Determination Of Organic Materials Based On Carbon Nanotube-modified Electrode

Due to their good chemical stability, extremely mechanical strength and excellent electronic properties, carbon nanotubes (CNTs) are a well-known one-dimension nanostructural materials. However, CNTs are difficult to be dissolved in water and many organic solvents, which limits their application in the fabrication of CNTs-based electrochemical sensor. When CNTs are modified by producing some active functional groups, such as -OH,-COOH and so on, the dissolubility and chemical properties of CNTs can be remarkably imrpoved.In order to get carboxylic CNTs, in this work, we purifyn and shorten CNTs by ultrasonication CNTs in mixed-acid of HNO3和H2SO4. The pretreated CNTs were characterized by transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FT-IR). TEM images and FT-IR spectra indicated that the impure carbon had been removed while carboxylic groups (ν(-COOH)= 1732cm-1) were formed on CNTs.These carboxyl-modified CNTs were dispersed in DMF by ultrasonication and then immobilized on the glass carbon electrodes (GC) surface to form a modified electrode. The electrochemical experiments such as cyclic voltammograms (CV) and electrochemical impedance spectra (EIS) were employed to characterize the modified electrode. The electrochemical behavior of L-tyrosine (L-Tyr), 2,4-Dinitrophenol (2,4-DNP), p-Nitrophenol (p-NP) and p-chlorophenol (p-CP) on the modified electrode was studied.The results indicated that the CNTs/GC electrodes exhibited a fast response towards L-Tyr with a detection limit of 4.0×10-7mol/L and a linear range of 1.0×10-6 to 1.0×10-4mol/L. When the scanning speed changes between 20~200mV/s, their oxidation peak current had the direct ratio with square root of the scanning speed, indicating that the oxidation process of L-Tyr on the modified electrodes are surface-controlled.The CNTs/GC electrodes exhibited an attractive ability to determine 2,4-DNP and p-NP simultaneously in the NaAc-HAc buffer solution (pH 5.2). The responses of 2,4-DNP and p-NP merged into a peak at a bare GC, while they yielded two well-defined oxidation peaks at the CNTs/GC electrodes. The experimental parameters were optimizes. And a direct electrochemical method for the simultaneous determine for 2,4-DNP and p-NP was proposed. The CNTs/GC electrodes showed good sensitivity, selectivity and stability.Moreover, the electrochemistry oxidation process on the CNTs modified electrodes of p-CP in pH 7.0 phosphate buffer solution can be accelerated. The peak current was linear to the concentration of p-CP in the range of 2.0×10?7 to 2.0×10?4 mol/L, the detection limit is 8.8×10?8 mol/L. Some inorganic and organic species did not interfere the determination of p-CP. The proposed method was successfully applied in the detection of p-CP in samples.