Yunze Long

University of Science and Technology, Beijing, Beijing, Beijing Shi, China

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Publications (22)73.78 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This article exposes a facial approach to self-assemble polyaniline (PANI) nanowires with thin diameter (approximately 10 nm) and high room-temperature conductivity (approximately 10(0) S/cm) by using Fe(2)(SO(4))(3) as a binary oxidant and dopant. The new method not only saves hard templates and postprocess of template removal but also simplifies the reagent. Formation yield, diameter, and room-temperature conductivity of the nanowires are affected by the molar ratios of Fe(2)(SO(4))(3) to aniline. The low redox potential of Fe(2)(SO(4))(3) not only results in a thinner diameter and higher room-temperature conductivity (10(0) S/cm) of the nanowires but also shows a much weaker temperature dependence of resistivity and smaller characteristic Mott temperature (T(0) = 2.5 x 10(3) K).
    The Journal of Physical Chemistry B 12/2009; 114(1):115-9. · 3.38 Impact Factor
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    ABSTRACT: The present article investigates a reversible structural phase transition, and related physical properties change in a new quasi-one-dimensional (1D) organic semiconductor crystal, DBA(TCNQ) 2 [DBA) dibutylammonium, TCNQ) 7,7,8,8-tetracyanoquinodimethane]. Differential scanning calorimetry traces reveal the DBA(TCNQ) 2 single crystal undergoes a first-order reversible phase transition at around 260-270 K, which is accompanied by a dramatic change in both conductivity and magnetic susceptibility. A direct correlation of physical properties with crystal structure is established. Detailed X-ray structure analyses indicate a reversible structural change related to dimer-tetramer transition along the TCNQ chain and disruption of the hydrogen-bonding chains as the temperature decreases from 270 to 253 K, which is the origin of the electronic and magnetic transition.
    The Journal of Physical Chemistry C 06/2008; 112(29). · 4.84 Impact Factor
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    ABSTRACT: The role of the nanowire diameter on the electrical properties of isolated poly(3,4-ethylenedioxythiophene) nanowires has been studied systematically by a four-terminal technique. A transition from an insulating to a metallic regime is observed when the diameter decreases from 190 to 35 nm and a transition from a metallic to an insulating regime takes place for the smaller diameters. These results are of importance for the different potential applications based on polymer nanowires or nanotubes.
    Applied Physics Letters 03/2007; 90(10):102114-102114-3. · 3.52 Impact Factor
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    ABSTRACT: Magnetic susceptibility measurements on conducting polyaniline and polypyrrole nanostructures with different dopant type and doping level as functions of temperature and magnetic field are reported. The susceptibility data cannot be simply described as Curie-like susceptibility at lower temperatures and temperature-independent Pauli-like susceptibility at higher temperatures; some unusual transitions are observed in the temperature dependence of susceptibility, for example, paramagnetic susceptibility decreases gradually with lowering temperature, which suggests the coexistence of polarons and spinless bipolarons and possible formation of bipolarons with changing temperature or doping level. In particular, it is found that the direct current magnetic susceptibilities are strongly dependent on applied magnetic field, dopant type, and doping level.
    The Journal of Physical Chemistry B 12/2006; 110(46):23228-33. · 3.38 Impact Factor
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    ABSTRACT: Conductivity and magnetoresistance (MR) measurements on pellets of conducting polyaniline and polypyrrole nanotubes/wires are presented. A transition from small negative MR to large positive MR was measured below 60 K. The positive and negative MR has been discussed in terms of a wavefunction shrinkage effect and a quantum interference effect on hopping conduction. In addition, further studies show that the MR of single polymer nanotubes/wires is very small even at 2 K (MR<5% at 10 T) compared with that of the pellets (40%–100% at 10 T), and no evident and stable negative MR is observed above 50 K. The results indicate that the MR in the bulk pellet samples made of polymer nanotubes/wires is dominated by a random network of inter-fibril contacts.
    Nanotechnology 11/2006; 17(24):5903. · 3.67 Impact Factor
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    ABSTRACT: We report the measurements of conductivity, I-V curve, and magnetoresistance of a single Au/ polyaniline microfiber with a core-shell structure, on which a pair of platinum microleads was attached by focused ion beam. The Au/polyaniline microfiber shows a much higher conductivity 110 S / cm at 300 K and a much weaker temperature dependence of resistance R4 K / R300 K = 5.1 as compared with those of a single polyaniline microtube RT =30–40 S/cm and R4 K / R300 K = 16.2. The power-law dependence of RT T − , with = 0.38, indicates that the measured Au/polyaniline microfiber is lying in the critical regime of the metal-insulator transition. In addition, the microfiber shows a H 2 dependent positive magnetoresistance at 2, 4, and 6 K. © 2006 American Institute of Physics. Both conducting polymers and metal nanoparticles par-ticularly silver, gold, and copper have attracted much atten-tion because of their interesting electrical and optical prop-erties and technological applications. Embedding of such particles inside polymers has become one of the popular and interesting aspects of nanocomposites because they often ex-hibit improved chemical and physical properties, and hence can be used in a broader range of applications such as non-volatile electronic memory, 1 independently addressable re-motely triggerable switches and gates, 2 spinnable bioactive coatings, 3 and gas-sensing devices. 4 By now, there are a number of reports on the gold-polymer nanocomposites. For instance, Au/polypyrrole nano-particles with a core-shell structure have been synthesized by polymerization of pyrrole on the surface of Au particles or through a one-step process. 5 Maggioni et al. 6 have reported Au/polyimide composite films that were prepared by Au-ion implantation. Recently, a sonochemical method for the syn-thesis of Au/polyaniline composites has been reported. 7 There are also several papers dealing with metal-polymer composites with a core-shell structure. For example, Zhang et al. 8 have reported the electrochemical fabrication of poly-thiophene film coated Au and Ag nanowire arrays. Obare et al. 9 have reported preparation of polystyrene-coated Au na-norods. Coaxial nanocables of Ag/polypyrrole Ref. 10 and Ag/polyvinyl alcohol Ref. 11 have also been reported. Although different metal-polymer nanocomposites have been reported extensively, Au/polyaniline nanocomposites with fibrillar morphology and especially electrical properties of a single Au/polymer microfiber have not been intensively reported yet. In this letter, Au/polyaniline microfibers with a core-shell structure have been synthesized by reacting aniline monomer with HAuCl 4 via a self-assembly process in the presence of camphor sulfonic acid as dopant and surfactant. A pair of platinum microleads on a single microfiber was fabricated by focused ion beam. The temperature dependence of resistance, I-V curve, and magnetoresistance of the single microfiber have been measured, and the results have been discussed and compared with those of a single polyaniline microtube. Aniline monomer was distilled under reduced pressure and stored under N 2 gas. D-camphor-10-sulfonic acid CSA and HAuCl 4 were used as received. In a typical procedure, 0.0165 ml of aniline An monomer mixed with 2.5 ml CSA aqueous solution An = 0.07M and CSA = 0.35M under stirring for 0.5 h to obtain a uniform emulsion. 0.5 ml aque-ous solution of HAuCl 4 HAuCl 4 = 0.05M was quickly added into that above emulsion. Then, the mixture was al-lowed to react at 0 – 5 ° C in an ice bath for 10 h without stirring. The product was washed with de-ionized water for several times, and finally dried under vacuum at room tem-perature for 24 h to obtain a dark powder of Au/PANI-CSA PANI denotes polyaniline nanocomposites. The samples obtained were characterized by scanning electron micros-copy SEM, transmission electron microscopy TEM, JEOL2000, 200 kV, no field emission gun, x-ray diffraction MAC Science, Fourier transform infrared spectrum Perkin-Elmer System, and ultraviolet-visible absorption spectra UV-3100 spectrometer.
    Applied Physics Letters 01/2006; 88. · 3.52 Impact Factor
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    ABSTRACT: We report on electrical and magnetic properties of polyaniline (PANI) nanotubes (∼150nm in diameter) and PANI/Fe3O4 nanowires (∼140nm in diameter) containing Fe3O4 nanoparticles with a typical size of 12nm. These systems were prepared by a template-free method. The conductivity of the nanostructures is 10−1–10−2S/cm; and the temperature dependent resistivity follows a lnρ∼T−1/2 law. The composites (6 and 20wt% of Fe3O4) show a large negative magnetoresistance compared with that of pure PANI nanotubes and a considerably lower saturated magnetization (Ms=3.45emu/g at 300K and 4.21emu/g at 4K) compared with the values measured from bulk magnetite (Ms=84emu/g) and pure Fe3O4 nanoparticles (Ms=65emu/g). AC magnetic susceptibility was also measured. It is found that the peak position of the AC susceptibility of the nanocomposites shifts to a higher temperature (>245K) compared with that of pure Fe3O4 nanoparticles (190–200K). These results suggest that interactions between the polymer matrix and nanoparticles take place in these nanocomposites.
    Physica B Condensed Matter 12/2005; 370(1):121-130. · 1.28 Impact Factor
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    ABSTRACT: This paper reports a functional dopant-introduced route to synthesize polypyrrole (PPy) nanofibers (60–100nm in average diameter) in the presence of p-hydroxyl-azobenzene sulfonic acid (p-OH-ABSA) as a functional dopant. The nanofibers show a high conductivity (120–130S/cm) and photoisomerization, which resulted from proton doping and photoisomerization of azobenzene moiety, respectively. Static and dynamic light scattering as well as freeze-fracture replication transmission electron microscope measurements (FFRTEM) showed that the self-assembled cylindrical micelles act as “soft-templates” during the formation of the nanofibers. Influence of polymerization conditions, such as the type of oxidant, the rate of oxidant addition, the concentration of reactants and polymerization time, on the fibrous morphology of PPy-(p-OH-ABSA) has been investigated. The characterizations of molecular structure, photoisomerization and electrical properties have been carried out. The method described in this study provides a simple and inexpensive route to prepare multi-functional nano-structured conducting polymers.
    Synthetic Metals 12/2005; 155(3):495-500. · 2.22 Impact Factor
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    ABSTRACT: In this Letter, we report on the temperature-dependent conductivity and current-voltage curve of a single CdS nanowire, which was synthesized by a simple aqueous chemical growth method. A pair of platinum microleads was fabricated on the single CdS nanowire by focused ion-beam deposition. The room-temperature conductivity and the band gap of the single CdS wire are 0.82 Ω−1 cm−1 and 0.055 eV, respectively. When the applied electric field is larger than 1090 V cm−1, the CdS nanowire shows a nonlinear I‐V curve at room temperature.
    Applied Physics Letters 04/2005; 86(15):153102-153102-3. · 3.52 Impact Factor
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    ABSTRACT: Completely doped submicrotubes (90–560 nm in diameter) of conducting polyaniline and polypyrrole have been synthesized by a template-free method. The measurements of resistivity, I-V curve and magnetoresistance of single polyaniline tube by a standard four-probe technique are presented. Due to the elimination of large intertubular contact resistance, the single polyaniline tube shows a considerably high conductivity and a small positive magnetoresistance. In particular, a crossover from Mott to Efros-Shklovskii variable-range hopping conduction at about 66 K is observed in the single polyaniline tube owing to a strong electron-electron interaction with a Coulomb gap of 11.2 meV. This strong Coulomb interaction is also proved by the I-V curves, which show an obvious zero-bias anomaly at low temperatures. In addition, the temperature dependences of electrical conductivity of single polypyrrole submicrotubes with different diameter have also been studied. The room-temperature conductivity of single polypyrrole tube increases from 0.13 to 73 S∕cm when the outer diameter decreases.
    Physical Review B 04/2005; 71(16). · 3.66 Impact Factor
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    ABSTRACT: A multiwalled carbon nanotube∕polyaniline composite with cablelike morphology has been synthesized by an in situ chemical oxidative polymerization directed with cationic surfactant cetyltrimethylammonium bromide. It is interestingly found that with increasing carbon nanotube loading from 0 to 24.8 wt%, the conductivity increases by two orders of magnitude and the Mott’s characteristic temperature T0 which depends on the hopping barrier decreases by three orders of magnitude. Furthermore, the low-temperature magnetoresistance has also changed the sign from positive to negative. The results reveal a strong coupling between the carbon nanotube and the tightly coated polymer chains, which enhances the average localization length and the electronic properties of the composites.
    Applied Physics Letters 09/2004; 85(10):1796-1798. · 3.52 Impact Factor
  • L. Zhang, Y. Long, Z. Chen, M. Wan
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    ABSTRACT: Polyaniline (PANI) nanotubes with an outer diameter of 165–240 nm and an inner diameter of 10–70 nm were prepared by a self-assembly process in the presence of six different carboxylic acids—propionic acid (PA), lactic acid (LA), succinic acid (SA), malic acid (MA), tartaric acid (TA), and citric acid (CA)—as the dopants. These nanotubes aggregated to form nanotube dendrites when the carboxylic acids contain an OH group. Moreover, the number of OH and COOH groups of the carboxylic acids affected the size, aggregated dendrite morphology, and thermal and electrical properties of the nanotubes. It was proposed that the micelle formed by the carboxylic acids acts as a template in the formation of the nanotubes, while the hydrogen bonds between the polymer chain of PANI and the OH group of the carboxylic acids supply a driving force to form the aggregated nanotube dendrites.
    Advanced Functional Materials 07/2004; 14(7):693 - 698. · 10.44 Impact Factor
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    ABSTRACT: A multi-walled carbon nanotube/polypyrrole (CNT/PPy) nanocomposite with cable-like morphology has been synthesized using an in situ chemical oxidative polymerization method. The temperature dependences of the conductivity and magnetoresistance (MR) have been studied. We found that the room temperature conductivity increases by two orders of magnitude with increasing carbon nanotube weight percentage. The temperature dependence of the conductivity follows a charge–energy-limited tunnelling model (lnσ(T) T−1/2) and indicates clearly that the CNT weight percentages of 9.1 and 13.04 wt% are below the percolation threshold and 23.1 wt% is beyond the percolation threshold. At low temperatures the 23.1 wt% composite shows a negative MR whereas the pure PPy shows a positive one. The results reveal that at the percolation threshold the complete CNT conductive paths can change and enhance dramatically the electrical properties of the CNT/PPy composites.
    Journal of Physics D Applied Physics 06/2004; 37(14):1965. · 2.52 Impact Factor
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    ABSTRACT: In this letter, we report the electrical properties of hollow polyaniline (PANI) microspheres. β-naphthalene sulfonic acid (NSA) and salicylic acid (SA) doped PANI microspheres were synthesized by a self-assembly method. The room-temperature conductivity is 8.6×10<sup>-2</sup>  S/cm for PANI–NSA microspheres (0.8–2 μm in outer diameter) and 5.6×10<sup>-4</sup>  S/cm for PANI–SA microspheres (3–7 μm in outer diameter). The conductivity of an individual PANI–SA microsphere is measured directly by a two-probe technique, about 8×10<sup>-2</sup>  S/cm (which is two orders of magnitude higher than that of a PANI–SA microsphere’s pellet). The measurements of conductivity, I–V curve, and magnetoresistance demonstrate that the electrical properties of PANI microspheres are dominated by the intersphere contacts due to the sample’s microscopic inhomogeneity. © 2004 American Institute of Physics.
    Applied Physics Letters 04/2004; · 3.52 Impact Factor
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    ABSTRACT: We report on the specific heat and magnetic susceptibility of polyaniline (PANI) nanotubes, which were self-assembled by a template-free method. It is interestingly found that an electronic specific heat is not observed from present data, and the lattice specific heat of PANI nanotubes can be interpreted in terms of the contributions from both the crystalline and the amorphous phases. The magnetic susceptibility includes a Pauli-like susceptibility and a Curie-type susceptibility. The results reveal an inhomogeneous disorder picture of PANI nanotubes (i.e., PANI nanotubes are composed of crystalline regions and amorphous regions). The crystallinity fraction Dg obtained from the specific heat is about 15% for the measured PANI nanotubes, which indicates that most of the polymer chains in the nanotubes are disordered.
    Journal of Physics Condensed Matter 02/2004; 16(7):1123. · 2.22 Impact Factor
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    ABSTRACT: New polyaniline (PANI) blends, PANI-camphor sulfonic acid (PANI-CSA) and PANI-dodecylbenzene sulfonic acid (PANI-DBSA) composite films with high room-temperature conductivity (∼200 S/cm) were prepared. The experimental data show a transition from negative temperature coefficient of resistivity (TCR) to positive TCR at around 210K. An equation ρ(T)=a·ρmexp(−Tm/T)+b·ρ0exp(T0/T)1/4 combining 3D variable-range hopping in disordered regions with quasi-one-dimensional metallic conduction in ordered regions has been used, which are consistent well with the resistivity data even from 1.8 up to 370K. It is found that the PANI blends show positive magnetoresistance (MR) from 240K down to 1.8K and show negative MR from 240K up to 350K, which can be attributed to different dominant conduction mechanisms in different temperature ranges.
    Physica B Condensed Matter 02/2004; 344(1):82-87. · 1.28 Impact Factor
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    ABSTRACT: We report on the electrical properties of a conducting polyaniline (PANI) derivative film containing azobenzene side chain. The freestanding thin film of HCl-doped PANI derivative was synthesized through an N-alkyl-substituted reaction. We found that the side of the film irradiated by a weak ultraviolet light during the preparation is a poor conductor at room temperature and shows abnormal V-I characteristics. Its resistance decreases sharply with increasing temperature. However, the other side of the film without irradiation is highly conductive. The room-temperature conductivity is about 1.2 S/cm, which is much higher than that of other N-alkyl-substituted polyanilines (10-2-10-7 S/cm). The temperature dependence of resistance follows one-dimensional variable-range hopping model.
    Applied Physics Letters 01/2004; 84. · 3.52 Impact Factor
  • Macromolecular Rapid Communications 10/2003; 24(16):938 - 942. · 4.61 Impact Factor
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    ABSTRACT: We report the electrical properties of a single conducting polyaniline nanotube measured by a standard four-terminal technique. Camphor sulfonic acid doped polyaniline nanotubes were self-assembled by a template-free method. The directly measured conductivity of the single polyaniline nanotube is very high (∼31.4 S/cm), and its temperature dependence follows the three-dimensional variable range hopping model. However, the bulk conductivity of the polyaniline nanotube pellets is much smaller than the nanotube itself (only 3.5×10<sup>-2</sup>  S/cm ) and ln  ρ(T) is linear in T<sup>-1/2</sup>, which is due to the large intertubular contact resistance. These results will help us to understand the conduction mechanism in conducting polymers. © 2003 American Institute of Physics.
    Applied Physics Letters 10/2003; · 3.52 Impact Factor
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    ABSTRACT: The temperature dependence of the resistivity of nanotubular polyaniline (PANI) doped with H <sub>3</sub> PO <sub>4</sub> and β-naphthalene sulfonic acid (NSA) synthesized by a “template-free method” has been investigated. The molar ratios of H <sub>3</sub> PO <sub>4</sub> ( NSA ) to aniline monomer (represented by H <sub>3</sub> PO <sub>4</sub>/ An and NSA/An) of the samples are H <sub>3</sub> PO <sub>4</sub>/ An =0.01 ,  0.05 ,  0.3 ,  0.5 and NSA / An =1 ,  2, respectively. It is found that ln  ρ( T ) is linear in T <sup>-1/2</sup> and the resistivity is sensitive to the doping concentration. For NSA / An =1 sample, a crossover at 57 K in the plot of ln  ρ( T )∼ T <sup>-1/2</sup> has been observed. On the basis of detailed analysis of the structure characteristics of the PANI nanotubes, we suggest a hopping–tunneling model to explain the experimental results. © 2003 American Institute of Physics.
    Journal of Applied Physics 04/2003; · 2.19 Impact Factor

Publication Stats

553 Citations
73.78 Total Impact Points


  • 2009
    • University of Science and Technology, Beijing
      • School of Materials Science and Engineering
      Beijing, Beijing Shi, China
  • 2007
    • Qingdao University
      Tsingtao, Shandong Sheng, China
  • 2006
    • Chinese Academy of Sciences
      • Institute of Physics
      Beijing, Beijing Shi, China
  • 2003–2006
    • Northeast Institute of Geography and Agroecology
      • • Institute of Physics
      • • Key Laboratory of Extreme Conditions Physics (1)
      Beijing, Beijing Shi, China
  • 2005
    • Technical Institute of Physics and Chemistry
      Peping, Beijing, China