Preparation Of Electrospun Zno-Carbon Nanofiber Composite Modified Electrodes And Its Sensing Application

ZnO is a good semiconductor material, It has a wide range of applications like battery、gas sensors、photoelectric catalytic and electrochemical sensors because of its excellent optical, catalyticel, electrochemical characteristics. Carbon nanofiber (CNF) has high surface area, good electrical conductivity, low cost, high stability and mechanical strength. These unique chemical and physical properties make CNF acting as a good supporting matrix for ZnO deposition. In this thesis, ZnO-CNF composites were prepared by electrospun followed by high-temperature thermal treatment. With Nafion as an additive, the ZnO-CNF composite modified glassy carbon electrode (ZnO-CNF/GC) was successfully constructed. The ZnO-CNF/GC was applied for the sensitive determination of trace Pb ions based on the interaction of Pb ions with the hydroxyl group formed on the ZnO particle surface. The major results and conclusions are as follows:1. ZnO-CNF composite fiber was prepared by electrospinning ZnO-PAN precursor followed by pre-oxidation and carbonization. The fiber was characterized by SEM, the contact angle measurements and electrochemical methods. With Nafion as an additive, the ZnO-CNF modified electrode was successfully constructed and applied for the determination of Pb(II) ions. A sensitive response of the ZnO-CNF modified electrode on Pb(II) ions in solution was obtained by SWV technique. Under the optimal conditions, a good linear relationship between peak current and Pb(II) ions concentration was achieved in the range of4.8×10-10～4.8×10-7mol/L (R=0.9971) by10min preconcentration at-1.0V in0.1mol/L NaAc buffer solution (pH=4.6). The detection limit was2.4×10-10mol/L (S/N>3).2. ZnCl2-PAN composite was preparated by electrospinning technique with ZnCl2-polyacrylonitrile (PAN) DMF solution as the electrospinning precursor. The morphology of the composite fibers was characterized by scanning electron microscopy (SEM). The effect of electrospinning parameters on fiber’s morphology and structure was investigated. It demonstrates that the stable and uniform ZnCl2-PAN composite fibers could be obtained under the optimal conditions of the ZnCl2/PAN ratio of3:9.The optimal electrospinning parameters were identified with the voltage of15kV, tip-to-collector distance of15cm, spinning speed of0.5mL/h and the environmental humidity of45%. And ZnO-CNF composite was obtained by following pre-oxidation and carbonization. The as-prepared composite films were characterized by scanning SEM, contact angle measurement, flourier-transform infrared (FIIR), X-ray photoelectron spectroscopy(XPS).3. With Nation as an additive, the ZnO-CNF/GC electrode was successfully constructed by dip coating. The modified electrode was applied to determine Pb(Ⅱ) ions by square wave stripping voltammetry (SWV). the major experimental conditions such as ZnO content in ZnO-CNF, concentrations of ZnO-CNF and Nafion in ethanol solution, carbonization temperature, in addition to the supporting electrolyte, accumulation potential and accumulation time in the testing solution were studied. The results demonstrate that the ZnO-CNF/GC electrode has sensitive electrochemical response to trace Pb(II). Under the optimized experimental conditions, a good linear relationship between peak current and the concentration Pb(II) ions was obtained in the range of2.4×10-10～2.4×10-7mol/L (R=0.998) by10min preconcentration at-1.0V in0.1mol/L NaAc buffer solution (pH=4.6). The detection limit was down to4.8×10-11mol/L (S/N＞3). The practical analytical application of the ZnO-CNF modified electrode was assessed by the measurement of the actual water sample. The result was consistent with that obtained by ICP-MS.