modified electrode exhibited excellent electrocatalytic activity towards metronidazole.The proposed sensor revealed linear response to metronidazole in the range of 0.1 to 150 ?mol L-1,with a low detection limit of 0.025 ?mol L-1 on signal-to noise of 3.Moreover,the sensor also showed good selectivity,reproducibility and stability.The proposed method was successfully applied for the sensitive determination of metronidazole in pharmaceutical and biological samples.Part 5.A nonenzymatic hydrogen peroxide sensor based on carboxymethyl chitosan-copper complexes/carbon nanotubes filmA nonenzymatic sensor for hydrogen peroxide was fabricated by coating the surface of a glassy carbon electrode with carboxymethyl chitosan-copper(CMC-Cu)complexes/carbon nanotubes(MWCNTs)film.The prepared CMC-Cu/MWCNTs modified electrode was characterized by cyclic voltammetry(CV),and the concentration of H2O2 was quantitatively analysed by differential pulse voltammetry(DPV).The scanning electron microscopy and energy-dispersive spectroscopy were used to characterize the electrode modification materials.The effects of potential scan rate and pH value on the response current were studied to probe the mechanism of the electron transfer process.Owning to the unique electrical conductivity and attractive electrocatalytic properties of the CMC-Cu and MWCNTs,the sensor exhibited excellent electrocatalytic activity towards the reduction of H2O2.The peak currents were linear with the concentration of H2O2 in the range of 0.01 to 16 mmol L-1.The proposed sensor showed high sensitivity of 6.496 ?A mmol-1 L,and low detection limit of 2.5 ?mol L-1 on signal-to noise of 3.The proposed sensor also displayed outstanding stability and remarkable tolerance to co-existing interferents.The sensor was applied to the determination of H2O2 in medical disinfector samples,and the RSD and recovery results were satisfactory.