期刊
NANOSCALE
卷 6, 期 1, 页码 181-189出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c3nr04152b
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资金
- National Science Foundation Nanoscale Interdisciplinary Research Team, and Materials Processing and Manufacturing [CMMI 10-30755]
- NSF [DMR 13-06392]
- China Scholarship Council (CSC) program
- Direct For Mathematical & Physical Scien [1306392] Funding Source: National Science Foundation
- Directorate For Engineering [1030755] Funding Source: National Science Foundation
Contrary to the observed positive giant magnetoresistance (GMR) in as-received multi-walled carbon nanotubes (MWNTs), pure polyaniline (PANI) synthesized with Cr(VI) as oxidant and MWNTs/PANI nanocomposites with ammonium persulfate (APS) as oxidant, a room temperature negative GMR of around -2% was reported in MWNTs/PANI nanocomposites with Cr(VI) as oxidant. Different from a frequency switch of permittivity from negative to positive in MWNTs/ PANI nanocomposites with APS as oxidant, unique negative permittivity was observed in MWNTs/PANI nanocomposites with Cr(VI) as oxidant within the measured frequency range from 20 to 2 x 10(6) Hz. The obtained unique negative permittivity was explained by the plasma frequency from the Drude model, at which the permittivity changes from negative to positive and the material changes from a meta-material to an ordinary dielectric medium. The observed positive and negative GMR behaviors in these disordered systems as verified by the temperature dependent resistivity exploration were well explained through a wave-function shrinkage model and orbital magneto-conductivity theory by calculating the changed localization length (a(0)).
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