Preparation Of Electrospun ZnO-based Composite Nanofiber Modified Electrodes And Sensing Application

ZnO as one of the representative semiconductor materials has been applied to a wide range offields, such as battery, photoelectric catalysis, sensing areas and so on, due to its excellent optical,catalytic, electrochemical characteristics. Electrospinning technique with the characteristics ofsimple process, environmentally friendly and efficiency provides a unique way to fabricatenanofibres compared with conventional methods. Electrospun nanofibers were successfullyextended to the electrochemical sensors application with controllable diameter, high surface areaand porosity, etc. In this paper, ZnO nanofibers and Pd-ZnO hollow nanotubes were successfullysynthesized by electrospinning followed by post-heat treatment with controllable fiber structure.The as-prepared composit nanofibers modified glassy carbon electrodes were successfully appliedfor the sensitive detection of trace Cd2+and dopamine, ascorbic acid as well as uric acid. Themain details and conclusions are as follows:1. ZnO nanofibers were prepared via electrospinning the mixtrue of PVP, PMMA andZn(Ac)2in diamethyl formamide(DMF) solution followed by high temperature treatment. Theeffect of added PMMA amount and the electrospinning parameters on the formation of ZnOnanofibers and the morphology and structure of ZnO nnaofibers were investigated. Itdemonstrated that the stable and uniform ZnO nanofibers could be obtained under the optimalconditions with the PVP and PMMA at the ratio of1:0.8, while the optimal parameters wereidentified with the voltage of11kV, receiving distance of15cm and spinning speed of0.5mL/h.The morphology and structure properties of as-prepared fibers were characterized by SEM、TEM、XRD、FT-IR and electrochemical methods. It found that ZnO nanofiber with diameter about200nm were composed of close-packed ZnO nanoparticles of ca.20nm and ZnO existed as ahexagonal wurtzite structure. The ZnO/GC electrode was successfully fabricatied by dip-coatingwith the mixture of ZnO NFs and Nafion.The obtained electrodes were applied to thedetermination of Cd2+by square wave stripping voltammetry (SWV). In addition, the effect ofdetection parameters on the response of stripping peak current was studied.Under the optimal conditions, a good linear relationship between peak current and Cd2+concentration was achievedin the range of2.610-8~8.910-7mol/L (R2=0.9957) by10min accumulation at-1.0V in0.1mol/L NaAc buffer solution (pH=4.6). The detection limit was8.910-9mol/L (S/N=3). Thepromising modified electrode was applied to the measurement of Cd2+in actual water samplesuccessfully.2. The PdCl2-Zn(Ac)2/PVP-PMMA precusor solution was prepared by mixing PdCl2withDMF solution containing PVP, PMMA and Zn(Ac)2. The final Pd-ZnO composite nanofibers wereachieved by electrospinning PdCl2-Zn(Ac)2/PVP-PMMA followed by high temperature treatment.The morphology and properties of the resulted Pd-ZnO composite nanofiber was characterized bySEM, TEM, XRD, XPS, and water contact angle measurement. It showed that Pd componentswere uniformly embedded into the ZnO particle surface. With the Pd concentration increasing, thestrcture of composite nanofibers could be conveniently tuned from fiber to nanotube structure.When the Pd concent was increased to1%. Pd-ZnO composite nanotube was formed with theoutside diameter of400nm and the inter diameter of240nm. Meanwhile, XPS implied that Pd incomposite nanofibers mainly existed in PdO form. The Pd-ZnO/GC electrode was successfullyprepared by dip-coating with Pd-ZnO and applied for simultaneous determination of DA, AA andUA by differential pulse voltammetry (DPV) with high sensitivity. The effect of various Pdcontent in Pd-ZnO and test parameters on response signals was studied. Under the optimalconditions, the stripping peak of DA, AA and UA without mutual interfering appeared around0.382V，0.25V and0.51V, respectively. A good linear relationship between peak current and DA,AA and UA concentration were achieved in the range of3.010-7~3.010-5mol/L(R2=0.9991),1.010-5~1.010-3mol/L(R2=0.9967) and6.010-6~6.010-4mol/L(R2=0.9935) by DPV in0.1mol/L NaAc buffer solution (pH=4.0), respectively. And the detection limits for DA, AA and UAmeasurement were1.010-8mol/L,1.010-6mol/L and3.010-6mol/L (S/N=3), respectively.