Preparation Of Electrospun Polyaniline/Noble Metal Nanotube Composites Modified Electrode And The Electroanalysis Application

As conducting polymers, polyaniline has many advantages, such as simple preparation method, easy doping, good stability and moderate conductivity and excellent properties of light, electricity, magnetism and so on. With the development of nano material science, different nano structured polyaniline(PANI) is successfully prepared, such as: nanoparticles, nanofibers, nanospheres, nanorods, nanotubes, etc. In all materials above, due to its large surface area, more contact surface for favorable electron transport and active sites for chemical reaction occurring. Electrospinning nanofiber has great specific surface area, uniform fiber structure and controllable process, so that it ws used as an template to fabricate a variety of multilayer nanostructures.In this paper, the electrospun polystyrene nanofibers were prepared as a template for the formetion of PANI nanotubes. The noble nanoparticles were decorated on the surface of PANI nanotube to get PANI/noble nanoparticles nanotube composite. The composites were further modified on glassy carbon electrode and successfully applied to the detection of ascorbic acid and hydrazine. Main contents and conclusions are as follows:1. With PS polymer as matrix, tetrabutylammonium bromide(TBAB) as conductive agent, both of them were dissolved in DMF to form the precursor solution, PS nanofibers were produced by electrospinning. With the concentrated sulfuric acid treatment, sulfonated polystyrene was got to improve the wettability and to facilitate the formation of PANI, and then oxidation polymerization of aniline happened on sulfonated PS fiber surface. Finally, PS was removed to get the PANI nanotube. The experimental results showed that in the presence of TBAB, the fiber became very uniform and thin, with the diameter of ~200 nm. The effects of the sulfonation time and the concentration of aniline on the structure of polyaniline nanotubes were studied by field emission scanning electron microscopy(SEM) and fourier transform infrared spectroscopy(FT-IR) characterization. It showed that increasing sulfonation time resulted in the increase of the proportion of sulfonic acid groups. When sulfonation time was 4 hours, aniline solution concentration of 150 mmol/L, the obtained prossessed PANI nanotubes uniform morphology with tube wall of 40 nm, tube diameter of 170 nm. FT-IR characterization showed that the PS nanofibers in PANI nanotubes were completely removed from the PANI nanotubes. The electrochemical behavior of PANI nanotubes modified glassy carbon electrode was studied. The PANI modified electrode had excellent electrical activity and reversibility, and the electrochemical behavior was a diffusion-controlled processs.2. PANI nanotubes were soaked in HAuCl4 solution, and the Au nanoparticles were deposited on the surface of PANI nanotubes by the self reduction of PANI to get Au modified PANI nanotube composites(Aunano-PANI), XPS proved that the Au on PANI nanotubes was zero-valent. The morphology and chemical property of Aunano-PANI nanotubes were characterized by SEM, transmission electron microscopy(TEM) and X ray photoelectron spectroscopy(XPS). The results showed that with the increase of HAuCl4 solution concentration and reaction time, the particle size of Au nanoparticles gradually increased, and the particles gradually began to aggregation. Aunano-PANI nanotubes were modified onto the glassy carbon electrode, cyclic voltammetry(CV), Differential pulse voltammetry(DPV) and other electrochemical methods were used to study the catalytic oxidation of ascorbic acid(AA) on the Aunano-PANI modified electrode. Compared with the bare electrode and PANI modified electrode, the oxidation current of AA on the Aunano-PANI modified electrode was greatly increased, indicating the existence of Au nanoparticles improved the charge transfer capability of PANI nanotube. The Aunano-PANI modified electrode was used for the detection of AA. In the range of 5 × 10-6~3 × 10-3 mol/L, the peak current and the concentration of AA were in good linear relationship. The detection limit was 1×10-6 mol/L, and the electrode had high stability and anti-interference ability. The electrode was used for the detection of vitamin C samples, and the results were basically consistent with the content of the labeled samples. It demonstrated that the electrodes can be used for the simultaneous determination of AA and dopamine(DA). There is no interference between each other. It is promising for the analysis of biological samples.3. The formation of Pd nanoparticles on the surface of PANI was further studied. Compared to the growth of Au nanoparticles, the oxidantion property of Pd2+ is weaker than AuCl4-, and Pd nanoparticles could not be obtained by the self oxidation-reduction of PdCl2-PANI. Therefore, the PANI/Pd nanotube composites were obtained using NaBH4 as reducing agent. SEM characterization proved that the concentration of PdCl2 solution affected the deposition of Pd nanoparticles. With the increase of PdCl2 concentration, the particle size of Pd nanoparticles and the particle density gradually increased. XPS further proved that the Pd particles loaded on the PANI nanotubes were zero valence state. The PANI/Pd nanotube modified glassy carbon electrode was fabricated by drop-coting the PANI/Pd suspension in waste water. Electrochemical tests were carried out to invesitageted the electrochemical properties. It was found that the PANI/Pd modified electrode was very sensitive to the catalytic oxidation of hydrazine. Under the optimized conditions, the PANI/Pd nanotube composite modified electrode had good linar relationship in the range of 2×10-5~1×10-4 mol/L and 7×10-5~7×10-3 mol/L, with the detection limit of 2×10-6 mol/L(S/N=3). The reduction of oxygen and the catalytic oxidation of methanol by PANI/Pd were also studied. the electrode material is expected to be used as a fuel cell catalyst due to the high specific surface area of the electrode material.