Papers by Author: Chun Xu Pan

Abstract: The surface chemistry of carbon nanotubes (CNTs) synthesized from ethanol flame was investigated using FTIR, TG, XPS and TEM. It is found that the CNTs inherently have functional groups on their surfaces without any post-treatment. SEM results confirm that the pristine F-CNTs can be well dispersed in the polystyrene matrix.

Abstract: By applying phosphoric acid in dispersion of fullerene in the fabrication of polypyrrolefullerene photovoltaic cells we present laminated active structure of polypyrrole and subsequent fullerene layers, with two other reference methods to incorporate fullerene: (i) in a physically blended monolayer; and (ii) in a blend from chemical reaction. I-V characteristics show that a blend monolayer cell can display photosensitive effect however without photovoltaics; a bilayer cell displays photovoltaics either in dark or in illumination, with its VOC up to1V and its JSC up to12.5 μA cm-2 under AM1 105 mW cm-2 condition. The results demonstrate that phosphoric acid is effective in dispersion of fullerene as well as combining it with polypyrrole layer in a photovoltaic cell. The effects of phosphoric acid in fabricating a bilayered photovoltaic cell are discussed mainly in terms of H-bonding.

Abstract: We report here a series of polypyrrole/C60-H3PO4 two-layer photovoltaic cells fabricated by varying the C60 ratio with regard to polypyrrole. It is found that a slight amount of C60 can remarkably improve photovoltaic properties by four orders of magnitude; with C60 ratio the open-circuit voltage and short-circuit current increase, and at higher C60 ratio the photovoltaic working threshold is lowered too, the cell can even work efficiently in dark, more approaching the efficiency under strong illumination. The optimized device yields 1.2 V open-circuit voltage and 14 μA/cm2 short-circuit current, and a power conversion efficiency 0.01%. Our results show that polypyrrole is a potentially good material for photovoltaic cells. The effect of C60 in combination with polypyrrole is discussed.

Abstract: The effects of dopant 5-sulfosalicylic acid on the conductivity of polypyrrole were investigated. Under the condition of fixed molar ratio of oxidant-to-monomer (0.75: 1.00), a dozen of polypyrrole samples were made from chemical polymerizing the monomer pyrrole in aqueous medium by varying the dopant-to-monomer molar ratio. It was found that the dopant affected the conductivity and particle size of the synthesized polypyrrole. A maximum value for electrical conductivity of 5575 S/m was achieved when the molar ratio of dopant: oxidant: monomer is 2.25:0.75:1.00.

Abstract: The effects of dopant 5-sulfosalicylic acid on the conductivity of polypyrrole were investigated. Being nonhygroscopic, ammonium persulfate was used as the oxidant. Under the condition of fixed molar ratio of oxidant-to-monomer (0.375:1.00), a dozen of polypyrrole samples were made from chemical polymerizing the monomer pyrrole in aqueous medium by varying the dopant-to-monomer molar ratio. It was found that the dopant affected the conductivity and particle size of the synthesized polypyrrole. A maximum value for electrical conductivity of 5575 S/m was achieved when the molar ratio of dopant: oxidant: monomer is 2.25:0.375:1.00.

Abstract: In this paper, a micro-arc oxidation (MAO) approach is introduced for “in-situ” preparing TiO2 composite layer upon the surface of titanium alloy (Ti-6Al-4V) substrate. The surface morphologies, chemical compositions, crystal microstructure and photocatalytic properties of the layers were investigated by using a field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), electro-chemical workstation and UV-Vis spectrophotometer. The experimental results revealed that photocatalytic performance of the TiO2 composite layers was much higher than that of the pure TiO2 layer and also exhibited absorption under the visible light irradiation.

Abstract: This paper introduces a novel process for growing one-dimensional nanomaterials. That is, firstly, preparing a pure metal nanocrystalline film by using pulse electro-deposition, then, using this film as a catalyst for synthesizing variant one-dimensional carbon nanomaterials and one-dimensional metal oxide nanoneedles. Comparing with the nanoparticle catalyst, the growth mechanism of the present one-dimensional nanomaterials belongs to the “base growth model”, and it has advantages such as a much simpler process and no post purification requirement. In addition, the present method provides a possibility for diameter control of the one-dimensional nanomaterials through grain size control of the nanocrystalline film by adjusting the pulse electro-deposition parameters.

Abstract: By varying the dopant-to-pyrrole ratio in a wide range from 0 to 60% a series of 5-sulfosalicylic acid sodium doped polypyrrole was synthesized in situ in aqueous solution with ferric chloride as the oxidant. The resulting polypyrroles were characterized with the four-probe, laser light scattering and thermo-gravimetry analysis, differential thermal analysis, respectively. Our results indicate that the particle size plays a determinative role to tune the conductivity in the studied range of dopant concentration; and this series of polypyrrole with size-tuned-conductivity exhibits little less thermal-stability although its size and conductivity changes simultaneously and acutely with the dopant concentration. The association of the conductivity with particle size was interpreted in terms of a theoretical model proposed by Baughman and Shacklelette.

Abstract: By varying the dopant-to-monomer ratio in a wide range of 0―110%, a series of polypyrroles doped with 9,10-anthraquinone-2-sulfonic acid sodium were synthesized by polymerizing the monomer pyrrole in aqueous solution of ferric chloride. The resulted polypyrroles were characterized with the four-probe, laser light scattering and differential thermal analysis, respectively. Our results indicated that the average particle size dominates the change in conductivity and thermal stability for the resulted polypyrrole at different dopant concentration.

Abstract: With four-probe technique, we investigated the effects of the mortar-pestle grinding on the conductivity of ferric chloride doped conducting polymer polypyrrole, which had been synthesized by in situ polymerizing the monomer pyrrole in aqueous solutions in the presence of the oxidant iron (III) chloride. As the mortar-pestle grinding duration increased from 0 to 4 hours, the conductivity of the synthesized polypyrrole was found to decrease from about 100 to 10 S/m. In the meantime, the sizes of the grinded polymeric particles were found to decrease from 40.6 to 3.36 m as the grinding duration increased from 0 to 4 hours. Our results demonstrated that the grinding shortened conjugation lengths of the polymeric chains should be responsible for the decrease in the conductivity of the polymer.